Myth Busted - cutter diameter same as shank

[David Buchhauser]

The down shear packs the cut full of chips and leaves too much of a mess (too much time) for cleanup when unloading. If I crank up the DC to pick up the chips, the dc will pull parts off the spoil board. These sheets will have a lot of small odd shaped parts nested, sometimes 50-75 parts on a full sheet. An up shear will also fight the vac and try to lift parts and the instant they begin to wear they raise a ragged edge on the top of the parts which is no good. To get these on, cut, and packed out the door, I want zero cleanup when they come off. No sanding off fuzzies, nothing, staight in the boxes and out with hopefully as little dust to pickup when emptying the table. The other big problem with thin material and spirals is they generally have a fairly long cut length so youve got a lot of bit that will never get used when I can run a 1/2" or 3/4" cutter length with the straight cutters. If the chips and the work holding werent an issue and I had a Dbit grinder I could lop the ends off and keep shortening them but again, the chips and the lifting with the spirals are the issue.

No disagreement about the brazed (or any small tooling) being very narrow at the core. The part that is impressive to me is that the two bits are identical until the fillet begins (perhaps .020" above the flutes) and the larger shank adds that much strength. I have literally never broken a 1/2" shank tool with a 1/4" or 7/32" cutting diameter even pushing them at 500ipm when they are dead dull. The cut just goes to pot but they keep on cutting. Even in the metal world with solid carbide tooling and pre-forms you will see very large shank diameters reduced down to a smaller tool, Im sure for all the same reasons, rigidity, heat, collet holding.

I can often come across 7/32" (undersized ply) bits at really good prices and use them for all sorts of mortising and dados on drawer boxes and so on where we need a snug 1/4".

Mark,
Thanks for that explanation. Very informative! Until Brian mentioned "brazed tooling" - I guess I didn't really understand exactly what router bit you were using. I think the one below must be similar to the 1/4" bits you tested.
David

[Jim Becker]

Most .25 " compression cutters seem to feature a 1" cut length...I actually had the opposite problem than you there...I couldn't readily get one that exceeded 1.25" without going to a larger diameter so I was right at the limit for cutting 1.25" exterior MDF.

[Mark Bolton]

Right but even with a 1/4" dia compression your up cut on the tip is usually 1/2" or more. So with 1/4" material there is no sense in spending the money on the rest of the "compression" portion thats never going to see a single wood fiber.

[Mark Bolton]

Mark,
Thanks for that explanation. Very informative! Until Brian mentioned "brazed tooling" - I guess I didn't really understand exactly what router bit you were using. I think the one below must be similar to the 1/4" bits you tested.
David

A 45204 is similar. Much shorter cutting length. But yes. The tool in your image would be a screamer (i.e. ears rattling) for me, and would likely have snapped far sooner.

[Jim Becker]

Right but even with a 1/4" dia compression your up cut on the tip is usually 1/2" or more. So with 1/4" material there is no sense in spending the money on the rest of the "compression" portion thats never going to see a single wood fiber.

The up-cut on the .25" compression cutters I use is 3/16". One is Whiteside; I forget what brand the other one is, but probably US Router Tools as it's the older one. I use it with 1/4" material all the time with no issues.