Router Bit breaking when making dados - Router Forums
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post #1 of 16 (permalink) Old 09-08-2010, 07:46 AM Thread Starter
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Default Router Bit breaking when making dados

Hi, I was wondering what I am or was doing wrong. I was making dados on my table mounted router. Actually I was making drawers the lock rabbet way. I am using 1/2" plywood (HD's baltic birch) with 1/4" drawer bottoms.

Anyway, when cutting the dados I went through 2 bits and almost a 3rd. The bits just burnt through. I was using a solid carbide up-cut bit at first then that broke off, then I went to 2 flute straight bit - then that broke off. Finally went to a table saw dado blade set.

Is plywood to tough for 1/4" bits for any length of cut OR was I pushing to fast (I seriously tried not to with the 2nd bit) OR what?

I did read somewhere that plywood is tough on router bits.

Then the bit only being 1/4". Would this also happen with a 3/8" bit too?

I only made 4 drawers - not that many and not that big.

Any suggestions OR just don't do that again?
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post #2 of 16 (permalink) Old 09-08-2010, 09:51 AM
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Originally Posted by FWFreitag View Post
Hi, I was wondering what I am or was doing wrong. I was making dados on my table mounted router. Actually I was making drawers the lock rabbet way. I am using 1/2" plywood (HD's baltic birch) with 1/4" drawer bottoms.

Anyway, when cutting the dados I went through 2 bits and almost a 3rd. The bits just burnt through. I was using a solid carbide up-cut bit at first then that broke off, then I went to 2 flute straight bit - then that broke off. Finally went to a table saw dado blade set.

Is plywood to tough for 1/4" bits for any length of cut OR was I pushing to fast (I seriously tried not to with the 2nd bit) OR what?

I did read somewhere that plywood is tough on router bits.

Then the bit only being 1/4". Would this also happen with a 3/8" bit too?

I only made 4 drawers - not that many and not that big.

Any suggestions OR just don't do that again?
Hi - Welcome to the forum
WOW! I don't know for sure. I've made a dozen or so drawers/boxes from the HD version of BB and haven't had a problem. Plywood is tough on bits from the standpoint of them staying sharp. Were your bits fairly new? You said they were just burning through. That makes me think the bits were dull. The only other thought that comes to mind is whether the bits were well seated in the collet. They need to be all the way down and pulled back up only 1/16" or so.

John Schaben

The problem with experience is I usually get it immediately after I need it.
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post #3 of 16 (permalink) Old 09-08-2010, 10:03 AM
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Hi

Use a slot cutter and you will not break any of your 1/4" bits...

http://cgi.ebay.com/11pc-1-4-Shank-S...item20b3807323

http://cgi.ebay.com/1PC-1-4-SH-Slot-...item1e5e1294da






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Quote:
Originally Posted by FWFreitag View Post
Hi, I was wondering what I am or was doing wrong. I was making dados on my table mounted router. Actually I was making drawers the lock rabbet way. I am using 1/2" plywood (HD's baltic birch) with 1/4" drawer bottoms.

Anyway, when cutting the dados I went through 2 bits and almost a 3rd. The bits just burnt through. I was using a solid carbide up-cut bit at first then that broke off, then I went to 2 flute straight bit - then that broke off. Finally went to a table saw dado blade set.

Is plywood to tough for 1/4" bits for any length of cut OR was I pushing to fast (I seriously tried not to with the 2nd bit) OR what?

I did read somewhere that plywood is tough on router bits.

Then the bit only being 1/4". Would this also happen with a 3/8" bit too?

I only made 4 drawers - not that many and not that big.

Any suggestions OR just don't do that again?



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post #4 of 16 (permalink) Old 09-11-2010, 07:47 AM
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Slow the router down and feed the plywood slower.
I never run the router at full speed.

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post #5 of 16 (permalink) Old 09-13-2010, 06:06 AM Thread Starter
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Hi. Thanks for the reply. Yes, the first bit was a solid carbide "upcutting" spiral bit - brand new. However, it was an inexpensive one from China or something (I don't know). The second was a Grizzly plywood bit.

The bit just sort of "burned" off at the point they were contacting the plywood.

This was just baltic birch from HD - nothing special.

So, after making 4 drawers (the sides and the drawer bottoms) I went through 2 bits.

I did think about getting a "slot cutter" for in the future. I would think the 3/16" would be perfect for the plywood as to the thickness. Although I will have to "sneak" that home hidden from the wife because I already went to Lowes to get replacement 1/4" bits for those that broke - they have a pretty complete line of router bits at my local Lowes - amazingly so - much better than HD. She already asked, "What did you buy at Lowes that was so expensive?"
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post #6 of 16 (permalink) Old 09-13-2010, 06:14 AM Thread Starter
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Wow, those look like great sets of bits!! Do they also come with 1/2" shank or doesn't it matter. That looks like you can do alot of exactly what I do. Thanks!!!!
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post #7 of 16 (permalink) Old 09-13-2010, 06:21 AM Thread Starter
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That's what I was thinking in retrospect - that I was running at to "high" a speed. I was running at full speed with the PC 7518.
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post #8 of 16 (permalink) Old 09-13-2010, 07:26 AM Thread Starter
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Have you had good luck with those bits? I mean, do they last and are they nice slot router bits? Not something that is a waste of money that I'll be replacing after a few uses? Thanks!
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post #9 of 16 (permalink) Old 09-13-2010, 11:16 AM
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FWFreitag, I have had a similar experience with 1/4" spiral bit, had two of them break in the router table. They cut great, but you have to be carefull with them. I have found that if I cut about an 1/8" deep each pass you will not have any issues. I have done this using my plunge router making 3/8" to 3/4" deep mortises.

I also avoid using that bit in the router table now too. I will use a straight bit or a slot cutting bit to accomplish what I need in the table.
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post #10 of 16 (permalink) Old 09-13-2010, 05:59 PM
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Default breaking bits

You are probably setting your bit too high and trying to take too much off in one pass. The smaller the bit the faster you run it(rpms) Try lowering the bit and making several passes.
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