Dumb question on R8 (i think) spindle

ddickey said:
You should really do this on the mill. Make a block for your boring bar. Put it in the vise straight up and have at it. You can set your depth with the quill lock.
Just an idea.
Click to expand...

This would be my first advice as well, with 1 caveat.

If it has junk bearings, milling it in place will permanently machine those junk bearings runout into the spindle. After that happens, you'll never have an accurate spindle again, regardless of how much you spend on bearings.

He can't put good angular contact bearings on that spindle, because it lacks the preload threads.

My opinion: experiment all you want with repairing this spindle, because in the end, you almost certainly be replacing it anyway.
 
Since you're not touching the taper the spindle can be placed in a vertical position.
Here a video of turning on the mill.
 
I had a round column Grizzly like that and replaced all the bearings in it. Unfortunately I can't remember if I had those threads.
 
There are precision AC, no-preload bearings available in that size, but they are for predominantly axial loads. Probably not the best idea for a mill spindle. Of course, neither would deep groove radial bearings, but that appears to be what it has.


For a low rpm knee mill (under 3000rpm) that may see both heavy radial and axial loads from operations such as using boring heads, and drilling, tapered roller bearings are probably best.

Tapered rollers in that size would be 30207. NTN makes them, 100$ ea on Amazon in P5 precision. They are 1.25mm thicker, but I don't think that would be an issue, as the Griz spindle has plenty of threads to accommodate the 2.5mm overall difference.


Here are the tapered rollers from NTN.

30207P5 - NTN - Precision - Factory New: Amazon.com: Industrial & Scientific

30207P5 - NTN - Precision - Factory New: Amazon.com: Industrial & Scientific
www.amazon.com

The last 2 of this type knee mill I worked on both had tapered roller bearings. One was a G0730 and the other was a Taiwan made version from KBC tools.
 
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After loosing track of this thread because, for some reason I stopped getting notifications for it, I just read the last 3 pages and have these thoughts.
Is there such a thing as an R8 reamer?
Why not make one of the popular ER collet attachments work there, if you could live with its limitations.
How did the previous owner use this thing?

Sorry if any of this has been discussed already.
 
These things are all copies of the old Clausing 8000 series mini knee mills, like the Clausing 8250. I believe back in the day, they were referred to as the "wood mill".



I used to own the version KBC tools sold, with ugly baby blue paint. It had the same threaded type spindle as the Griz version, with cheap Chinese p6 tapered rollers. The guy I sold it to got a smokin deal. The NSK P5 tapered rollers I installed after I bought it cost about half what I paid for the thing.
 
Okay I got it. I have 5C collet blocks, are those appropriate for this operation?
 
I'm not sure. What do you have in mind with the 5c collet blocks?

For holding the boring bar in a vise, and boring the spindle in-place on the mill?

If so, then yea, that would probably work as well as anything for holding the boring bar vertically.

Take off as little as possible.
 
Yes sorry I intended to quote Brinos post describing the operation but apparently failed
 
Here is a long boring bar in a 5c collet block.

Now I need to replace the bearings and have at.

IMG_0109.jpg
 
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