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PM1022V Spindle Bore

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neodem

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#1
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?
 

BaronJ

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#2
Hi Neodem,

Probably a nominal figure. You could take a boring bar to it and open it out, but I wouldn't. Also it could be that the bore is actually 25 mm, which it probably is if its a metric lathe. In which case its the nearest conversion value to inch.
 

neodem

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#3
Just curious why you would advise against opening the bore. Is it because I could damage something easily? I would imagine I would only need to take off .001 or so..
 

BaronJ

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#4
Hi Neodem,

Chatter ! The only good way to open that bore a few thou would be to take the spindle out and either line bore it and hope you get a good finish or have it ground. Its just not worth it !
 

mikey

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#5
Just curious - what is the OD of the bar you used?
 

DHarris

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#6
+1 to Mikey - also, is your bar perfectly straight?
 

pdentrem

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#7
Use a brake cylinder hone. It will take some time to do the job, at the same time it will smooth/polish the surface!
 

T Bredehoft

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#8
Be aware, some commercial drill rod is centerless ground. I've found that I can turn (skin cut) drillrod and leave lands uncut while taking off .0005 to .001 on the in-between lands. Thinking about this, it was on my Clausing/Atlas MK2. Can't believe I did work this accurately.
 

BaronJ

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#9
Just curious - what is the OD of the bar you used?
Neodem wrote the OD of the bar he used in his initial post !
 

mikey

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#11
Okay. I don't assume without verifying but that's just me.
 

mikey

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#12
I decided to elaborate. If I just spent a couple thousand dollars on a new lathe and it didn't pass a 1" bar through the spindle as it is specified to do, I don't think I would accept being told to bore it out.

In order for PM to say it has a 1" spindle bore, it is understood that it will allow a 1" rod to pass. That means the actual spindle bore must be larger than 1". The only way a 1" bar will not pass is if the spindle bore is exactly 1" ID or smaller or if the test bar is significantly larger than 1" or if the bar is not straight. Personally, I would confirm the OD of the bar and put it in V-blocks to confirm it is straight. Then I would call Matt himself and discuss options with him but boring or honing it out is not reasonable on a new machine.

And as an aside, I would not use drill rod for alignment. I would use Thomson linear shafting. It is case hardened, round, consistent in size and is straight. Drill rod has too many variables, straightness being an important one.
 

neodem

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#13
Thank you for saying that. I kind of agree. This was a giant purchase for me and after the hell of getting the machines into my basement and mounted on my benches I can't imagine returning them. So I figured that I'd act like a hobby machinist and fix the issue on my own.

The idea of the v blocks is a good one. I will buy some and measure again. But I'm pretty sure the OD is correct.
 

mikey

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#14
Your first lathe is not only a major purchase in dollars; its a big deal in your hobby career. The lathe should work as specified. I think a discussion with Matt is in order because fixing this issue is not a little thing.

Boring it is not realistic. You need a 3/4 to 7/8" carbide bar (major bucks, and you actually need to know how to bore) due to the size and depth of the bore, and that will only get you halfway into the bore; you can't bore the other half, at least not accurately. Honing might work better if you can find an extension to go 8" deep and hone from each end.

Do you not have a micrometer to confirm the OD? How about a decent dial or electronic caliper? Just something to measure it so you can tell Matt that the test piece was confirmed to be 1" OD.

Correctly checking for straightness requires V-blocks, a surface or height gauge, an accurate indicator and ideally a surface plate. In your shoes, I would just find a really flat surface and roll the rod on it to see if it jumps. I have seen drill rod with significant warpage, which is why I suggested linear shafting instead.
 

neodem

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#15
I have a regular caliper but not a micrometer.. (I bought one but it hasn't arrived yet). I do have a few nice indicators and a surface plate so I feel like I can come up with a way with vblocks to check the straightness.

Is Matt the owner of PM? I've been just dealing with people via emails..
 

mikey

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#16
Yup, Matt is the owner and you should be speaking to him. He has an outstanding reputation on this forum. I'm sure he will make things right.
 

BaronJ

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#17
Hi Guys,

I bet that a 25 mm gauge rod fits perfectly !
 

T Bredehoft

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#18
Hi Guys,

I bet that a 25 mm gauge rod fits perfectly !
That would leave about .016 to remove, too much to ream, but a 1" drill should work well, if it's long enough.
 

BaronJ

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#19
Hi Tom, Guys,

A "D" bit would laugh at taking off 16 thou, and could easily be done from the tailstock.
Lots of lube and a nice slow feed !
 

Janderso

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#20
Drilling out a spindle bore on a new lathe or any lathe without proper "line bore milling" set up and equipment would scare the hell out of me.
I am leaning toward PM products down the road. This post concerns me. If it is a metric size, they should advertise the correct spec.
My 2 cents.
 

mikey

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#21
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.
 

markba633csi

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#22
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
 

magicniner

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#23
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"
 

Chipper5783

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#25
[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
 

BaronJ

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#26
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.
 

bretthl

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#27
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.
 

Bob Korves

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#28
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.
 
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Bob Korves

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#29
Where on earth did you get that from?
No wonder the USA has problems with the Metric System! :D
25.4 mm = 1" -- exactly! I think Mark's error was just a typo, he knows better...
 

Tozguy

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#30
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. :)
 

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