Carbide router bit and acrlyic

Read this group all the time, but wow, haven't posted here in years. Now I have a question concerning the use of a router bit to round off the edges of a piece of acrlyic. Good idea or bad? Will the acrlyic piece tend to shatter or get hot and just kinda melt and gum up the router bit? It's a piece of 1/8" thick and I won't be taking much material off. Thanks.
--
Paul O.


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On 10/15/10 3:27 PM, Paul wrote:

No experience at all doing it, but I've used a router a lot and I have to think that, even on it's slowest speed, it's just going to melt it.
Off the top of my head..... I've seen guys bend that stuff using a torch to soften it. What if you softened it with a torch and followed behind with something that had the profile you want? Sort of like a concrete worker forming an expansion joint.
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-MIKE-

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The flame, with a steady, but quick hand, will melt the edge to it's own, clean natural edge. Cast acrylic will behave a bit differently than extruded acrylic.
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Robatoy wrote on 16/10/2010 :

And just in case. Polycarbonate is near immpossible to flame smooth. It bubbles and looks terrible. Polycarbonate looks much like acrylic but with a blue tinge and is stronger and more expensive..
--
John G



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If the bit is fresh, sharp and no seized bearing, it will cut the acrylic just fine. I do that all the time, even with router bits way bigget than what you're planning on. But at that little roundover, flaming will do it too, but that takes practise. A sanding block works, with 220 grit, but it will be a matte/dull finish. A flame IS the way to go once you get the hang of it.
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On 10/15/10 3:44 PM, Robatoy wrote:

Right on. That was totally counter to what I speculated. I'll tuck that away in the ol' brain for future use.
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-MIKE-

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I do not know if you know how to modify a drill bit for acrylic, but if not, you change the cutting edge from positive rake like most drill bits, to a 0 degree rake or a 1 or 2 degree negative rake, so it scrapes the material, instead of grabbing off more than you want and chipping or cracking it.
It would follow that such a mod on a HHS router bit would be necessary if you were to ever want to use a router on acrylic.
--
Jim in NC


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We used to knock off the sharp edge on a new drill bit, jes touching it to the wheel at a 45 deg angle to the apex. We'd use these for both plexi and brass. I was thinking the same for a router bit, but have never used a router on plexi.
Call a TAP plastic outlet. They do plexi/lucite by the ship load.
http://www.tapplastics.com /
nb
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wrote:

I "usually" go for a little more precise modification, by using a dremmel cutoff wheel, and turn it sideways to the leading edge of the bit, grinding a small amount of the leading edge back a bit to produce a 0 degree face. I then paint the bit with a bit of orange spray paint. The paint wears off the outside of the bit, but enough remains down in the flutes to make quick work of identifying it as a modified bit.

A safe bet, but where is the adventure, in that? <ggg>
--
Jim in NC


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Considering that I rout out large letters out of 1/4" acrylic all the time, the one common denominator is that the 'special' acrylic bits are highly polished as to not to give the acrylic much to grab on to when a 22K PRM spinning bit loiters somewhere during the toolpath. This is cut from the back with a regular bullnose bit and lit from the edge. (Not mine) http://www.vectric.com/forum/download/file.php?id=17159&mode=view
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Done with a V shaped router bit http://www.vectric.com/forum/download/file.php?id=17187&mode=view
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On 10/16/10 11:16 AM, Robatoy wrote:

Guess I won't shy away from routing acrylic should the need arise.
--

-MIKE-

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Cool. Done with a CNC setup?
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Jim in NC



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Lots of woodworking tools work OK in acrylic, but the combination of router speed and 'not taking much material off' leads to disaster. You'll have better finish if you just build a wood-and-hacksawblade scraper plane for this job.
Impact from a router cutting edge can fracture and flake bits of acrylic. If you make a shallow cut, the acrylic will slightly bend and flex, which causes friction and melting.
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Few surprises see pix (
http://patwarner.com/images/fig20b.jpg ). Anticlimb cut only at 18-25KRPM. Secure your work, wear eye protection. ********************************************************************************

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Thanks everybody. Think I'll try the torch method and see if I can get the hang of it, if not, I'll get out the ole sanding block.
--
Paul O.


"Paul" < snipped-for-privacy@gmail.com> wrote in message
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A little more info: [http://www.plasticsmag.com/routing.asp ? fIssue=Mar/Apr-03&aid751] Also, Google: acrylic router bit
Ken
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