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Chinese 3-in-1 toolpost mounting.

Posted: Sun Jan 22, 2012 10:32 am
by Torch
I have the archetypal Chinese machine that the BB3323, G9729, HF44142, et. al. are based on. One of the great mysteries of life is the interface between the tool post and the table. As those of you with one of these knows, the table has two slots -- one on either side. The tool post has one set of keys right down the centre, so that it can either be mounted to the left side of the table or to the right side of the table -- and either way a significant portion overhangs the side of the table! In my case, the accessory lead screw protectors prevent the table from travelling all the way to the chuck, so if it is mounted in the right slot it the tool can't reach all the way to the chuck (even with a QCTP mounted). And if it is mounted on the left slot, even a live centre mounted in the tailstock won't reach as far as the tool.

What's really needed is a slot down the centre of the table, but of course, the cross-feed screw mechanism is in the way since the table is too thin. Well, they have adapter plates to mount various chucks, right? Why not an adapter plate to mount the tool post? Something with the bottom keyed to the existing table slots:
But with the top grooved down the centre:
No need for t-nuts, just tapped holes aligned to the centre of the mounting ears:
Now the tool post has better overall support, the tool bit reaches the chuck and the tailstock centre reaches the tool. With the compound raised by the thickness of the adapter plate, the shim block under the QCTP was no longer required. So less leverage is applied at the base of the post -- it has been transferred to the base of the compound, which of course is significantly wider.
I also took the opportunity to dump the stupid riveted degree graduations label and engrave the base itself.
(just don't examine my stamped numbers too closely. I really need to make some sort of a jig before attempting to stamp a round surface again!)

Re: Chinese 3-in-1 toolpost mounting.

Posted: Tue Jan 24, 2012 12:31 pm
by ken fox
Interesting--From the pictures I have one that is pretty much the same and I've been thinking along the same lines. What material did you use for the adapter plate?
That hybrid milling vice/compound rest in one of your pictures is a big pain when the vice jaw interferes with the work. I finally cut off the vice jaw so I could properly use the compound rest and bought a couple of milling vices. I also made a big ugly tool post which works very well for axial or radial cutting, ( not for tapering).


Re: Chinese 3-in-1 toolpost mounting.

Posted: Tue Jan 24, 2012 4:35 pm
by Torch
The adapter is just milled from a piece of HR. A36, I think. I'm quite pleased with where the compound is positioned now. Much more convenient and I think it also aids in rigidity, although I haven't really put that to the test yet. I was pushing it a bit yesterday, peeling off hot blue chips with M42 tooling and getting a very nice finish, but that was on O1, which has always been a nice material to work with. I'll have to try it on a piece of Monel that was frustrating me previously.

Someone else mentioned cutting off the stationary jaw, and I thought about doing that. However, with the BXA tool post, it's not really in the way and I like to clamp it tight for additional rigidity when I'm not actually feeding with the compound. As a milling vice, it's pretty much useless. I've used it once or twice to hold something steady for drilling some quick holes (popping the toolpost off only takes a moment and is quicker than installing a milling vice).