Clamping fixtures

[44man]

Someone here suggested to get the fixture clamps no. 06947204 from MSC. I need to mill aluminum without having clamps on top. I can't find the nice person that sent the info or my original question! :-?
I went to the MSC site but can't figure how they work.
Can someone send a picture showing how they are mounted to the mill table and how they hold parts? Are they mounted to a plate with a variety of holes?

[jhrosier]

You need a grid plate to use those.
If you get the larger thread sizes, they can be used with "T" nuts.
I find that style of clamp to be difficult to use because they want to move the part when they are tightened. They will also bow the stock if they are too tight and let it go flying if too loose.
I prefer to leave an "ear" on the stock for clamping and cut it off after or fasten the stock to a larger piece of stock for clamping, if a few extra holes are not a problem.

I make moulds and other tooling for thermoforming plastics from aluminum. If you could describe the machine, stock size and machining operation briefly, I may be able to help.

Jack

[44man]

I have the Smithy Granite and use scrap aluminum to make boolit mold blocks. I hate to keep moving the top clamps to make room to mill. Many times I do not have a perfectly flat surface on the table to start with so moving the clamps can change what I get on top. Sizes of the scrap varies from just enough for blocks to a long piece. They are just sawed out with a bandsaw.
Using a vise is not ideal either.
The hardest part is to get a perfect rectangle to start with.
Even when I run out of this scrap and have to buy aluminum, sides are not flat.
I need one continuous flat surface to start with and since each piece varies in size, I can't make just one setup.

[Red River Rick]

Have you tried using double-sided carpet tape? Make sure the table and workpiece are clean.
Don't use coolant, and shallow cuts, 0.010 - 0.015".

RRR

[No_1]

Hey 44Man,

Off the top of my head, based on what you said I think I would utilize the alignment pin holes as a way to hold down the blocks. I would drill the alignment pin holes under size and tap them. I would then make a plate that attached to the table of the mill. This plate would be drilled through and counter bored from the bottom side. I would then use cap screws to bolt the raw blocks to the plate (from the bottom side up). Once the plate is bolted to the table you can mill all sides except the side that is facing down. Once you only have 1 side left, flip the block(s) and do the last side. Taking it further, I would make the plate to hold both (or maybe even more blocks) in a straight line separated with enough space to cut the sides between them. You could even cut the slot for the handles while they are lined up. Flip them over, bolt them down again and cut the vent lines with a fly cutter. Once they are finished, you drill the pin holes to size, cleaning up the hole of threads, install the alignment pins and cut the cavities with your prefered method.

BUT

If it were me doing it, I would cut the pieces close to size, drill the alignment holes, hang the blocks in a vice, skim cut those faces, mill the slots, flip the blocks to cut the vent lines, install the dowels, put the blocks together, hang that in a 4 jaw lathe, face it off (so the bore is perpendicular to the face), drill then bore the cavity. I believe the only thing critical in making a bullet mould (beside a flat mating surface) is the base of the bullet being perpendicular to the length of it.

This has the potential of being a very interesting thread. I look forward to other comments as well as reading of your experience.

Robert

[jhrosier]

44man,
I've looked at pictures of the Smithy and here is what I would do:

1. Fly cut the top of the table just to clean it up and square it with the spindle.

2. Make a sub table from a 1" or thicker piece of aluminum tooling plate.
--The tooling plate comes ground parallel so it will not need further machining.
--I have aluminum sub plates on 3 mills and they work fine with reasonable care and occasional flat filing.

3. Mount a machinists vice on the sub table.
You can get the vise #425-7240 from Enco for about $80.

Jack

[44man]

Some good ideas! I have to play with it. Here is a picture of a piece I start with. It is aircraft aluminum.