90's Nakamura not making a round part

358Mustang · Dec 28, 2019

My machine will consistently cut an out of round part somewhere around .0008".

I went from a piece of 2" aluminum in a chuck , to swapping the collet nose with a piece of 1" stock hanging out about 2". I still get the same result...

I also noticed that it repeats with the position of the spindle, as in if I make a mark on the spindle where one part measures high, it will repeat this...

Finishes look pretty good, but I am wondering if it is a bearing or possibly something bent?? I indicated the spindle face before putting the collet nose on and it had about .0001" run out..

If I put the indicator on the side of the collet nose and pulled perpendicular with the machine I could get it to move about .0005" and spring back.. I would think it should be rock solid there :confused:

Hardplates · Dec 28, 2019

358Mustang said:
My machine will consistently cut an out of round part somewhere around .0008".

I went from a piece of 2" aluminum in a chuck , to swapping the collet nose with a piece of 1" stock hanging out about 2". I still get the same result...

I also noticed that it repeats with the position of the spindle, as in if I make a mark on the spindle where one part measures high, it will repeat this...

Finishes look pretty good, but I am wondering if it is a bearing or possibly something bent?? I indicated the spindle face before putting the collet nose on and it had about .0001" run out..

If I put the indicator on the side of the collet nose and pulled perpendicular with the machine I could get it to move about .0005" and spring back.. I would think it should be rock solid there

Just for the hell of it I checked my supermax and with a 4' aluminum bar prying under the spindle I get a tenth or two. Doesn't move at all if I just grab the collet nose. It sounds like you have found your problem

If something was bent (within reason) I would still expect round parts....

358Mustang · Dec 28, 2019

Hardplates said:
Just for the hell of it I checked my supermax and with a 4' aluminum bar prying under the spindle I get a tenth or two. Doesn't move at all if I just grab the collet nose. It sounds like you have found your problem

If something was bent (within reason) I would still expect round parts....

Bummer, I believe that is likely the issue too.. Thanks for checking that for me, I checked an old Mori SL1-A at my work and found the same results that you did...

Seems like the bearings are shot on it? I wonder if there is any preload adjustment on the bearings. In the parts book it looks like their may be some sort of pre load collar on the end of the spindle. But I am not sure if that just clamps down on a solid collar between the bearing stack.. :skep:

Spruewell · Dec 28, 2019

I am experiencing a similar issue with my Miyano, I haven’t tried pushing on the spindle yet, but I am experiencing a .0005” out of round condition on my parts.

Hardplates · Dec 28, 2019

358Mustang said:
Bummer, I believe that is likely the issue too.. Thanks for checking that for me, I checked an old Mori SL1-A at my work and found the same results that you did...

Seems like the bearings are shot on it? I wonder if there is any preload adjustment on the bearings. In the parts book it looks like their may be some sort of pre load collar on the end of the spindle. But I am not sure if that just clamps down on a solid collar between the bearing stack..

There are guys here that have forgotten more than I know about spindles but my guess is it can be adjusted but once it starts wearing its not long for this world and adjusting it won't buy you very much time....I could be wrong tho. From my experience Nakamura lathes are really nice machines and worth putting a spindle in provided it doesn't have other major issues.

358Mustang · Dec 28, 2019

Hardplates said:
There are guys here that have forgotten more than I know about spindles but my guess is it can be adjusted but once it starts wearing its not long for this world and adjusting it won't buy you very much time....I could be wrong tho. From my experience Nakamura lathes are really nice machines and worth putting a spindle in provided it doesn't have other major issues.

I sure hope there is some adjustment, that would be awesome...

The machine works good I can still make parts, but I want round parts.. Especially when it is just solid bar, haha

Hardplates · Dec 28, 2019

358Mustang said:
I sure hope there is some adjustment, that would be awesome...

The machine works good I can still make parts, but I want round parts.. Especially when it is just solid bar, haha

There has to be adjustment for preload. Weather its a ground spacer or threads is a different story.

Delw · Dec 28, 2019

Just out of curiosty what do you get if you put a indicator on the I.d. of the collet nose and spin it by hand. not really worried about the face of it.
now put a part in machine and clamp and unclamp it(but dont turn the spindle). put a indicator on the od of the chuck or collet nose does it move?
now try it on the face

try putting a indicator on the spindle house where it mounts to the frame. see if you get movement
try it on the actuator and see if you get movement.
try it spinning by hand and not spinning also but hand pressure

Kallam · Dec 29, 2019

Spruewell said:
I am experiencing a similar issue with my Miyano, I haven’t tried pushing on the spindle yet, but I am experiencing a .0005” out of round condition on my parts.

I just replaced the spindle bearings on my lathe for the same reason .0004 runout. Triplex set in the front and duplex in the back. I was still getting a great finish just .0004 out of round part in the same spot all the way down . I thought I had a bent spindle or a chip stuck on one of the pulleys.
Well new bearings fixed it but I can't figure out with rolling balls inside a bearing why it would cut .0004 in the same spot down the length of the shaft.

If your looking for new bearings try Super Precision Angular Contact Bearings - Quality Bearings Online

Thy are based in UK and ship to USA the prices are about 1/2.
of USA
The spindle bearing i got were p3 class its a class 7 bearing but it turns round as a class 9.
I now get a 8 micro inch finish on aluminium and my parts are round. And the spindle is almost silent.

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90's Nakamura not making a round part

358Mustang

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358Mustang

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Spruewell

Hot Rolled

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358Mustang

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Delw

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Kallam

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