Seeking dimensions advice BXA & CXA

[1949DC]

First time purchase of QCTP. My center height from compound rest to center of spindle is 1.65” 15” swing. I looked for info on the Aloris sight but I’m not finding range of height adj of tool holder. I did find good info on Shars site. Assuming the clones are all made with near physical sizes it would suggest my lathe will take either a BXA or CXA. My concern using CXA would be more over hang and reach. The ranges according to Shars is following: BXA range is .7 to 2.2” dead center is 1.45” A CXA range is 1.125” to 2.125” dead center is 1.625” Given my center height is 1.65” this would suggest the holder is centered better in the CXA. BUT the CXA has a larger foot print and overhangs from center ie: original lantern post mounted dead center of compound. I am not finding dimensions of the difference between BXA and CXA tool holders for Length. My T slot and base of compound rest would accommodate either post but I’m questioning the added expense and / or benefit of a larger post.

[NP317]

My 14-40 lathe has a BXA quick change tool post. It is robust and has work well for all my applications.
The tool holders usually position mid-adjustment range to align the tools at spindle center.
Unless you plan on doing some very large-piece machining that requires the extreme range of the lathe, the BXA should work for you too.
RussN

[AllenH59]

I have a 16" Indian lathe, and it has step on on the compound slide, and I have to use a BXA on it. Which is really ok, as the lathe is only stiff enough for BXA tooling anyway.

[1949DC]

If a BXA moves the cutting tool closer to center of the compound than a larger post like a CXA then I’d be better off staying with the smallest size. Only drawback is that the size of tool is limited but maybe that’s a good thing. My search finds many threads about the desire to move into the largest tool post possible but little to no mention of reduced rigidity having the tool hanging more off center and furthermore so much is made of the lathe swing size. Even the mfg. state swing size more than center height. On top off that if the lathe isn’t rigid enough and using larger cutters the problem is magnified. ie; Its not wise to extend the boring bar or lathe tool out further than is required regardless of the size of “ SWING” . Maybe I’m looking through the telescope a bit different than most.

[Steggy]

First time purchase of QCTP...

I'd go with a BXA for your lathe. Typically, BXA posts are used with lathes having a 10" to 15" swing. I think you will find the CXA post a bit cumbersome on your machine.

[armscor 1]

What size tool holders, mine are 3/4", that will dictate size of QCTH.

[1949DC]

Tool size is wide open for purchase yet. I have found oversized BXA holders that will accept 3/4” if needed. The BXA size is what I’ll buy. I don’t understand comments made that a larger post will be more ridgid given the reasons I’ve explained. I’m thinking out loud on this forum and thought I was missing something.

[Steggy]

Tool size is wide open for purchase yet. I have found oversized BXA holders that will accept 3/4” if needed. The BXA size is what I’ll buy. I don’t understand comments made that a larger post will be more ridgid given the reasons I’ve explained. I’m thinking out loud on this forum and thought I was missing something.

Ultimately, the rigidity of the QC post is determined by the diameter of the hold-down stud, since it is the stud that has to resist the bending moment that occurs as the tool bites into the piece being machined. A quality BXA post will ship with a 5/8" (or thereabouts) stud, which will give you ample rigidity.

BTW, many QC posts are shipped with a "blank" T-nut. A hole will have been tapped for the hold-down stud but the "wings" of the tee may not be present. If that is the case, you will have to machine the nut to fit your compound.

[whateg0]

I know a guy who runs a smaller KDK size than recommended because it lets him put the tool closer to the compound. He had to shim the tool post up, but that's easier than trying to get it lower. I am quite happy with the BXA on my 10ee. Decide what size of tooling you want to use and then take some measurements to see which one works best for you.

Dave

[whateg0]

Both of my tool posts were bought used, so the nut that came with each was worthless. I welded a bolt into a piece of steel and use a nut on top. I don't know if it's any better, but it works and is easier to use, IMHO.

Dave