PM1022V Spindle Bore

Hi Guys,

I bet that a 25 mm gauge rod fits perfectly !

You might be right but this lathe is supposed to be spec'd by an American company and is being sold to the American market. If they say it has a 1" spindle bore then it should pass a 1" bar.

I have confidence that Matt will make this right.
 
I would be nervous about re-boring the spindle taper, but the clearance bore is not so critical. Go for it. 1" = 25.38 mm
0.38 mm = .38 x 0.0394 = 0.0150
M
 
You can't fit 1" bar down a 1" bore.
The bore might be 25mm but a 1" bore would still be useless for 1" stock unless it is stated a "clearance for 1" stock"
 
[QUOTE="t the clearance bore is not so critical. Go for it.
M[/QUOTE]

I agree with Mark. The through bore is not a precision deal. Measure the ID as best you can in from each end (several locations). Make up a test plug 1/64" over 1" (1.016") - see if it will start from each end, and how far it will go. Clearing out a slight amount of room would be accomplished by a number of methods. I would get a regular drill bit 1-1/64" (1.016") - you'll probably need to make up an extension, but nothing very fancy (the drill will follow the existing hole). Suggest drilling from the tool post with a fairly slow feed rate, since all the action is right at the corners of the drill, it is easy to feed to fast and chip / burn those corners.

Let us know how you make out. David
 
Hi Chipper,

I agree that a test plug could be used, but I disagree with trying to do a bore job from the tool post ! You would have to get both the hight and cross center dead on to avoid binding ! This is why I suggested doing it from the tail stock, which should be perfectly in line with the spindle bore.
 
So I just took possession of a new PM1022 and I bought I long drill rod (1" OD) to use to test the alignment and even though the PM has an advertised bore of 1" I found that I couldn't pass the rod through the bore. It ended up getting stuck about 1/2 way through.

Apparently it's not exactly 1" but a fraction less. The PM support person suggested that I could use a boring bar to open it up a little bit. Has anyone done this before?

A few thoughts on passing half way through:

Does the drill rod stop gradually or abruptly? Can it be pulled easily after stopping or does it bind? Does the end of the drill rod stop at the same point along the spindle when fed from inboard and outboard?

1. Cosmoline. I have not checked the bore of my PM so not sure if it gets coated at the factory. May be worth cleaning the bore on yours.

2. Abrupt transition in the spindle. Try putting a chamfer on the rod.

3. Gradual binding as the rod is inserted (bent spindle or bent drill rod). Indicate the rod and spindle nose.

I would not try to bore the spindle. it is too long to attempt with the tail stock and will probably void the PM "warranty". If the bore is truly 25mm the go w/ a slightly smaller OD drill rod.
 
Simply switch to a 7/8" test bar to test the lathe, no big deal, do not use drill rod. The accuracy of the seller's advertising is a separate issue. Whether a 25 mm bore (?) is acceptable to you instead of a 1" bore, only you can answer that question...

Edit: I would not try to modify the spindle bore of a new lathe.
 
Last edited:
So I just took possession of a new PM1022 and I bought I long drill rod (1" OD) to use to test the alignment and even though the PM has an advertised bore of 1" I found that I couldn't pass the rod through the bore. It ended up getting stuck about 1/2 way through.

Apparently it's not exactly 1" but a fraction less. The PM support person suggested that I could use a boring bar to open it up a little bit. Has anyone done this before?

I almost did, sort of:

The spindle bore on my lathe was large enough but it was off center.

It bothered me so I considered ways of boring it straight.

I made up a telescoping boring bar that worked well. I was able to chamfer the sharp steps (shoulders) in the bore quite easily.

But I got cold feet when it came to actually boring the full length of the spindle. There seemed to some risk of changing the stress pattern in the spindle and throwing it off. And there was absolutely nothing concrete to gain from it. So I quit while I was ahead. :)

IMG_1488.JPG


IMG_1487.JPG


IMG_1492.JPG
 
Back
Top