What's a Tubular T-Nut

Last night's bedtime story was from ME3663 (Aug 1981). In his article on 'A Graduation Marking Tool', Mr R Main writes:

I am sure there are hundreds of the model engineering fraternity who, having wasted many hours and much material with inadequate boring cutters and crude clamping lash-ups, now call a blessing upon George Thomas' head for his notes on boring tools and tubular T-Nuts.

Expect I've not been paying attention again, because George Thomas is so well-known, but what exactly is a tubular T-Nut and why are they wonderful?

Dave

PS. I don't know how to pronounce 'foliot' either.

I think these are what was being referred to.

from GHT Model engineers workshop manual.

Mike

Edited By Mike Poole on 19/09/2020 13:20:05

fo·​li·​ot

Is it because they are used as a bushing sort of . So the thread of a normal t-nut has side play in whatever is being clamped. Where the tubular ones would be a snug fit stopping any chance of side slip. Trouble there if i am correct you would need lots of different sizes.

Steve.

Well, they could give a greater length of thread engagement than the plain type, but you pay for that in the smaller thread diameter.

You could get more precise location, perhaps to holes in the base of whatever they're retaining. Same price, plus fiddly and potential binding whilst sliding along slots.

Difficult therefore, AFAICS, to justify an unrestrained paean of praise...

Edited By Mick B1 on 19/09/2020 14:12:32

.

... with just the right emphasis on the last syllable, that it does not sound like foliate

[ which could be, but is probably not, etymologically related ]

MichaelG.

.

Merriam-Webster suggests : Foliot : French, from Middle French, probably from folier to play the fool, from fol foolish, mad

I think the tubular bit is bigger diameter than the width of the the tee slot so you can get a bigger thread in. Having said that you can easily get 1/4" or M6 thread into a normal nut, and that should provide enough clamping force for a fairly light machine like a Myford

those pictured are how I make them. Mainly because I can make several at a time in the lathe from a length of bar. Turn the bigger diameter along the whole piece, then the tapped hole, then the smaller diameter using stops and part off. Add the flats for the T-slot putting as many as you can fit in the mill vice.

Using my 5" lathe is much quicker and easier than using the mini-mill to make the whole part.

GHT makes it clear somewhere in his writing that the point of the tubular T nut is that the longer thread engagement means you can have a set of T bolts at longer intervals than with regular T nuts and still be able to grip work of any intermediate size.

Rod

Strange that this subject has cropped up just as I made one. I recently bought a NOS compound for a Smart & Brown model A. Of the two types that were made for this lathe, this is the one with the tee slot. The tee is part of the two way toolpost that I have made to fit on the compound. I made it out of 60mm diameter EN24T and the centre boss is 21mm diameter, drilled and tapped 12mm to just above the top of the compound. The 21mm projects 15mm and is the pivot for the toolpost. I increased the width of the slot on the compound to 14mm and the result is two flats on the 21mm part to fit the 14mm slot width. The toolpost has a spring loaded indexing plunger and there are two tapered holes in the teenut spaced 48mm apart. The indexing is not perfectly repeatable as the tee has a certain ammount of play in the slot. With a manual machine, this hardly matters. Also as the toolpost only locks at 180 degrees, using a boring bar would be a matter of lining up by eye.

Edited By old mart on 19/09/2020 21:20:23

Edited By old mart on 19/09/2020 21:20:56

i have tried to add a couple of the correct pictures to illustrate my last post:

Edited By old mart on 19/09/2020 21:24:19

If I need a strong one I just weld the threaded rod into the tnut and use a double nut

You can shape the weld to the top of the slot

edit: a tnut clamps the top of the slot between the tnut and the workpiece

a tbolt is trying to tear the tnut part out of the slot? no?

Edited By Ady1 on 19/09/2020 23:04:01

Thanks for the info. I shall make a few when I'm in the workshop.

Re: foliot, there are a few pronunciation websites that speak words. The only language on these that recognised 'foliot' was Catalan, pronounced fo-li-ot. Found Google Translate has listen buttons too. It says 'folio' in both Catalan and English. Reckon you guys are more reliable.

Cheers, Dave