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TOPIC: RPM, depth of cut & feed rate

RPM, depth of cut & feed rate 29 Jan 2018 11:26 #1

  • John Miller
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Hi all, I'd like to get some advice on machine settings for cutting acrylic. Maybe I'm too cautious with my settings.
I'm about to cut a bunch of letters from a 3/8" acrylic. My rule of thumb has always been never cut deeper than the diameter of the cutter so that would mean three passes, but at what feed rate? The tool manufacturer recommends
an RPM of 18k. Any help would be greatly appreciated. My software says 1hr and 52 min to cut my job. By adjusting feed & depth of cut I could possibly save time on this job and those to come in the future. BTW, I'm using a single flute
bit designed for acrylic.
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RPM, depth of cut & feed rate 02 Feb 2018 10:16 #2

  • James Dawson
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Use chipload data and figure from there. 3/8" we would cut in 2 passes with a 3rd finish pass that takes .005 off the width and .01 off the depth to remove tooling marks from the separate passes.

Our 3/8" acrylic bit runs 200 IPM @ 20,000 rpms and gives us an almost perfect edge.

RPM, depth of cut & feed rate 02 Feb 2018 10:34 #3

  • John Miller
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James, Thanks for that info. What diameter bit are those settings for, we're using a 1/8" bit.
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RPM, depth of cut & feed rate 02 Feb 2018 10:39 #4

  • John Miller
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Oh... dumb me I just re-read your post, that was for a 3/8" bit. So, for a 1/8" bit what we ended up using was
18,000 RPMS which amana recommends, 70 IPM and .090" each pass. We got great results but it took quite a while. I'd like to do the job faster but don't want to break the bit.
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RPM, depth of cut & feed rate 02 Feb 2018 14:18 #5

  • James Dawson
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We rarely cut plexi with a bit smaller than 1/4" and most of the time we use 3/8" .

These are the bits we use. Onsrud 2 flute.

We have ran the 3/8 as fast as 300ipm. 1/4" around 150-200 ipm.


3/8 Plexi Spiral bit - 52-638
1/4" Plexi Spiral bit - 52-624

RPM, depth of cut & feed rate 02 Feb 2018 15:26 #6

  • John Miller
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We sometimes need to cut small letters which should be done with a laser but we don't have one.
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RPM, depth of cut & feed rate 02 Feb 2018 15:29 #7

  • James Dawson
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why in the world would such a small letter need to be 3/8" thick? You have more patience than I do, thats for sure.

RPM, depth of cut & feed rate 02 Feb 2018 15:45 #8

  • John Miller
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I will post a picture when we install them. :woohoo:
Someday every things gonna be different... When I paint my masterpiece

RPM, depth of cut & feed rate 03 Feb 2018 11:27 #9

  • David Ridge
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Hi. I cut these on my router all the time. For 3/8 I use a 1/8 bit at 18000rpm 120 ipm depth of .320 for the first pass. Second pass at .385 depth at 1900rpm 100 I’m with an offset of .005. These second pass cuts thru and cleans the edge. I also use transfer tape and spray mount them to the table. Even my 10hp vacuum can’t hold down the little pieces. Good luck.


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