Learning blade specifications

[rtdreep]

I'm not a machinist, but have been tasked with editing some content that contains specifications for Sawzall blades. My question: What does it mean to have a blade that is 4-6 or 8-12 TPI? That doesn't make sense to me, as other saw blades have a single digit for teeth-per-inch. How can a blade have a range of teeth-per-inch? Or, are 4-6 and 8-12 a different designation?

Thank you for any info you can provide. --Rick

[christinandavid]

In what context are you given these figures?

You would possibly see this format on the machine itself, as a recommendation for a specific thickness or material eg for 2" thick material use a blade 4-6 TPI. Maybe?

Or maybe a blade with the same tooth profile would have a different TPI depending on blade diameter?

DP

[ctate2000]

The pitch alternates. The purpose of this is to allow you saw a wider range of cross sections. I think the rule of thumb is three to four teeth in the cut at any time.

[Pandinus]

I recently bought a bandsaw blade that was variable pitch... 10-14 tpi... the teeth get closer and farther apart... cuts real nice... don't know if that applies here.

[djr76]

Originally Posted by rtdreep I'm not a machinist, but have been tasked with editing some content that contains specifications for Sawzall blades. My question: What does it mean to have a blade that is 4-6 or 8-12 TPI? That doesn't make sense to me, as other saw blades have a single digit for teeth-per-inch. How can a blade have a range of teeth-per-inch? Or, are 4-6 and 8-12 a different designation? Thank you for any info you can provide. --Rick

Tooth Pitch is always measured in the number of teeth per inch---from tip of tooth to tip of tooth. Variable Tooth blades are indicated by two numbers since the tooth pitch and the gullet depth varies.

[rtdreep]

Thank you all for your input; it's much appreciated!

[Delw]

Originally Posted by rtdreep I'm not a machinist, but have been tasked with editing some content that contains specifications for Sawzall blades. My question: What does it mean to have a blade that is 4-6 or 8-12 TPI? That doesn't make sense to me, as other saw blades have a single digit for teeth-per-inch. How can a blade have a range of teeth-per-inch? Or, are 4-6 and 8-12 a different designation? Thank you for any info you can provide. --Rick

Rick on my band saw I run a 4-6tpi
the way I understand it is 6 teeth per inch how ever they throw the 4 size in there for clearance, so you have 4 small teeth and 2 big teeth.

I just got one a bit ago I will check it out and verify

[Delw]

looked up a better example

http://www.worldwidesaw.com/faq/

Variable pitch blades are usually preferred in most applications because of the varying teeth configuration per inch. Beacuse the teeth vary between fine and coarse, sawing harmonics vary, thus vibration and chatter are dampened. Adjusting the blade speed is another way of reducing sawing harmonics problems. Think of a washing machine that speeds up during the spin cycle. At a certain point the rotation of the drum hits "resonance" and the washer want to start walking across the room. Soon the rotation speed increases and the washers stops walking and shaking. You don't want to have your saw hit resonance and stay there. Variable pitch blades accomodate a wider range of material cross sections and are particularly useful when cutting rounds and tubing, due to the fact that the top and bottom of the curved workpiece will have a smaller cross section than the middle of a round solid and this is where the harmonics problems tend to be the worst (entering and leaving the workpiece). For tubing and pipe, the top of the material cuts like a solid, then the sides of the tubing cut like thin flat stock.