Wooden Thread Tap

[David Weaver]

You can get dowels up to baseball bat blank size. Past 1 1/2 inches, they start to get expensive fast, though, and I don't know if the ones that aren't baseball bats are easy to find in a specific hardwood. Even at 1 1/2 inches, you get birch or maple from woodcraft, though there is a local supplier here that has maple for about $6.00 a dowel at that size.

The last 1 1/2 inch dowel I got from woodcraft was maple, though, and good quality.

I can't remember where I saw the bigger ones, but it wasn't woodcraft.

[Pam Niedermayer]

I do not advise trying to use a dowel. Gluing it into the handle will probably soon fail from twisting stresses. Also,are there any 2" dia. dowels?

Since I don't use dowels,I'm not familiar with what's available.

I haven't a clue, usually dowels are too short grained. However, I'm not precluding that there aren't sufficiently large dowels of sufficient quality - they may be out there, maybe from an individual making dowels.

Pam

[Craig Dupler]

I thought I would add to this thread about making larger wood screws (i.e. larger than 1.5") a bit since much has become available (except new tools) over the past three years. There are a lot of videos on the topic on YouTube, but I've only found a couple of guys that seem to have really figured it out. I like the young Mr. Carter the best. In summary, to make a proper screw box, one first needs something to keep the screw advancing properly, i.e. a nut. The very first nut one makes almost certainly requires the slow scraping method because the German taps are not available separately from the dies, and the dies are what make the price so out of sight.

There are several videos out there that talk about using large bolts or even large UNC taps and dies. However, the thread sizes and profiles are all wrong for wood, and produce needlessly weak threads in too fine of a pitch. This is also true of inexpensive screw box kits except for the two smaller sizes (1/2" and 3/4"). The 1" kit is set to 6 threads per inch when it should be 5, the 1.25" kit is set to 6 when it should be 4, and the 1.5" kit is also set t 6 when it should be 3.5.

One thing that the new kits do get right is that they come with two taps, one with a normal taper and one for bottoming. So I think that the real best answer is to make one's own taps by carefully filing the out of thick walled mild steel tubing and to then heat treat them (YouTube has several good videos on this as well).

More later.

[george wilson]

You can't just "heat treat" mild steel tubing and get it to harden. There is way too little carbon in it. Mild steel comes in many types like 1018(.18 carbon),1020(.20 carbon) and various other types.You must have at least .75 carbon to make a decently durable tap. Also,filing out large threads from large steel tubing would be a nearly insurmountable task. You would be removing a triangular shaped volume of steel the dimensions of a THICK saw file,and over 2 feet long.

The most practical way to make a large enough tap would be to have to buy a 2" diameter round piece of drill rod,that costs about what? $200.00? It only comes in 3 foot lengths. You CAN buy it shorter,but then they really jack up the price for the cut off fee. Then,you'd need a powerful metal lathe to cut those large threads. Next,you'd need a good electric furnace (gas would do,but electric is cleaner for the steel) to heat the massive piece of steel up to hardening temp(about 1450º or more,depending upon what type drill rod you used).

I have such facilities,and have thought of making such a tap,and cutting the threads on the male screw with my large lathe. But,then I'd need to have a lasting supply of 4x4" hard maple. I have some,but keeping a steady supply I found was hard as toolmaker. When I did find it,they wanted a fortune for it.

On top of all that,I doubt many would buy these screws. $145.00 has been mentioned as high,but it really isn't when you understand the costs involved. I think I'd be setting myself up for a bunch of work without much of a market.

[Roderick Gentry]

You can harden 1020 with super quench, and you can also build up the edge with hard surfacing rods, none of these are likely to be appreciated by your market.

You may need more than a sturdy lathe to turn your tap threads on since few lathes will produce really large threads. It seriously wears them out, as the loads on the cutter, and the speed the gears need to run at are not conducive to longevity. There is an acme thread that runs the carriage for the cutter, and it has some practical threading to it, conducive to strength, wear, and standard threading work. To get the carriage to move at the rate needed to cut 2-1 threads is just outside the range of most machinery, otherwise it would be easy to turn wooden screws on a metal lathe as is. The South Bend Heavy 10 I have, which is a large small lathe maxes out a a 4 tp1 pitch, and the ability to cut coarse threads doesn't seem to go up much in the larger machines. I understand some users have changed the gearing somehow.

I haven't tried it but other than a CNC lathe, the best results I have seen are from carving the thread. Apparently this can be done successfully, there was an article in FWW at one point.

[george wilson]

The trouble making the tap is the problem with a small lathe,true. I have a 16" x 40" lathe that can do it,though I'd divide up my threading cuts carefully. I have found extra gears for my lathe that greatly extend it's coarse threading(but only for cutting WOOD). It will do 2 TPI with the original gearing. BUT,I'd certainly take auxiliary cuts and build up to the finished cut in tool steel.

I have tried super quench with just slightly improved hardness in mild steels. That is very old information.And,overblown,too. Also,you would have no wear resistance at all. You need carbon content for that. Cutting a thread through a hole is very punishing for the tap. Building up a hard cutting edge might be a way to go,though I'd have to precision grind the weld to get the profile back. Then,there's the internal shape of the cutter to deal with. Look at the closeup of a tap below. At least,the kind I make. An inserted cutting edge is a possibility. But,I'd hate to go to the effort just to find out the cutting edge is coming loose! I prefer solid tool steel,with the punishment the cutting edge takes. A 1/2" deep V in ONE pass!

With these problems,I think I'd just buy the drill rod.

Cutting the actual wood threads is no problem. I use a router mounted at 45º,fed into the wood. No strain on the lathe at all.

Here's a 12" ,6 tpi. one I made for a giant cider press. I made this about 1982. And a few wood taps I made. Some are both right hand and left hand,for making wooden cooper's compares. Also see the thread box for them.I am always making custom wood tap since I often make missing parts from mechanical antiques. The largest one here is 1". These were made to match existing threads on other parts of an antique. You cannot buy decent taps. They all make threads that are too small for wood.

The 6" screw is for the press in the Book Binder's Shop. I am on the left,looking much older!! Jon,my journeyman,a master in his own right,is the other person. Some silly person many years ago,made their book press with a square wood thread,and it fell apart.

I know you are a smart guy,but I hope you see that this is very old hat for me. There were many,many things in the museum needing wood threads,from a bookbinder's stitching frame to the cider press. We even made marking gauges with 3/8" dia. wood screws in the thumb screws. I made the tap for that,too. It's the little one in the picture. I had to take on all comers for 39 years. Toolmaker is not an adequate term,but I could not think of a better one.(Everything maker?) Just doesn't sound right!!

Jon was a gunsmith. He got tired of dealing with the public,and joined me in the behind the scenes toolmaker's shop. Jon is one of a few people in the World who can hand forge up a wrought iron gun barrel from a flat kelp. Then,hand ream the tole,and hand rifle it,taking about 600 passes to cut the rifling with a wooden machine. You pull the cutter through by hand,guided by a wooden spiral cut shaft. They make complete guns with the very simplest of tools in the gunsmith shop.

[Dale Coons]

lakeerietoolworks.com makes 2 1/2 inch screws for vises. 2-3 weeks lead time. never done business with them, just know they exist.

maybe they have something reasonable for you?

d

[Jessica Pierce-LaRose]

I have a Lake Erie screw on my bench. I'm very satisified.

[george wilson]

I hope someone makes them. I am tired out at my age,and do not intend to get back into production. My skeleton is pretty worn out. Bone on bone joints,constant pain,have to be careful how much I lift,etc.. I used to be 2" taller.