Rockwell Jawhorse for Outboard Turning

[dkerfoot]

I am carrying this over from another thread where the merits of the jawhorse are debated: http://www.bt3central.com/showthread.php?t=48480

I have been thinking of getting one, but can't decide if I want to pull the trigger. I have also been looking at doing some outboard turning on my Shopsmith MK5 (I have the speed reducer).

In my search, I started looking at the base of the Vicmarc outboard tool and started thinking about how it bore a resemblance to the Jawhorse....

My first thought would be to simply grab the vertical post of the standard Shopsmith tool rest with the jaws. It would be even better to mount the toolrest off to one side of the jawhorse so I wouldn't have it in the way. I could pick up an old SS carriage to do so. Alternatively, I do also have the new Universal Toolrest (3rd image) that mounts over the carriage. I could attach it instead to 2' long 4x4 and clamp the free end of that in the Jawhorse.

Does anyone know the height (to the top of the jaws) of the jawhorse? Is it 34"?

Any thoughts? Is there something I am not thinking about? I have never done any outboard turning, so advice is appreciated!

[Uncle Cracker]

Does anyone know the height (to the top of the jaws) of the jawhorse? Is it 34"?

According to the Rockwell knowledge base, it's 35" tall...

[affyx]

In order to outboard turn on the shopsmith, wouldn't you have to remove the carriage assembly to move the head unit (and speed reducer?) all the way to one end? And even then, have to extend the quill a bit?

Presumably this would be to turn something beyond the 16" swing of the SS, unless it's relatively thin stock (like for a big platter) won't you be hanging a lot of weight off the right-hand side? (By "right-hand side," I'm assuming you are facing the speed control and the quill extends to the right.) I'd be worried about the whole thing tipping and therefore would probably weigh the left side down with sandbags or something (how much weight can the waytubes handle?). Also I'd be concerned about how much (unbalanced) weight the quill could handle.

Neat idea; I'd also want to hang some cement bags from the rockwell to try to minimize it "walking" from the vibrations coming through the tool.

It's a noble effort & creative idea! If you go for it, please post pics of you setup.

[dkerfoot]

In order to outboard turn on the shopsmith, wouldn't you have to remove the carriage assembly to move the head unit (and speed reducer?) all the way to one end? And even then, have to extend the quill a bit?

Presumably this would be to turn something beyond the 16" swing of the SS, unless it's relatively thin stock (like for a big platter) won't you be hanging a lot of weight off the right-hand side? (By "right-hand side," I'm assuming you are facing the speed control and the quill extends to the right.) I'd be worried about the whole thing tipping and therefore would probably weigh the left side down with sandbags or something (how much weight can the waytubes handle?). Also I'd be concerned about how much (unbalanced) weight the quill could handle.

Neat idea; I'd also want to hang some cement bags from the rockwell to try to minimize it "walking" from the vibrations coming through the tool.

It's a noble effort & creative idea! If you go for it, please post pics of you setup.

Great questions and I have answers for most of them...

I did some testing and found it works to mount the speed reducer all the way to the right, then extend the quill across the carriage to power it. This leaves the headstock a fair bit back from the right legs, especially since they flare outward. The weight would be born by the speed reducer, not the quill. If you look at it from the side, most of the weight would be born directly over the right leg because it extends out at an angle. Plus, I always keep my bandsaw mounted on the left side which adds much needed mass and in this case should keep it from being tippy.

I am primarily thinking of doing platters and fairly shallow bowls outboard. With this setup I doubt I'd ever attempt a deep vessel.

The part that isn't so obvious to me, never having used an outboard toolrest, is how much torque is developed from the tool meeting the wood when the toolrest is not part of the lathe. It seems to me that because of the direction of spin, the forces would be trying to lift the right end of the shopsmith. My concern would be if it makes the whole unit shaky.

The shopsmith drive shaft is at about 39". I have found two references saying the Jawhorse height it 34", but that might be to the top of the platform, not the jaw? In any case, a workable solution for that height should be possible. Soon, I am hoping to build a heavy rolling base to replace the SS legs. I'd make it about 2" taller to put the lathe at a more comfortable level. (I never use the TS because I have a CM 21829) The SS is my lathe, bandsaw, horizontal drilling and sanding station.

.

[Uncle Cracker]

The part that isn't so obvious to me, never having used an outboard toolrest, is how much torque is developed from the tool meeting the wood when the toolrest is not part of the lathe. It seems to me that because of the direction of spin, the forces would be trying to lift the right end of the shopsmith. My concern would be if it makes the whole unit shaky.

With a detached outboard tool rest, the rotation of the work will be trying to a) push the tool rest down into the earth, and b) trying to lift the lathe off the ground. Assuming the tool rest isn't going anywhere, then yes, the force (and subsequent vibration) will be felt in the lathe. This is why many folks with lathes drape sandbags over the crossmembers on the legs, or build underboxes in which they stack bricks or pile sand. Otherwise, the machinery can literally walk across the floor...

Also, here is the Rockwell link where I found the 35" height reference...

[dkerfoot]

If anyone is interested, I snapped a couple pictures of the SS set-up for outboard turning. It is a little hard to see because of the cluttered background, but the chuck is positioned far enough out to give a swing of about 32" - way bigger than I'd ever even think of attempting.

[affyx]

Nice setup!

[guycox]

The outboard turning that you are describing is not going to require a complex toolrest setup -- so you might actually be able to get by with a big plywood box filled with concrete holding a metal pipe that is sized to post of the toolrest. The extra little piece on the delux rest could be used to give you a bit of fore-aft adjustment. If you designed it just-so you could acutally fasten the end of the SS to the box ( maybe with a couple of really large U bolts) - to really beef it up and to make it all seem like a single unit.

At least you aren't going to have flip-flop all you skills as a normal outboard turner would -- this needs another name rather than outboard ( back of the headstock) -- so maybe offboard.