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SOMEONE ASKED ABOUT THE TAPER IN A JACOBS SPINDLE CHUCK

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#1
About a week or so ago, someone posted a question about what inside taper a Jacobs spindle chuck has. I was on the road, but promised to check when I
got home, since I have the part that came out of mine. For the life of me, I can't find that post, can't figure out who posted, and can't find my reply in
my content. Maybe it was lost during the server change: I don't know.

Anyway, in case the OP is still looking for this, my chuck is a 58B, and was equipped with a Morse #2 inside the threaded portion of the chuck. The OP
said that that was to make it possible to mount to the tailstock as well as the spindle. The other end of that part measures 1.024" long,
.728 at the smaller diameter, and .795 at the larger. These numbers are pretty close to what I show for a Jacobs #3. Hope this helps.
 

wa5cab

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#2
Note that it is possible that only those 58B's sold by Atlas have a taper inside of the threads. The Jacobs catalog that I have doesn't mention a taper, and I have a 58B that has a straight through hole. It is also possible that a PO bored the taper out.
 

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#3
Good question Robert. My 58B came with the Logan when I bought it. I knocked out the MT, and will use
it on the lathe as well after I can get a rebuild kit for it.

Have you ever seen an MT equipped 58B listed as an option in the old Atlas catalogs?
 

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In the catalogs, no. I don't think so. But it is mentioned in the MOLO. Page 75 in the V9's from 1968 on and page 77 in the earlier versions.. But it doesn't say what the taper is. And the MOLO mention also says or at least implies that the 59B doesn't have the taper
 

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Interesting, BUT, the OP said his had a taper as well. Maybe it was an experiment by Atlas that didn't pan out and they just dropped it.
 

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#6
No. I don't know why Jacobs doesn't mention it in their catalog, but my guess is, after again looking at their catalog, that there just wasn't enough space for them to print both 1-1/2"-8 and 3JT. Their cutaway photo of what I assume must be the 58B clearly shows the taper. They just don't mention it. As far as Atlas goes, I have an original of the Copyright 1937 V1 wire-bound MOLO that must be a 2nd or third edition and a 1988 V9 (and every version if not edition in between and they all mention it and have the cutaway photo that shows the taper. Now whether it was done at the request of Atlas or not, I have no way of knowing. But the photo in the early 60's vintage Jacobs catalog would indicate that Jacobs didn't just make the spindle chuck with the 3JT for Atlas.
 
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