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To harden or not to harden that is the Question

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Dell26/12/2021 15:36:16
101 forum posts
34 photos

But what is the answer to the question

spent the afternoon milling some long small long T nuts ready to fit the Multifix QCTP they are 50mm long 6mm thick , had to file the last 1/2 mm because I couldn’t get enough meat above the vice and get a good grip, once fitted they should not have to be removed the only bit that will be undone fairly regularly will be the 10 mm bolt in centre of the 8mm plate that is going on to the T’s so do I need to harden and temper them.

thanks Dell5f17f978-5206-4dec-b214-66086b94557c.jpeg


Bill Davies 226/12/2021 15:42:32
276 forum posts
11 photos

Personally, Dell, I would keep them soft. If they have to deform slightly, say, due to a speck of swarf caught between the tee nut and slot, better that than a stress concentration that may break the top of the slot.


JasonB26/12/2021 15:45:58
22555 forum posts
2634 photos
1 articles

Assuming you only used mild steel then I can't see much point in case hardening them. If you wanted to through harden then you would have needed to start with something that had more carbon in it.

Tony Pratt 126/12/2021 15:55:03
1924 forum posts
12 photos

Leaving them 'soft' will be no problem. Use a clamping lever on top of the tool post to tighten & loosen as required, loctite stud into T nut.


old mart26/12/2021 15:57:28
3717 forum posts
233 photos

I dont think you would need to. If you are worried, then remake them in en19T or en24T but it would make very little difference.

Howard Lewis26/12/2021 15:59:42
6004 forum posts
14 photos

Wouldn't bother.

It is not as if they were subjected to constant movement under load, like slide bars on a loco.

Tee nuts only see motion when being slid into position, carrying almost no load. Once in position, they are tightened to prevent movement.

The only area to see motion under load is the thread

Have never hardened any that I have made, and had no obvious problems.


Dell26/12/2021 17:03:13
101 forum posts
34 photos

Thanks for replies everyone

that is what I thought but it’s always good to get other opinions especially when there thinking is the same as what I thought, it’s when you get loads of differing opinions that it’s a problem deciding what opinion’s to take.

Many thanks Dell

Ronald Morrison27/12/2021 10:55:30
83 forum posts
4 photos

After you get the stud hole drilled and tapped, peen the backside so the stud cannot be screwed all the way through. That will keep you from accidentally screwing it in so far that it breaks the T slot on the mill.

Dell27/12/2021 16:12:27
101 forum posts
34 photos
ce7a8ac7-e4fc-49c6-bda2-2287f3d28d96.jpegPosted by Ronald Morrison on 27/12/2021 10:55:30:

After you get the stud hole drilled and tapped, peen the backside so the stud cannot be screwed all the way through. That will keep you from accidentally screwing it in so far that it breaks the T slot on the mill.

I had to cut the bolts down so I purposely cut them slightly short just to be sure they didn’t go to far but I also peened over last thread anyway.


Tim Stevens27/12/2021 17:16:59
1584 forum posts

A dodge for the next time: To help holding them when milling the sides, drill and tap the holes first. Then each long T-nut can be bolted to a straight-sided off-cut, and you can mill as much off as you need.

In passing - I note that there are off-cuts listed on auction sites. What I don't understand is 'How do they know what sizes you are going to want?'

Seasonable wossnames to y'all - Tim

Dell27/12/2021 19:11:00
101 forum posts
34 photos

Thanks Tim

i never thought of that thanks for the tip, I don’t buy off cuts I buy what I need from Rapid metal no minimum order , if you want 10mm they will sell you 10mm.

have a great new year Dell

Sandgrounder27/12/2021 19:55:32
243 forum posts
6 photos

About 25 years ago I bought some machined lengths of 'T' strip from Myford Ltd, this was not hardened as you had to both cut it to length and tap to it suit.


Chris Trice27/12/2021 20:09:04
1375 forum posts
10 photos

Female threads are in compression and stronger than their matching male threads which are trying to sheer off the central core of the stud. It's why high tensile bolts can have mild steel nuts.

Dell28/12/2021 13:54:47
101 forum posts
34 photos

Thanks for all the advice from everyone, it all up and working and I am very pleased with the almost finished job , I say almost because I have to make some sort of handle for tailstock as it’s very smooth and my grip is not very good.

First job completed was a leaver that was missing and I am very impressed with the industrial sewing machine motor with the foot pedal it is very controllable and has plenty of torque even at very slow speed.
once again many thanks everyone and a happy new year Dell

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