QCTP Base

J

jonathan01

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Hello, on my QCTP, the base the slides in the T-slot in my coumpound rest doesn't fit. My lathe came with a 4 way, and a QCTP, the bottom half of qctp base is 0.030" thicker than the 4 way base is. Would it be better to have the whole bottom milled down, or have the two lips milled down?

View attachment T-POST.bmp
 
Just dealt with this yesterday, I milled everyting on the top side because it was all too big and taking anything off the bottom won't keep the top of the T nut from being too high to tighten (it may contact the base of the holder & not pinch the compound) good luck
 
From your inquiry I assume you don't have a mill. If you have a 4 jaw you could chuck it up and face the bottom and then the top if it projects up to far. Kinda depends how large your machine (lathe) is. Possibly you can do it with a 3 jaw but that might get a little hairy if you're not careful. Now you've got a reason to get a mill ! Never ending quest for more tools.
dickr
 
I have a 1340 lathe and a 4 jaw chuck, but I don't have shims or anything to set the tool height on the 4 way post.

I think I will just mill the bottom down. I don't have to worry about the top being too tall, I have enough space for it to tighen down.

Thanks
 
How critical is tool center for facing the bottom of the base? Being that the base has a hole in the center, the whole thing will get faced.

I may try putting it in the 4 jaw, and face it. I could adjust the base in the 4 jaw to get the center fairly close.

Thanks again
 
I'm not sure I understand your ? But when you mount the base in your 4 jaw the hole in the center should be within .015. The closer the better, under by a few thou is better than over. You can take a parallel or similar and rest it on the face of the 4 jaw and your base so the face of the base is also parallel. It (base) will have to stick out enough for the facing operation. I'm not sure if this confuses it more or not. Hopefully better than smoke signals. Holler if it doesn't make sense.
dickr
 
dickr said:
I'm not sure I understand your ? But when you mount the base in your 4 jaw the hole in the center should be within .015. The closer the better, under by a few thou is better than over. You can take a parallel or similar and rest it on the face of the 4 jaw and your base so the face of the base is also parallel. It (base) will have to stick out enough for the facing operation. I'm not sure if this confuses it more or not. Hopefully better than smoke signals. Holler if it doesn't make sense.
dickr
Click to expand...

What you are saying is put the base flush with the 4 jaw and it should be square within 0.015", right?

What I was asking was about the tool height. If I face the qctp base on my lathe, I have to do it with the 4 way post, which I don't have shims to adjust my tool height with on the 4 way.

How close to center does my tool height have to be for facing the base?
 
Not really all that critical considering it has a hole, and you won't need to face down to zero diameter. But you need to be below center, if anything, never above. And the face you will machine will need to be out past the jaws, that's that dickr was also pointing out. You will need machine access to the entire surface without hitting the jaws.
 
Like Tony said it's not necessary to be right on center just not above. But your QCTP base (body) must be square (perpendicular) to the side of it or the center hole. Other wise your QCTP will sit at an angle on your cross slide. You'll have to dig up some shims or a block to hold your cutting tool solidly while cutting your base. This is where your ingenuity comes in to put that together for a one time shot.
If you don't have an indicator you could use your tail stock with a live or dead center to align the tool post. once it's tight you can back it off. Just be careful as you face across. Light cuts
More Greek huh ? At least we're not the Israelis and Palestinians trying to figure it out. We'll keep trying.
dickr
 
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