How-to Thread and Tap Large wooden Vise Screws and Nuts

Thread box tutorial

Alright, A while back I said I was going to do a thread about how I hand cut Vise screws and nuts. After a bunch of real life stuff getting in the way, I still haven't completed that tutorial, and will have to get around to doing carving another one to get pictures for it.

Since I am not sure when I will get around to it, I figured I would post the more "production" way to cut the threads.


I do not have pictures of all of the process, but will document it best I can.

The first step is to make the tap.

This is for screw 2 1/4" in diameter, 2 TPI (approximately)

1. Stock for tap

Acquire a blank about 12" long, 2" in diameter, or 1 65/64ths. Make sure you have a good strong head for a handle, and that the blank is strong enough to withstand extreme pressure without splitting.

2. Layout

Layout a 2 tpi spiral on the blank. First, draw a line length-wise on the shaft. Mark it every half inch. Then, take a long piece of paper and make a 1/2 strip of it, and wrap the strips around the shaft, lining them up with your 1/2" marks.

(You can do this more accurately with a little geometric arithmetic and more lines evenly spaced on the shaft, but I have found that you can do this with enough accuracy by eye.)

3. Cut Spiral

Once you have your spiral laid out, it is time to cut a saw kerf along the spiral. Using a stair saw, back saw or whet ever you so choose, cut a kerf along the spiral. Make this relatively consistent in depth. (I use a cheap gents saw with a board bolted to the blade as a depth stop.)

Continued. . .

4. The Cutter Housing

Following the threads angle, cut a mortise into the shaft to accept a 1/2" cutter. You can do this any number of ways, the simplest being by eye, using the spiral kerf to guide your chisel. Then, cut a wedge to match the mortise. Make sure that the cutter and wedge can both fit inside the mortise.

I like drilling a hole in the shaft on the kerf, also by eye. Then, flattening the bed of the hole This allows me to drill a second hole perpendicular to the the hole, and insert a nut (or brass threaded insert) and a steel bedding iron. I then use a machine screw to tighten the cutter, and advance it with a light tap with a punch.

Whatever way you do it, make a recess for the chips to gather in front of the cutter. This one has a very large recess, but is also able to cut very deep nuts because of it.

Continued. . .

5. The advancement regulator.

The advancement regulator (nut) has several parts. a block, two spacers, two wedges and two pieces of sheet metal.

Take a block of wood 2 inches thick and drill a 2" hole though the center.

Take two scraps of wood roughly 1/2" thick and clamp them together, edge to edge. drill a 2" hole though them.

Insert the shaft in the hole. Clamp the shaft and the block in place.

Align the first scrap with the shaft, and trace the spiral angle on it. remove, and repeat with the second scrap.

Plane these down to the line, and screw to the back of the block. Make sure you recess your screw heads.

Take two pieces of sheet metal and grind out them out to fit the kerf in the shaft. remove any burrs and screw to the wedges.

Now, on the front of the block, screw two 1" spacers to allow room for the cutter when it passes through the nut.

I put a scrap piece of wood on the bottom of mine to facilitate clamping or bolting it to the bench.


Continued. . .

6. The cutter

The cutter is a thick scraper, 2" long, 1/2" wide. mine is 1/8" thick, O-1 Tool steel, but I would recommend using an old file as well.

Grind one end at a 90 degree angle AS IT EXITS THE MORTISE! the point needs to line up with the saw kerf, and do your layout from that point. When you grind it, leave a fine burr, just like you would on a lathe chisel.

I have a backing iron in mine, which is lightly shorter than the cutter, and provides enough support for the cutter to reduce chatter and to prevent it from bending. (I bent 3 cutters into horseshoes before adding the backing irons into the mix.)

Now. . .

Take a block of wood with a 2" hole insert the shaft though the nut block and the advancement regulator, engage the tap and start threading the nut!

Take light passes, clearing ships from the cutter after each pass. Cut, advance, cut, advance. ad naseum. for your first nut, make it slightly deeper than the 90 portion of your cutter. This will become your nut for your male threads.

For each nut after, get to just under the 90 degree portion, remove the shaft, and test a screw for fit.


Thread box will follow. . .hopefully soon, but no promises.

Very Nice,

I would buy a Rectangular Tool Bit from ENCO for the cutter..
http://www.use-enco.com/CGI/INPDFF?P...MITEM=383-5324

A file maybe a bit too hard but with lots of grinding may temper it enough so it dosent chip to easy and is still hard enough to cut a long time..
A tool bit will stay very hard and not chip after lots of grinding and best choice IMHO

PS:
Threads are formed at 60º in the USA and in the UK they did use 55º before metric became in use..
45º maybe a bit to shallow but 60º this is what is used in metal not wood and I'm not an expert in wooden threads and maybe wrong :)

Johnny. . .

Thanks!

I would agree that a tool bit might be best. However I had the mild steel and the O-1 already, so they won out for the time being.

One note I will say, no matter what you use as a cutter. . .Insert what a machinist would call a "mouse" between the screw and the cutter, if you go that route. This is just a small shim of metal. Otherwise, the screw will move the cutter slightly when you tighten and loosen it. A small piece of the same sheet metal you use for the advancement regulator should work just fine.

If your cutters are getting bent back,they are way too soft. You can use 01,but at least heat it up to orange,quench it in oil,sand off to bright and heat till it turns medium brown. A 90º end on the tool is fine for wood threads,and used to be the norm. Later on,in the 19th.C.,they started to make threads at 60º,like in metal,but they are too steep and delicate for wood threads. 1/8" thick isn't really thick enough for your cutter either. When it is hardened,it could snap off. You would save yourself a lot of grief by making it out of a square section HSS lathe bit,which only costs a few dollars. Make sure the lathe bit is at least as wide as the widest part of your threads. A local machine shop might just give you a used lathe bit. It does need to still be long enough that it can't tear out of the hole it's in. I'd make the lathe bit long enough that it just doesn't make it to the thread depth on the opposite side.

Take light scraping cuts until your thread is deep enough in the hole. It would be best if you had the male thread finished first. Then,you could check the fit of the male thread in the hole. Don't make the fit too perfect,either,or the screw will forever squeal,and may bind up eventually,so you can't turn the screw when humidity enlarges the screw a bit. Let the fit be a little rattly.

Matt - Thanks for posting this. Roy's book has the same type of screw-cutting mechanism described in detail from an historic text, but the engraving accompanying the description is a bit opaque - your pics make it a bit easier to understand in the details. I wish Beall made a 2-1/2 or 3" mechanism with a coarse thread for a router, but I suppose there's not enough of a market for bench screws to make it worth their while....

Thanks for the post!

George, I agree with the O1 bot being hardened and tempered well enough. The issue (I think) is that I only hardened the tip, and should have hardened the entire piece. I will likely use something much thicker for the next cutter (particularly since the o-1 I have left is all slated for plane blades)

The 90 degree angle Idea I got from you a while back. The smallish screw threads that I had been doing were 60 degree, and they are far too delicate, as mentioned.

You are also spot on with the fit. That squeal is one of the most horrendous sounds one could ever hear.

David,

I got about half the idea for this from Roy, but you are right. . .his book is really vague. I really want to redo this post later one with a good set of build pictures.

I can say this. . .2 TPI on a screw is awesome. Never a metal bench screw for me again, that's for sure. Who needs a quick release when you have a screw that acts that fast anyhow? Just one more thing to get fouled up.

Can't wait for the next installment. Thanks for taking the time to document your approach and posting it here.

Very cool. I've wondered how one would go about cutting threads manually, finally I can understand how.

Making the internal threading jig eliminates the need to buy a $1500.00 German large size tap and die set. With the jig,you can also generate the internal threads to make your own wooden thread box to cut the male threads with. Large thread boxes are wise to have 2 cutters opposite each other. The first cuts half the thread depth. The other one finishes it. These can be tricky to make work right,and the cutters need to be VERY sharp.

Here's a not too good picture of a 5/8" right and left hand threading box I made to make wooden cooper's calipers with. It shows how single type cutters are installed. I don't have a large 2 cutter type to show,but the other cutter would be opposite the first one.

Great thread, and very timely! Just last week I pored over Landis and Underhill's diagrams and texts and drew up a sketch of something very very similar to what you describe. I plan to try this approach in the coming months to build a twin screw vice for my new bench.

George, I was thinking similarly regarding cutting the outer threads. I've heard that really big screwboxes are a real bear to turn.

Fabulous Matt!

This one is really inspiring me!

Bob