trim/pattern bit diameter

[igor]

Other than concerns about inside corner diams., what diam. size trim/pattern carbide router bit should I get? Also, 2 flutes or 3? Probably getting MLCS standard carbide bits (though open to suggestions on their "Katana" line or other brands). 1/2" shank.

Some uses:

1. cutting opening in new router table top for plate, mdf
2. trimming edge tape on ply
3. trimming wood edge strip on ply to match ply thickness?
4. following patern to route edge of birch veneer ply
5. cutting undermount sink opening in "butcher block" maple countertop (After cutting basic opening with saw, first go 'round router series will use pattern; 2nd go 'round will use top bearing bit that follows edge made by first series.)

TIA. -- Igor

[Routerman P. Warner]

Pattern your pattern bits after this pattern bit set:

*****************************************************************> Other than concerns about inside corner diams., what diam. size

[igor]

Thanks for the reply, but I am looking for information, if it exists, as to why (for example) one would use one diam trim bit versus another or one w/

2 flutes versus 3 when straight trimming an edge. So, for example, is a 1" diam trim bit better than a 3/4" one for veneer trrimming? Are 3 flutes better than 2 for a clean cut? -- Igor

[patriarch]

igor wrote in news: [e-mail]:

I'm not sure of the technical reasons, but my 3 flute, spiral cut trim bit from Amana gives better, cleaner results than the less expensive, two flute designs sold under the Rockler name. There are probably a number of reasons.

That having been said, there are many uses for which the blue bits are just fine, and the price means I can have a wider assortment.

I prefer a larger diameter bit to a smaller one, whenever feasible, providing you have the power to turn it. This again is without substantial examination of the physics, and may just be a Binford factor.

BTW, I thought Pat Warner's set was very clever. But then, his thinking is usually pretty helpful on these things.

Patriarch

[igor]

Thanks.

[Morris Dovey]

Igor...

I'm neither router nor bit expert; and most of my routing is done on a CNC machine - but if what I've learned in that context applies to your hand routing then:

• Choose the largest radius bit that's the same size or smaller than your smallest cutout radius - but small enough that you can control the router! FWIW, I won't even try use a bit as large as

1" freehand /or/ with a pattern because of a couple of scary experiences.

• Feed the router in the direction that pulls the router against the pattern edge (conventional rather than "climb" cutting) - and clamp things so that neither the workpiece nor the pattern can go anywhere.

• When there's a choice, select the shortest bit with the shortest (and fattest) shank that'll do the job. Believe it or not, router bits do flex as they cut - and too much flexing /will/ cause a bit to break (especially solid carbide bits - I broke another one last month by trying to cut too agressively which flexed the bit too much.)

• Larger diameter cutters (depending on cutter geometry) may present fewer heating problems.

• Three-flute bits should allow higher feed rates than two-flute bits to produce the same quality cut.

• Three-flute bits seem to allow more tolerance for pausing during a cut without taking an extra "bite" (making a small bit-size notch in the edge of the cut). My understanding is that three-flute bits are preferred by many signmakers for this reason.

• Remember that heat is one of the worst enemies of router bits, that most of the heat is carried away by the wood chips, that larger chips keep the bit cooler, and that the only way to make the size chip that best carries the heat away is to keep the feed rate up. If the appropriate feed rate makes the router difficult to control, then make a less agressive (which usually means more shallow) cut - and maintain the feed rate.