What is the acrylic glass thickness for the McWire Cartbot? [And other acrylic questions.]

What thickness of acrylic does the McWire Cartesian Bot v1.2 [reprap.org] use? The documentation doesn't seem to specify, and neither does the kit with all the precut parts at RRRF [store.rrrf.org].

I'd like to see if I can buy and cut the acrylic myself if it is enough of a cost difference, as I'll have to buy and cut acrylic for my bootstrap extruder anyway.

Also, does anyone know how difficult it is to countersink the parts? Could I do it with a hand-held drill, or would I have to rig up some support structure to hold the drill straight (improvised drill press)?

Lastly, the pistol-grip drill I'm using doesn't have a clutch for torque adjustment. It does speed up and slow down with more and less pressure on the trigger, respectively, but I'm not sure if this adjusts torque (I don't think it does). Will this be a problem when drilling the parts for the McWire (the acrylic and the PTFE bearings)?

From the bottom of this thread [forums.reprap.org]

"most of the pieces should be 1/4" thick. there is one piece that should be 1/2" thick which is the 'vertical base' part."

Thanks!
I don't know why I didn't see that.

Edit:
Is that smiley a guy with a toothbrush? I thought it was a guy with one of those plastic things you blow into to make that duck-like noise at wacky parties. So my intent was to "celebrate" the knowledge with the smiley... but if it's a toothbrush, that's just weird.

Edited 1 time(s). Last edit at 07/22/2008 11:54AM by Joshua Merchant.

When drilling acrylic you need to go very slowly otherwise it melts and snatches the drill. With small holes it is a good idea to use a pecking action to stop the swarf building up. I find silicon grease spray helps.

In contrast drilling PTFE is very easy, it goes through like it was cheese.

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[www.hydraraptor.blogspot.com]

Quote from Joshua Merchant:
Is that smiley a guy with a toothbrush? I thought it was a guy with one of those plastic things you blow into to make that duck-like noise at wacky parties. So my intent was to "celebrate" the knowledge with the smiley... but if it's a toothbrush, that's just weird.



Nah - It a beer bottle so that your project will all come together with a big bang but with enough of them you'll not notice.

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Bob Teeter
"What Box?"

nophead Wrote:
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> When drilling acrylic you need to go very slowly
> otherwise it melts and snatches the drill.
>
Truer words were never spoken. It's a bastard to get off the drill bit afterwards without breaking the bit, too, if you are drilling small holes.

... i mill acrylic, all thermoplastics and aluminium with coolant - simply windscreen washer-fluid from a squeeze-bottle - some drops every 5 seconds are enough, so the shavings stay wet and the drill and material won't get hot ...

POM and most duroplastics don't need coolant - here the temperature of the drill can go up to 100

You can get broken drill bits and taps out of acrylic by pushing them with a fine soldering iron bit. I had to do both recently

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[www.hydraraptor.blogspot.com]

I was drilling an acrylic bass guitar to install a relocated bass bridge. One
drill bit (tiny) broke off. Two other drill bits froze in the acrylic. They also
are quite small drill bits. How can I get them out, yet get the holes drilled?

... make them hot, so they'll melt the acrylic around and pull them out.

For 'safe' drilling try cooling with water or a soap-water-mixture and 'pecked' drilling - e.g. stepwise drilling with repeated removing and reinserting the drillbit, so it's cooled every time it's reinserted ...

Viktor

If you can't grip it or push it perhaps heat it and use a magnet to pull it out.

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[www.hydraraptor.blogspot.com]

To answer the part about countersinking:

Countersinking is relatively easy with a hand held drill. You might want
to practice on a few holes in scrap first so that you get the feel for keeping the drill vertical.
Most likely the first couple of holes you will not countersink enough and will have to go deeper.