thin plate machining

[tmt_92021]

what's the best way to hold down large thin sheets of aluminum for machining? Thanks.

[Runner4404spd]

double sided tape

[DEAN]

How about that Mitee-Grip stuff from Mitee-Bite

[mxtras]

A vacuum table is another option.

Scott

[JPMach]

Where is a good source of thin double sided tape?

How hard can you mill a part without worying about it lifting? Say a 1/4" endmill in 1/8" material.

JP

[DEAN]

Home depot has the wide carpet double sided tape.

[tomc3700]

Originally Posted by tmt_92021 what's the best way to hold down large thin sheets of aluminum for machining? Thanks.

You can sandwitch it between 2 pcs of thin scrap wood and strap it to
your table.



Tom C.

[cdlenterprises]

How thin? How big? What do you have to do to the parts? It's pretty tough to beat vacuum when dealing with thin stuff. Whether you use vacuum or double sided tape I would go easy with the feedrates. One trick we used to use was use an end mill with a left hand helix (right hand cut, left hand helix). The helix angle will actually push the part down vs. pulling it up like a standard helix.

[mxtras]

Another option is that if the finished part has any holes, drill/bore them first, then anchor the panel to a fixture/board through those holes.

If not, then find three or four locations outside the perimeter of the finished profile and anchor the plate down to the machine in those areas. Then, when profiling the shape from the plate, simply leave a small tab in place near each anchor point that will keep the part in place. Snip the tab off and sand that spot.

Scott

[psychomill]

All of the above are good suggestions... add to that, moving clamps around.

One trick we used to use was use an end mill with a left hand helix (right hand cut, left hand helix). The helix angle will actually push the part down vs. pulling it up like a standard helix.

Huh?

Left hand or right hand helix will exert the same "pulling force". It's the helix angle that will change this somewhat. Actually, it alters the direction of the cutting force. The only way a left hand helix will push down (so to speak) is if you still ran it in M3 (normal) spindle rotation. But then again, you might as well buy standard tooling and run it in M4 (reverse rotation). But that won't help you much for tool life, finishes and will probably launch the part.

Something to consider to get the chip and part to "go down" is the use of router tooling like from Onsrud. They make down cut spiral flutes that will change the force direction.

For the most part though, a good vacuum chuck or tape will suffice....

[cdlenterprises]

[QUOTE=psychomill;208058]
Huh?
...The only way a left hand helix will push down (so to speak) is if you still ran it in M3 (normal) spindle rotation. But then again, you might as well buy standard tooling and run it in M4 (reverse rotation).

www.mscdirect.com look at page 388 lower left hand corner Item #81864324 Putnam HSS LHS(left hand spiral)RHC(right hand cut) end mill. If you bought standard tooling and ran it in reverse then your not cutting are you? Hence the left hand spiral(pushes down as you say) with the right hand cut(cuts like we need) It was a long time ago, but I'm pretty sure that this was the type of cutter we used to push the part down onto the fixture plate

[keebler303]

yes left hand spiral cutters are available and are meant to cut in the standard direction. They are meant for applications where you want to push the chips through the part for some reason. ie through-cutting where there is a space below the workpiece for the chips to fall.

Matt