Horizontal mill spindle in 618 lathe?

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Chrispy

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I have a spare 618 that I'm trying to piece back together. I purchased it as a basket case and it has lived up to that description. The spindle was "converted" to a dual thread. That means that someone threaded a 1"x8 tpi onto the 1"x10 tpi nose of the spindle. :nono: Now neither TPI will thread on all the way. I have a spare spindle from an Atlas horizontal mill that has the correct 1x10 nose.It looks like it may fit - has anyone ever done this? My only other option would be to machine away the current threads and press fit a collar which I would then thread. If you aren't familiar with the 618 lathes the early models had a 1x8 spindle thread and the later models had a 1x10.
Thanks,
Chrispy
 
I have an Atlas mill headstock casting and was looking into using a 618 spindle, but as I recall, they were sufficiently different in length/different bearings/different bull gear alignments to make the idea unworkable or unappealing. Since you have one of each, you could quickly determine whether I was right, or if there's a workaround.
 
I for one would not trust a press fit spindle nose, even if you could get it close enough to zero runout to use. Replacement spindles for mills are bound to be in shorter supply than replacement 618 spindles. I would sell the mill spindle and use the funds to purchase the correct lathe spindle. I.e., anything worth doing is worth doing right.

Robert D.
 
Mr Inq - it does at first blush look close but different. I will do some measurements and report back here.

Robert D. - you make some good points that I will have to consider. I think (please correct me if I'm wrong) that the threads are just to hold the chuck on while the register ( both the horizontal and vertical faces) at the back of the spindle is what actually squares and centers the chuck. I know this has been hotly debated before but that is my understanding. My thought with the sleeve was to only do it on the buggered thread area and to leave the register alone. It would however be much easier and less time consuming to buy the correct spindle.

Thanks guys,
Chrispy
 
Chrispy,

I only have one mill manual, on the MFC/M1C/MHC. In it, there are a few parts whose part numbers begin with M6, meaning that they are also used on the later 6" lathes. But the spindle on the mill is M1-31 whereas the three 6" variants are L9-31, L9-31A and M6-31. Looking at the parts that fit onto the mill spindle, the front bearing and all four dust covers plus the back gear lock pin and associated detent spring and ball have M6 numbers. Everything else that goes on the spindle has M1 numbers. The rear bearing cup OD must be the same as the 6" one as the rear dust cover is an M6. But the cone must be different So I surmise that the remainder of the spinde is a different diameter and maybe different lengths.

My understanding of the register (round part and front of flange) is the same as yours. My reservations about turning the threads down and sleeving it are that the sleeve might come loose plus there wouldn't be much material left of the original spindle at the outer end of the 2MT hole.

Robert D.
 
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Robert,
Thanks for the info on the part numbers. Sounds like I'll be searching for a 618 1x10 spindle...
Chrispy
 
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