[airbrush]

Going to be cutting some parts on my machine out of aluminum. Was planning to leave an onion skin to hold the part rather than tabs...just didnt want to raise or plunge the tool around tabs in aluminum.

So how much is a good thickness for holding parts?
0.010"?
0.020"?

...cutting 3/8" plate aluminum...was thinking 0.020" onionskin to hold it??

suggestions? experiences?

thx

[crazydiamond]

I usually leave between 0.002" and 0.004" (yes thou). I'd experiment a bit because it really depends on a few factors (type of tooling, grade of aluminum, table flatness etc.) but that should be a good place to start.

Good luck!

[airbrush]

yah table is not absolutely perfect...think i would leave it at 0.01 then just to be on the safe side...

[wizard]

yah table is not absolutely perfect...think i would leave it at 0.01 then just to be on the safe side...

If the parts are repetitive and suitably large you might want to consider supplementing with vacuum hold down. Obvioysly it depends upon how many parts you need to do but a vac hold down may even allow one last pass to remove the oinon skin.

Note you dont need to turn your entire table into a vacuum table. There are many factors to consider, such as how large the parts is, machine size and your ability to prep on other hardware. For example if the parts are conducive to being cut out of small squares you could cut the squares to size on a table saw and then use vacuum and clamps on a small sub table. Effectively you would be doing the work like a CNC mill owner would.

Obviously the parts need to be amendable to this approach but it should provide you with high quality resilts. You might rightfully say that this complety misses with the whole idea of a machine with a lsrge work srea capable of doing sheet goods and you might be right. I look at it as an alternative approach for modest volumes where high quality is desired. This could also get around your problem of a table not being too flat as you could machine the sub table true. .

[louieatienza]

If you have a spoilboard and leveled it with the spindle, you should be able to get it pretty thin. I also try for around .004". Though with Mic-6, I actually onion skin all the way down to the plastic film coating of the plate!

[ger21]

How are you removing the onion skin? I'l sometimes leave .01 or .02, trim off the excess on the bandsaw, and clean it up with a flush bearing bit in a router table.

[airbrush]

probably just dremel through the onion skin...its outer profile and doesn't need to be perfect.
Just wanted a way to hold and wanted to avoid tabs to ramp or plunge over...

I've onion skinned wood at 0.03 before...so thinking i'll try it at 0.01 and see what happens.