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3 tooth rule for bandsaw blades, but what if your cutting multiple bars?

Edster

Diamond
Joined
Feb 8, 2003
Location
Illinois
I was cutting 24 bars of 4" x 1/8" 6061 Aluminum today on the horizontal band saw. I was cutting the whole bundle at once so it was like cutting a 4" x 3" bar. I was talking (more like arguing) with one of the guys at the shop about the three tooth rule for bandsaw blades. He was trying to say that it didn't matter that I was cutting 24 pieces at once, what mattered was the material was only 1/8" thick and I should have minimum of three teeth in each piece of material.

I know that the bundle won't act like a single piece of stock would, the chip will break between the individual bars. But there is still the fact that the blade is passing through 3 inches of material and there has to be enough space in the gullets of the blade for the chips. A blade with less teeth will have more room for chips. My theory is to use a blade somewhere in between what would be used for one bar 1/8" thick and one bar 3" thick. I ended up using a 6-8 tpi blade and it worked good. I have also used 4-6 tpi blades with good results on this job in the past.

So what do you guys think? The three tooth rule seems to work good for cutting individual pieces, but what about cutting multiple bars?
 
Just like when we were kids and some wise guy would ask which weighed more a ton of bricks or a ton of feathers ;)

Seems like you did just right to me as you don't want the gullets to fill up or the blade stops cutting.
 
Three teeth in a 1/8" thick piece of material? That would be an absurdly fine blade for cutting any aluminum. The three tooth rule is a guide at best but you have to be practical in applying it. For virtually all of our cutting--in a job shop where material can vary from 1/2" round to 6" square tube--we have found that a 1" x 5-8 vari-tooth blade cuts well and lasts for a reasonable length of time. If you're cutting a lot of one size of material a better matched blade may be appropriate but if you're constantly changing materials--and operators--blade changing gets old in a hurry...
 
I would have cut the whole bundle as you did and wouldn't have thought twice about it. The 3 teeth rule more applies to cutting thin sheet or rod. When the work piece can fall between two teeth is when you can have a problem. The blade will want to sheer the material instead of cut and make a chip. For example, a lot of blades get trashed when someone tries to run a piece of 1/16" steel sheet on the vertical bandsaw that's equipped 4-6 tpi blade. "I'll just zip off a few pieces of shim stock real quick.........:mad5:"

I gave up years ago trying to get people to change blades for the material they're cutting and focused my efforts on being able to change out a trashed blade really quickly. Part of my job is changing out blades after non machinists use the saw. It's impossible to stop the blade trashers.
 
What matters a lott is what type of feed you have
with manually downfeed your saw can sort of fall over the material with a coarse saw
But with powerfeed the saw lowers no more as set for, so you can use a much coarser saw

peter from holland
 
To answer your question, yes, it works both. Even if you’re cutting multiple bars at a time, the three tooth rule still apply. Let’s take your situation as an example. You’re first cutting individual 4”x 1/8” aluminum bars. Then you bundle all 24 pieces at once. It wouldn’t really matter. It is just like you’re cutting two aluminum bars with different dimensions. One is a 4” x 1/8” aluminum bar and the other one is a 4” x 3” aluminum bar. The only thing that will matter is the tpi of the blade that you’re going to use. A vari-tooth blade’s average tpi multiplied to the bar stock size should follow the engagement rule of a minimum of 3 teeth in the cut and a maximum of 24. The optimum number of teeth engaged in one cut is 6 – 12 teeth. The best blade to use with the aluminum bars that you’re cutting is a 2-3 tpi blade because it will yield an optimum no. of teeth engaged in one cut which is 10 teeth engaged. Plus, a 2-3 tpi blade has bigger space for the chips.
 
I would have cut the whole bundle as you did and wouldn't have thought twice about it. The 3 teeth rule more applies to cutting thin sheet or rod. When the work piece can fall between two teeth is when you can have a problem. The blade will want to sheer the material instead of cut and make a chip. For example, a lot of blades get trashed when someone tries to run a piece of 1/16" steel sheet on the vertical bandsaw that's equipped 4-6 tpi blade. "I'll just zip off a few pieces of shim stock real quick.........:mad5:"

I gave up years ago trying to get people to change blades for the material they're cutting and focused my efforts on being able to change out a trashed blade really quickly. Part of my job is changing out blades after non machinists use the saw. It's impossible to stop the blade trashers.

Maybe a padlock on the power switch!!:D
 
What matters a lott is what type of feed you have



Agreed. The "three teeth engaged" rule is to prevent you, the terrible collection of pathetically inaccurate muscles, from jamming the part into the blade and ending up with an excessively large chip load. If you have a feed mechanism that has a set feedrate then it doesn't matter.

If the feed mechanism has a set feed *pressure* then it does matter.

Incidentally, i've never heard anyone say you have to have exactly 3, as if that was a magic number. Just that 2 or 1 is unacceptable. 3 teeth engaged is the minimum.
 
Treat the stacked pieces as a solid. Every blade rep I've ever talked with takes the amout of material in the cross section and that gives you your material thickness. Take structural 12ga tube. One piece will destroy a 6/8 blade, but stack up 10 pieces or so(2X5), and you can cut all week long. .1" wall thickness x 2walls x 5 pieces= 1". The more you can cut at once the better. I used to work for a place that cut a few tons of 10, 12, and 14ga tube per day with 6/8 and even 4/6 pitch blades with no problems.
 
For best results, a minimum of 3 teeth engaged in one cut and a maximum of 24 should be observed. It doesn’t have to be exactly 3 and 24. The three tooth rule serves as a guideline.
 
I would have cut the whole bundle as you did and wouldn't have thought twice about it. The 3 teeth rule more applies to cutting thin sheet or rod. When the work piece can fall between two teeth is when you can have a problem. The blade will want to sheer the material instead of cut and make a chip. For example, a lot of blades get trashed when someone tries to run a piece of 1/16" steel sheet on the vertical bandsaw that's equipped 4-6 tpi blade. "I'll just zip off a few pieces of shim stock real quick.........:mad5:"

I gave up years ago trying to get people to change blades for the material they're cutting and focused my efforts on being able to change out a trashed blade really quickly. Part of my job is changing out blades after non machinists use the saw. It's impossible to stop the blade trashers.

I think this is pretty funny - sounds just like our shop.

We did a big fish bbq at our place a month or so ago and I used the bandsaw to rip a bunch of cedar and alder planks from 3/4" thick to half that so that I could cook the fish on wood planks. Filled the bandsaw with wood sawdust. When I was done, I opened up the saw to find that it hadn't been vacuumed out or chip bin emptied since the last time I was into the saw about a year ago.

So if you are in there changing the blade . . . clean the damn saw while you are at it!! :codger:
 
I think this is pretty funny - sounds just like our shop.

We did a big fish bbq at our place a month or so ago and I used the bandsaw to rip a bunch of cedar and alder planks from 3/4" thick to half that so that I could cook the fish on wood planks. Filled the bandsaw with wood sawdust. When I was done, I opened up the saw to find that it hadn't been vacuumed out or chip bin emptied since the last time I was into the saw about a year ago.

So if you are in there changing the blade . . . clean the damn saw while you are at it!! :codger:



With the saw turned off, of course.
 








 
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