Official Luthiers Forum!

So one of the first things I learned when starting to use routers a few years ago is that straight bits dont like certain grain patterns - esp end grain.

So much in fact that they will often rip large chunks out of expensive exotic woods...forceing the hapless wood worker to scrape themselves off the floor and start all over again with a new peice.

However, I was at Home Depot today and noticed that they stock two or three straight cutters with slightly angled blades, and I assume this is designed to prevent tear-out, no?

Anyone experienced with these bits?
Are they 'safer' to experiment with on end grain?

the shear cut bits will help reduce end grain tearout, but are no guarantee to stop it. that is why end grain should be routed first, often with a climb cut to start, before the adjacent cut with the grain is made.

[QUOTE=highdrawlicks] Do you mean that the flute is angled so the cut is actually a shearing motion upward or downward? If so, there are quite a few bits out there like it. A lot are solide carbide and come it cut diameters as small as 1/32". These specialty bits can be found on Stew Mac's website for one--listed as downcut spiral bits, I believe[/QUOTE]
I dont mean spiral bits no. Imagine an ordinary straight bit with a 'slighty' anled flute.

With a spiral bit the flute twists halfway round the shaft.

The ones I saw at Home Depot were made by Freud, but I cant find a decent pic that shows the angled flute.

I usually get my bits from Vee Valley, and they dont stock em.

I will only shape curves with a Robosander (50 grit), and finish off with a spiral bit to remove the heavy sanding scratches.

I think those are just the shear bits. I have a couple and they work pretty good. The shear bits are different from the spiral down/upcut. Eagle has them.

Ron

_________________
OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

This is what I'm talking about:

down shear router bit



Ron

_________________
OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

the principle is the same as a spiral, just a cheaper way of doing it. they both cut with a shearing action. the one you pictured is an upcut shear.

Yep. That's the photo Eagle had with the downcut info.

Ron

_________________
OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

[QUOTE=old man]

down shear router bit



Ron[/QUOTE]
Thats it exactly, nice work OM!

they made a mistake with labling the photo. given the orientation of the cutting edge shown, the first part to begin the cut will be toward the bottom, with the cut progressing up as the bit rotates further, i.e., up cut. a down cut has the edge oriented the opposite way, the top of the bit leads into the cut and the cut progresses down the bit, i.e., down cut.

if you look at their photos of their spiral cut bits you can see side by side the difference in cutter orientation.