Plywood help

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Plywood help

Post by Webdirector » Thu Mar 05, 2015 8:05 pm


I do not seem to be able to get a good clean cut on 4mm plywood

see picture:
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I am using this flute:
FullSizeRender 2.jpg
FullSizeRender 2.jpg (423.45 KiB) Viewed 2239 times
I am cutting at 10000rpm and feed rate 560

What do you use to get a clean cut edge ?


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Re: Plywood help

Post by WillAdams » Thu Mar 05, 2015 8:19 pm
Switching to a spiral up-cut endmill for better chip ejection is an obvious choice (to the detriment of cut quality and increased chipping at the top surface when cutting plywood).

combination --- bottom portion of the cutting area is up-cutting and the upper portion is down-cutting, resulting in a better edge finish in materials which chip easily such as plywood.
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Re: Plywood help

Post by twforeman » Thu Mar 05, 2015 8:26 pm

Yes, that's an up cut bit which will cause fuzzing at the top. A down cut bit will cause fuzzing at the bottom. A compression (combination) bit really only works if you are cutting in one pass (cleaning up an edge.)

I would go for a two flute carbide router bit. Unless you are doing 3D profiling I think the best bits for wood are carbide router bits. The are, after all, designed to be used in a router to cut wood.

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Plywood help

Post by Jimf » Thu Mar 05, 2015 8:44 pm

Most standard endmills are up cut which will leave a ragged edge on plywood. I use downcut carbide when I cut ply.

If I plan to paint plywood afterwards, sometimes I will put a coat of clear poly on it and let it dry. This will harden the fibers and make a cleaner cut. Couple coats of poly on MDF is great if you need to hold fine detailed carvings too.

I rarely use woodworking type router bits on my CNC. I find that good endmills are sharper and last longer. I buy Onsrud a lot.

Or if you do through cuts, put the good side of the plywood down if you use a up cut bit and a backer board.

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Re: Plywood help

Post by CastIrony » Thu Mar 05, 2015 8:54 pm

What are people's opinions on straight flute bits for wood?
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Re: Plywood help

Post by Jimf » Thu Mar 05, 2015 9:22 pm

CastIrony wrote:What are people's opinions on straight flute bits for wood?
Only good for wood and plastic. Wouldn't use one on metal. They are inexpensive compared to solid carbide/hss bits. Since there is no helix, chip evacuation is poor therefore you need to run them much slower than regular high helix bits. Nothing wrong with using them for wood.

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Re: Plywood help

Post by Harasi » Fri Mar 06, 2015 8:54 pm

I have been getting smooth cuts using single flute bit cutting 9mm plywood but haven't tried it for engraving.
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