Craftsman spindle bore question

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Oldwing76

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hello, I have a Craftsman 6” lathe ( atlas 618? more or less, with sleeve spindle bearings) .It has served me well for 30 years of hobby work but finding myself with a project that needs A spindle bore of .590”. Ive lurked here for years and thought I remembered a post of increasing the bore some. I have searched and cannot find any results. I realize the lathe is not a strongly made machine and the manufacturer determined the bore from a strength standpoint, , but what are thoughts of boring the spindle to this size? Looks like increasing the bore about 060” in diameter. Thanks for any replies.
 
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The small end of a #2 Morse Taper is 0.572, so boring the spindle out to 0.59 would effectively shorten the length of the taper somewhat (about a third of an inch if I'm calculating it properly.) I'm not sure what the real world effect of that or the thinning of the spindle wall would be; I'm just saying....
 
The OD on my MK2 618 is about 0.870", but there are some retaining ring grooves at the pulley end that would have to be considered. A long time ago, when I was into minilathes, there were a number of guys who wanted more spindle capacity and they reamed their spindles. 0.590" is just under 15mm, so that sized reamer might work. There are YT videos out there on enlarging the minilathe spindle as well as discussions on the Groups.IO minilathe forum.

Minilathe tailstock rams have an MT2 taper and I could get a 1/2" capacity chuck on the one I had. The 618s have an MT1 taper. Fitting that large a reamer on the 618 tailstock could be a challenge, as would reaming the spindle. 0.060" is likely too heavy for a single pass with a reamer. Probably have to do it incrementally with drills, but they would have to be long drills. Boring would be a problem due to deflection.

How long is your workpiece? What about holding it in chuck and supporting the outboard end in a steady rest?
 
I have an air rifle with heavy pitting in the last 3” of the barrel. Barrel with breech is 18” long. It’s a fairly high quality gun and shoots badly due to the pitting. I’m thinking of trying to counterbore the barrel. Thanks for the replies
 
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I don't recall the thread that you think that you recall (which doesn't mean that it didn't exist). But what are all of the dimensions of the part that you need to make and how many parts need to be made? On the other hand, if there is a good reason, for making the parts, probably a better idea would be to buy a larger lathe. I forget the exact dimensions at the moment but both the Early and Late Atlas and Craftsman 10" and/or 12" have greater than 1" bores
 
I have only the air rifle barrel project in post #5. The barrel’s diameter is 0.588” . I could take it to a shop but I would rather give it a go. A larger lathe isn’t in my future. Maybe 50 years ago but not now.
 
Are you trying to repair it or make a new barrel?
What is the OD, ID and length?
What happened to the original?
 
Oldwing76 said:
I have an air rifle with heavy pitting in the last 3” of the barrel. Barrel with breech is 18” long. It’s a fairly high quality gun and shoots badly due to the pitting. I’m thinking of trying to counterbore the barrel. Thanks for the replies
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I find a steady rest works well without the need to jam your work through the spindle. Assuming you have enough bed length to manage the 18" barrel plus tailstock. Either use a boring head in the TS or just adjust the TS with the alignment screws to make your cuts using a boring bar. You'll have plenty of cross-axis working range to make such a small bore cut using either method, you don't need the carriage to do it.
 
wa5cab said:
but both the Early and Late Atlas and Craftsman 10" and/or 12" have greater than 1" bores
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I’m sorry but that’s not correct. Atlas 10”and 12” came with a 25/32” through bore. AFAIK it never changed throughout the history of its production.

Not that it matters, since the OP isn’t gonna get one.
 
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