making tee nuts

Hey All,

was going to make some tee nuts and studs for a vertical milling slide for a lathe.

Do i need to harden and temper them, or just leave as mild steel?

thanks

No you don't they will be fine.

I would only use mild steel as well.

Edited By Buffer on 27/11/2021 08:29:41

When you make them be sure not to run the tap all the way through to prevent the studs hitting the bottom of the tee slot in use. If you have already tapped through place a ball pein hammer hammer on the bottom of the tapped hole and wack it with a hefty copper mallet.

I prefer alloy for Tee nuts, especially on smaller machines.

Reasons :-

1) Any swarf that gets between the Tee nut and the top of the Tee slot will embed in the nut rather than the slot. Annoying but relatively easy to dig out of the nut. Shifting it from the machine slot is a royal pain. Often any swarf embedded in the machine will be just big enough to prevent free movement of the Tee nuts along the slot which is, um, frustrating. My Bridgeport suffered so when I got it. Had to get creative with tooling, methods and vocabulary to get it all out.

2) An alloy Tee nut will generally be weaker than the machine table so if you do over tighten the nut thread should strip before the table distorts. The smaller the machine the greater the disparity between cast iron table strength and steel nut strength. Given decent technique things don't have to be held down super tight on machine tables. Thin card or alloy sheet gaskets between work and table are very effective at stopping slippage when the work isn't quite as flat as the table so contact area is limited.

3) If, perchance, the two sides of the Tee on either nut or slot aren't at exactly the same level an alloy nut can distort a touch to take up the difference more easily than a steel one.

When you make your nuts remember to leave the bottom thread incomplete, or close it up with a ball bearing either squeezed or hammered onto it, so you cannot run a stud right through and jack the nut up against the slot. A good way to break things. Alternative is to make the studs asymmetric with a short thread one end that isn't long enough to go right through the nut. Asymmetric studs are theoretically good but, in practice, tend to unfortunate comments after about the tenth time they get screwed in the wrong way round!.

Another approach is to fit the nuts with short studs and screw a long joining nut on top to locate the Tee nut before screwing the actual holding stud on top. Can be handy to fix the Tee nut position first but it does make the effective minimum length of a stud around an "inch'n a bit" which may be an issue. Locking the Tee nut into the slot with a nut on top is kinder to the machine.

Clive

PS Chris Evans posted whilst I was typing.

Edited By Clive Foster on 27/11/2021 09:59:27

For the studs use stainless steel studding - cheap and perfectly fine for the job. (The clue is in the name!)

John,

Lots of tips and Ideas but my vote goes to mild steel - it will be fine for home use.

Phil H

If you use bright MS, and intend to make a longer length of "tee nut section" to cut into individual nuts, best to first normalise the material by heating dull red for a couple of minutes and allowing to cool slowly. Otherwise the stress induced in the surface layers can cause it to warp. Guess how I know? And that was with 3/4 square bar.

Many years ago I became fed up with T-nuts, and began to use modified coach-bolts (the things with shallow domed heads). Simply file opposite sides of the head partly flat, so the head slides into the T-slot. Then you have a stud ready-made, and items can be locked in place with a nut threaded onto the bolt. I suppose the length of the protruding shank of the bolt could be a problem, but coach-bolts are dirt-cheap, and come in different sizes, with fully or partly threaded shanks, so simply buy or cut the bolt to the length you need.

The bolts are usually mild-steel,so they fit the requirements described in this thread, and there is no worry about screwing the stud through a T-nut and jamming in the slot, and also the protruding shank of the bolt makes it easy to get it back out of the slot - no T-nut buried in swarf in the slot.

Because I only have a small mill, I find it easier to do most of the work in the lathe using the power feeds and extra power.

Operations in the lathe:

Drill and tap the centre hole.

Turn down the narrow part of the 'T' to a length slightly less than the depth of the slot and width.

Turn the larger diameter so that it's consistent, although the actual size isn't particularly important. Do this first if using a long length of bar as it saves time making several nuts.

Part off so the length of the large diameter is slightly less than the depth of the slot.

Operations in the mill:

Line up several nuts in the milling vice, and mill the first flat on the large diameter to depth

Turn them over, with the flats on a parallel and mill the other flat.

I find this much quicker than milling them out of rectangular stock, and it has the added advantage of using up the short stubs of material that really ought to be thrown away.

Edited By Nicholas Wheeler 1 on 27/11/2021 11:26:52

Clive F, just to be pedantic (and not to offend), steel is much an "Alloy" as Aluminium alloy. The term Alloy is much abused ! It is the same as the term "Use aluminium strip" , Pure aluminium is a very soft, ductile material whereas some of the aluminium alloys are quite hard, difficult to machine and almost impossible to bend without fracturing.

Bob

Yes T-nuts from bar stock are quite useful, I made some to fit the slots on my WM250 lathe.

More detail *** HERE *** not that you really need a description of how to make them.

John

That's exactly what I made, as I needed four for the better compound slide clamp.

And another four for the vertical slide mount - I want each tool ready to fit without having to faff about removing fixings from the previous tool.

The 25mm diameter is probably the smallest you want, but bigger wouldn't matter especially if there's some scrap available.

Journeyman's pattern is the same as Myford's.

I confess that I have used hex material to save the milling operation.

NB also GHT's tubular tee nuts>

Edited By ega on 27/11/2021 12:26:25

Lots of advice and opinions here but no mention of allowing plenty of clearance. Don't be tempted to make them a snug fit, jammed nuts and frustration will result.

Adrian.

I suggest round headed t-nuts, such as coach bolts, should be used with caution. Tables are often made of cast-iron which is weak in tension. In consequence, they're rather easily broken, especially thinner lathe cross-slides.

In the diagram below, the bearing surface of a round nut (in red) is compared with that of a square T-nut (red AND green):

When the round T-nut is tightened all the pressure is taken by the red area and increases the risk of breaking the table. The problem is exacerbated because the round form also concentrates stress at one point on the table. Conversely, a square T-nut increases the bearing area considerably and shares the bending stress along the slot.

Dr Stephen Hawking observed that each appearance of a mathematical formula in a book halved the number of people prepared to read on! Such slack-shouldered cowardice would never happen on a forum full of engineers. To us maths is just another tool so being asked to do the sums won't cause mass-desertions. Therefore, today's homework is:

In the diagram above, the open slot is 15mm wide and 25mm wide underneath. What's the bearing area of a 24mm square-nut (red and green) and what's the red area under the diameter of the round head?

Dave

PS I haven't tried to solve it myself yet...

Using allowable engineering approximation:

area of square t nut 576, area of slot 360, so area in contact 216mm square

Area of circle 452, area of slot approx 360, so area in contact with circle approx 92.

Or under half…

Dave

Please Sir, I left my homework book on the bus ! Noel.

Sorry Sir,

The dog ate my homework !

Derek

I’ve made both turned and milled nuts from mild steel for my machines and they seem to work well enough. I’ve not had any problems so far anyway. I’ve never considered aluminium alloy Tee nuts before, probably because I’ve not seen any but I don’t see why they wouldn’t work well enough? At least they can’t go rusty!

No problem, it's not due in until Monday. There's plenty of time to do it again...

Thanks for owning up. Now the headmaster is taking a personal interest in both of you!