3 jaw questions

Brian, what did the dykem show?
There are quite a few nicks on the backplate so it might have been mistreated. Or maybe the backplate was not machined well enough to fit the spindle properly.
Either way why not remove the back plate and chuck it in the 4 jaw. Check concentricity and square of the register surfaces and threads. Single point the internal threads a bit to get better clearance and concentricity. The thread fit is not critical. The register surfaces are. To me this a great learning opportunity for you.
 
I googled metric size X8 but didnt turn anything up. Where can I find info on it?

That is one of the problems it is off sized and cannot find anything about it I finaly found some information on some of it by searching the web. But found nothing specific. I made a plug to test with, It is not real acurage but enough for me to check ones I find. The regiser area is about 51or 52 mm or 1.8 something inches. The threads are under that when measured. Some people call it a 2 inch x8 tpi also. I have two Taiwan made 10X24s one is a Jet 10X24 PY that has this spindle.

If you have anything that screws on, Then check things against that, then try the Dykem and see where you are hitting.

Ken
 
What is the thread minor diameter measurement of the chuck backplate in question?
 
To me this a great learning opportunity for you.

Yes it is, I've already learned a lot! I do not have any thread wires, might need to get some. The lathe itself is still at the sellers place(10 minutes away, I took only the accessories home), I'm going over there later on to check the spindle size on it and take a face plate that fits my lathe spindle and check with that.
Brian
 
Last edited:
Sorry I though you had them both at the home already. YOu are doing smart taking one that fits your other lathe that you know what it is them.
 
I went to check out the lathe( cz300), took the back plate I removed from the lathe's chuck and a face plate from my 12x36 Jet(a known 2 1/4 8tpi). The backing plate spun right on, smooth and no resistance. The face plate would only thread on a short distance, then resisted in the same manner the back plate does on my Jet. My thread gauge showed a perfect fit for 8tpi so....sorta strange. I googled cz300 and found a lot of stats but no mention of spindle thread size in any manual or manufacturer spec sheet; I did see someone on a forum state it is 2 1/4 8tpi but that doesn't seem to be the case. If I find anything out I'll post here. I'll also watch some inter web vids on how to use thread wires.

Brian
 
if i'm not mistaken, i remember seeing somewhere that 58mm x 8 tpi was the spindle dimensions
i have a shenwai 1236, i should pop the chuck off and see if i can verify.
 
A 3mm thread is so close to 8tpi it is hard to see with a thread gauge. And 57mm= 2.24409
 
Last edited:
So basically we know that the CZ300 spindle does not have the same nose thread as your other lathe. If interchanged parts only go on a turn or two then it seems to me that we have a close enough diameter but with a different pitch, although not by enough to see with a thread gauge. Chances are using wires to measure pitch diameter will not show much if the problem is actually thread pitch.
 
if i'm not mistaken, i remember seeing somewhere that 58mm x 8 tpi was the spindle dimensions
i have a shenwai 1236, i should pop the chuck off and see if i can verify.

So basically we know that the CZ300 spindle does not have the same nose thread as your other lathe. If interchanged parts only go on a turn or two then it seems to me that we have a close enough diameter but with a different pitch, although not by enough to see with a thread gauge. Chances are using wires to measure pitch diameter will not show much if the problem is actually thread pitch.

Ulma Doctor, that would be great if you can do that.

Tozguy, yep, but thats better to know than thinking a broken thread is the causing the problem(I've learned a lot here). The cz apparently has some gear issues which I knew about before purchase. I bought it for parts, probably to difficult to sell as is, thinking I may part it out. I've not machined a back plate for a chuck so I may give that a try for the cz chuck, or find someone with the same dimension spindle and sell it.

Brian
 
Last edited:
Back
Top