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 Post subject: CNC Celluloid Inlays?
PostPosted: Wed Aug 26, 2020 3:37 pm 
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Cocobolo
Cocobolo

Joined: Tue Jun 03, 2008 1:12 pm
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Location: Plainfield, IL (chicago)
Hi all,

I am new to CNC and will be doing some restoration work that requires celluloid inlays. I have my designs laid out in CamBam (thanks Steve Wheeler) but when talking to Precise Bits, they cautioned me on cutting plastic with small bits. I will be talking to them again soon, but was wondering if anyone has experience with Pearloid and Celluloid? None of the parts are that small (.500x .375 block letters) but do have some sharp corners. (IE: the capital letter E for example)

What are you using to hold down the sheet material?
Are you leaving tabs so that your inlay stays in place?
specialty bits?
Any caveats?

THanks!

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PostPosted: Wed Aug 26, 2020 10:56 pm 
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Cocobolo
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Joined: Sat May 02, 2009 2:59 pm
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First name: Marcus
Last Name: Bailie
City: Kirkland
State: WA
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They may have cautioned you because celluloid is a plastic and will melt at the cut if you dont machine it properly. Plastic is usually a "high feed rate, low cut-depth" type of operation. I suspect as soon as you move into the "high feed rate" realm for small bits, they will break quite easily.

I don't really have answers to all your questions as I am still fairly new to the CNC game. But I hope this helped at least a little.

I did route my logo (just the letter 'B') out of pearl recently. I just used the masking tape and super glue trick to keep it down. Seemed to work pretty well. No tabs required. I used an 0.5mm rotary bur.

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PostPosted: Tue Sep 01, 2020 10:25 am 
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Celluloid cuts like buttah. I took a quick look and I'm cutting at 18krpm@25ipm using a .024" tool for some celluloid inlay I did last year.

Generally speaking, the stuff cuts great with small tools. you might have to adjust your feed up a bit to keep from melting but it's not too hard to get dialed in.

As to work holding, for celluloid the best method I've found is the tape & superglue trick: https://www.youtube.com/watch?v=r6DCvtcU8_M

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PostPosted: Tue Sep 01, 2020 2:15 pm 
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Cocobolo
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Thank you. The celluloid is only about 0.040 thick, so I would think it would cut easy too. I think the worry is about melting and clogging of the bits etc.

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PostPosted: Tue Sep 01, 2020 5:04 pm 
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Celluloid doesn't melt much when cutting. The chips do kinda stick in the slot but they come off easily. Of bigger concern might be having it catch fire while cutting! (although I know there are people cutting celluloid with a laser somehow without burning down their shops so it's probably a very small risk ;) )

The celluloid I was cutting was .080 thick and I did it in two passes with the .024" tool. How small a tool will you be using?

The pearloid stuff I've cut also cut great. About the only thing I've had major problems with melting and small tools is regular old clear acrylic. Pearloid acrylic (of some sort) seems to cut better than the hard clear stuff.

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PostPosted: Tue Sep 01, 2020 5:22 pm 
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Cocobolo
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If I pre drill the tight corners (.010?), I am sure I cam use .020 bit for the main cuts. I need to do a little homework to see if I really need that tight of Corners. These are block letters 1/2” tall. Think E and T for example. Ron from precise bit thought I could use .020 for the entire cut.

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PostPosted: Tue Sep 01, 2020 5:27 pm 
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Cocobolo
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I do make lots of jigs and templates out of clear acrylic. So was planning on using the CNC for that too. May have to investigate that next. Those would be much larger bits and cuts. (Think headstock templates, pickups, and other routing )

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PostPosted: Tue Sep 01, 2020 5:56 pm 
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I think a .020 tool would do fine without any pre-drilling or anything. .024" cutters are dirt cheap on e-bay though (like $5/each) - I'd use that instead. Little bit stronger than a .024", possibly by up to like 20%.

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PostPosted: Fri Sep 04, 2020 10:53 am 
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Cocobolo
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Thanks Andy, I order some bits from eBay that you recommended. My machine and the bits should be here in a week or so. Then I can practice and get the setup honed in.

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PostPosted: Wed Oct 07, 2020 10:34 pm 
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Cocobolo
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Joined: Tue Jun 03, 2008 1:12 pm
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Location: Plainfield, IL (chicago)
As a follow up, my CNC is up and running and I am cutting my celluloid inlays. Actually they are coming out nice. Bought bits on eBay Per Andy’s suggestion. For this cut I am using (0.0234“) two flute. Tool Path set for 30ipm and it seems just right. Right now I am double face taping it down on hardboard. I do have to pick tape off the bit at the end of each machine process but in this Case, that equals one complete inlay.

Thanks Andy and others for your comments and recommendations.

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PostPosted: Fri Oct 16, 2020 9:59 am 
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Walnut
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Zip/Postal Code: 20657
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Check with Precise Bits again (they are very knowledgeable) but we routinely use MM208-0313-013F 2 fluted bits. We do not have any issues with "burning" and some of the parts are quite small. We glue the material to a piece of masonite with elmers. Once the parts are done we simply soak the board in water and out come the parts.

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