[mattnedgus]

Hi,

I posted this over at mycncuk.com but wanted to hedge my bets someone over this end might have an answer:


Does anybody have any alternative part-holding suggestions to using tabs please? (cutting a part from a whole sheet that's screwed down). I can't use screws, clamps, nails (the part comes off 'finished') or a vacuum bed (I think the parts are too thin)...

I've been finding that when I come to cut the tabs off with a flush-trim hand-router, where the hand-router has cut, it ends up a different shade when the light bounces off it because it's cut at a different feed/speed to the rest of it which was CNC machined... I'd like to be able to not need to sand and blend in this part and leave the parts finished with a machine-cut surface.

Unfortunately the parts I've been cutting can't be screwed down or have clamps on them.

I've been using 20mm long, 4mm deep 3D tabs with good work holding success and was wondering whether I could maybe use say 100mm+ long, 0.5mm deep non-3D tabs perhaps? Maybe I could then run around with a knife and then the trim router set to a fraction of a mm.

Does anyone have any experience with this?

I was even wondering if anyone might use some kind of double-sided tape?

Thanks in advance, Matthew

[mattnedgus]

I might have found a solution - I can't find any double-sided tape larger than an inch or two in width but a different Google search to the searches I had been trying brought me to this:

http://www.cnczone.com/forums/genera...utting-2d.html

Which I thought might be useful for anyone who comes across this post in the future.

"Onion skinning" (first time I've heard of it!) commented by Ger21 in that post seems like it could be well worth a try... It's just a lot lower (1/2 to a 1/4!) to the 0.5mm 'onion skin' I was contemplating using (at between 0.127 - 0.254mm or 0.005 - 0.01").

[dogsop]

For simple wooded parts I've had good luck using blue painters tape on the bottom of my stock which I then spray with 3M spray adhesive and mount on 1/8" hardboard. The hardboard gives me a margin around the stock which I clamp to the CNC base. I can get relatively wide painters tape and I just overlap the strips so that I make sure that the bottom of the work piece is completely covered and doesn't get any of the spray adhesive.

What I found is that the blue painters tape comes off my work piece without the residue that I would get with double sided tape. In most cases I can reuse the hardboard, the 3M spray adhesive doesn't permanently bond to the hardboard, but the important part is that I'm able to cleanly peel my work from the painters tape.

[mattnedgus]

Oh wow thanks, that's a good idea, I'd never considered single-sided tape and gluing it to a board! I'll see about getting some hardboard when I'm next wood shopping...