# Homemade T-Nuts



## AmericanMachinist (Sep 7, 2020)

As you may notice in one of the pictures, my current hold down capabilities consist of 3/8" carriage bolts with flats filed into the flanges.    I am turning this bar of "unknownium" alloy (something 1.5" x 0.75" with slight scale) into 14 T-Nuts for the mini-mill.

The mill I stumbled into because it was cheap at an auction... I'm starting to learn how to use it to it's strengths and for small, non-precision work it seems to get the job done.

Most of the metal removal here was with a 5/16" 4-Flute short Carbide End mill (HTC).   At one point I tried a 3/4" HSS cutter, but need to learn more technique with it...      with the 5/16" carbide tool, cuts were about 1/4" deep and 0.040" depth of cut. 

The slight chamfer on the long edges is the result of slightly engaging a ball-nose endmill.   I need to acquire a 45* cutter (other than a countersink which I have)

The holes are tapped 3/8-16, and are not through holes.  I blind-drilled 7/16" of the part's 1/2" depth with an end mill (conveniently 5/16 tap drill size for 3/8-16 threads!).  Because of the short depth only the bottoming tap really did anything, but a new USA tap cut like butter.  The remaining operation is to slit the two halves of bar apart and then separate the 7 nuts per half. ...and then cold blue them.


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## francist (Sep 7, 2020)

Interesting, I don’t think I’ve ever seen anyone mill them back to back like that. Cool. I think I see the impetus behind the new slitting saw arbor... 

-frank


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## AmericanMachinist (Sep 7, 2020)

francist said:


> Interesting, I don’t think I’ve ever seen anyone mill them back to back like that. Cool. I think I see the impetus behind the new slitting saw arbor...
> 
> -frank



If i was buying material i probably wouldn't have done it this way either.   I had this on hand that would work, and so here we are


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## AmericanMachinist (Sep 8, 2020)

Time to put the new slitting saw arbor to work!    I had to get creative with the fixturing, to get set up so the arbor could clear the fixtures.   Fortunately, I bought a package set of used 123 blocks, and two of them have all 3/8 through holes, so I was able to screw one set of blocks to the other (necessitated by the screws inserted vertically from below the upright 123 blocks into the bottom holes in the T-nuts... 





The saw is about 1/16" thick and the most I could take in a pass was about .125" deep at what I calculated to be roughly 1 IPM.   Beyond that, the mill motor would stall.   Oil helped an appreciable amount.





The surface finish....  The last pass I had to take from the back side, because the 123 blocks protruded just far enough that I couldn't make it all the way through from one side.





Just had to do a test-fit at this stage.


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## mike44 (Sep 9, 2020)

AmericanMachinist said:


> As you may notice in one of the pictures, my current hold down capabilities consist of 3/8" carriage bolts with flats filed into the flanges.    I am turning this bar of "unknownium" alloy (something 1.5" x 0.75" with slight scale) into 14 T-Nuts for the mini-mill.
> 
> The mill I stumbled into because it was cheap at an auction... I'm starting to learn how to use it to it's strengths and for small, non-precision work it seems to get the job done.
> 
> ...


I made T-nuts from scrap aluminum. I have a clamping set but needed a few extra T-nuts. I milled the channels with an end mill and drilled and tapped them for 1/2-20 threads. I bored straight thru and cut 4 burrs with a cold chisel on each t-nut. I like your idea of tapping blind holes.
I use these T-nuts to hold a post that an air valve is fastened to and an indicator for the Y axis.
mike


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## Flyinfool (Sep 9, 2020)

Curios why you went for blind holes. I hate tapping blind holes. For a T nut it is a good place for swarf to hide.

I tapped mine thru so chips and stuff can fall thru. Then I used a plug tap and stopped tapping 1 turn before full thread so that the studs would still bottom out on the last incomplete thread.


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## Bob Korves (Sep 9, 2020)

I make my own t-nuts from mild steel, and make them fit the t-slots nice and snug, but easy to slide.  I carefully debur and round all the edges.  That is way better than the hardened ones I have bought that have sharp corners, fit poorly in my t-slots, and damage the t-slots of my machines when they are tightened down.  It is really worth the effort to make them yourself...


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## AmericanMachinist (Sep 9, 2020)

Flyinfool said:


> Curios why you went for blind holes. I hate tapping blind holes. For a T nut it is a good place for swarf to hide.
> 
> I tapped mine thru so chips and stuff can fall thru. Then I used a plug tap and stopped tapping 1 turn before full thread so that the studs would still bottom out on the last incomplete thread.


Thanks for the insight.  These are my first T nuts so i hadn't thought of swarf, but i like your idea for through holes while not quite fully threading them.  

I'll see how these work and if needed perhaps drill the holes out the rest of the way. 

Thanks for the comment and the good idea!


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## AmericanMachinist (Sep 10, 2020)

In retrospect i wish i had tapped a few 5/16-18 to use with 5/16 through holes on 123 blocks.  I may locktite some 1/4-20 to 3/8-16 inserts in a couple.


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## NortonDommi (Sep 10, 2020)

I tap all the way through and stake the bottom. Studs can't go all the way through but are nice and free all the way to the bottom.


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## AmericanMachinist (Sep 11, 2020)

I finished the T-nuts this evening.  Cut, softened the edges, cleaned, and twice into cold blue.  Shown with a light coat of cutting oil applied with an acid brush.


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## brino (Sep 11, 2020)

Well done.
Thanks for sharing your build!
-brino


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## chips&more (Sep 11, 2020)

It is typical to find “T” nuts with through treaded holes. And on the bottom side of the nut, the last couple of threads are pinched. This prevents whatever is threaded into the T nut to go all the way through and jam into the valley of the T slot.


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## brino (Sep 11, 2020)

Those look great!
What cold blue process did you use?
-brino


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## AmericanMachinist (Sep 11, 2020)

brino said:


> Those look great!
> What cold blue process did you use?
> -brino


Thanks!   Cleaned with acetone and isopropyl alcohol, once into Brownell's Oxphoblue.   Scuffed with green scotch Brite which lightened them up quite a bit.  Rinsed im alcohol and into the cold blue again.   Then rinsed in water in a collander dedicated to the shop.  Air dried and brushed on a bit of oil.  I didn't scuff or buff them after the 2nd cold bluing, so not sure how quickly they will lighten with use and wear.

Edit:  i also made a mistake in not getting the tapping oil out of the threaded holes as well as i thought i did.  Unfortunately the next morning i woke to find the threads rusty.   Apparently they didn't blue as well as i thought.  I'll try to clean them and apply some more cold blue.


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## Flyinfool (Sep 12, 2020)

Blueing does not slow rust down at all. If you did not get the threads oiled after blueing, yes they would rust very quickly. Brushing the oil on you may not have oiled the threads.


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## 9t8z28 (Feb 20, 2021)

NortonDommi said:


> I tap all the way through and stake the bottom. Studs can't go all the way through but are nice and free all the way to the bottom.


How do you stake the T-nut?  I know the reason its done, just not sure how its accomplished.


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## 7milesup (Feb 20, 2021)

Very nicely done American Machinist!


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## mmcmdl (Feb 20, 2021)

9t8z28 said:


> How do you stake the T-nut? I know the reason its done, just not sure how its accomplished.


Find an appropriately size ball bearing , place in the bottom of the thread , smack the crap out of it with a good size fine adjustment tool !   This will deform the last few threads and stud will not pass thru .


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## davidpbest (Feb 20, 2021)

mmcmdl said:


> Find an appropriately size ball bearing , place in the bottom of the thread , smack the crap out of it with a good size fine adjustment tool !   This will deform the last few threads and stud will not pass thru .


And if the threads are oversized and fit too loose, just cross-thread them.


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## Flyinfool (Feb 21, 2021)

I usually stake threads with a center punch and a BFH. Don't need the "good size fine adjustment tool", save that for when you need to beat it till it fits.......


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## davidpbest (Feb 21, 2021)

Flyinfool said:


> I usually stake threads with a center punch and a BFH. Don't need the "good size fine adjustment tool", save that for when you need to beat it till it fits.......


Hack, hack, hack.  Anyone care about best practices here?


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## Flyinfool (Feb 21, 2021)

Best practice was already mentioned, tap to one turn short of going through with a bottoming tap and you will have machined exactly what you want/need without having to bend metal to make it work.

A center punch and hammer is actually quite common for staking threads on commercially made equipment. I have found it used on Lawn equipment, cars, trucks, motorcycles, and even airplanes. Yes there are also times where a press is used with a die for a mor controlled or repeatable end result. But there is not always room to do that.


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## mike44 (Feb 21, 2021)

9t8z28 said:


> How do you stake the T-nut?  I know the reason its done, just not sure how its accomplished.


I cut the bottom thread in 4 places with a sharp rap of a cold chisel on an angle, maybe 15/20°. This deforms the last thread.


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## 7milesup (Feb 21, 2021)

@American Machinist, while laying in bed this morning I was thinking about yer nuts. You could nickel plate them too. Very easy to do, they look great and will not corrode.


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## savarin (Feb 21, 2021)

I need some new T nuts and had the thought of keeping the T section as a long bar with the two studs that fit the distance between the two holes in my tool post.
The idea being that it can slide in the channel but the studs are the correct spread to just sit the tool post into place.
Can anyone see a reason this is not done?


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## 9t8z28 (Feb 22, 2021)

mike44 said:


> I cut the bottom thread in 4 places with a sharp rap of a cold chisel on an angle, maybe 15/20°. This deforms the last thread.


Ive done it this way on a couple of T-nuts but it seemed to give out and allow the stud to go all the way through after a while.  I do use my clamp kit quite a bit and after resetting the work a few times the studs eventually thread though


savarin said:


> I need some new T nuts and had the thought of keeping the T section as a long bar with the two studs that fit the distance between the two holes in my tool post.
> The idea being that it can slide in the channel but the studs are the correct spread to just sit the tool post into place.
> Can anyone see a reason this is not done?


Are you talking about a lathe tool post?


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## savarin (Feb 22, 2021)

9t8z28 said:


> Are you talking about a lathe tool post?


Actually the solid plinth the qctp sits on.
The solid plinth can slide up the cross slide


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