Simple Question? Hacksaw blade teeth / inch?

[CuriousInventor]

I've been trying to sort out some conflicting information about choosing the best teeth per inch on a hacksaw blade.

Many sources say that the only thing that matters is getting at least 2-3 teeth in contact with the metal at all times. But others say that higher teeth/inch numbers should be used for harder materials, and lower for softer materials.

I imagine this recommendation has to do with the teeth filing up or clogging. If you had too small of teeth for a large piece of material, it makes sense that they could clog up.

I haven't read anything to support this, but my guess is that, to cut the fastest, the goal should be to use as many teeth as possible as long as they don't start clogging.

Any thoughts on how teeth count relates to cutting speed / ease and hardness of material?

thanks, --Scott

[martinw]

Originally Posted by CuriousInventor I've been trying to sort out some conflicting information about choosing the best teeth per inch on a hacksaw blade. Many sources say that the only thing that matters is getting at least 2-3 teeth in contact with the metal at all times. But others say that higher teeth/inch numbers should be used for harder materials, and lower for softer materials. I imagine this recommendation has to do with the teeth filing up or clogging. If you had too small of teeth for a large piece of material, it makes sense that they could clog up. I haven't read anything to support this, but my guess is that, to cut the fastest, the goal should be to use as many teeth as possible as long as they don't start clogging. Any thoughts on how teeth count relates to cutting speed / ease and hardness of material? thanks, --Scott

Dear Scott,

That is a very good question, and, writing as one who always has disasters with hacksaws, I eagerly wait the replies. I have always assumed that bigger teeth will give a less cloggy cut, but at the price of a rougher cut, no matter the thickness of the material. I could well be wrong. Material hardness and lubrication come into this, but I do not know how.

Thanks for posting the question

Best wishes

Martin

[vulcom1]

There are two types of blades that you can purchase at most stores. I like using the higher tooth count for thin materials and the coarse for thick. The two types are the regular blades and the other is bimetal. Cutting alum. or soft metals the regular works okay. I only purchase the bimetal as for the few cents more it will also cut materials like stainless steel. Won't last long but the regular blade will lose there teeth on the first or second stroke.
John

[CuriousInventor]

From what I've read (not necessarily seen in stores), the bi-metal blades are the 'best-of-both-worlds' between carbon steel blades and Molybdenum HSS. The HSS blades are hard throughout and, because of this, are likely to snap, but apparently work well in very rigid setups. Plain carbon won't be able to cut harder materials and lasts some 70% as long as bi-metal.

The bi-metal blades have hardened teeth and a flexible back so they'll last longer, cut hard stuff and be less likely to break. Then there are the carbide grit blades for cutting really hard stuff, but I'm not sure what hardness level would cause you to switch over from a bi-metal to a carbide blade.

Briney's Home Machinist's Handbook seems to recommend using more teeth for harder materials, but I doubtful of this. The machinery's handbook recommends tooth pitch purely on the size and shape of the work, and only tooth form and type based on material. It only talks about band-saw blades, not hacksaw blades, though.

Still not sure how hardness / pitch / cutting speed relate.

thanks for the help, --Scott