# Question about uneven cut



## AndyGTC (Aug 30, 2006)

Hi guys,

Wonder if someone can advise.

When I cut the bearing (bevelled) edges on the top and bottom of my drum shells on the table, I quite often get an uneven cut and some chipping. I always increase the cut in small increments so the cutter isn't doing too much work. However, I still get this. The internal edge of the shell I always turn clockwise and the external edge is turned anti-clockwise. I don't think I have this the wrong way round as doing the opposite is definitely not a cleaner cut. What could be causing this? I'm obviously doing something wrong somewhere. Any ideas?


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## bobj3 (Jan 17, 2006)

Hi Andy

It just maybe the bit 


All router bits are not the same and it's true you get what you pay for when you buy router bits,if they would let us play with them b/4 we buy them you and I would see and feel what bits are SHARP and what bits are almost sharp.

If you look a router bit and it has a small back cut on the cutter it's a good chance it's good and sharp, try this pull a router bit from your drawer and take a good look at it most have a carb.tip that is a sq.cut but no back cut on the cutting edge.

When I say back cut, it's like if you would take a round grinding tool and put it on the cutter, just behind the cutting edge.

The mirror test is also a good way to get sharp bits, if you can see yourself in the cutter part it's a good chance the bit is sharp but most of the time you will not.  but the back cut is a true tip off,the Mfg. took the time to do that one extra step.

I have found one Mfg. that makes great router bits but they are NOT cheap (CMT) all most of the the bits have a back cut on them, other Mfg. do this also but it's hard to tell from a picture. (hands on thing).

http://www.sommerfeldtools.com/search.asp just type in " bits "

Bj


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## Mike (Nov 22, 2004)

Andy, it sounds to me like you are following all the correct steps. Another possibility is a resin build up on the bit. That could cause your bit to stick and pull at the grain. Aside from a bit that is dull or out of specs your problem may be the wood itself. When you assemble your wood into the drum shape are the growth rings all in the same direction or alternating as if you were glueing up a panel or a table top? I am guessing you are having the bit grab on the growth rings and this is why you are getting tear out. What type of woods are you using, and what percentage of moisture do they contain? It is possible some of your wood has cured longer than the rest and is at a different moisture level. Since there is no way to be sure how long the wood has cured unless you cut it yourself, a moisture meter may be the solution. Your wood may be fine at 12% moisture and sticky at 14%.


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## AndyGTC (Aug 30, 2006)

Guys, appreciate the responses. I should have clarified in my first post. The problem occurs mostly on the ply drums. The stave drums are fine, no real issues there, it's just the ply. The shells are made up of 4 layers of 1.5mm ply and are nice and solid. It's just this odd chipping and occasional uneveness in the cut. But I'll have a good look at the cutter as well, as I have a suspicion that's where the fault may lie now. Guess I really need to think about getting a few more decent cutters then!

Thanks again, appreciate it.


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