Monday, our own reality show

Re: Monday, our own reality show

I suppose I could shave a little time it takes to answer, but I don't want to plug any particular product.

John

Re: Monday, our own reality show

I'll give you a plug, and perhaps the shave, but you'll have to explain further to get full credit. I think I know where you're headed but you still have to choose the correct path.

Re: Monday, our own reality show

a hole saw removes a plug from wood. it is limited by the depth of the cup , usually about 1". A forstner bit drills a hole turning all of the interveening wood into shavings. It is limited in depth only by the lenght of the bit and the power of the drill behind it. In a hole saw there is only a pilot bit in the center and a saw edges circumference. in a forstner bit there are one or more shaving surfaces between the center point and the edges. It actually planes off the surface of the wood as it rotates.

John

Monday, answer

John gets a star for the difference between hole saws and Forstner bits.

True Forstner bits do not have teeth, although through common terminilogy sawtooth bits also get called Forstner bits-- and there is no other name for the sawtooh variety. I call them Smyth bits (why not), they look real enough but only work better in select applications. The ORIGINAL bits were for cutting through face grain. But they are very hard work drilling end grain--especially in larger diameter holes, so somebody thought of adding teeth to the rim to make them cut easier. When made well they can shave the wood and are supposedly cooler running too, but that is up to debate.

So the answer is the bits with teeth are intended to make them cut larger diameter holes easier into end grain. In that sense they saw first on the edge then shave as the bit decends.

Still, as a purist of sorts, I believe that a true Forstner bit has no teeth. You can make your own choices but a look alike regardless of manufacturing process in my opinion does not a Forstner make.

As to the hole saw, it is intended to make a through hole, it does not remove the core until completely through the medium. A hole saw does not take out the middle (core) portion of the cut. With a hole saw a partial depth �trapped� flat bottom hole is not possible. Plug cutters are essentially a hole saw but because of the diameter of the cut the center portion can be levered out --but that is a different solutiom for a different question.

More: Forstner bits, named after their inventor, Benjamin Forstner, bore precise, flat-bottomed holes in wood, in any orientation with respect to the wood grain. They can cut on the edge of a block of wood, and can cut overlapping holes. Because of the flat bottom to the hole, they are useful for drilling through veneer already glued to add an inlay. They require great force to push them into the material, so to restrict freedom are normally used in drill presses or lathes rather than in portable drills. Unlike most other types of drills, they are not practical to use as hand tools.

The bit has a centre point which guides it during the cut (and incidentally spoils the otherwise flat bottom of the hole). The cylindrical cutter around the perimeter shears the wood fibres at the edge of the bore, and also helps guide the bit into the wood precisely. The bit�s radial cutting edges plane off the material at the bottom of the hole. Sawtooth Forstner bits are available, with many more cutting edges in the cylinder. These may cut faster, but almost always and over time produce a more ragged hole.

Forstner bits have no mechanism to clear chips from the hole, and chips must be lifted out periodically to do this.

"Forstner" bits of both styles are commonly available in sizes both standard and metric.

That's a "bit "of a long tail : )