D style Cam lock chuck backing plates

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Glenn Brooks
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D style Cam lock chuck backing plates

Post by Glenn Brooks »

Ok, so looking for a 12” independent 4 jaw chuck for my 14” lathe.

All the 12” chucks I saw on line were advertised with either D1-6 or d-1-8 size cams. My South Bend Fourteen lathe is set up for d-4 size cam locks, Am I correct in observing that D style cam lock backing plates are sized according to the size of the chuck? E.g. larger the chuck, larger the cam lock size??

As I read the D style chart, every size increment has a distinct, and unique, set of measurements, even the included angle changes on the registration ring,

If so, how does one fit different large and small size D chucks, to a large lathe? Doesn’t make sense....

Glenn
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John Evans
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Re: D style Cam lock chuck backing plates

Post by John Evans »

First I think a 12" chuck is too large for a 14" lathe. Trying to grab a 12"work piece with the jaws reversed most likely jaws will hit the ways. If you are looking at direct mount [ie taper and pins built into the body] that will explain why the larger chucks have the larger mounts. Simple answer is separate back plate in D1-4 and a flat back chuck, modify a 10-12" face plate to be a chuck back plate.
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pete
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Re: D style Cam lock chuck backing plates

Post by pete »

Yep I think as the chuck sizes go up so does the D series there made to use. D1-4 on a 14" lathe seems more like something you'd find on a 12" swing lathe. But South Bend must have had a good reason for choosing that. I haven't checked the exact oversize dimensions Glenn. But semi finished back plates are available. When they use that term I assume the taper and pins are already done and it's up to the end user to O.D. turn, face to dimension and drill the chuck to back plate bolt holes. Failing that there might be the only option of starting with just the raw casting and make your own. Yeah pita to get that taper match perfect. Bison while not cheap are one I know of who offer raw castings and semi finished back plates.

Some years ago there was a thread on the PM forums about using smaller than average high precision plain back chucks on at least a D1-6 or maybe it was a D1-8 spindle. Afaik nothing was ever found on the market and the thread poster ended up having to machine his own. Using smaller or larger chucks doesn't seem to be that much of an unusual requirement so it's a bit strange there's not an easier solution. Definitely not ideal because of the extra distance from the head stock bearings, but as John just mentioned you could also add a steel/cast iron 3/4"-1" thick sub plate between a D1-4 back plate and the 12" sized chuck recess. Then use two sets of bolts to adapt the whole thing together.
LIALLEGHENY
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Re: D style Cam lock chuck backing plates

Post by LIALLEGHENY »

Glenn

Most 4 jaw chucks don't require a backing plate the same diameter of the chuck. Just find yourself a 4 jaw chuck with a plain/flat back , and a backplate can be machined to fit. Backplates for D1-4 are available up to 10" diameter.

Nyle
Glenn Brooks
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Re: D style Cam lock chuck backing plates

Post by Glenn Brooks »

Thanks guys, after more research, I realized the 12” chuck I was looking at, is probably not practical due to the jaws hitting the ways, when fully extended - e.g. clamping 10” work... so the alternative is mount the wheels on an axle, or stud, and turn on centers.

On my existing Fourteen, at least, a 10” chuck seems about the largest chuck one can reasonably mount. Due to the extended jaw issue.

My old 12” Standard modern took a 12” chuck with ease. But it used d1-5 cams, which were stout Enuf for the heavier chuck and larger work holding. Wonderful machine - 1950 5 HP old school machine. But worn out and worn down from 40+ years in constant Naval and industry use. I guess that spoiled me for easy setup for larger diameter turning,,,

Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
pete
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Re: D style Cam lock chuck backing plates

Post by pete »

Old school now and I'm not sure if they were ever made in the smaller sizes to fit any lathes we have Glenn. Armstrong? I think made bolt on chuck jaw assembly's to fit large lathe face plates. I've seen the same used in old machine tool books on what were known as pit or fly wheel lathes. It's an idea worth knowing about at least since an old cheap 4 jaw independent could be cut up to do much the same if you ever got desperate enough. :-)
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