There's not a huge difference in my experience. The saw teeth generally come with the larger bit sizes and are often mixed with the plain sort in sets of Forstners (I think the term "Forstner" actually refers to the sort without teeth but the bits have become pretty much interchangeable in the cheapish sets one can buy.
The biggest difference between bits I have found relates to the efficiency with which they clear chips. The smaller sizes especially are prone to clogging as soon as the bit head gets below the surface of the work. Unless you retract the bit and clear it frequently, it will get very hot, expanding in the process and jam and burn your work.
When sharpening these bits (use a fine file), only attack the inside bevelled edges of the bit, do not try to sharpen the outer diameter or the flat part of the inner cutters, you will only ruin the bit in all likeihood
Alternatively, if the work allows it, you can bore just deep enough so the central pilot point breaks through, and then flip the work over and drill the rest from the other side.
I believe the saw tooth type are supposed to be better for boring into end grain, and the smaller sizes are always smooth rather than saw toothed 'cos there just isn't the space, or need probably, for the teeth. I'm not sure, but I think the saw teeth may be a recent innovation; I've never seen a forstner bit for a brace with them and they don't seem to feature in the 1935 Buck & Hickman catalogue either. Possibly created for the benefit of turners?
Neil, yes those do look the business and in my effort to equip my workshop with bits that cut and not just pretend I might be tempted to invest a little hard earned cash in the sizes I use most often :wink:
I've tried the 'cheapo' so-called Titanium Coated efforts from ebay etc, more like gold coloured metal, the lorry delivering them to the shop may have past by a titanium coating factory but these bits haven't seen anything like that as I cut one in half and it was a gold colour right through, not just a coating. Some are genuine though as they are generally hss with, presumeably, a titanium coating, can't say I've noticed much difference in cutting quality so it's the good stuff from now on
Good Idea Dog, My girls bouhght me a set from Machine Mart, I coulnt bring myself to ask how much they spent but the things are next to useless, they appear to have the edge holding properties of pastry and the cutting ability of a dead worm. I would not recomend them :twisted:
Don't know when the saw-tooth type was developed but it it certainly the preference, and commonly used by woodturners, for boring into end grain. Either type is fine for boring into cross grain but definitely look to use a saw-tooth for a clean, efficient cut into end grain.
Can I just ask a quick stupid question?
Is there much difference between the cutting abilities of forstner bits and spade bits?
I know spade bits don't clear the debris very efficiently when they're withdrawn, but is this the only difference?
Forstner bits are far superior, giving a very clean cut and smooth operation in a drill press. It is safe and easy to overlap holes if need be, which is more dangerous with spade bits, and forstners are available in very large sizes.
Yours was a very sensible question compared to some of the ones I ask :wink:
Make sure you do invest in a good set though, as I and others have said already the cheap ones aren't worth the bother, better to get the best you can afford and if that means saving for a while, do it :wink: