Traditional Joinery: Riveting

written by Ted McNett? in the Hammer & Tong May/ June

This past October I received a BGCM scholarship to attend Mark Sperry's "Traditional Joinery" class. Mark demonstrated a scrolled wall bracket project (See the full size sketch on the page following this article) to teach three traditional joinery techniques: riveting, mortise and tenon, and collars. These simple skills have really increased my ability as well as the complexity of projects. The basic skills require simple tools that you can make and the proper order of procedure. As you follow this series of articles I will try to guide you through each step from my class notes and experiences. This will include required tooling, tool making, and the step-by-step process to complete the traditional joinery technique. I hope to include illustrations and photographs of the process.

Rivet - a metal bolt having a head at one end, the other end being passed through holes in the things to be joined together and then hammered into another head. ("Rivet" Thorndike-Barnhart Student Dictionary, Updated Edition, 1997)

Riveting - the process of joining two or more pieces together using a rivet.

For the purpose of the article we are focusing on traditional solid steel round head rivets. The actual shape of the head can be changed by you when making the rivet and the shape of the rivet block that you use. You may choose to purchase solid steel round head rivets from a variety of sources, Centaur Forge, MSC Supply, Grainger, or a good old fashioned hardware store. Purchasing rivets is the easy way out and the final product is not as satisfying. We used store bought rivets in the class and focused on the process of riveting, not rivet making. I will discuss rivet making because it will help with the mortise and tenon joinery. Rivet making is a simple process if you practice it. Just like anything else the first time you try it, it may not be perfect. Don't get frustrated; Mark said; "after about 10,000 nails, it starts to get easy," or rivets in this case.

There will be two techniques described for rivet making: upsetting and necking in. As most of you know upsetting can be just that. Be patient and think about what you are doing. We will use ¼ inch round stock for upsetting and 3/8 inch round stock for necking in.

Upsetting

This is the process of increasing the amount or mass of steel at a specific location of the bar. For rivet making the mass is required on the end. When upsetting keep the steel very hot, a high yellow heat. If the end starts to move off center or bend stop and straighten the piece gently. If you hit the upset end to hard you have thinned the bar back to the original diameter. Once the bar is about ½ again as large and ½ inch long you have upset the bar enough.

HINT: Use a heavy hammer for more effective upsetting. The laws of physics do work in blacksmithing.

Option 1: Heat the ¼ inch round bar to a high yellow heat. Place in a vise across (parallel) the jaws. Leave ½ inch outside of the jaws. Strike the end of the bar with the hammer

FIGURE 1

face perpendicular to the bar. If the bar bends the face of the hammer is angled, not perpendicular. Make adjustments so the hammer face is perpendicular. Once the bar is a red heat, stop hammering and put it back in the fire. Remember to straighten the bar carefully in the vise jaws if it has bent at all. Repeat this step until you have about a 3/8-inch diameter ½ inch long head on the end.

Option 2 There is more than one way to skin a cat. If you were upset with Option 1 than try this on a London Pattern anvil or a section angle iron on a hardy stub for those double horn people.

Heat the ¼ inch round bar to a high yellow heat. Use your water can to quench all but the last ¾ inch of the bar. Place the bar in the corner of the shelf (cutting table) at the base of the horn and strike back towards the end of the bar. It is helpful to brace your tong hand against your thigh or waist for support. Make sure that the hammer face is perpendicular to the rod.

FIGURE 2

HINT: As you hammer rotate the bar 90 degrees with each hammer stroke. This will help compensate for any angle or non-perpendicular hammer blow.

Option 3 This option drives the rod down onto the anvil face or an upsetting block on the base of the anvil or your shop floor. An upsetting block is a large mass of flat steel attached to the base of some anvils. You can use a large piece of steel laid on your shop floor as well depending on the overall length of the bar that you are upsetting.

Heat the ¼ inch round bar to a high yellow heat. Use your water can to quench all but the last ¾ inch of the bar. Hold the bar perpendicular (vertically) to anvil face. Drive the bar down into the anvil face or upsetting block. As soon as you see the bar start to bend carefully straighten it. The bending does not direct the energy straight back into the bar so you are wasting time and energy upsetting a bent bar. Remember to rotate the bar 90 degrees with every hammer blow as in Option 2.

FIGURE 3

HINT: Chamfering the end of the bar will help increase the mass of the bar. This localizes the energy allowing for more effective upsetting. This is especially true in larger bar stock. This also will help prevent elephant foot. This is where only the very end of the bar expands.

You should practice upsetting until you are comfortable with your ability. It is difficult to keep the mass centered on the bar. This is critical for rivet making. If the mass is off center than the rivet head will be offset as well.

Necking In

This process involves decreasing the diameter of your bar stock to the desired rivet diameter. For a ¼ inch rivet you should start with 3/8 inch round stock. As with upsetting there are several techniques that can be used: hammer, spring fuller, or guillotine tool.

Hammer - This requires very good hammer control. One wrong blow and you may have to start over. Heat the 3/8-inch round bar stock to a high orange or yellow heat. Place the steel on the nearside of the anvil. Leave enough material on the anvil face to create the desired rivet length. Hit straight down with the hammer even with the near edge of the anvil. This will create a shoulder for the head on two sides. Rotate the bar 90 degrees and repeat the hammer blow. Once the shoulder is formed you may round out the shaft of the rivet.

TOP VIEW

Side View

Spring Fuller - The spring fuller is an easily made tool that provides consistent and accurate "indentations" directly opposite of each other. The spring fuller can be made from mild steel of any diameter. For the rivets a 3/8 inch round bar will work. Start with 27 inches of round bar. Mark the bar into three 9-inch sections. The center 9-inch section will be flattened for the spring. The two end sections are the top and bottom fullers. Heat the center section up to a yellow heat. Mark the ends of the center section with a near side half face blow and a far side half face blow. The mark should be about half the thickness of the bar deep. The 9-inch length between the two marks should be flattened to about the same thickness as the marks, 3/16". Try to spread the metal width wise with the pien of your hammer. You do not need to stretch the length any.

Half face blows at the 9 inch marks

Once the center 9 inches is spread wider and is 3/16 inch thick you are ready to shape the spring into a circle. If the spring is too thin it will break.

TOP VIEW

SIDE VIEW

The top fuller section needs to be bent at about a 60 degree down angle to the spring section. This angle allows the two fullers to be parallel when the spring is formed. The angle can be adjusted for a final fit at the end of forming the spring.

The 9-inch spring section will get bent around into a 3-inch diameter circle. Heat the entire 9-inch spring section up to a nice even orange. Bend the spring section into a circle until the two fullers are parallel. (About a 3 inch radius)

No more than 3/8 Inch spacing

HINT: Heat the end of the spring and top fuller to adjust the top fuller until it is parallel with the bottom fuller. Once the fuller is shaped as desired you may weld on the appropriate hardy stub.

Guillotine Tool

This tool is also known as a "smithing magician". It is available through the Blacksmith's Journal and some other retailers. There is one at the Farm Museum for you to see and use. The tool works by holding the top and bottom fuller die in a frame. This ensures exact alignment of the dies as you strike. The dies are made from ¾ inch by 2-inch steel. Blacksmith Guild of Central Maryland

This is the extra hand to hold the top tool for you.

Rivet Header

This tool will hold the original size bar stock allowing for the head of the rivet to be formed with either a set tool or hammer. The rivet header may contain several different size holes for various rivet sizes. It is recommended that you make the rivet tool out of tool steel for durability. However, mild steel will work just fine unless you plan on mass-producing rivets.

Rivet Header -

At least 3/8 inch thick, preferably ¾ " or thicker. The thickness helps keep the rivet shaft straight.

HINT: Drill the holes 1/64 larger than the size rivet. This will allow for easier insertion and removal of the rivet.

CUT OFF HARDY This is an essential tool. To make a simple cut off hardy you need a small piece of high carbon steel, leaf springs work well for this. Cut a piece of the leaf spring about 3 inches long and the width of the spring. There is no need to cut down the width of the spring. If you use a torch to cut this that end must go down. The torch damages the steel for use as a cutting edge. You may also use an abrasive chop saw, angle grinder cut off wheel, or hacksaw if the piece has been annealed.

Grind a bevel on the cutting edge of the leaf spring. You may choose a double bevel or a single bevel straight cut. The double bevel is the standard. Since this is a hot cut tool the bevel can be steep.

Hot cut--------------------------Cold cut ------------------------ Straight cut

The straight cut's single bevel looks like a chisel blade. This leaves one side of the cut bar straight, not beveled.

Weld on the appropriate hardy stem for your anvil. Once you have ground the edge and welded the hardy stem you may normalize, harden, and then temper the cutting edge.

NORMALIZING

For the cut off hardy this is not critical because the piece has not been stressed with hammer blows. If you forge the cut off you will need to normalize the steel. Normalizing removes the stresses in the steel from hammering. It helps realign the structure of the steel for strength and lessens the chances of cracking during hardening and use, especially knife blades. To normalize heat the entire hardy to critical temperature, non-magnetic, this is usually a cherry red, not very hot. If you overheat it at this point it is not a disaster. To prevent overheating check it regularly with a magnet. When the magnet does not stick to the steel bury the piece in a pile of coal on the forge or somewhere it can cool slowly out of the air. This is not annealing. You can even leave it on the forge surface. The piece should not touch cold floors, steel, or anything that will cause the steel to have heat drawn out of it. Once the steel is cool to the touch it has been normalized. Remember this is not a critical step for this cut off hardy as long as you have not hammered on it. This is the same process required for a punch or chisel.

HARDENING

Leaf springs are generally 5160 steel. This requires the steel to be quenched in oil. Due to health and environmental reasons you should not use motor oil. Use vegetable, peanut, or olive oil for this. If you can get it there are special hardening oils available.

Once again heat the piece to non-magnetic, critical temperature. Check the piece with a magnet frequently. Do not overheat the piece or it could crack when you quench it in the oil. If the piece is beyond critical temperature do not harden the piece, allow the piece to normalize again. Make sure the entire cutting edge is evenly heated. Once the piece is non-magnetic quench in the oil. Be careful of flash and the smoke. Move the piece slowly in a figure 8 motion in the oil. This movement prevents bubbles and an air jacket forming around the steel. Keep circulating the piece until it has thoroughly cooled. The piece is now hardened to the point of being brittle. It must now be tempered to make it tough.

HINT: Use a metal container with a metal lid so that you can smother the fire in case it does flare up. All you have to do is place the lid on the container and the fire will go out Then you may continue to circulate the piece in the oil. Try not to remove the piece from the oil during this process.

You may test the hardness with a file. Draw a file across the cutting edge, if it was successfully hardened the file will "skate" across the edge. If the file bites into the edge repeat the hardening process.

TEMPERING

Tempering is removing the brittleness and increases the toughness of the steel. Once the piece has been hardened you will need to sand or polish the top half of the cutting hardy. This shiny area allows for you to see the tempering colors "run". The colors represent different amounts of heat. Randy McDaniel?'s "A Blacksmithing Primer" has an excellent color chart and specifics on this. For the cut off hardy you want the cutting edge to obtain a purple color. You will heat the piece slowly and watch the colors run from a light straw, dark straw, purple, blue, and gray. When you see the purple color on the cutting edge quench the piece in water.

There are several methods used to heat the piece to draw the colors; a propane torch, an oxy-acetylene torch, a hot metal chunk, or the forge. For simplicity of process and equipment we will discuss the propane method.

Light the propane torch and place it on a steady surface. Hold the hardy stem with a pair of tongs and place the bottom edge of the leaf spring in the flame. Hold the cutting edge up, heat rises. You will need to move the piece back and forth to get an even heat across the width. It takes a while to start to see the colors. Doing this with direct sunlight on the piece will help you see the colors. After several minutes you should see the polished surface turn light straw close to the propane flame. Keep the flame in the same area across the width of the leaf spring. You should start to see dark straw appear as the light straw moves up toward the cutting edge. Eventually purple will appear, then blue, and finally gray. Follow the blue or gray up the leaf spring with the propane flame. When the purple reaches the cutting edge quench the piece in water until it is cool to the touch. Take the piece out and inspect the color along the cutting edge. It should be a nice consistent purple along the edge. If there is some dark straw that is fine, however if there is light blue or gray you may have "softened" this edge too much and re- hardening is required.

Hint: If the colors are not running evenly across the width hold the torch longer on the slower side of the colors. This will apply more heat and the colors will catch up.

Because of the width of this piece it has been recommended to me that this process should be repeated two or three times to ensure an even temper along the cutting edge. Now you are ready to cut off the rivet.

HEADING THE RIVET

Back to the rivet making, once the piece of rivet stock has been upset or necked in appropriately you need to shape the head.

If you upset, heat the piece of stock in the forge to a yellow heat. Use your new cutoff hardy to cut ½ to ¾ of the way through the bar stock at the appropriate length below the upset shoulder. Reheat the bar to a yellow, remove from the fire and grab the rivet "head" with a pair of tongs, twist the rivet off and place it in the rivet header.

½ to ¾ cut off

If you necked in, heat the piece of stock in the forge to a yellow heat. Use your new cutoff hardy to cut ½ to ¾ of the way through the bar stock about 2 to 2 ½ times the diameter of the rivet above the necked in shoulder. Reheat the bar to a yellow, remove from the fire and grab the rivet "head" with a pair of tongs, twist the rivet off and place it in the rivet header.

½ to ¾ cut off

Quickly place the header and rivet shaft over the pritchel hole and pien the head to shape. You may choose to use the flat side of your cross pien to form a rose head rivet; or you may use a ball pien to form a round head rivet.

Start with a hammer blow straight down on the center of the rivet head. Then work your way toward the outside edges to obtain the final shape.

Rosehead

Use angled hammer blows to create the flats

A rose head rivet should only take five hammer blows, one straight down and four to form the flats on each side of the square.

The round head will take many rapid hammer blows working in an increasing circular motion towards the outside.

Each circle line above represents a line of hammer blows with the ball pien. Start in the center and rotate in an expanding circular motion with quick hammer blows. You may choose to angle the hammer as you move outwards. This will help obtain the round head.

PRACTICE, PRACTICE, PRACTICE

Once you have made all of the tooling it is time to make some rivets. As with anything practice will make you better. Expect the first dozen rivets to be souvenirs. Look at each rivet you make. Is the head centered? Is the shaft straight? Is the rivet as long as you wanted? Is the head the size and shape you wanted? Learn from your mistakes and successes of each rivet you make. Eventually, it will become second nature. Keep practicing, in the next issue I will discuss riveting as well as mortise and tenon joinery.

-- RebStaup - 10 Feb 2008