Freud PG12-150 Router Bit

[Charlie Cobb]

So I bought a sheet of 3/4" plywood to make a case for some audio/video components. I also bought the Freud PG12-150 Router bit to route some dados for shelving. I made some test dados and the dado is not big enough. Can someone tell me why it didn't work? I am a relatively new woodworker and it said that this was the correct bit for "today's 3/4" plywood." The bit dimensions are 12/32" D x 1 - 1/4" L. Did I buy the wrong bit? Which bit should I buy? Thanks in advance for your assistance.

[glenn bradley]

I also bought into the "plywood" bits when I started. Even with the best of intentions by the makers, bits cannot possibly account for the wide variations in plywood thicknesses we come across. This is even true on the same sheet of ply in some cases.

I use a bit that is smaller than the desired final thickness and take two passes to get a dado that is a good fit. On short runs I use a dado stack on the tablesaw but rather than shim my brains out I just use the same two pass technique.

Something like this (http://www.sawmillcreek.org/showthread.php?t=46406) may help you. Took me about an hour to build, 3 years ago, and I still use it.

[Jim Rimmer]

The bit dimensions are 12/32" D x 1 - 1/4" L.

Am I having a senior moment or is that a typo? I keep looking at 12/32" D and coming up with 3/8":confused:

[Matt Armstrong]

I use kempston plywood bits... Most plywood fits but sometimes you have to take two passes. Some plywood was .745" and some was .708", etc... I had a heck of a time when I started - some pieces fit snug and excellent, others were not going in under any circumstance. Just take two passes on the thicker pieces.

[Curt Harms]

except I didn't use a router bushing. Most of my dados are for 3/4"nominal ply. I use a 1/2" diameter 1/2" cutting depth top bearing pattern bit. The jig is 3/4" MDF so when the bit if resting on top of the piece to be dadoed the bearing will ride on the wall of the jig. Set the width of the crack in the jig to the thickness of the plywood to be fit into the dado. Perfect fit every time regardless of the thickness of the plywood. There are some disadvantages to this--It wouldn't work well for dados less than 1/2" wide--I don't recall ever having seen a pattern bit less than 1/2" diameter. But for stock wider than 1/2" it works really well. I make 2 passes. Make the first pass shallow for a clean surface cut, make the second pass to final depth.

[Charlie Cobb]

That was a typo 23/32"

[Peter Quinn]

You can make your life easy by skipping the plywood bits altogether. By a 5/8" bit, make 5/8" dados, then make a tall fence for the TS and trim the ends of the sheets that will fit in the dado to match the dado width. If you are uncomfortable with that you can do it on a router table, though it is slightly more accurate to run the cutter "above" the work, so a slot cutter would actually be better, or a rabbit bit with a long shaft. Think of it as a tongue and groove or M&T. You always make the groove, then fit the tongue to that. Same idea.

Plywood is all over the board in terms of thickness, and sometimes a single sheet may be different thicknesses from edge to center or end to end, so no bit is going to cover it all. Sometimes that darn metric system pops its ugly head up too. Who do those Europeans think they are to force their arbitrary measuring system on us over our native arbitrary system anyway just because its easier to divide by 10? Fit the plywood to a predetermined dado somewhat under 3/4" and you have eliminated the plywood's thickness as a variable over which you have no control. Do not be a slave to your sheet stock! Free your self from the tyranny of industrial manufacturing inaccuracies and international commerce I say and do so at once!:D