GHT Tee nut?

[pelallito]

Hello,
In GHTs book ME Workshop Manual, he specifically mentions using f.c.m.s. (not leaded) for the TEE-NUTS, pg 47. I wondered if that is because of a problem with the strength of the material or just his preference.
I wanted to make some for my Atlas mill, so I am going to alter some of his dimensions.
Thanks,
Fred

 

[GWRdriver]

Fred,
I think that was because FCMS was readily available and relatively inexpensive, and because the typical amateur machinist would rarely if ever exceed its capacity in normal usage.

 

[smfr]

To save anyone else from looking it up, I believe FCMS is "Fast-Cutting Mild Steel". Is that the same as 12L14?

 

[Lew Hartswick]

To save anyone else from looking it up, I believe FCMS is "Fast-Cutting Mild Steel". Is that the same as 12L14?

Don't you just LOVE these "technical" terms? FCMS
...lew...

 

[rkepler]

FCMS = 12L14 or 1117 - if non-lead is specified it's likely the latter (basically a resulphurized low alloy steel, AKA "screw machine stock")

But if you're making low stress t-nuts I'd suggest using anything you have handy and is easily worked.

 

[jstinem]

Tee nuts are not rocket science. Just use whatever steel you in hand. If you have to tighten a setup tight enough to strip the threads you really should stop and think about what you are trying to do. Do be sure to omit or destroy the last thread on the bottom of the nut so the stud can't pass through the nut. If the stud can pass through the nut and come tight against the bottom of the tee slot then the nut will climb up the stud as you try to tighten the top nut and break the table before you know what's happening.

 

[terryd]

To save anyone else from looking it up, I believe FCMS is "Fast-Cutting Mild Steel". Is that the same as 12L14?

Hi,

FCMS stands for Free Cutting Mild Steel,not necessarily fast though if you work like me! Seriously, it should be fine for tee nuts, just heed the warning about the jacking effect above from jstimen, I have seen tee slots jacked out on Bridgeports especially if bolts are used instead of studs. I use a punch to close the bottom threads to prevent screw-through, but importantly don't over use the wrench (spanner), excessive force is not needed when clamping work.

By the way smfr, I am also refurbishing a Stuart mill and boiler, but mine was damaged in my workshop fire and subsequent collapse. I managed to salvage most of it (among other stuff) from the scrap men sent in by the builders to clean up. I may post a few pictures for your interest.

Terry

 

[smfr]

Hi,

FCMS stands for Free Cutting Mild Steel,not necessarily fast though if you work like me! Seriously, it should be fine for tee nuts, just heed the warning about the jacking effect above from jstimen, I have seen tee slots jacked out on Bridgeports especially if bolts are used instead of studs. I use a punch to close the bottom threads to prevent screw-through, but importantly don't over use the wrench (spanner), excessive force is not needed when clamping work.

Yeah, the table on my Emco Maximat was damaged by an "over-tighener". There were bolt indentations all along the T-slots, and the lips of the T-slots were raised. Luckily I had a spare. Someone dropped that one on an end, but at least that damage is localized.

By the way smfr, I am also refurbishing a Stuart mill and boiler, but mine was damaged in my workshop fire and subsequent collapse. I managed to salvage most of it (among other stuff) from the scrap men sent in by the builders to clean up. I may post a few pictures for your interest.

Terry

I would love to see them, Terry! I'm sorry to hear about the fire; it must be so disheartening to see damaged things that you've put so much time and effort into

Simon

 

[pelallito]

Thanks for all of the answers. I was just curious about his choice in material
And if it might have had something to with case hardening
the pieces, but he doesn't harden them.
These are hollow tee nuts of ,I believe, his design.
Thanks again,
Fred

 

[moconnor]

Hello all,

To collapse the last thread on the T-nuts that I make, I use an old ball bearing of an appropriate size and an arbor press to neatly compress the last thread and prevent any stud or bolt from passing through and blowing out the T-slot that it is used in.

Regards,
Mike

 

[rake60]

The strength of a T-Nut has as much to do with the bolt length used as the material it is made of.

The problems with a bolt passing the whole way through a T-Nut has already been stated here.

A bolt that is too short to reach the wider lower section of the T-Nut can be worse.
I have done that several times over the years. That narrower top section will break loose
and pop off very easily if all of the bolt tension is on it alone.

Rick

 

[pelallito]

Mike,
I like that trick. :bow:
Rick,
That must have gotten exciting.
It feels better answering from the computer than over the phone.
Thanks,
Fred

 

[Spurry]

I use an old ball bearing of an appropriate size and an arbor press to neatly compress the last thread

Similar result can be obtained by using the ball of a ballpein hammer and giving it a whack with a copper hammer.....just in case you do not have an arbor press handy.
Pete

 

[Lew Hartswick]

I've been thinking about this for a day or so now. I seem to have a problem
un-screwing the stud from the "buggered" thread at the bottom of the T nut often.
SO! How would it be to cross drill the stud at an appropriate location and put a small
spring pin (Roll pin) that will limit the insertion depth to just shy of the binding point?
In the case of a Bridgeport size mill the studs are 1/2" and I cant believe a cross
pin hole about 1/16" would weaken it dangerously.
Comments???
...lew...

 

[Dr Jo]

I must be honest I do not like using Tee nuts with bolts as it is so easy to use a bolt that is too long and when you think that you have tightened up the work all you have really done is forced the bolt into the bottom of the slot and the nut onto the top. Too short a bolt can mean that there is insufficient threads to cope with the machining forces. Either way it is when you start machining that is when you find that the work had not been properly secured.

I used to use captive studs in the tee nuts and then add a nut and washer onto the stud.

I have now moved over to using something similar to a tool maker's clamp for all my machine bed clamping. The center thread being mounted using the tee stud with a washer + nut at about the right height to prevent the clamping bar moving upward and the second stud at the end of the clamp used to adjust the tension against the work piece. (The second stud acting against the packing piece or machine bed, not the work). To protect the machine bed from the tension stud I have made brass/aluminium "feet" that fit to the end of the thread.

Jo

 

[purpleknif]

I gotta ask if I'm missing something here. Why not just stop tapping before it goes thru ?

 

[pelallito]

purplknif,
GHTs Tee nut does exactly that. I described them incorrectly. Instead of hollow, which is what I wrote initially, GHT called them Tubular and the threaded section is completely encased by steel. The stud or bolt cannot go through and hurt the table of the machine.
In my case, I started with 5/8th steel. Turned down a section to 7/16" by 1.125" and drilled and tapped that to 5/16" nc. Then I took a light skim cut on the 5/8th section and marked it at 1 and 15/32" and cut it off. I still have not taken the next step of making .25 wide cuts on the piece between the 5/8 and 7/16th step. I will need to cut that down to .370 for clearence on my mill. It will be just under the drilled hole. I was making a milling machine stop yesterday, copying Bogs recent design. I have a couple more pieces to finish and then I can have repeatable cuts on my mill after removing and replacing a piece.
Some of the dimensions are from his book, and some are modified for my machine. His were for a myford lathe.
LH,
Some tee nuts are hardened. Why not measure and turn down some steel to an interference fit and push it in. Then cut off the excess and grind or cut it away?
Spurry,
I don't have a big arbor press at home, but several ball peens! :big: