Phase II QCTP. Not what I expected.

I have BXA and CXA from the guy in Illinois. You might need to clean and lube.
Dan Coleman
 
Once a thread is tightened there is no "freedom" of movement! Chatter has to do with flex more than anything. Perhaps you could get some flex by great changes in the stress on the threads causing them to stretch within their elastic limits. Another source could be that the male & female pitches are slightly different so that only a few threads are being stressed in tightening. That would put those threads into a state similar to a spring. It would require a fairly sloppy fit or a shallow range of engagement.
I suspect that the majority of problems with chatter is long tool stick-out or cutting edges that are too rounded for the depth of cut. Another source, the compound being extended too much for the forces being applied.
Like you said, lots of potential causes, maybe several interacting.
 
Larry42 said:
I watched the video, BUT I don't seem to understand why the "slop" that he measured would matter.
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As far as functionality goes it does not. Nothing wrong with improving the fit but you will always need some play to prevent binding of the worm.

The import manufacturers use much looser tolerances to ensure the parts fit together but not necessarily fit well.

Where I have found the most of the excessive play with import tool posts is the fit of the gib to the gib slot, fit of the gib teeth to the worm, the fit of the worm bolt to the worm and the fit of the center bot to the worm bolt. The later two can be improved upon but not the first two.
 
Thanks for watching the video. The original complaint was regarding the play of the mechanism, specifically the round part. That is the same play I had. Hope this helps.

Larry42 said:
I watched the video, BUT I don't seem to understand why the "slop" that he measured would matter. Seems like what matters is the movement of the tool holder when the wedges are tightened. My lathe/tool post is Chinese. I wiped the wedges & tool holder sort of clean. Mounted my dial indicator to a mag base mounted on the cross slide. Tightened the holder lever and measured the change. That would be the relationship of the tool to the cross slide, .0003". I repeated the process several times getting very nearly the same answer every time.
Then I tried loosening the tool post, pivoting and returning, tightening. I got about .0003 in the opposite direction. I attribute that to the fact that the "TEE" head of the post that goes into the cross slide is quite a bit thinner than the slot. Probably one of those universal fit things. I could make a new Tee bolt if that .0003" got to bothering me, BUT since it doesn't hardly vary from one tightening to another....
I've not had any problems with chatter or a nub when parting off or facing why worry about .0003" and just compensate for it if you can/need to.
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If you disasemble your QC to lube, remember all of the parts are "timed" to go back correctly. You may need to install the "scroll? a few times to get it correct.
Just saying.
Dan Coleman
 
That was very revealing to see the innards of the tool post, thanks for posting. I have an older (offshore) piston style purchased long time ago before I knew there was a difference or advantage to wedge. Its remarkably consistent which maybe suggests I got lucky & build quality trumps style. Its the usual crap shoot. Anyways good job on figuring it out. Unrelated but I liked your spindle replacement vid too btw. Keep up the good work!
 
Thanks for your kind words.

petertha said:
That was very revealing to see the innards of the tool post, thanks for posting. I have an older (offshore) piston style purchased long time ago before I knew there was a difference or advantage to wedge. Its remarkably consistent which maybe suggests I got lucky & build quality trumps style. Its the usual crap shoot. Anyways good job on figuring it out. Unrelated but I liked your spindle replacement vid too btw. Keep up the good work!
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It is all about what you are used to I suppose. Our manual shop has CXA all the way up to EA in Aloris, Dorian and DTM, so that is what I was used to when I got my PM1236. If this wasn't the case I would probably have no desire to change anything.

The QCTP that came with it is surprisingly repeatable minus the bit of slop that was addressed in the video on the last page. I just have a need to have higher quality stuff I suppose. Call me a princess, but I will gladly pay $450 or so to get a quality BXA at some point.
 
COMachinist said:
I have found it depends where you buy it counterfeiting is not a crime over there. China’s industry are owned by the Commie gov. So they are all phase II no mater who makes them. Most of the factorys are owned by the Army and the stuff from them is junk. The ones that work with the supplyer/resellers tend to be better quality. The BXA I got from PM with my PM-12x36t was junk, it now has my Alais BXA. Untill you have a really top quality QCTP you will always have problems with registration, finish quality and repeatable tool changes. I know there are some China QCTP that do a passable job, but for the most part they don’t. Least ways the the 4 I have in the junk pile don’t, by buying top quality I only cry once.
Good luck
CH
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Wow all of a sudden I don't feel so good... My PM-1236T will be here in 2 months loaded with PM-BXA junk... As far as I know I don't think I can cancel the stuff... K ima go hide and cry now..!
 
Mr Mike said:
Wow all of a sudden I don't feel so good... My PM-1236T will be here in 2 months loaded with PM-BXA junk... As far as I know I don't think I can cancel the stuff... K ima go hide and cry now..!
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That post was also from almost 4 years ago. Who knows now. Give it a chance and go from there.
 
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