QCTP base question

[Tozguy]

Erik,
Not sure that you and Bob are talking about the same T nuts.
The two nuts holding the compound to the cross slide are high wear items. Mine were upgraded to grade 8 nuts and bolts. The heads of the bolts had to be machined to fit in the cross slide and slide easily in the round channel. Even though the nuts are never tightened to extreme, grade 8 bolts have closer fitting threads and wear much less.

 

[litewings]

Is there a corresponding hole in one of the lips on your compound? No there isn't. I do have the standard tool post also and plan on trying that t-nut bolt combo in the QCTP. Haven't measured the bolt yet to see if its compatible.

Did you just get the machine and the QCTP from P-M or did you score them used? Bought both new from PM

The round nut ("O" nut?) works but has less than half the contact surface as a full size t-nut has. Afraid over time it could deform the compound. And the OCD in me just doesn't like the way it looks.

 

[ErichKeane]

I'm not sure I would be too worried about it, but if it concerns you, they are easy enough to make on the lathe

I'm surprised that is the TNut that came from PM... Even the cheap Chinese tool posts come with what is just a fairly sizable hunk of steel with a bolt hole and oversized T area.

 

[Tozguy]

Being a belt AND suspenders man myself I get the OCD thing, But if the bottom of your tool post is perfectly flat (worth checking) then the area of contact as outlined with a black marker in the photo is entirely adequate. There is no deflection of the compound because there is clearance between the parts.

Note that a full contact T nut would only add contact at a distance from the bolt. There is a corresponding decrease in holding pressure in proportion to the distance from the bolt due to deflection of the T nut.

The conversion from a four way holder to a QCTP on my compound required that a new bolt be fitted to the original T nut. The shoulder on the original bolt did not work with the QCTP. But I eventually ended up using the bolt and T nut blank that came with my QCTP.

 

[middle.road]

Is there a corresponding hole in one of the lips on your compound? No there isn't. I do have the standard tool post also and plan on trying that t-nut bolt combo in the QCTP. Haven't measured the bolt yet to see if its compatible.

Did you just get the machine and the QCTP from P-M or did you score them used? Bought both new from PM

The round nut ("O" nut?) works but has less than half the contact surface as a full size t-nut has. Afraid over time it could deform the compound. And the OCD in me just doesn't like the way it looks.

I would contact P-M and ask them about it and see what they say. They may not have seen the T-Nut when it came through their shop.
It should be a full square matched to the compound IMO.

 

[bakrch]

My PM1236 (Chinese) came with the same base for the QCTP. My guess is that it's standard.

 

[Latinrascalrg1]

Look at this members recent thread, post #6, and see if there is anything recognizable!

 

[darkzero]

My PM1236 (Chinese) came with the same base for the QCTP. My guess is that it's standard.

Yep my PM1236 also came with a "round t-nut" with the QCTP that was included with the lathe. It didn't have that slot though & was in addition to the 4 way tool post & t-nut. I never used it though & sold that QCTP w/ the nut right away but it should work perfectly fine. Don't need to make a new one if you don't want to.

IIRC they include these cause they're quick to make but mainly to get the customer started so they can use their lathe right away. I could be remembering wrong though but that's what I recall. Not all people will already have a mill so this is a great courtesy which they don't have to do.

 

[LEEQ]

I have that t- bolt on my G4003. It was holding the bxa piston, Now I have it holding a bxa wedge. It works fine. I don't have a peg or detent in the hole in the compound and get along great. Try it out before you give up on it. You may discover it's more than enough before you find an easy avenue to replace it. OR, and I'm just throwing this out there, Buy a mill because this part needs made and you want to mill it. (to be fair I never said I was a good influence)

 

[Titanium Knurler]

I don't have anyone around that I know of besides machine shops in the business. Will have to give them a try to see how much $ to machine a T-nut. This nut I have is just strange. No clue what the notch is for on the one edge. Tool post otherwise seems good so far.

Litewings, I have a PM 1236T that came with a similar T-nut. It worked fine but I pretty quickly changed to a Dorian QCTP and machined my own T-nut but you don’t have a mill or a nearby machine shop so this does not seem to be an option for you. If you really want a “conventional” T-nut you can have Aloris make you one for you. I am not sure of the lead time or cost.