# Why is my plywood fraying on the edges



## Kirstmccall (Aug 1, 2018)

I’ve tried several different downcut bits to cut monograms out of birch plywood with my CNC machine. But the edges always come out so frayed. What bit can I use to stop it from fraying? Is there such a bit? It takes me forever to sand each monogram after I cut it and it’s almost not even worth my time!


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## Stick486 (Jan 4, 2013)

welcome to the forums N/A..

what brand of bit are you using??
have you cleaned it recently and is it sharp???


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## Kirstmccall (Aug 1, 2018)

Yes, if does this with brand new bits too! I have used a spiral downcut but, a straight flute bit and another type of downcut bit! Would an upcut but work better? They are just hard to find! No one local sells upcut bits


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## Nickp (Dec 4, 2012)

Welcome...you will get some good advice I'm sure...

In the meantime...feed rate, bit speed, depth of cut, direction of cut could affect quality...

Is the cutting side of bit fraying or trailing edge...?

Is the cut width you desire the same size as bit...? Maybe a smaller bit with direction change on second pass...?

Again, welcome...lots of talent here...


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## Stick486 (Jan 4, 2013)

where are you???
you need to fill out your profile...
we work better w/ more information...


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## Cherryville Chuck (Sep 28, 2010)

Have you considered using a synthetic material? All told it may be cheaper in the long run. Any time you cut across the grain you are likely to have problems. One other idea. Are you taking a very light finish cut(or maybe two)?


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## Multiwood (Feb 24, 2013)

Welcome to the forum N/a


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## difalkner (Jan 3, 2012)

Welcome to the forum! When you get a minute complete your profile with first name and location.

The only plywood I cut is 1/2" Baltic Birch and most of the time I use a 1/4" downcut spiral 2-flute bit. The edges come out clean. Are you cutting too much in one pass, possibly? I take a roughing pass and then come back with a final pass to remove the last 0.005". I do the same thing when I engrave with a V-bit, too. 

This is the only photo I have of a freshly cut piece and you can see the edges are pretty clean.








David

PS - I'm using a Whiteside 1/4" spiral downcut bit but they also have it in upcut. Matter of fact, I have both upcut and downcut in 1/8", as well.


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## marecat3 (Nov 30, 2010)

I use a freud 75-103 up sprial bit for most cut out letters. Never had a problem unless the bit is not sharp.


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## MEBCWD (Jan 14, 2012)

Welcome to the Router Forums.

I have a few questions.

Do you have any pictures of your machine and of the cut left when cutting the plywood? You can post pictures that are on your computer.

Is this new plywood or has it been stored for a while where it might have been subjected to heat or moisture? How thick is the plywood? 

What size bit are you using? Is your feed rate, spindle speed and depth of cut correct for the bit, material and machine?

What kind of CNC machine do you have? Homemade MDF, DIY kit, plug and play hobby machine or something else? Is there any looseness in the machine and if so can it be adjusted to tighten up the machine?

Do you have a spindle or a router? Could the mount be loose? Have you checked the collet for runout? Are the bearings good or could they be causing runout?

It does help when you fill out your profile with the tools and other information about your shop.


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## rkaligian (Jan 22, 2011)

I have yet to find a domestic or offshore birch plywood that can be cleanly machined using a CNC other than Baltic birch as a previous member made note of. The only solution that worked most of the time was to cover the face of the plywood with a high quality painters tape. Make sure you use a roller or credit card to "burnish" the tape into the plywood face before you mill it.

Remember that plywood face veneer can be produced in a variety of ways, be it a rotary or rift cut etc. Wood grain strength varies when presented with these different methods used to create the veneer at the sawmill. I only use domestic birch plywood for cabinet carcass work, otherwise it is Baltic birch all the way!


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## DaninVan (Jan 1, 2012)

In answer to the question, I was going to say 'A frayed knot' ...but then I repented.


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