The secret sauce for a lot of very clever machine work is in the fixturing and workholding, so I always pay attention when people are posting pictures of their fixtures (he’s a poet and just don’t know it, yeah right!). Here is a nice simple little fixture from Travis on CNCZone:
It’s kind of like 4 little vises, and you could stick this fixture into a machinist vise (or 2) as a pallet. Pallets are great because you can be setting up parts on alternate pallets while the machine runs. This particular fixture is made of aluminum, which, as the CNCZone thread commenters say, won’t last too long. Steel would be better, but more trouble if you don’t need a lot of parts.
You won’t save time and money every time making a specialized fixture. In fact, we added a special Fixture Calculator to our G-Wizard Estimator to help you figure out when it makes sense. But there are some kinds of fixture tooling that are generic, and could be used in a variety of jobs once made up. This is that kind of fixture, so it might be worth it to have a few of them hanging around.
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Bob is responsible for the development and implementation of the popular G-Wizard CNC Software. Bob is also the founder of CNCCookbook, the largest CNC-related blog on the Internet.
I am making a fixture with pit bull clamps like that right now, but it has ends to attach to 4th axis and tailstock to rotate the parts too.
FYI Mighty bite is the company that makes the pit bull clamps.
Heli coil the threads from the get go and threads last way longer as well as better control over torque.
Ken, don’t waste your time. I did the same thing and when you have any drilling on the 4th axis that is against the clamp (force going into it or into the rail) it will slip. This is how we started, and fought it for a while! Tried putting talon grips on the rail too.
Now I use the same carrier plates pinned to the tombstone but bolt the stock with SHCS’s and it works perfectly.
The mitee-bites are just not as great as I thought. SHCS is actually far better, if you can fit it into your part design.