MT3 Cleanup

jfcayron

jfcayron

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H-M Supporter Gold Member
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FYI this is about an Atlas/Craftsman lathe, but I believe it is not relevant to the question.
If I am wrong posting here, please move to appropriate forum.
:whiteflag:

Probably going to get a "duh" answer, but I'd better be safe than sorry. :halo:
My spindle has an MT3 taper.
The spindle itself runs VERY true, but when I put in my MT3 dead center, I see anywhere between .004 and .010 runout. :yikes::faint:
I can feel small nicks inside the taper, enough to explain the problem.

Here is the question: How do I fix it? :dunno:
My first thought is to run a MT3 reamer (finishing).
But is it a recommended way, is it the only way etc?
 
You will need a good bright light, a good magnifier and a fine grit half round hand stone. Holding the stone in line with the taper, work on getting the high spots with the stone. Try your best to match the taper ( slope) so you don't gouge the "good" taper. Turn the spindle so you can work the stone in the spot that is most comfortable for YOU.

This isn't a two minute job, take your time.
 
Message received! I will start there.
Any comment on the reamer option?

Thanks!
 
Spindle should be fairly hard, MT reamers expensive. Once you hone out the lumps, you might want to lap it out with a new, known good taper on a drill or something. Just clean very well afterward, get all the abrasive out.
 
Could maybe be a bad center? Have you checked the Morse taper itself by putting a dial indicator tip on the inside?
 
I reamed my TS cause it felt kind of rough & my drill would come loose ( I always seat the drill chuck with a mallet). I got my MT3 reamers on ebay, a roughing & a finish. One is Chicago Latrobe NOS & the other is import, Interstate brand. I think I paid more for the import one which was $30 new. I reamed it by hand with support with a center in the spindle. It came out ok, much better than it was before & my tapers seat nicely now.

If you just need to clean up a few high spots & the taper is ok, a reamer might not be worth it. Might take off much more metal than needed.
 
Thank you all for the good advice received.:man:

I started by blueing the taper to locate the highs.
I scraped the spots that were all in the first 3/4" or so.
Also the first 1/8" of the taper was really messed up, so I ran a boring bar and sacrificed that part of it by boring it up one thou. Note, that reduces the fitted surface, but does not change the seating depth.

Outcome: less than half a graduation on the TDI, I believe about 2 10-thousands; I call it perfect. :high5:

One more time, thank you all for your help. I will post pictures later today.:thumbzup:
 
OK, here they are.

The "blue" is in fact red Dykem, chosen for visibility in the dark spindle.
MT3_01.jpg

Very clear mark on the center.
MT3_02.jpg

Another spot, visible in the bore.
MT3_03.jpg

After scraping and turning.
MT3_04.jpg MT3_05.jpg

The measuring setup, set to zero.
MT3_06.jpg


About 1/2 division, 2 ten-thousandths. :rocker:
MT3_07.jpg

MT3_09.jpg

MT3_01.jpg MT3_02.jpg MT3_03.jpg MT3_04.jpg MT3_05.jpg MT3_06.jpg MT3_07.jpg MT3_09.jpg
 
Thanks Jeff.
Is that a Kawa triple in your avatar? :drool:
 
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