Thread: T nut issues

If your special T heads were tapped you wouldn't have to weld them on and risk distortion. Drop of Loctite, Bob's your whatsaname. But I'm thinking you probably thought of that and have reasons for the way you've described.

Not positive but you may find it quite hard to find a unc that is not ht.

Bryan the 1/2UNC thread would make a series of cutouts down each side of the nut until it got to the bottom of the T(when the T is up the other way). If I got it in the middle that is . I had thought of putting a M10 thread in the nut and on the end of the stud but I thought that may weaken the stud to much.

pipeclay I could pein(peen)(can you pein the inside of a ht stud?) the end of the stud into a counter sink in the T nut, but I think I would still need a weld to stop it turning. I guess I could make my own if I have to.

Stuart

Originally Posted by Stustoys

Bryan the 1/2UNC thread would make a series of cutouts down each side of the nut until it got to the bottom of the T(when the T is up the other way). If I got it in the middle that is . I had thought of putting a M10 thread in the nut and on the end of the stud but I thought that may weaken the stud to much.

Stuart

Ah yes, that problem. I got around it with my toolpost insert by going down one size and using a UNF thread to compensate. But that may not be enough for you. Hmm. I think my answer is 'no, I can't see a better way'.

You can happily pein the stud threads into the nut regardless of your grade of steel. You only need 5 threads to achieve 90% of holding power (that's why nuts are made to a specific thickness) and anything more than 7 threads is pointless as there is no further holding power to be had. I would still use Loctite high strength stud lock as well though.

An old clamping set I had at work years ago had the bottom threads of the T nuts peined so that the stud would jam in when fully screwed home without protruding out of the bottom of the nut.

Have you thought of using galvanised all-thread? It's readily available in 1/2" UNC from the Big Green Shed and you can cut it to any length you like. Plus it's not high tensile if that is a worry for you to weld. I've gas and TIG welded 8.8 grade HT steel for similar applications and never had a problem with bolt breakage.

The gib should be adjusted so that the vice still opens and closes easily but has no play in the slide .
Id remover the gib and go over it it with a fine stone to remove any burrs from the grub screws ,dimple the gib where the grub screws sit and replace the grub screws .
Put it back together and then adjust the gib , by adjusting the screws closest to each end first ,test the action of the vice and adjust accordingly ,when you get it right adjust the center screw/s
and lock the screws.

Kev.

Originally Posted by Chief Tiff

You can happily pein the stud threads into the nut regardless of your grade of steel. You only need 5 threads to achieve 90% of holding power (that's why nuts are made to a specific thickness) and anything more than 7 threads is pointless as there is no further holding power to be had. I would still use Loctite high strength stud lock as well though.

Its not the holding power of the threads that I'm worried about its the thickness of the sides of the nut which will be in tension when the nut is bridging the damaged area.

Originally Posted by Chief Tiff

Have you thought of using galvanised all-thread? It's readily available in 1/2" UNC from the Big Green Shed and you can cut it to any length you like. Plus it's not high tensile if that is a worry for you to weld. I've gas and TIG welded 8.8 grade HT steel for similar applications and never had a problem with bolt breakage.

Good enough for me. I have to get some HT studs anyway as I need some really short ones to bolt the swivel base to the table. I'll try using the HT but I'll get some all-thread as well as it will be handy to some about anyway.
Thanks

Originally Posted by Woodlee

The gib should be adjusted so that the vice still opens and closes easily but has no play in the slide .
Id remover the gib and go over it it with a fine stone to remove any burrs from the grub screws ,dimple the gib where the grub screws sit and replace the grub screws .
Put it back together and then adjust the gib , by adjusting the screws closest to each end first ,test the action of the vice and adjust accordingly ,when you get it right adjust the center screw/s
and lock the screws.

Kev.

Thats what I figured. The gib is already dimpled, it was just that the dimples were deeper then the pilot(?) machined on the end of the grub screws so the thread would jam against the gib and stop turning. All fixed now.
Thanks
Stuart


Thanks
Stuart

Originally Posted by Stustoys

Its not the holding power of the threads that I'm worried about its the thickness of the sides of the nut which will be in tension when the nut is bridging the damaged area.

If I've interpreted your drawing correctly the narrowest part of the T nut is 19mm, which in old money is near as dammit 3/4". 1/2" UNC nuts are only 3/4" AF anyway so tapping into the nut won't stress the nut any more than if it was a normal hex.

What material are you going to use for the T nuts? Is the weakness you're concerned about more due to the shear stresses on the corners when the whole shebang is under tension? Once again going by your diagram I would say you have designed it with a more than adequate amount of material so MS would be suitable.

Bearing all the above crap in mind, I actually like your idea of welding them together anyway!

Hi Cliff
Looks like I'm going to have to get a CAD, my paint drawings aren't the best

The top view is at the top of the page. The width of the T slot is 12.7mm, so I've got 12.5mm for the width of the nut. The nut is curved because the slot is a circle, if I made it straight it would get thinner still. This assumes that I can machine the curve by mounting the nut in the vice over the slot and hand feeding the vice past the cutter.

As for material, pretty sure its just going to be m/s I could only get m/s bolts in 1/2 UNC and only S/S in threaded rod, damn that's tuff stuff. So I have the short studs I need to mount the swivel base made. I've also drilled, taped and faced the 4 nuts I need from 50mm BMS, 40mm would have done but I bought 50 by mistake so that's what they will be. Just have to work out how to machine the hex head without a index head.
I really dont like the design because the welds will be doing all the work. Granted it shouldnt be a issue but that doesnt mean I have to like it. I'm still thinking about piening the bootom and welling the top

Stuart

Hi Stuart,
Have you thought about threading the bottom of the bolt where it goes into the nut 3/8 instead of just turning it down to be a tight fit. That way it will have a bit of meat on the side of the nuts and have the strength of the thread. I am sure they would still be strong enough. If you went this way it would be up to you whether you either put a dot of weld or pein them over.

Your idea with machining the curve in the nuts is something I thought of also, and don't see why it wouldn't work. You could clamp a piece of steel to the side of the vise for a handle and for a bit more leverage. I have rounded over plenty of flat bar holding it while it rotates on a round pin in the vise, just take small cuts.

For the top nuts I would put 2 pieces of thread rod vertical each end of the vise, screw your new nut on and then a standard nut on top and lock them together. Machine your new one using the top one as a guide. When your close all round finish it up with a file.

Dave

Hi Dave I did think of that but thought the root Dia off 3/8 (only have M10) might be a little small. But I could try it. I can always drill the thread out and weld it up anyway, Would only cost me a couple of M/s bolts at worst. Besides it would give me a chance to try and pick up another lenght of 1/2UNC S/S all thread for $11

The only 1/2UNC nuts I have are flanged

I'm working on an indexing head(sort of) to finish the nuts off.

Back to the shed
Thanks
Stuart

This is another thing that ER collets would come in handy for. RC built a ER collet dividing chuck a while back for this type of job.
https://www.woodworkforums.com/f65/er...-chuck-113924/

Dave

Nice idea.
The bearing I am using to do this dividing had some sort of collect chuck fitted to a spindle(its the rusty thing to the left of the bearing in the picture,you can only see the back of it). I'm going to mount a 48 tooth change gear on an arbour to the flanged end with 1/2 unc running through to the front holding the "nut" to the front. The spindle is locked by a bolt each end squeezing the casting. The indexing will be done by a pin from the square bar on the top. Should be close enough of a nut. Being that the nut is 50Dia I'm going to make the nut the 35mm, biggest that will fit into my shifter, as the nuts can only be 19mm thick.

Stuart

Well the dividing head is ready. With luck I'll get the nuts finished tomorrow. Then I can get started on the tee nuts proper.