1/2 x 13 tap for wood

[Perry Hilbert Jr]

The head stock spindle on my spinning lathe has a 1/2 x 13 thread. I can use a standard metal cutting tap to tap in wood, but I thought perhaps the cutter edges might be slightly differently shaped to cut wood cleanly. I have lots of small round sugar maple blanks to make chucks. Woodcraft lists a 1/2 wood tap, but doesn't say what thread count. They have not responded to my email yet.

[Dwight Rutherford]

I’m not aware of any “wood specific” taps. Different types of wood accept threads differently, closed grain hard woods are best. I bet the taps offered by Woodcraft are standard taps.

[Peter Blair]

I would soak with CA before threading and after threading.

[Ron Selzer]

I have had good luck threading wood for casters. I do use CA after tapping
good luck
Ron

[John K Jordan]

The head stock spindle on my spinning lathe has a 1/2 x 13 thread. I can use a standard metal cutting tap to tap in wood, but I thought perhaps the cutter edges might be slightly differently shaped to cut wood cleanly. I have lots of small round sugar maple blanks to make chucks. Woodcraft lists a 1/2 wood tap, but doesn't say what thread count. They have not responded to my email yet.

I bought taps and dies from Woodcraft many years ago. I’d have to go look but I think the 1/2” wood tap is much coarser than 13 tpi.

The standard thread pitches for 1/2” are 20 for UNF (fine) and 13 for UNC (coarse). Bit even the coarse is difficult to tap in wood unless the wood is very hard and fine grained. Sugar maple may qualify although some is much harder than other.

I’d try two things for wood - one, pick a drill size “slightly” larger than the one specified for 60% threads in metal. Two, as mentioned applying thin CA (or sanding sealer) after drilling may help prevent tearing the threads as much. I apply wax to the tap to lubricate. Once the threads are tapped it may help to apply more CA, let cure completely, then run the tap through again, also with lube.

If the wood is a bit on the soft side, I often don’t bother with a tap since it is likely to tear the wood. Instead, I’ve had success in making a tap of sorts with a bolt or threaded rod with the same thread. I either use a triangular file or a thin metal-cutting disk on a Dremel and cut a series of angled slots through the threads on a short section on the end of the bolt. Using this as a tap deforms the softer wood rather than trying to cut clean threads and can minimize tearing the wood. I’ve used this method many times successfully. Here again, I first drill a hole larger than I would for metals and plastic, just barely smaller than the OD of the bolt.

One more method I’ve used to tap clean threads in softer wood: drill a hole big enough to glue in a plug of much harder wood and drill and tap that. I used this method to make a compression chuck from soft cedar - I glued in a plug of much harder dogwood which was easy to tap cleanly and has held up to repeated use.

JKJ

[Brice Rogers]

The head stock spindle on my spinning lathe has a 1/2 x 13 thread. I can use a standard metal cutting tap to tap in wood, but I thought perhaps the cutter edges might be slightly differently shaped to cut wood cleanly. I have lots of small round sugar maple blanks to make chucks. Woodcraft lists a 1/2 wood tap, but doesn't say what thread count. They have not responded to my email yet.

I think that the profile of the cutter teeth for wood and steel are the same profile (60 degree included angle and short flats on the root and peak). So, if you found a tap made for metal it should work. The difference between the two taps is that the wood-tap is shorter and the lead in is less. So it is closer to a bottoming (metal) tap in its form. But the actual cutter teeth profile are the same AFAIK. After all, the threaded block has to screw onto the spindle thread that is a standard US profile.

The other advice that you have received is "spot on".

I'm wondering if there could be some benefit to using a coarser thread. I'm wondering if the small 1/2" dia and the 13 TPI might cause the wood thread to strip out. To use a coarser thread would require an adapter from 1/2-13 to something like 1x8. 1x8 Beal taps are pretty common. Just a thought....

[Dwight Rutherford]

Apparently there are in fact taps made for wood. I stand corrected.

[Keith Outten]

http://www.bealltool.com/products/threading/threader.php

JR Beale has been selling custom wood threading taps for many years. I purchased his threading jig over 20 years ago and I recommend his products highly. I have on a couple of occasions talked to Mr Beale on the phone, he is an amazing guy with a lifetime of machining experience.

Side Note:
The walnut threaded fasteners in the picture below were made from some walnut boards I purchased from Richardson's Mill in Williamsburg Virginia about 20 years ago. The tree grew right beside the Williamsburg Capital building, when it was cut down and they counted the rings they estimated that it was planted in 1776. At the time I was a good customer of Richardson's Mill, my Dad and I were operating a kiln in those days so we were allowed to purchase two boards from the Williamsburg tree. All of the lumber was used for very special projects by local woodworkers. I made a variety of wooden nuts and bolts ( 1/2"-8 tpi ) that I gave away to close friends and a hay wagon that had threaded axles and nuts for the wheels. The walnut fasteners were stained with walnut stain, waxed and buffed on my lathe.

[Perry Hilbert Jr]

apparently, the wood taps and dies for wooden screws use a standard 8 threads per inch regardless of diameter. and do not follow the same v profile as metal threads, they are more rounded, but not flat topped like Acme threads. Which I guess is why a Beall tap for wood to screw onto a head stock spindle has the V threads instead of the more rounded wood threads. My lathe came a few wooden chucks for spinning and they all have the same 1/2 x 13 thread. I can't tell what sort of wood they are. The one to make small pie tins looks like it might be a laminate of some sort.

[Brice Rogers]

Perry Hilbert wrote: "apparently, the wood taps and dies for wooden screws use a standard 8 threads per inch regardless of diameter. and do not follow the same v profile as metal threads, they are more rounded, but not flat topped like Acme threads. "

I took a close look at my 1x8 Beall spindle tap a couple of minutes ago. And it's profile looks the same as a 1 x 8 bolt. When I meshed it with a commercial bolt and held it up to the light, they both had the same profile. It did not look more rounded.

I am an amateur machinist and have single-point turn (on a metal lathe) and hand tapped several threads including 1 x 8" and 1.5 x 8" - - I always have to take out my Machinery Handbook to double check the specs. In fact, I have manufactured my own tap at one point. So, I have some experience with threading.

BTW, acme threads and UNC threads are vastly different and are generally incompatible with each other. But some people who make threaded brooms and broom handles may use an acme thread because it is a little stronger. It may even be more coarse than 8 tpi. Also, you'll see acme threads on things like metal C-clamps that need the higher strength and more "meat" on the threads. So, perhaps the wood tap AND die set that you are looking at are for Acme threads. If you order a beall spindle tap it'll have threads that look like a commercial bolt. If you want to make your own 1/2 x 13 tap, you could do it from a commercial bolt and an angle grinder (or mill, etc.). It might cut a bit undersize though as most bolts are a bit on the low end of their tolerance.

But I can assure you that the Beall spindle tap (1x8) follows the UNC specs.

https://lh3.googleusercontent.com/proxy/5mLfbU7ikFB274tqiYMhUMGqFbTv0jwcQ7KTE6Em2YfX0-tT3Y9w55MvexqXl8ZFHAtgiS_Osa02Bj_L6ap5DJPmrLiHWuTd NebSVdNFmgjAHDNfNYGkzo8

[Perry Hilbert Jr]

Mr Rogers, you are sort of correct. The Beall taps are for threading, but not for wood on wood, where the rounded threads of 8 per inch are used. Beall taps are used on wood so they will fit standard machine threads on metal head stock spindles. Hence the fact that Beall also made a 3/4 x 16 tap to fit a wood chuck to the machine threads on a head stock spindle .. The Beall threads are therefore indeed to match standard metal machine threads because their purpose is to thread wood to fit metal machine threads. It is additionally confusing that the taps for wood on wood applications are 8 per inch, but they do not have the same "v" profile as machine threads. They are indeed a bit more like Acme threads, but with rounded tops at least on the old wooden carpentry clamps I have..

[John K Jordan]

Here is a closeup of the threads made by one of the threading tap/die sets I bought from woodcraft long long time ago.

https://sawmillcreek.org/attachment.php?attachmentid=426130&d=1581977166

Glued threaded handles can keep the gavel head from loosening as it sometimes can with glue alone due to seasonal changes and a lot of pounding.

https://sawmillcreek.org/attachment.php?attachmentid=426129&d=1581977166

JKJ

[Brice Rogers]

Perry, in your initial post, you mentioned that you were looking for a metal tap to cut threads into a sugar maple blanks to make "chucks".

You might try just buying a metal tap (1/2 x 13tpi) and try that now that you know that the metal tap will make a threaded hole that should fit your spindle. (As others have said, you CA glue to help stiffen the wood). The 13 tpi may be a little fine for a good wood thread, but it would be an interesting experiment. As you know, the thread profile in the wood from a metal tap will fit your matching spindle.

Or alternatively, you may want to pick up some 1/2 x 13 nuts or (better yet) some couplers of the same size. You would drill a slightly undersized hole in the blank, press in the nut or coupler and drizzle in some epoxy in the gap between the hex nut and the round hole. You would put the nut on the outboard end so that it is in compression. If you really enjoy chiseling, I suppose that you could alternatively chisel a round hole into a hex and then epoxy the nut in. After it has cured, screw it on your spindle and turn out any runout.

[Jamie Buxton]

Tapped holes in wood are much stronger, and much easier to make, if the hole runs across the grain direction. Tapping into end grain creates threads which are little short-grain parts which are easily ripped away from the body of the wood.

[Perry Hilbert Jr]

Yes I want a tap to cut standard 1/2 x 13 threads in wood. As I recall, the Beall taps have special cutting edges to cut the threads in wood. I was certainly not as eloquent about that as I could have been. My concern was that a tap for "wood threads" would not be acceptable to fit ANC threads and a standard ANC tap for metal may not have the best cutting edge to make the threads in wood, (as I understand the beall taps are designed expressly to do.) I am a retired attorney and once represented a fellow who suffered severe burns when a threaded coupling on an industrial acid pump separated. I actually sat in for a week of evenings a local machinist class at the community college to learn about threading systems. I bought the text book and studied that. When I finally had the chance to examine the actual pump from the incident, I noticed that one side had a standard V thread the other side had some strange rounded top skip tooth thread. The parts would hold until subjected to heat, once the plastic parts softened from the heat they blew apart. The heat came from the fact that the pump was washed out after every use and then used again before all the water was dried out of the pump, add high concentration hydrofluoric acid to a small amount of water and there is a huge release of heat. The engineer that "designed" the pump, left it up to the draftsmen who did the tech drawings to decide on the threads. The two parts were sent to two different draftsmen who specified two different threads. A few years later I had a case with gun that "failed" where the barrel was screwed to the action. Both the action and the barrel were threaded 1 x 14. The reason for the failure was that the action threads were ASE standard threads for American threads with the same thread side angles. The barrel was 1x14, but was made in England to English standards and had different height threads. The barrel was made out of mild steel and the shooter was shooting smokeless powder in a barrel intended for black powder cartridge pressures. The threads slowly became loose and eventually there was enough slop that the case fractured and gas went back damaging the shooters eye. This time I represented the insurance company for the company that made the action. The shooter got nothing.

[Perry Hilbert Jr]

Thanks to all of you. Mr Buxton I should have realized that and didn't. Some of my blanks are end grain and I will mark those for another use.

[John K Jordan]

Tapped holes in wood are much stronger, and much easier to make, if the hole runs across the grain direction. Tapping into end grain creates threads which are little short-grain parts which are easily ripped away from the body of the wood.

I agree in principle. But I think the type of wood makes a huge difference.

I like to use dogwood for threading since it is quite hard, very tough, and fine grained. I almost always drill and tap into the end grain.

I've made lots of things that screw onto the Oneway live center (3/4x10) and the headstock spindle of my lathe (1-1//4x8). The threads cut cleanly with a tap made for metals for the live center and one made by Beall for the headstock spindle. There is typically no tearout. I do treat inside of the hole with CA glue after drilling and lubricate the tap with beeswax. I think lubrication is important as well as is tapping very slowly. Something else that is important is keeping the tap perfectly aligned with the hole. I use a spring-loaded guide held in a Jacobs chuck in the tailstock, hold the tap with a wrench to keep it from turning, and tap by turning the wood held in a scroll chuck on the lathe. Taps are typically made with either a center depression or a center cone to allow such alignment. A tap guide is not expensive: https://www.amazon.com/gp/product/B005317ZMC

This is a spring compression chuck I made to hold wooden eggs for finishing the round end. I made the chuck from eastern red cedar since it is soft and glued in a cylindrical dogwood end-grain plug to drill and tap. The threads remain clean and unbroken after many uses. I think the combo of the dogwood and the coarse thread helps. (I do lubricate the wooden threads with wax occasionally for use.)

426258

Things tapped with the finer thread do have more tearout in end grain in some woods. The two wooden adapters for the live center in this picture are made from maple and lignum vitae (which is pretty tough.) Although there are more torn threads in the maple piece enough remain to hold it nicely.

426259

However, there is not much force on these things, just compression from the tailstock. Something made for a fine-threaded lathe spindle to make jam chucks or faceplates might experience a lot more force.

JKJ

[Clint Bach]

Would t-nuts perhaps work for this application?

Cpb

[Perry Hilbert Jr]

Interesting question. The ultimate purpose of the threads is too hold the wooden chucks for metal spinning. The force is applied to the metal to cause it to form to the shape of the chuck and the stock and chuck dpin. So if there is a shape out 5 inches from center, the chuck must be solid enough to hold fast despite the pressure pushing against the wooden chuck. That would be quite a bit of leverage against the chuck out from the center, Trying to get the metal pressed into that final outer shape would create a great deal of stress on the threads holding the chuck. I suspect a "T" nut might just be a weak link. I'll have to think about it a bit more.

[Clint Bach]

My guess is t-nuts would be many times stronger than wood threads. If installed properly they clamp the wood between the t-nuts and the spindle. That's a very firm connection.

Spindle, face plate, t-nuts installed from the face of the faceplate, then a wood plug to make the faceplate surface all wood.

To fail the t-nuts would have to be ripped through the wooden faceplate. Much stronger than wood threads in my opinion.

If installed improperly from the spindle side of the faceplate yes they probably fail spectacularly.

Cpb

[Clint Bach]

I worked with cable on large wood spools. Three feet in diameter or so loaded with several hundred pounds of cable. The spool ends were held together with long bolts and t-nuts. Occasionally the spools would fall off the truck and break the spool. The t-nuts never failed. Ever... They earned my respect.

Cpb

[Alex Zeller]

Would it be possible to use a bushing? Say aluminum, since it's easy to work with that had an inner hole that was 1/2-13 and the outside could be threaded in a different pitch that works better with wood? I'm not sure how much you want to invest in this project but depending on the outside diameter of the bushing you would get quite a bit of strength. If the wood shapes are going to be reused you could even glue the bushing into the wood.

[Peter Blair]

I rely on the tap I got from Beale for my Oneway headstock, It is similar but not quite the same as a metal tap. Still makes a huge difference depending on the wood I tap I always drill coat with CA tap then redcoat then run the tap again. Air tight as well.