7 1/4" Blades on BT

[ke4rdb]

Has anyone tried using 7 1/4" blades on there BT3100? I've noticed you can get some big time bargains on this size blade (example:Freud for $7.50). I would think for thin (ner) stock (up to 4/4) it would work fine! What do you think?

James

[Knottscott]

If the arbor bore is 5/8", they should work. You lose height capacity, and the angle of attack is different from a 10" blade due to the tighter radius. Also, many have very thin kerfs....thinner than a standard 3/32" TK, so try to stay with high quality.

[LCHIEN]

Has anyone tried using 7 1/4" blades on there BT3100? I've noticed you can get some big time bargains on this size blade (example:Freud for $7.50). I would think for thin (ner) stock (up to 4/4) it would work fine! What do you think?

James

you'd lose 2-3/4" diameter or 1-3/8" radius so your max depth of cut would be 2-1/8" approx.
You would also loose tip speed, same RPM but less feet per minute and cuts per minute at the perimieter of the blade so it might be less smooth
cutting.

I don't see much point in it unless you plan to cut some hardiplank or something like that where a 7" diamond blade might be a lot cheaper than a 10" blade...

[Tom Miller]

I guess a show-stopper for me would be the fact that it wouldn't work with my riving knife. And I'm not sure that you could make a riving knife thin enough to work.

I usually steer clear of "absolute" statements, but "I don't cut without my riving knife" is the closest I've come.

Regards,
Tom
p.s. I don't go through blades so much that I'd need to save much $$ there.

[LarryG]

Subject to the obvious limitations, there's no technical reason this wouldn't work. After all, a lot of us use dado sets that are only 6" in diameter.

That said, Tom's point about the riving knife is a good one.

But THAT said, this might be a good dodge for those who cut a lot of MDF, particleboard, or plywood, all of which are h3ll on carbide. The kerf cut of sheet materials are not as prone to closing up as grained lumber, which makes the RK less necessary, so if one could find a good-quality 7-1/4" blade at a lowball price, use it until it's used up, toss it, slap on another ... yeah, that could work. I'm going to give this some thought for my own shop, in fact.

Only other caveat I can think of offhand is to make sure the blade is rated for the ~5000 RPM at which the BT motor turns.

[Tom Miller]

The kerf cut of sheet materials are not as prone to closing up as grained lumber, which makes the RK less necessary....

I wasn't even thinking about the how the RK keeps stock from closing on the blade. I was thinking about how the back side of the blade can pick up your piece of sheet goods and "present" it to you, frisbee style. At least that's how I became a lifetime member of the "Riving Knife Good!" society. (Or was it after my "thumb" incident?)

But, having said THAT, how about if you put a couple of these blades together? Does that get you to 3/32" or more? Do you still save enough $$? I recall reading about a guy who used to make 1/4" dados with a handful of these blades. (Or did I dream that?)

BTW, I'm not proposing that lack of riving knife should be a show-stopper for everyone. But it does get my attention.

Regards,
Tom

[Jim Boyd]

I have used a 7 1/4" blade on numerous occasions. I never noticed any problem with the riving knife cause I never had it installed I always chose the thinnest blade I could get and matched them to a ZCTP made for them. I used them to cut thin veneers and pattern pieces for segmented pens and bowls. I still use them with my Unisaw.

[Pappy]

I have a Freud TK303 that I use when I need a extremely thin kerf.

[vaking]

I see no reason why 7-1/4" blade cannot be used but the benefit is not so clear. I think even the not-so-good 10" blade will still outperform any 7-1/4 blade. The not-so-good 10" blade can often be had for small money, in fact you can get even very good blades on clearance. I am currently using a "woodworker's choice" blade (High end of Oldham brand) and it is my general all-purpose blade and I am happy with it. I can easily compare it to the original Freud blade that came with BT3100. I am using a 40T blade which I got for $10. The only time I can see a use for a small blade is if you need to cut something you know will kill your blade and you want to save a better blade.