I’m designing a small vice to use with my Shapeoko and came up with a fairly simple design that I have seen done before online.
The only tricky bit is that I need a lead screw that has a thread that starts from each end and meets in the middle. i.e. left hand on one side and right hand on the other side.
anyone have any idea where I can find one of these?
They’re used in hand screw clamps, and some woodworking shops sell kits to make them:
http://www.leevalley.com/us/wood/page.aspx?p=69826&cat=1,43838,47843
I needed a clamp to hold a small (repetitively used) part on the S03. I bought the cheapest hand screw I could find at Woodcraft and cut the necessary profile into it. You might find that a hand screw does just what you need it to do with a little modification.
Another note. If you look at hand screws, the holes the acme screws go through are oval and not round and they use those captured barrel nuts so they can move. If you don’t build in slack there, you will have to turn both the left and right screws almost simultaneously otherwise they will bind up.
The two rods on the sides are just shafts! I was planning on one screw down the middle 
Ah. I see now. I built a polishing machine with that exact design. I have two outside aluminum rods as guides and a center regular threaded rod that pushes and pulls the polisher. There’s never been any binding and it’s worked great for about 10 years.
I think that is what i’m going to do. Just have one of the jaws fixed and use a normal threaded rod!!
I’ll be following to see how this works out. I was thinking of designing and machining my own vise, based on the accessory vise that you can get for the Nomad. The problem I found is that buying a proper dovetail cutter makes it cost prohibitive for a one project use. Most dovetail cutters are only available in 3/8" or 1/2" shanks. I couldn’t find one for a 1/4" shank that didn’t have a tiny cutting diameter on it. Probably a good reason for that.
If you change your design to an acme screw with just threads in one direction, it seems like this might be pretty reasonable cost wise. I looked into buying a machinist vise and everything is either professional shop grade (and hundreds of dollars minimum) or it is a cheap drill press vise made of chinesium. Very hard to find a well made, affordable machinist type vise for the hobbyist. Probably not enough market yet to justify a company making them commercially.
I’ll keep you informed! yes sorry I meant I will be using a ACME thread in one direction!
This is very true… however more and more desktop CNC machines are coming to market!
