Mill Clamping

Now that my shop build is finished I can get on with some projects. Some of my upcoming projects will need a way to hold small irregular parts in the mill/drill. Several home shop machinists on the web describe making a mini pallet system to hold parts in the mill.

A mini pallet is a metal plate that can be attached to the milling table or held in a milling vice. The plate has an array of tapped holes that allow toe clamps to be attached to the plate with screws where needed.

I found a roughly 5″ X 14″ X .75″ 6061-T6 aluminum plate in my stock pile that was just the right size for my pallet. Four counter bored holes at the ends allow the plate to be attached to the mill table with cap screws and Tee nuts. The counter bored holes let the top of the pallet be clear of any obstructions. The rest of the plate is drilled and tapped 10-24 on a 1″ grid. Even with the holes drilled for a 40% thread it was very difficult to tap the holes all the way through so I drilled the holes over half of the depth from the back to clearance size. Even so the tapping takes a lot of time, backing up several times for each hole. My plan is to only tap a few of the holes and tap the rest as needed.

The other thing I needed to make were the clamps. These were machined out of 5/16″ X 1/2″ cold rolled 1018 steel. A tapped hold in one end allows a screw to be inserted to adjust the height of the clamp to suit the part being clamped and there is a slot for the hold down screw. I made two sizes 2″  and 1.5″ long.

One thing I wanted to try out was putting a nice surface finish on the clamps. Something that would help keep them from rusting. I hear a lot about Parkerizing (manganese phosphate)  for firearms but not so much for tools. It seems like most steel tools that are black are black oxide treated. To me manganese phosphate is a good choice for a surface treatment. You can get ready made Parkerizing solution but of course I had to mix up my own. To get the parts ready they were sanded on the belt sander then sandblasted. That was the first use of my new sandblasting cabinet. Then I soaked the clamps in the hot Parkerizing solution for about 10 minutes at a time taking them out to inspect and clean based on several tutorials on the web. There really was not much to clean off the parts and I think it would have worked better if I had just let them soak for about an hour or so. This was my first attempt at Parkerizing and I was happy with the results. I do think a bit more attention to surface preparation and a longer soak would have given better results.

One of the suggestions I found on the web was to use a case to store the screws and clamps. I also included an Allen key for the screws in the case.

The picture above is an example of how the mini pallet works. The part is a standard for a Stuart model steam engine. You can see that would be difficult to hold in a vice. The standard needs 4 holes drilled into the feet.

References:

My pallet attaches to the table directly rather than in a vice and has a square 1″ hole grid rather than a diagonal grid.

My Toe clamps a mostly the same as these except for 5/16″ thick instead of 1/4″.

https://www.milsurps.com/showthread.php?t=43247 Contains formula for solution and some how to.

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