Replies

1. 
   Quickstep | Mar 13, 2009 11:49pm | #1

   Only thing I can think of is that the surface the bearing is riding on isn't perfectly square. It only takes a tinch. (See attached drawing)

    

    

   I've seen bits overcut because I pushed too hard and the bearing was actually denting the surface it was riding on making it over cut. The only other thing that would cause your circumstance would be if the bit had been sharpened; slightly reducing its diameter

   
2. 
   mike4244 | Mar 13, 2009 11:53pm | #2

   The bearing should be the same exact size as the cutter.If the bearing is larger,than you will get these results. How much are you talking about? I always sand the edge with/32" 150 grit when done to break the sharp edge. If the edge protrudes more than say 1/32" then buy a smaller bearing.

   mike

3. 
   BruceS | Mar 14, 2009 02:19am | #3

   + or -  .005 on a router bit is pretty much the industry standard and the same goes for the small bearings they use, though slightly less .  So you could end up with a .010 difference or possibly more.   That's enough to catch a finger nail on.   Router bits are not nuclear grade.

   Work Safe,  Count to 10 when your done for the day !!

   Bruce S. 

    

4. 
   rdasilva | Mar 14, 2009 06:47am | #4

   I agree with Quickstep. If your countertop edge is even a bit out of square, the cut will exhibit the situation you describe.

5. 
   hammer1 | Mar 14, 2009 07:57am | #5

   I've used a lot of flush cutting router bits and never found one that cut absolutely flush. With plastic laminate, you want the edges to make full contact, being a touch proud is good. Otherwise, the contact cement will keep the surfaces from meeting tightly. Normally, you gently hit the edge with a file to remove any bit marks after flush trimming. When the top laminate lays over the front edge, the flush trim bit is followed by the chamfer bit. You can adjust the depth on these and tune it in to cut the bevel flush. Again, it's typical to leave it just a little proud and finish with a file. It's real easy to set the bevel bit too deep. Then you will remove some of the face color on the front edge piece. Don't do that.

   If you are pattern cutting with a flush trim bit, the work piece is going to be a little larger than the template when you finish. If the cutters and the bearing were perfectly flush, you would have troubles with the bit skating, loss of control and the high probability of the cutters hitting the pattern or adjacent surface. On laminate, try to set the bit depth so it just goes deep enough to cut the plastic plus 1/16"-1/8". This will help if the front edge isn't perfectly square to the top. You will get an easier cut and less glue build up on the bit if you keep the extra overhanging waste down to 1/4" or so.

   Beat it to fit / Paint it to match

6. 
   dmdnk | Mar 15, 2009 09:51am | #6

   I've noticed that I sometimes get poor results while flush trimming if I don't use adequate pressure against the bearing surface (or too much!)- especially when the density of the materials differ...

   Is the edge difference enough that it will cause a problem with the application of the laminate?

7. 
   Cincinnati | Mar 15, 2009 01:58pm | #7

   Easiest troubleshoot may be to just buy another bit and try it out.

   Is this a new bit? Has it ever been sharpened? Get a micrometer or dial calipers and check the bit/bearing diameters. If the bit/bearing difference is the same as the trim difference you are seeing, there is the problem. Replace the bit.

   If you have never sharpened the bit: If they are different, I would call Oldham (or the maker of Viper bits) and ask them about the tolerance on their bit diameters. Bearing tolerances are going to be in the tenths of thousandths so doubt it is a bearing issue.

   Many who laminate countertops use a designed slightly tapered trim bit and adjust the depth of cut to get a flush surface at the glue line.

   Greg

   •••••••

   Exo 35:30-35

8. 
   Dave45 | Mar 15, 2009 04:39pm | #8

   Is the outer surface of the guide bearing perfectly clean? I've seen those "ridges" when "stuff" had collected on the bearing which made its diameter slightly larger than the cutting edge diameter.

1. 
   davcefai | Mar 16, 2009 12:51am | #9

   My experience is that this is the rule rather than the exception. Out of square makes it worse.Have you tried bringing the bearing up as close to the laminate as possible? This minimises the out of square aspect of the problem. I usually file or plane the laminate at 45 degrees to both cure this and to blunt the rather sharp edge that the router leaves.