Alburnam's Archive

Ó 2000-2001  Stephen A. Shepherd

Repairing Chairs

Chair Maker

Chairs are the most mobile pieces of furniture and because of that movement and use they are also the most damaged piece of furniture.  Also contributing to the large number of damaged chairs is the fact that there are usually four chairs for each table, they just outnumber other pieces.  It would be difficult to discuss all types of chair repair because of the endless variety of styles and types.  There are some repairs that are common and with some guidelines that can prepare you for the problems you may encounter.

The most common problem with chairs is that of loose joints, next are broken parts then worn and missing parts.  Some chairs are easily damaged because of their delicate nature; others are damaged from excessive use and abuse.  Whatever the problem, they need to be repaired in order to prevent further damage; it must be at least stabilized.  As with other old furniture, only the minimum amount of work should be done and as much of the original as possible must be preserved and maintained these old pieces.

Chairs in the nineteenth century were invariably glued together with hide glue and after time drying out the wood and glue the joints sometimes fail.  Unfortunately modern glues have been used to repair much old furniture and this can actually cause more problems that it attempts to remedy.  The glue is so strong that the joints don’t fail; the wood fails causing much more damage than a simple loose joint.  Do not use modern glues to repair any old furniture, always use hide glue, fresh hot hide glue is the best but you can use liquid hide glue which is readily available and much better than any modern glue for this purpose.  See Using Hide Glue.  Some modern glues can be softened enough to loosen the joints by soaking the joints with water, this is a drastic step to undo an incredibly unfortunate choice of glues.  People without experience do many repairs made to chairs and seldom are the joints properly cleaned, prepared and clamped.  If the chair has never been repaired with modern glues then you will be dealing with hide glue that was used on the original assembly.  Old hide glue does not necessarily need to be cleaned from the joints as the newly introduced hide glue will reconstitute the old glue and the joints should be just fine.  If you can expose the joints any loose glue should be removed, as should any dirt and debris that might have accumulated over time.

Some loose joints on chairs can be repaired while the chair is still together or if you determine that you can’t take the joints apart to do a thorough repair.  This is done by using a hypodermic syringe with a fine needle and hide glue.  Liquid hide glue works well and hot glue needs to be thinned in order to work in the syringe.  It also helps to keep the syringe in hot water to help lower the viscosity of the glue.  Insert the needle around the loose joint and push it in as far as possible and start injecting the glue into the joint.  Move the needle to a different position and inject until glue starts coming out of the joint on all sides.  The joints can be clamped, the chair squared; the excess glue wiped off with a wet rag and it is allowed to dry overnight.  While this technique works on simple loose joints it can be a lot of work to go around to each joint and inject the glue, so if it is possible to disassemble the chair it can make for easier and better restoration work.

If it is possible to disassemble all of the joints then it is important to label or number the parts so you can make sure they all go back in their original position.  Many old hand made chairs will only go together in one way, each joint being individually fit, so keep track of the parts.  Clean off the excess glue on the tenons and also in the mortices.  On some drilled round mortices you might be tempted to just use a drill and drill out the old glue.  This is not a good idea as the drill bit can enlarge the original hole leaving a sloppy joint.  I sometimes use a smaller bit to clean out the glue in the mortice then clean out any excess that remains.  I will sometimes take a proper sized drill bit and advanced into the hole by hand to insure that the mortice is completely clean and ready to accept the tenon.  Just be careful not to enlarge any of these holes.

Some spindles and legs that attach to the seat such as a Windsor chair go all the way through the seat and are wedged on the opposite side.  These wedged joints are usually quite strong but some can become loose with age.  If you have to remove one of these spindles you must first remove the wedge.  Choose a drill bit slightly smaller than the width of the wedge and carefully drill out the wedge.  Once a few holes are drilled you can use a small chisel to remove any remaining wedge.  When you make a new replacement wedge, make sure you match the material of the original and make it a little thicker.  Once you remove the leg, use a saw to clean up the slot for the wedge.  Some of these wedges were inserted into saw kerfs cut on the end of the spindles or legs.  Others are inserted in a split in the end of the spindle or leg made with a chisel, then the wedge is glued and driven into the end and cut off flush and finished smooth on the top.  Some spindles and legs are blind wedged and can present a problem, as the wedge will prevent the spindle or leg from being removed.  This is a good candidate for injecting glue into the joint with a syringe, as they can be difficult to remove even when loose.  Other chairs might have bellied tenons turned on the ends of the spindles or legs.  This barrel shaped tenon is inserted and glued into a mortice drilled in green wood.  As the green wood shrinks the mortice shrinks around the tenon and holds the spindles or legs securely.  This joint can come loose yet not able to be completely removed; again another use of the syringe can deal with this problem.

Some joints might be pegged to reinforce those joints and if the peg needs to be removed, this should be done carefully.  If I have to remove an exposed peg or dowel, I choose a smaller drill bit and carefully drill down the peg or dowel.  Be careful even when using a smaller bit to make sure you are just drilling out the peg hand not into the chair itself.  Once you drill out the center of the peg it can be removed without damaging the surrounding hole.  Just break it towards the hole until all pieces are removed.  I then use a proper sized drill bit and gently by hand run it down the hole to clean off any pieces of wood, glue or other debris.  I make the new dowel from the matching materials.  See Making and Using Dowel Pins and Pegs.

Repairs to seats are usually straightforward and require only cleaning the joints that have come apart and re-gluing and properly clamping until the glue is dry.  Some seats will develop spits in the wood or will have just minor cracks in the joints that need to be filled and stabilized.  Of course choose a wood that matches the original as close as possible.  Old woods such as walnut, cherry, maple and the softwoods will change color with age so select as close a color as possible, keeping in mind that the new wood will also eventually change colors.  I use a fine saw and run it through the split to make a uniform kerf for the replacement piece.  This will also help clean out the split and give a good gluing surface.  Cut the piece of new wood to fit into the kerf and carefully fit it up.  I always remove any excess from the new piece so I don’t have to work it much after it is glued in place.  This protects the surrounding surfaces.  I then glue and clamp the replacement wood in place, clean up the excess glue and allow to dry overnight.  I always clamp even the smallest pieces to insure a proper bond of the new materials to the old.

Any damage should be repaired as soon as possible after it occurs to insure that any broken edges are sharp and crisp.  A fresh break is easier to repair requiring less touch up than an old break where the fresh edges have been rounded over.  Make sure that everything is properly lined up when you clamp it into final position.  It might shift and dry in the wrong place and that is one of the advantages of hide glue is that it is reversible if a problem arises.

Broken spindles, stretchers, rails, arms and legs need to be repaired in order to stabilize the piece and also to make it serviceable.  Instead of replacing broken parts it is always important to maintain the integrity of the piece by properly repairing them to preserve their history.  The damage and the repairs are all part of the provenance and heritage of old furniture and they need to be done in a neat and proper manner.

Turned members such as legs, spindles and stretchers usually break at their thinnest place or on the tenons on the ends and are usually perpendicular to the grain.  Lateral fractures along the grain are fairly easy to repair by cleaning the break and re-gluing.  The longer breaks provide good glue surfaces making repairs fairly easy.  Cross grain breaks require reinforcement in the form of an internal dowel peg.  This requires drilling a hole down the end grain of both broken parts in the exact center of each piece to a predetermined depth.  A dowel is made to the exact length of both holes less about 3/32” to1/8” to allow for glue.  If it is too short it won’t provide enough strength and if it is too long it will prevent the break from coming together.  I slightly chamfer each end of the dowel to make assembly easier.  The dowel and hole should be sized to provide enough internal strength as well as leaving enough wood around the hole to provide proper strength there as well.  I usually make repair dowel pins from straight grain hickory, which has the best strength, is flexible and glues well.  While I usually always match wood species, for hidden dowels I will select a wood that will replace the integrity lost when the piece broke.  Dowels can also be used to reinforce flat broken pieces such as rails or square legs, spindles or broken seats or failed butt joints.  These holes must be exact and match each other in order to make a proper repair.  Take your time and carefully locate the center of the turned spindle.  The broken end grain can be difficult to get a bit started so I always use a small gouge to excavate a starting point for the drill bit.  It is also very important that the hole is drilled straight down the spindle along the center axis.  I also countersink each hole slightly to provide a space for the glue and to make assembly a bit easier.

 Tenon repair using original parts with dowel reinforcement

A very common problem with turned parts is tenons that have broken off in other parts.  While some of these can be removed and doweled back onto the end of the spindle most are lost when trying to extricate them from the mortice.  If I can remove them, I clean the broken area and glue and clamp the short tenon back onto the spindle, wipe of the excess glue and allow to dry overnight.  The next day I carefully drill down the tenon into the spindle with a proper sized drill to a depth 2 ½ times as long as the tenon.  I then glue in a dowel of the same length to reinforce the joint.  All to often the tenon is lost when removed and needs to be replaced.  I select material that matches the original and turn up a new tenon with a step down and a turned tenon to act as a dowel.  Then the end of the broken spindle is squared off and a hole is drilled down the center axis of the piece to a depth slightly deeper than the length of the turned dowel on the end of the tenon.  I then clean out the hole, apply glue and clamp.  I clean off any excess glue and allow to dry overnight.  

Tenon repair using new shouldered tenon

Sometimes the end of the spindles that have broken off tenons are themselves cracked or split and this may need to be repaired before a new tenon is glued back on.  I open up the splits as much as possible, clean them out if necessary and introduce hide glue into the splits.  I then use waxed string or cord to tightly wrap (served around) the splits forcing them back to their original position and holding until the glue dries.  The wax prevents the string from becoming glued to the spindle and after it dries, the glue on the surface is cleaned off with a damp cloth.  I have also used hose clamps of various sizes but the metal parts need to be protected to prevent the hide glue from rusting, if you use this use waxed paper in between the clamp and the wood.

When I glue the spindles back together I use a bar clamp to hold them from each end and gently apply just enough pressure to bring the break tightly together.  I check to make sure that the spindle is perfectly straight.  I have even used my lathe as a clamp by centering up the spindle and applying pressure with the tailstock.  I can turn the work by hand and make sure it is perfectly oriented.  Do not apply too much pressure or you can break the spindle, usually at the weakest part around the drilled mortices for the dowel.  Wipe off the excess glue and allow to dry overnight.

Missing spindles and legs should be made from matching materials and should exactly match the original missing parts.  Some old turned parts have become slightly oval in profile after years of drying out.  I always try and match the surfaces of other parts so I add wear and age in the proper places to imitate the use it would have received over the years.

Legs on old chairs can be worn off on the bottoms from frequent use over the course of their history.  If it is determined that the bottom of the legs need to be replaced matching wood should be chosen and you need to figure out what the original might have looked like.  Examine books and original examples to decide how to best shape the missing part.  I use the same method for adding turned leg ends as I do for replacing broken tenons on the ends of spindles.  I turn a new part and it has a shoulder that steps down to a tenon that is centered in the new foot of the leg.  I drill a hole centered in the bottom of the squared off leg.  You loose a little wood when you square off the end, if it is a real steep angle that the leg has worn off, I will sometimes just flatten it then shape the turned shoulder to match the flattened but not square bottom.  A square bottom on the leg is the easiest method for making a good serviceable repair.  The hole is drilled slightly deeper than the length of the shouldered tenon.  I also turn a slight chamfer on the end of the tenon and slightly countersink the hole on the top edge for a space for glue and ease of assembly.  I apply sufficient glue on both the tenon and the mortice as well as the shoulders and clamp the leg and check for straightness.  I wipe off any excess glue and allow to dry overnight.

Rocking Chairs present the usual problems of loose joints but they can also have broken or heavily worn rockers.  In the West most all of the chairs made during the pioneer period before 1869 were constructed of pine and other softwoods and were painted and grained.  Many of these old rockers have flat spots on the bottom of the pine rockers making them quite thin in the middle.  I clean off the bottom carefully before using any fine hand tools to flatten them out.  These old rockers can have rocks and other grit pressed into the wood and this can damage the cutting edge of hand planes and chisels.  I flatten the wood, then add on enough wood to be able to reshape the rocker to its original shape.  I rough the surfaces with a keying or toothing plane or a rasp to provide extra glue surface area to make a tight fitting, long lasting joint.  I apply glue, clamp, wipe off any excess and allow to dry overnight.  The next day I mark the shape of the rocker on the new wood and shape it to its final outline.

I do all of the repairs to the individual parts first before I attempt to reassemble the chair if that is possible.  When ready to assemble the chair I always warm up the parts to make using hot hide glue a little easier.  I will usually dry fit everything together to make sure I am not going to having any surprises when I am gluing up.  I have all of my clamps ready, make sure the joints are all clean, the glue is hot and fresh then I begin my intense clamping moment.  I do not like to be disturbed when I am gluing, I need to focus all of my attention to the situation at hand.  Make sure there is sufficient glue to coat all surfaces that come in contact with other surfaces.  Use plenty but you can use too much in mortices that can cause hydraulic problems when trying to force the tenon into place.  Trapped air can also cause problems of not allowing the parts to go together.  This is when it gets exciting.  You can twist the spindles or legs a bit to break the seal and allow the air or excess glue to come out as the chair is clamped.  Too much glue might require the joint to be opened and the excess glue removed, so be careful when applying glue to mortices.  Get all of the parts together as soon as possible after the glue is applied.  Apply the clamps and use the proper pressure for each application.  You can also clamp pieces too tight, squeeze out all of the glue and starve the joint, so be careful.  Check and make sure everything is fitting properly and make sure that the chair is sitting on a flat surface as it dries to insure that the chair won’t rock or wobble.  A weight on the seat can help hold the chair flat.  Also check for squareness and other angles of legs and backs as is appropriate for each individual chair.  Wipe off all excess glue and allow to dry overnight.

If a chair is upholstered then it is better to do the repairs without taking the chair apart.  You may have to remove part or all of the upholstery for some repairs, so you either need to become familiar with these techniques or have a professional remove the upholstery, you can do the repairs then have it reupholstered.  If you do the work yourself, make careful notes on how you take the upholstery off.  This allows you to properly put the upholstery back on the way it was originally.  Try and keep the original upholstery material, if you are going to put new fabric on, put it on over the original material to preserve it with the chair.  I tighten up any loose webbing on the chair, clean the padding materials of dust and clean the fabric (using proper techniques) if necessary.

You will encounter many types of damage on chairs, from being over weighted to being chewed by animals.  You will find breaks in places you wouldn’t think the wood could break.  You will find chairs that are in excellent condition with only a few loose joints or you might get a sack of parts that barely resemble a chair.  I have had to undo many poorly done repairs and have worked on chairs that have been repaired so many times that none of the joints have sharp edges and all are very loose when assembled.  You may have to get creative by wrapping tenons with string or cloth and a lot of glue to make these joints serviceable.  You will be required to improvise ingenious clamps where normal clamps won’t work.  And, you will never run out of chairs to repair, so repair them in a neat and proper manner using original materials and techniques to preserve the integrity and maintain the history of the chair.  See General Repairs.

For information of the care of furniture see Moses T’s Guide to Furniture Care and Finish Restoration. Click Here

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Spokeshaves, Travishers, a Buzz and a Jarvis

These tools are wooden handled planes and scrapers with special smaller soles designed for specific purposes.  This is a step up from the drawknife and offers more control and can impart a smoother finish.  The two handles give the user more control over the direction, shape and depth of the cut.  Early nineteenth century handles tend to be larger and with less curves than those of later manufacture, although this is not a hard fast rule.  Some early designs have flared oval handles with fine lines.

Wooden Spokeshave, note handle shape

Spokeshave is a wooden double handled tool with a steel cutter that is used to shape of all things wagon wheel spokes, hence the name.  The blade is held into the body with two tangs that pierce the body in square tapered mortices that hold the blade at the correct position by a friction fit.  The bevel side of the blade faces up with the flat side on the sole.  The body of the spokeshave usually made of beech or other hard dense wood has handles molded on both sides of the narrow thin body that holds the blade.  The small sole or face of the spokeshave allows the tool to work on tight inside or outside curves as well as for straight work.  The sole of the wooden spokeshave just ahead of the mouth and blade may be equipped with a wear plate.  Some come from the manufacturer as brass plates fixed with iron screws.  Others are added as the original sole wears out and small pieces of dense material such as bone, ivory, boxwood, lignum vitae or apple wood is dovetailed into the base and can be easily replaced as it wears.  Most soles on spokeshaves are flat but some are made with soles that are rounded from front to back to allow working tight inside curves and surfaces.

The cutting depth of the wooden spokeshave is determined by how far the blade is projecting below the base or sole of the spokeshave.  The more the blade is projecting the greater the cut.  By tapping on the tangs the blade is moved out.  Tapping with a wooden mallet on the base of the blade at the tangs decreases the cut of the spokeshave.  If the tangs become loose in their mortices small thin hardwood wedges can be made to secure the tangs.  They are placed on the end grain side of the mortice to push out in the proper direction to prevent the spokeshave body from splitting.

Not limited to wagon wheel spokes, the spoke shave can be used to shape slats for chairs, rough out work for turning on the lathe or making other spindle work.

Using a spokeshave is like using a small two-handled plane and should be worked with the grain of the wood, as you would do with a low angled hand plane.  Working the spokeshave blade at a skew to the grain of the wood will produce a finer cut.  On tricky grain changes you can work cross grain to smooth out the work.

You will develop a feel for this tool and in some cases you will use it on the push stroke, which seems to be the more common method of using this tool.  You will also find that it can be of help to be able to use the tool on the pull stroke.  Your grip on the handles will give you the necessary control to be able to present the blade to the wood at the proper angle.  The oval shape to the handles also gives better leverage and control when using this tool.  See Wheelwright. 

Metal Spokeshave - Cast iron body, steel blade

Metal Spokeshave was introduced in the nineteenth century and used extensively by the coach making and wheel making trades.  Its popularity stems from its durability in a hostile shop environment.  Coaches are made in the center of the shop on sawhorses and the tools were frequently on the floor among the chips, shavings and sawdust.  Stepping on a wooden handled spokeshave could ruin the tool and with the Industrial Revolution in full swing, cast metal spokeshaves were a boon for the coach making trades.  The configuration of the metal spokeshave is different from the traditional wooden spokeshave in that the blade is more like a plane blade with the bevel down.  Metal screws or thumbscrews hold the blade in place and makes blade adjustment easy.  These are available with flat soles or curved soles and a flat blade; others have convex or concave sole and blade for special purpose shaping.  This tool never completely replaced wooden spokeshaves as they are completely different tools and work in distinct ways.   See Sharpening.  

Wooden Travisher

 Travisher is a spokeshave with a convex blade and is used for hollowing on seat bottoms, bowls, trenchers and other inside curves.  Some of these early examples have beautiful curves to the base and the handles.  The configuration of the blade is the same as a wooden spokeshave with the low cutting angle on the blade; the difference is the large sweeping curve of the blade and body.  When the tool becomes dull, it tends to chatter and catch in the wood, so keep the blade sharp to make your work easier.  This tool is easier to work on the push stroke because your thumbs need to be held down on the body to give you a purchase on the tool and to keep the blade engaged with the wood.  If you try and pull the tool towards yourself, the leverage will work against you.  It is much easier to work on the push stroke.  To clean up the bottom of a cut, the travisher is used across grain to deal with the changing grain direction and using at a skew can also help smooth the grain.  There is also a scraper version of this tool that has an almost vertical blade sharpened like a cabinet scraper.  It can be used to smooth up after the spokeshave version as brought the work to rough shape.

Wooden Buzz - simple cabinet scraper

Buzz is a term for a simple cabinet scraper.  A common use of these tools was to smooth down the outside of coopered barrels.  These tools can have a flat base but most are concave to handle the curved staves of the barrel.  It is used in the direction of the grain of the wood, so the concave sole is from side to side.  The staves are worked from the center bulge of the barrel to each end.  The blade is sharpened like a cabinet scraper with a bevel ground on one side to a 60 to 70° angle and a burr is turned towards the flat side.  The angle of the blade can be at 90° to the sole or it can slat forward 5° or so.  The two wedges hold each edge of the scraper blade tight in the body of the buzz.  A small piece of leather or veneer is placed behind the blade before it is secured.  This will cause the blade to bow out slightly producing a fine cut when properly sharpened and set.  It may require a bit of fussing getting the bow just right but then once you get it right it becomes quite easy.  If the tool chatters during use, it usually means that the blade is set too proud.  When the shavings from this tool turn from clean thin scrapings to powder or dust the tool is dull and requires re-sharpening.  Versions with flat soles can be used just as a cabinet scraper; the flat bottom helps keep the scraping flat and smooth.  This tool is usually worked by holding with both hands, with the thumbs down on the body of the tool and pushing the tool away from yourself.  You can also pull the tool towards yourself but the control may not be as exact as with the push stroke.  This tool also cuts well against the grain of the wood, but produces the finest cut when worked in the direction of the grain.  See Cooperage and Scrapers.

Wooden Jarvis & blade detail

Jarvis is a tool similar to a buzz a cabinet scraper built for a specific purpose.  Used to smooth tool handles, spokes and other round cylinders of wood.  After a split of wood is roughed out using an ax, drawknife and spokeshave, the Jarvis is used to scrape the wood smooth.  If the wood is cut rather than split then attention needs to be paid to the grain direction and as always work with the grain.  A split of wood insures that the grain of the wood runs from end to end.  On splits of wood, one end will be slightly larger that the other as the tree gets smaller towards the top of the tree.  Start at the large end and work towards the smaller end to prevent the tool from digging into the grain.  This is more important with cutting tools more than with a scraping tool like a Jarvis.  Scrapers will work in both directions of the grain of wood, but with the grain is always smoother.  When the fine shavings turn to dust or powder instead of fine thin shavings, the tool is dull and needs to be sharpened.  See Scrapers and Wheelwright.

 

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Drawknives, Scorps, Jiggers and Inshaves

Robert Sorby Drawknife, note round handles

These are double or single handled tools designed to remove more wood than planes and less than an ax.  In some cases these are the roughing tools used to get pieces of wood to their desired rough shape.  In other cases these tools are used for the final finish work and no further smoothing is required.

Proper method of use

Drawknife is the classic roughing tool that gives more control than the ax.  The drawknife is a wide U shaped tool with wooden handles on each leg and a steel blade in between.  American versions usually have longer turned cylinder shaped wooden handles while European have spherical shaped handles.  In almost all cases the tangs on each end of the drawknife are bent or clinched over on the ends of the drilled handles.  Some are reinforced with washers on the clinched, riveted or peen ends and some have ferrules at the other end to prevent splitting.  This tool is grasped with both hands and pulled towards you.  Pulling a long sharp blade directly toward yourself can be a bit intimidating at first and you should use caution when working with this tool.  The tool is usually used with the bevel facing up, but in some circumstances of difficult grain or shape the tool can be used bevel down.  This is useful for working inside curves with flat bladed drawknives. These tools have flat blades but most have a gentle sweep to the blade.  They can be used perpendicular to the grain of the wood but holding them on a skew angle to the wood will make it cut easier as with all edge work.  Also work with the grain of the wood see illustration above for proper orientation.  Because it doesn’t have a mouth like a plane or spokeshave, the drawknife can dig in deep to the wood so care must be exercised when using this tool to prevent if from cutting too deep.  Folding handles on drawknives were introduced in the mid to late nineteenth century.  With bolts and wing nuts the handles could be folded against the blade to offer some protection to the blade as well as making them easy to transport.

One handed ScorpOne-handed Scorps One handed Scorp   Scorp, single handle

Scorp is similar to the inshave but has only one handle.  The tangs on each end are shaped to fit in one handle, are smaller than the inshave and used for lighter duty wood removal in bowls, seat bottoms and other hollowed work.  Because of the smaller size the scorp can make deeper cuts and is easy to turn to deal with changes in grain direction.  When cutting at the bottom of an excavation in wood the grain converges and presents a problem.  When it starts going up the other side the grain dives into the wood and will chip and split out.  If you use the scorp at 90º to the grain at the bottom it will finish of this difficult area.  Using the tool on a skew can also facilitate easier cutting.  

Jigger

  Jigger is a combination drawknife and inshave.  The tool is identical to the drawknife except part of the blade is usually bent into a convex curve and part of the blade is straight.  This allows the worker to change from flat to hollowing cuts without changing from a drawknife to a scorp or inshave.  Coopers use this tool for rough shaping the ends of the barrel and can be used to make the chime and the howel.  A Jigger can be a cost saving tool as it incorporates a drawknife and an inshave all in one tool.  See Cooperage.  

Inshave

  Inshave is a tool similar to a drawknife with a deep bent blade and is used for hollowing out seat bottoms, trenchers and large bowls; anywhere depressions in wood are required.  The offset handles and curved blade gives excellent control over wood removal.  The tool is usually used with the grain but on certain woods and cuts it is used cross grain.  The depth of the bend blade and the length of the handles are important to consider.  I once saw an old inshave that had very little wear on such an old tool.  The answer was the fact that the blade and handles were of such length and angle to make the handles hit the work before the blade could engage the wood.  It looked good, but it had never been used.

 Coach Makers Router with 3 blades

 Coach maker’s Router comes in two forms the first in wood and the other in metal.  The metal version of this tool looks like a drawknife in overall shape but has small (sometimes interchangeable) cutting irons.  These tools are used to make grooves in the curved framework to receive the panels common in coachwork.  They are also used to bottom out the recesses and mortices to receive the ironwork that is let into the wooden framework.  With the handles positioned the way they are the cutter can be easily controlled but lacks a depth stop that some of the wooden versions have.  A little tricky to use but once you get the feel of the tool it can be a very handy and useful tool.   See Making and Using a Router for a discussion on Wooden Coach Maker’s Router.  

Shaving Horse or shaving bench is a tool used to hold work while using a drawknife, spokeshave and other hand tools.  This tool has a place to sit, a ramp to hold the work and a head that holds the work to the ramp.  The head or jaw is actuated by a foot lever and by pressing down with your foot; the work is clamped to the ramp securely and can be easily worked and repositioned.  The jaw and all edges are rounded on their sharp corners to prevent them from marring the work being held.  The shaft from the jaw to the foot pedal has holes drilled in different locations along its upper length to make it adjustable for different thickness of wood.  It can also be adjusted along the length of the ramp to position it where it is needed.  Work is usually done towards the worker and pressure on the foot pedal will force the jaw to pivot and hold the work to the ramp.  The work can be easily repositioned easily by releasing foot pressure and moving the work to a new surface to be tooled.  Longer pieces can be held with the length running down the ramp by either side of the shaft.  The Jaw should be as wide as the ramp; if it is narrower it can be difficult to get up close to the edge, if it is wider than the ramp it also gets in the way.  When I build a shaving horse I make it so that the jaw with open naturally by gravity.  There also designs using wooden springs to open the heavy head of some shaving horses.  While this is not necessary, it is very handy if the jaw will open up by just releasing pressure on the foot pedal.

Shaving Horse

 

Handle or Spoke Vice is a tool similar to a bar clamp or a lathe, that is used to hold tool handles or spokes while they are being shaped.  There are two metal center points one in a fixed head, the other in an adjustable head that holds the work.  These vices are secured to a bench or convenient location and adjusted to the approximate size of the work.  A threaded metal center point on one head is adjustable to tighten against the center of the end of the stuff being worked.  The work can be turned by hand to a side that hasn’t been worked yet, the threaded center is tightened and the work is at a good height and place to work with the above tools.  When doing repetitive work this is a handy tool for holding pieces at a convenient height to easily work.  The work can be turned to expose a new side to work and continued around until the piece is finished.  The open exposure of the work when held in this clamp or vice is indispensable for shaping, carving and countless other applications.   Can also be used to hold a pattern that is being reproduced on a turning lathe.  See Wheelwright.

Handle or Spoke Clamp

  

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Cutting Wooden Threads

Spiral threads have been cut in wood for centuries.  During the nineteenth century the tools had been perfected but still retained their original design.  There are two components to threading; there is the screw and the nut.  The screw has external threads and is referred to as the male element and the nut has internal threads and is referred to as the female.  While these can be meticulously cut by hand, it is much easier to accomplish this by using some simple tools.   There are two tools used to make the threads by hand and they are the tap and the die or die box or screw box.  Wooden threads can also be cut on specialized lathes from a design first proposed by Leonardo da Vinci.  This discussion will be about using the two hand tools to make the threaded screw and nut.

There is nothing quite like creating wooden threads.  The process is a unique experience and the results can be rewarding.  You are capable of making your own wooden screw clamps, veneer presses, vices and adjustable items such as music stools, embroidery frames and candle stands.  Threading wood is something unique, a wooden nut and bolt is unusual, something that few others have.  The projects, tools, furniture and fun things you can make with a set of these tools are endless.  Wooden threads have always intrigued me; there is just something fascinating about them.

Wooden Thread Cutting Tools

There are two ways to go, the first is to buy a set of wooden thread cutting tools or you can make your own.  The new wood threading tools are of good quality and generally follow traditional designs.  If you choose to make your own you will need to have made a tap of the proper size that you are interested in making.  This should have sharp edges to make clean cuts; a machinist or good blacksmith can fabricate a tap to your particular dimensions.  These taps are similar to modern metal cutting taps except they are larger and have fewer teeth per inch.  Eight teeth per inch is about the minimum for a ½” tap and larger should have 6 teeth per inch and on very large screws for presses 4 TPI to withstand the pressure.  To make a tap the threads can be cut in the metal for the tap and then the four sides flattened to produce 4 cutting edges at each thread.  Regular taps have a tapered end to make it easy to start the tool into the wood.  Bottoming taps are not tapered but will cut to the end or the bottom of a blind hole.  Do not use a bottoming tap for initial threading as it can easily cut off centered internal threads.   There is another old design that has the threads machined on the outside and a hole drilled in the center of the end of the tap.  On the end of the tap, the threads are machined down to form the taper and at the first thread a small hole is drilled at an angle into the large center hole.  This forms a very sharp tooth that cuts and the chips go through the small hole and out the larger hole in the end of the tap.  This type of tap does produce a very smooth cut, but the traditional 4-sided tap, if it is sharp and used properly will also produce clean cuts.  The wooden handle should be strong and long enough to give leverage for the sometimes difficult process of cutting internal threads.  The handle should be rounded and shaped to fit the hand as the hand is touching the handle a lot during tapping.

Once the tap is made it is possible to make the die box and all that is required is a V-shaped cutter that is secured in the box and cuts the external threads.  Unlike the tap, which will cut with four cutters on each thread, the die has only one cutter that cuts all of the threads.  A proper sized hole is drilled for the tap into a piece of hardwood such as beech or maple, see list below.  This hole must be square to the body of the die box.  The holes are then chamfered or countersunk to prevent the tap from splitting out the wood as it enters and exits the hole.  The tap should be lubricated with linseed oil to make the threading easier.  The tap is then inserted carefully into the hole and started squarely to insure a straight threaded hole.  It is very important that the tap is started perpendicular to the surface and square to the hole.  If the tap binds up gently  back a ½ turn then start again, if it becomes too difficult, remove the tap, lubricate and try again.  Make sure the exit hole is countersunk to insure that the tap doesn’t break out any wood when it exits.  Now that you have the die box drilled and threaded, the next step is to cut a mortice for the V-shaped cutter that is on the front leading edge of the die box.  The cutter is positioned right over the first complete thread peak at an angle of 30ºand the leading edge of the cutter should engage the wood at the widest part of the cutter first to score the wood being removed.  The end of the cutter is ground at an angle of 15º with the top of the V leaning forward, with the bottom of the V trailing.  The cutter needs to be sharp and set to cut just slightly deeper than the threads that were cut by the tap.  This insures that the newly cut external threads will not bind up in internal threads of the die box.  The die box can also be equipped with a removable plate that will center round pieces as they are fed into the screw box.  The plate needs to be thick enough to line up the piece to be threaded and removable so the external threads can be cut all the way up to the shoulder of a turned piece if necessary.  The internal threads of the screw box should be well lubricated to make the cutting of the screw shaft easier.

Cutting Wooden Threads

Metal tap with wooden handle

Nut – The Nut is the part with the internal threads that are cut with the Tap.  The nut is prepared by drilling the hole using the following starting holes sizes.

 Starting holes:

½” threads use a 3/8” drill

¾” threads us a 5/8” drill

1” threads use a 7/8” drill

1 ¼” threads use a 1 1/8” drill

1 ½” threads use a 1 3/8” drill

1 ¾” threads use a 1 5/8” drill

2” threads use a 1 7/8” drill

2 ¼” threads use a 2 1/8” drill

2 ½” threads use a 2 3/8” drill

 

It is important that the hole is drilled square and perpendicular the flat surface of the nut.  The wood for the nut should be a wood that is capable of taking the threads.  While most hardwoods will hold the threads some are better than others.  Beech, maple, hickory and oak can be used for nuts and will take threads, as can alder, elm and poplar.  Some brittle woods such as cherry are difficult to thread, but it can be done.  The thicker the piece of wood that is threaded, the stronger the threads will be.  On thin pieces for the nut, the threads can easily be cut at an angle, so make sure the hole is straight and the threading is done properly.  When threading in an angled hole, the grain orientation is important as is beginning the cutting with the tap.  The tap needs to go straight down the hole, if you get off at an improper angle the threads will be too deep on one side and too shallow on the other.  While the internal threads on the nut are not as critical in terms of strength, the screw needs to be constructed of specific woods.  

Hole and Countersink Internal Threads

After the proper sized hole is drilled, the edges need to be chamfered or countersunk to prevent split out during the entry and exit of the tap.  This must be done on both sides, as the tap will chip out the wood.  The tap is lubricated with linseed oil or beeswax and it is inserted in the starting hole.  It is very important to make sure that the tap is perfectly square and lined up with the hole.  The tap is twisted and forced into the wood, taking care to make sure that it is perpendicular to the surface of the nut. Enough downward pressure is exerted to engage the tap into the hole, after the cutting begins, the tap is self-feeding.  If the tap binds in the hole, gently and carefully back it off a half a turn and start again.  If it still binds, back the tap out of the hole, lubricate it again and carefully start the tap back into the cut threads.  Be careful when doing this so you don’t cross thread the screw and ruin your work.  Every once in a while, back the tap out a half a turn and continue until cutting becomes more difficult, then repeat and go at it again.  It is better to take your time and make sure that the work is done properly.  Continue until the tap comes out the exit hole, clean out the shavings and back the tap out of the hole.  If you are threading a blind hole, your starting tap will hit bottom, then back out the tap, remove the dross and carefully place the bottoming tap into the threads and run it down until it cuts the internal threads on a blind hole.  If the wood is fuzzy on the inside of the threads, I wet the piece with water and raise the grain.  I allow it to dry completely and run the tap down the hole again to remove the raised grain and fuzz.  Sometimes running the tap in from the opposite direction will remove the fuzz and clean up the internal threads.  

Screw or Die Box with starting plate    Steel Cutter showing sharpening and position

Screw – The Screw is the part with external threads and is cut by the Screw Box or Die.  The selection of the material for the screw is important as certain woods make excellent threads while others are more difficult.  Softwoods are difficult without an extremely sharp cutter in the screw box.  Hardwoods are preferable and woods such as beech, maple and hickory are the best for wooden bolts or screws, those with external threads.  Strong, tough woods such as elm are better than brittle woods like cherry.  Walnut also accepts threads as well.  With care any wood can be threaded.  It is also important that the grain be as straight as possible.  This is for strength and for a more uniform cut.  The piece to be threaded should be turned to the size of the thread box.  Therefore if the threads are for a 1 ½” screw then the dowel or piece should be turned to just under 1 ½”.  All it takes is just a 32nd under to make the piece just the right size.  If it is too large it will not fit into the screw box and if it is too small it will not properly thread through the screw box.  A slightly smaller screw works much better than one that is too tight.  I like nice crisp threads, so I always turn the pieces just under the required size.  For some applications where you don’t necessarily need sharp peaks, such as heavy duty tools, the screw blank or dowel can be slightly undersized producing flat topped threads instead of sharp peaks.  Small fine threads such as 8 threads per inch can be difficult and these fine external threads can easily break off.  Denser woods work better for these fine threads.  If the dowel is undersized, it is important to make sure that the screw box travels over the dowel in a uniform  manner to insure proper threading.  If flat-topped threads are required, I usually turn the dowel to the proper size, thread the piece, then re-chuck it in the lathe and turn off the peaks.  When you turn the screw or dowel on the lathe, just use your gouges and chisels, do not use sandpaper.  The sandpaper can leave residue in the wood fibers that can dull the cutter in the screw box.  Also you will want to chamfer the edge of the dowel or screw blank to make it easier to start the screw box.  

Dowel before and after Chamfering

I always dip the end of the screw blank or dowel in linseed oil to provide lubrication for the cutting process.  I usually clamp the screw blank in a vice to hold it during the threading process.  It is important to make sure that the screw box engages the screw blank or dowel perfectly square to insure accurate threading.  I always look down the waste hole in the screw box where the chips come out to see how the cutter engages the threads.  I try and exert enough pressure to engage the wood on flat grain first rather than the side grain.  It just seems to start better if the cutter enters the wood on the flat grain. Once the cutter has began to make threads they engage and pull the screw blank into the screw box, so the pressure can be reduced.  After cutting begins, simply turning the screw box is sufficient.   When the cutter has made the first part of the threads, they will engage the internal threads of the screw box and advance the screw into the tool creating a perfectly cut spiral thread.  The first ½” or so is usually not perfect and I always allow for an extra half inch or so to cut off after the threads have been cut.  Once the cutting has started, the tool should ‘sing’ through the work.  If the stuff is tight in the tool, the  cutter may be set too shallow or the dowel is too large.  Most screw boxes have a removable plate that guides the screw blank into the screw box.  This is removed if the threads are to be cut up to a shoulder.  The plate should be used to cut well into the screw blank and can be removed to thread just the last inch or so.  A properly positioned and very sharp cutter will make the cutting much easier.  

External Threads

It is important that you keep your tools sharp and well maintained.  The teeth on the tap need to be clean and sharp at their cutting edges.  The V-shaped cutter in the screw box should be ground at the proper angle of 15º and should be very sharp and properly positioned.  The bevel is ground on the outside of the cutter.  Your holes need to be clean, straight and countersunk and your turnings need to be of the proper size and chamfered to produce the desired results.  Use linseed oil or beeswax to lubricate the parts being cut, it just makes the job easier.  Make sure the tool engages the work squarely to produce quality work.  Clean out any shavings that can interfere with the cutting operation.  Work slowly and carefully.  This is not like cutting metal threads; it is a continuous operation, only backing out when the cutters jams or the cutting is complete.  After you are finished using the tool make sure to clean off all excess linseed oil before it dries!  There is no end to the possibilities for using wooden threaded devices and the results are delightful.  Wooden screws are capable of exerting incredible pressure when used for clamping applications and can provide for ease of assembly and disassembly for transportable furniture.  There are endless applications and uses of wooden threads and they are fun to make.

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