Drilling and tapping wood

[David Nelson1]

Pretty much sums up my question. The tail vise I'm going to install ask you to drill and tap holes in the bench top. (which is wood) Hole would be 1/4 and 5/16 SAE. If my top was hard maple or some other type of hard tight grained wood I might buy it more readily. I'm using white oak so.............. I'll try it on a piece of scrap. Anyone else tried this with success?

[Thomas Hotchkin]

David
I have found in taping wood as in taping metal you need a cutting fluid. I use paint thinner, wet walls of drill hole with Q-tip dipped in thinner. If you can use some type starting block to keep tap straight, and a coarse thread count will help. Tom

[David Nelson1]

What type wood have you tapped Thomas?

[ian maybury]

It works pretty well David, but is probably at its best in something like birch ply because in natural wood the grain direction will weaken it at two sides of the hole. Not sure how well it would do if the plan was to frequently insert and remove the screw, but it gets a good grip and in the end it's probably not that different to a wood screw. A screw in threaded metal insert might be an option too if fitted from the other side...

Running some of the low viscosity/watery super glue into a tapped hole (hit it with some accelerator after it's had long enough so that what's going to cure naturally is gone off) to saturate the wood probably toughens it up a bit. Tap it again when the glue is fully cured to clean it out. Don't let thick layers build up as any unevenness might displace the tap - on a small part you can bang it on a hard surface to shake out any surplus. :) Harder with a bench top...

ian

[Thomas Canfield]

The threads for 1/4 and 5/16" SAE are rather shallow. I would think that it would be imperative to use the correct size drill bit and not any oversize. I would also think that it might be a good idea to use thin CA in the drilled holes prior to cutting the threads to harden the wood to get the best cut, and then follow up with second application of CA and retap. I tap 3/4", 1", and 1 1/4" and do use thin shellac on cut threads and then retap for wood faceplates for turning.

[Paul Saffold]

I've tapped wood, both HW and SYP and MDF, without any trouble. Use the correct size drill for the tap. I'm sure if you Google it you'll get a list of the correct sizes. I've never used any lubricant while tapping. I have used CA glue after the hole was tapped especially for the MDF. I smear Vaseline on the bolt/screw and run it in and out a few times AFTER squirting the CA glue in. Wood is even easier than cast iron to tap. I use a cordless drill on low speed to run the tap in. You don't need to back up like you do for steel. I saw a video somewhere. If I can find it I'll post it. Try it on scrap then give it a go.
Paul

[Bill Huber]

Could you not just use thread inserts, they work very well and are somewhat easy to install. I have use them am surprised at how good they hold.

[pat warner]

Few surprises, something I do (http://www.patwarner.com/images/mag3.jpg). In nearly all hardwoods for 5/16-18, drill to .250". Leave the tap in the quill and hand spin the pulley for centricity and squareness.
For more details see FWW no.88

[David Nelson1]

Could you not just use thread inserts, they work very well and are somewhat easy to install. I have use them am surprised at how good they hold.

I could use an insert if it would fit in the recess. I have a quite a few of the smaller sizes left over from the machine shop days. They are called big locks or bigserts something along those line. The intended purpose was to repair a hole that is outside the scope of a normal helicoil. Of course I could always use a helicoil which I literally have hundreds of. I'm going to play with it in some scrap before I drill my bench top. Matter of fact I'll document the Lie Neilson tail vise install.

[Kyle Iwamoto]

Drill and tap into side grain. If you tap into end grain, your results may be poor. For smaller tap sizes and items such as bottle stoppers, a weak thread tap into end grain may not be a problem, but for a vise, I'd want a more solid thread.

[Larry Browning]

I could use an insert if it would fit in the recess. I have a quite a few of the smaller sizes left over from the machine shop days. They are called big locks or bigserts something along those line. The intended purpose was to repair a hole that is outside the scope of a normal helicoil. Of course I could always use a helicoil which I literally have hundreds of. I'm going to play with it in some scrap before I drill my bench top. Matter of fact I'll document the Lie Neilson tail vise install.
David,
They make threaded inserts specifically for wood. These have the course deep threads on the outside needed for wood and the machine threads on the inside. most often they are made of brass. I would think that tapping machine threads directly into wood would fail almost immediately.

[Dale Cruea]

Most tap/drill sets today are setup for 70% thread engagement.
Meaning that the minor dia. ( tap drill size) is larger than than the minor dia. of the tap.
The top of the screw thread will not contact the bottom of the nut or tapped hole.
A 5/16-18 tap uses an "F" drill that is .257"
You can use a 15/64" drill in wood for a tap drill to get more threads.
You will be cutting some of the minor dia. with the tap.
It will be harder to tap and may not look as pretty.
You will get about 100% of the threads.
I use bees wax on my tap in some hardwoods but, most of the time I tap dry.
Clear the tap and hole several times while tapping to keep from messing up the threads.
Add either bees wax or just wax of some type to lube the threads.
Tapped threads in wood should not be used dry. Always lube the screw with something.

[Ray Newman]

See what bill Huber posted.

[Dave Richards]

In woods that aren't all that great for threading, I drill a slightly oversized hole and fill it with epoxy thickened to a putty consistency with fumed silica. After the epoxy cures I drill and tap as if it was metal. Very good threads that way. this is a method used on some high performance sailboats to attach hardware on deck. This is hardware that often sees very high loads and these attachments are very secure.