Bandsaw blade TPI

[David Romano]

I'm trying to understand the relationship between TPI, board thickness and number of teeth in the stock at one time and also how this affect the quality of cut vs speed of cut. What I've learned so far makes sense for thin stock

TPI = board thickness x number of teeth in the stock

where more TPI = finer cut with the upper limit being overheating of the stock and/or blade

Miminimum recommended number of teeth in stock is 2 - 4 typically and so 6 tpi is popular for 3/4" boards

I use a bimetal blade with a 4/6 variable TPI, so that averages 5 TPI. The cut quality is really good but I find that 4" thick is a practical limit for stock thickness. This equals 20 teeth in the wood at one time. Going thicker slows the cut too much and burns the wood/clogs up the gullets.

If I apply this knowledge to 12" stock, I'd need about 1.5 TPI and the cut quality would be terrible. Yet, I see that it is popluar to use a 3 TPI blade on stock this thick. That would be 36 teeth in the wood. Why does the equation change? Is it the greater gullet depth at 3 TPI? If so, this leads to the next question which is: For a given tooth pitch, do all gullets for hook tooth blades have the same depth? Or do some blades have extra deep gullets?

I'm considering buying a bimetal 2/3 TPI blade for stock 4 - 12 inches.

David

[Myk Rian]

I'm considering buying a bimetal 2/3 TPI blade for stock 4 - 12 inches.
I use a 1/2" 3tpi TW blade for the thick stuff up to 12". Works great.
For everything else, a 1/4" 6tpi. Just bought a 3/16" 10tpi for the small stuff.

[Phil Thien]

I'm considering buying a bimetal 2/3 TPI blade for stock 4 - 12 inches.


Are those available in a 1/2" blade? Or do you have to go wider to get that low a tooth count in variable pitch?

[Pete Bradley]

Having a minimum of 2 or 3 teeth in the cut helps to maintain control and avoid splintering. However that's a minimum, not a rule for thick stock. As you go bigger, you need bigger gullets to clear chips effectively.

Smaller teeth don't necessarily equal smoother cuts. A good 4 TPI band can deliver a cut that needs minimal planing.

I run 3/8" X 4 and 1/2" X 3 almost exclusively on my 20" machine. Either will resaw out to the machine's max of 13", though the 4TPI is slower.

Pete

[David Romano]

Hi Phil,
The 2/3 pitch is on a 1" blade.

Still love that baffle, thanks again!

David

[David Romano]

....
I run 3/8" X 4 and 1/2" X 3 almost exclusively on my 20" machine. Either will resaw out to the machine's max of 13", though the 4TPI is slower.

Pete

Pete,
Thanks for the input. So now I'm wondering, since most people use a 3 TPI and this is probably not a bimetal blade, what brand of bimetal blade has the equivalent gullet. I'd like to go with the 2/3 variable, but since most bimetals are designed for metal cutting, are the gullets smaller than they'd be for a "wood cutting" blade?

David

[bob hertle]

David,

I don't know whose blades you're looking at, but Lenox makes an excellent 3/4-3H bimetal in the "classic". Another excellent blade is the Olson MVP bimetal in 1/2-3H. Your 4-6 vp blade is probably not hook teeth, but 0 degree rake which indeed makes it harder to feed than an equivalent tooth count hook blade. I haven't seen 2-3 varipitch in anything smaller than a 1 inch wide blade in bimetal. That's not to say somebody doesn't make one.

Personally, I'm with Glenn, in that most of the time I resaw to max capacity (11 inches) on my saw with a 1/2-3H. I have modified a couple of 3/4-3 carbon blades to 1.5 tpi by grinding off every other tooth. The finish in 11 inch white oak, and maple, is better than the 3tpi blade, but all my resaws go thru the planer or a widebelt anyway, so what I care about is flat and true surfaces, not necessarily pretty ones.

Good luck in your quest for the perfect blade!

Bob

[David Romano]

The blade I use is a Starrett Gladiator 3/4" 4/6 pitch. It has a 10 or 12 deg rake. The 2/3 pitch I'm looking at are all 1" blades which is fine with my 18" saw.

I looked a bit further and found a partial answer to my question about gullets. The bimetal Lenox LXP info says that it has an "extreme positive rake tooth and deep gullets for improved chip carrying capacity". This is what I've been searching for. It implies that the gullets are deeper than Lenox's other blades with equivalent tooth pitches. The rake is probably not more than 12 deg. Kaufman has it for $41, which seems like a steal to me.

David