Aloris tool post T-nut

[Shaun5]

I bought a new lathe with a new Aloris CA quick change tool holder. The T-nut came machined by Aloris. I’ve measured the T-nut and I’m not 100% sure it is below the compound when nut is tightened down. The tool holder seems tight to the compound, but I have occasionally noticed when changing tools that the whole thing moves as the T-nut moves in the slot.

Is this normal? What are my options to make the setup more rigid?

 

[awander]

your tool post should not loosen up in its mounting to the compound when you change tools.

The toolchange tightness and the toolpost mounting tightness should be complete independent.

 

[Rudd]

deck the top of the nut down a bit, mill, or face off in 4 jaw.

 

[EPAIII]

It is not clear just what is happening. The tool holder (post) seems to be tight to the compound but you say it moves when changing tools. You can't have both at the same time.

The tee nut apparently fits in the tee slot in the compound. So far, so good.

Something must be tightening when you tighten the upper nut. But what? The nut on the top of the tool post should be drawing the nut upwards so the stud is probably not hitting the bottom of the tee slot. You could check that by putting a strip of paper in the tee slot and tightening the nut. Then take it off and examine the paper: it should not be marked by the stud. But I doubt that is the problem.

The next most likely problem would be the height of the center, vertical arm of the tee nut. Just because Aloris made it does not mean that it is correct for your lathe. Put either the stud from the toolpost or another stud or bolt in the tee nut. With the tee nut in the tee slot, pull upwards on the stud or bolt. Now, while pulling the tee nut upwards check to see that the top of that vertical arm of the tee nut is BELOW the top of your compound. There must be some clearance so that the tee nut is bearing on the bottom edges of the tee slot and not against the tool post. Nothing except the stud/nut should be above that top surface of the compound. If there is no clearance there, you need to reduce the height of that vertical arm of the tee nut.

Beyond that, I would look for burrs or other imperfections inside the tee slot and on the tee nut.

 

[Shaun5]

I think the T-nut must be extremely close to even with the compound, probably no greater than .001 in a direction (just not sure which direction)...

Is there a ‘standard’ for the topside clearance for the T-nut? What does pining the T-nut add?

 

[johnoder]

is there a ‘standard’ for the topside clearance for the T-nut?

Its top MUST be below top of compound when the clearance has been removed in the process of tightening the tool post to the compound - and clearance on the sides of the tee nut had been taken up in the process

Its easy - pull up the nut by hand until it stops and see if the "tongue" top is still noticeably below top of compound

 

[eKretz]

I think the T-nut must be extremely close to even with the compound, probably no greater than .001 in a direction (just not sure which direction)...

Is there a ‘standard’ for the topside clearance for the T-nut? What does pining the T-nut add?

No there is no standard clearance. As the others have already told you, it just needs to be below the top of the compound. It doesn't matter if it's .001" below or 1/16" below. That surface is clearance.

 

[Superbowl]

Check the bottom ot the tee nut like everyone else says. Also make sure you have enough thread on the shaft. If not install a fat washer.

 

[Homebrewblob]

If his tee nut is proud and there’s no stop to the tnut threads then he could over run the shaft below his tee nut.

Then with the shaft and nut pinned solid (incorrectly) he could of went and cranked the tool post down onto the top of the proud tee nut (not compound).

This would leave you with a falsely tight/secure tool post that may (or may not) rock/move when Disturbed.

Check that your tee nut is loose AND not proud in the tee slot of the compound.
It’s really not rocket science but with that said we’ve all overlooked things less complicated before!

I’ll always remember that time in high school when I forgot how to spell the word “of”
So I sounded it out, “oven”... “OV”? That sounds right. No ones perfect, what ov it?

 

[thermite]

I bought a new lathe with a new Aloris CA quick change tool holder. The T-nut came machined by Aloris. I’ve measured the T-nut and I’m not 100% sure it is below the compound when nut is tightened down. The tool holder seems tight to the compound, but I have occasionally noticed when changing tools that the whole thing moves as the T-nut moves in the slot.

Is this normal? What are my options to make the setup more rigid?

Send the whole dam' lathe back. Or peddle it to some other Pilgrim who DOES have at least a smattering of "mechanical aptitude".

Buy a video game or three instead.

You haven't figured this simple s**t out in under one wall-clock-minute by hand and eye?

You are clearly in the wrong line of work, and in for loooong years of serious agonizing over it!

I kid you not.

 

[donie]

OH OH! termite is acting like a bully again, better watch it little bug, I will swat you around.
Besides termite, isnt it time you plugged your 4 way toolpost, you dont need tool holders, you so smart, yuh yuh yuh!

 

[Sharps1874]

Just turn or grind a bit off the top of the tee nut, and you should be OK. But if you want to be sure that's the cause, then just mount the tool post with shims underneath and see if the problem disappears. Make sure the shims are right next to the slot, or you may break it out

 

[edwin dirnbeck]

You are a machinist.Use your head. Figure it out.This is a basic problem. If you cant figure this out yourself,you probably should not be running a lathe. They can hurt you bad. Now after you solve the problem,throw the T NUT away.Make a full size custom t nut for your lathe.Next get a piece of high tensile threaded rod from mcmaster carr . Thread the rod thru the tnut and weld it on the bottom side. FLush grind the weld. Now you have a LIFETIME PERFECT FITTING TBOLT NOT A CHEESY T NUT.I have seen and repaired many compound t slots ,that were cracked by some idiot running a bolt out the bottom of the tnut. Edwin Dirnbeck

 

[thermite]

You are a machinist.Use your head.

Well put.

But not YET, he ain't. And that IS the classical "barrier to entry".

Problem-solving aptitude ... that originates between the ears.. so hands and skill have a path to follow.

Or not...

Figure it out.This is a basic problem. If you cant figure this out yourself,you probably should not be running a lathe.

Nor even a wheelbarrow, actually...

 

[dgfoster]

I’ve posted about this several times in the past. Besides the good advice concerning tee nut height in a few of the posts above, the contour of the base of the tool post itself makes a difference in how solidly it locks down to the compound.

https://www.practicalmachinist.com/...ee-nut-fit-lathe-compound-291143/#post2376382

Since you are dealing with a nearly “sanctified” brand of tool post, you may be reluctant to alter it from its brand new “perfect” state to make it better. Too bad.

Denis

 

[Richard Winn]

prolly need to tighten the spanner nut

also debur and lube the nut itself the part inside toolpost

spanner nut will turn and release the holddown bolt/ stud

 

[eKretz]

I’ve posted about this several times in the past. Besides the good advice concerning tee nut height in a few of the posts above, the contour of the base of the tool post itself makes a difference in how solidly it locks down to the compound.

https://www.practicalmachinist.com/...ee-nut-fit-lathe-compound-291143/#post2376382

Since you are dealing with a nearly “sanctified” brand of tool post, you may be reluctant to alter it from its brand new “perfect” state to make it better. Too bad.

Denis

I was going to mention that also... It may not just be the toolpost - or not the toolpost at all, considering it's an Aloris. They are generally pretty darn good about getting things that and true. The top of the compound not being flat can also cause this issue. Check that first. Either fixing it or relieving the center of the toolpost a smidge can fix it.

 

[dgfoster]

I was going to mention that also... It may not just be the toolpost - or not the toolpost at all, considering it's an Aloris. They are generally pretty darn good about getting things that and true. The top of the compound not being flat can also cause this issue. Check that first. Either fixing it or relieving the center of the toolpost a smidge can fix it.

Even if the Aloris base is very true(very likely) and the compound is true (I had scraped mine flat to within a Tenth) the tool post will still be much more resistant to turning or moving if relieved in the center. Otherwise all steel (even Aloris steel ) will deform due to pressure so that most of the bearing occurs at the point with least leverage—-the area nearest the bolt. Transferring that bearing surface radially greatly improves its effectiveness and, incidentally, reduces the adverse effect of any unflatness of the compound.

Denis

 

[eKretz]

Even if the Aloris base is very true(very likely) and the compound is true (I had scraped mine flat to within a Tenth) the tool post will still be much more resistant to turning or moving if relieved in the center. Otherwise all steel (even Aloris steel ) will deform due to pressure so that most of the bearing occurs at the point with least leverage—-the area nearest the bolt. Transferring that bearing surface radially greatly improves its effectiveness and, incidentally, reduces the adverse effect of any unflatness of the compound.

Denis

Yes, that is so. However... With the top of the compound in good contact, a good fit on the t-nut and 4 or 5" of steel on top it isn't likely to flex much. Doesn't take a lot though if you're pushing the machine a bit.. I would not as the relief unless necessary, but that's just me.

 

[dgfoster]

Yes, that is so. However... With the top of the compound in good contact, a good fit on the t-nut and 4 or 5" of steel on top it isn't likely to flex much. Doesn't take a lot though if you're pushing the machine a bit.. I would not as the relief unless necessary, but that's just me.

I will submit that it is true that the tool post will cinch up if the compound is flat and the tool post is flat. But it cinches up more easily and more securely if centrally relieved.

I’ll grant you that the relatively tall column of the tool post probably does not deflect that much though steel is simply rubber in disguise. However the top of the compound is not nearly so thick and is also made of rubber—-cast iron rubber, but elastic material nevertheless. If you consider how the top and to a lesser extent the tool post, being elastic, have to deflect under load, getting the load bearing points distributed radially improves their ability to resist rotation substantially. I have tested this out in practice and will submit the difference is significant. I also know of one other case where a friend followed this advice and found a big difference. The amount of torque needed to cinch up the post reliably was about 1/3 that of an unrelieved post.

There is room for both opinions as there should be. Just trying to flesh out the reasoning behind my suggestion.

FWIW,
Denis