Sieg C3 Lathe 7x14 Mounting either a 4 or 5 Inch 3 Jaw

[wmgeorge]

I have a C3 Sieg lathe from Little Machine Shop 7x14 came with a 3 inch 3 jaw. I would like either a 4 or better yet 5 inch 3 jaw. The through hole on the 3 inch is way to small. Anyone used the 5 inch on theirs and can you chuck up the rated 4 inch round stock without the jaws hitting the bed?

[OaklandGB]

Measure the distance from the ways to the centerline. You can probably find a 5" chuck to mount there, but beware, the closer the chuck's outer body is to the bed, there is a limit on how big a work piece can be mounted as at some diameter, the chuck jaws will protrude outside of the chuck body and at some point, hit the bed.

I put my gloves on and measured my Sanou 5" chuck. With the jaws set even with the surface of the outer diameter, it will hold a 0.75" work piece. If it was a 1.00" piece of stock, I assume the jaws would protrude half the 0.25" increase in diameter or 0.125" With your known clearance, you can calculate an estimate of how much jaw protrusion would result in a crash of the jaws against the ways.

Please verify all chuck measurements with the manufacturer, the above are just those I found on my Sanou 5", 3 jaw chuck. I'm a rank amateur, so maybe others have a better way of figuring out how much chuck you can get away with on your machine.

Oh, on second thought, there might also be some limitations on the carriage body clearance, or your tool holder's clearance. Not sure if a 5" is also going to claim more of the bed's working length.

[J Tiers]

Most lathes have several swing ratings. Swing over bed, swing over carriage, swing over topslide. What's important depends on other factors, such as with max sized work, getting the carriage under it so you can do any actual machining.

But, with your chuck, did you get only the "inside" jaws (the ones most folks usually have on their chucks)? Because with the "outside" jaws, you can grip any size up to a diameter where the jaws are not held securely anymore. The limit vs the bed is that 2x the largest size jaws plus the work diameter has to fit over the bed (or carriage, etc).

The outside jaws should get you up to at least a 2.5" diameter, unless you really need to pass it into the chuck through hole for some reason.

[BCRider]

Measure the distance from the ways to the centerline. You can probably find a 5" chuck to mount there, but beware, the closer the chuck's outer body is to the bed, there is a limit on how big a work piece can be mounted as at some diameter, the chuck jaws will protrude outside of the chuck body and at some point, hit the bed.

I put my gloves on and measured my Sanou 5" chuck. With the jaws set even with the surface of the outer diameter, it will hold a 0.75" work piece. If it was a 1.00" piece of stock, I assume the jaws would protrude half the 0.25" increase in diameter or 0.125" With your known clearance, you can calculate an estimate of how much jaw protrusion would result in a crash of the jaws against the ways.

Please verify all chuck measurements with the manufacturer, the above are just those I found on my Sanou 5", 3 jaw chuck. I'm a rank amateur, so maybe others have a better way of figuring out how much chuck you can get away with on your machine.

Oh, on second thought, there might also be some limitations on the carriage body clearance, or your tool holder's clearance. Not sure if a 5" is also going to claim more of the bed's working length.

Yes to this. Back when I had a Myford the stock 4" chuck was missing the outside jaws. So I bought a Bison 5 inch chuck thinking I'd be able to hold some bigger items. Well it turned out that due to the jaw limit described by OaklandGB that the old 4" chuck could hold bigger diameter pieces than the 5" chuck. I still had the issue of no outside jaws so I ended up going back for the 4" Bison. And kept the 5" to use for other things.

Since the old Myford 7 has, no surprise here, swing of 7" I suspect that you'll find the same issue if you try to jam a 5" chuck onto your 7x14. The center hole might be bigger but for stuff which you could hold where the jaws stick out the 4" would be better.

Also consider that the extra mass and diameter of a 5" chuck will take longer to speed up and have a longer coasting time. By quite a bit I suspect. That might get pretty annoying in a hurry if you do a lot of stuff that requires stopping to measure stuff.

[wmgeorge]

I just ordered the 3 jaw- 4 inch one with the adapter from LMS.

[old mart]

I recon you chose the right size. 5" will fit, but take up more centre distance and you would notice that straight away. Holding large work in the 5" means being careful how much the jaws protrude and the jaws on the 4" will end up having nearly the same capacity. I have a 7 X 12 and ended up getting a better quality 80mm three jaw and a 100mm 4 jaw independent. Having the use of a bigger lathe, I was able to modify the rear of the 4 jaw to fit directly and not loose any more centre distance than absolutely necessary. I wish mine had the extra 2" between centres.

[RB211]

5" is too big from what I remember when I did it two decades ago

[old mart]

This site is worth bookmarking: www.mini-lathe.com

[BCRider]

.....I wish mine had the extra 2" between centres.

The 12" version always made me wonder too. It didn't take much figuring out that even with a fairly compact drill chuck in the tail stock and suddenly the 12" c-c ends up being more like 7 to at best 8" or so from jaws to jaws. And a 1/2" drill when in the drill chuck sticks out about 5" of that and suddenly we're left with at best 3" of actual room past the jaws for a block of metal.

The 14" or better yet the 16" versions of these machines always made more sense to me. The 14" being a little stiffer due to the length perhaps being the best of the lot. But the 16" would take that claim if correctly bolted down to a good rigid and heavy base that supported the bed against flexing.

[RB211]

I remember on Mini-lathe.com where their beginner guide said to use motor oil for way oil. I guess you really do want that detergent to cling all the metal particles together and suck them in under the ways which most likely aren't even making proper contact for the majority of the surfaces.
I stopped going there after I rear that.

[BCRider]

To be fair on a flat surface like that the swarf is going to stay mixed in with non detergent oil as well. The only proper course of action is to fit the carriage with functional wipers.

I say "functional" wipers because I've seen too many soft plastic wipers even on new machines that are not even in contact with the bed ways. They aren't "wipers" but "hover'ers"....

[J Tiers]

I remember on Mini-lathe.com where their beginner guide said to use motor oil for way oil. I guess you really do want that detergent to cling all the metal particles together and suck them in under the ways which most likely aren't even making proper contact for the majority of the surfaces.
I stopped going there after I rear that.

And way oil does NOT do that? Ummmm..... YES IT DOES, at least to the same degree that the other il would. Neither really "cling particles together", they are just sticky and hold the particles so they do not slide off the ways.. The detergent part of the motor oil acts on smaller particles anyhow. And 30wt oil is available in non-detergent, which is also used in motors and would be "motor oil". I used that on ways before getting a gallon of Vactra.

[The Metal Butcher]

I remember with motor oil and old wipers I oiled the bridgeport about every 2 hours. With good wipers and vactra, about once every 8, and it generally doesn't really need it.

[Mike Burch]

The Sieg C3 7x14 which I sold three years ago had an 80mm (3") three-jaw and a 100mm (4") four-jaw. Both were fine for that little lathe, but yes, the problem of the sticking-out jaw was occasionally a nuisance. I know that I was tempted to get a 5" chuck until I realised that the jaw stick-out would be even more of a problem.
The sad fact is that it's just a small lathe, and a perfectly fine one if used within its limitations. Eventually you'll get something a bit bigger and gruntier. Maybe next Christmas?

[wmgeorge]

Nope no more shop tools. Trying to downsize and realized that 3 inch 3 jaw was limiting what use I had of the lathe. The 4 jaw I have is 4 inch but can not find the adapter plate?? Did all those 4 inch 4 jaws need a plate??