problem with band saw when cutting a bowl blank

[Stefan Antwarg]

I use a 14" jet band saw and I had a 1/4" blade on it. I had a 4 inch thick piece of pine on my homemade circle cutting jig. The more I got into the cut, the more sideways pressure was being put on the blade. Finally, the blade just ate through the plastic blade block (I don't know what they are called). The blade was really bending to the right. Anyway, I had to get the blade out of the blank and finish it freehand. Any suggestions.

Stefan

[Tony Laros]

I don't what others use for cutting bowl blanks, but I bought a 1" 3tpi blade, set the tension tight and have had no problems since. I did have problems earlier with the smaller blades.

[Jim Becker]

Stefan, it's important that you use both the correct blade for this operation and have it tensioned properly. If that 1/4" blade had more than about 3tpi, it's not going to cut efficiently nor will it be able to clear the dust out of the kerf of that thick material. If the wood is not "dry", the blade may also be too thin. Also, the behavior you describe is that of a dull blade and/or too little tension.

I find that a 1/2" 3tpi Timberwolf "AS" blade usually works best for me in cutting turning blanks, especially out of wet wood. Th "AS" blade is slightly thicker yet can still be tensioned by a 14" bandsaw. The 1/2" width will tend to wander a little less.

One other thing...there really isn't any good reason to try and cut a perfect circle when you are making your blanks. Just draw a circle and free-hand the "circular" blank out with relatively straight cuts...you'll be re-balancing it on the lathe in a few minutes anyway. You'll end up with a bunch of triangular pieces that make excellent kindling. :D I did that just yesterday on the blank for the ash bowl I posted in another thread...and I was using a 1" blade that just doesn't go around in circles!

[Tom Hintz]

I also use a 1/2" Timber Wolf blade for "rounding" bowl blanks. I think mine is a 6 tpi, but it works very well.
I measure across the blank in a couple of places, mark the approximate center and then use a compass to draw a rough circle on the blank. I saw the corners (mainly) freehand and then finish rounding it on the lathe, as mentioned before.
I used to use the circle cutting jig but it was too time consuming and the results weren't noticibly better than freehanding it.
Another thing that can load the blade is if the circel cutting jig is "walking" away from the pressure being applied to the blade. My old jig did this so on my new version, I built in a lock that prevents the jig from moving away from the blade.

[Stan Smith]

Here's a simple method. What blade to use has already been discussed. I cut a bunch of graduated 1"circles out of 1/2" plywood. First a try to get a flat surface on one end that will sit on the bs table. I Put the plywood circle pattern on the other end and draw a line around the outside with a yellow or white crayon. Then, as Jim suggests, just cut off the wedges along the circle line. This does safe time but if you are doing something small, it's probably just as fast to turn it to round on the lathe.

Stan

[Stefan Antwarg]

Thanks for the advise everyone. Blades and blade tensioning has just been a mystery for me. I have purchased the Timberwolf blades and tried to tension it according to the instructions. It says to tension until there is no wobble, then just one more turn. That method just doesn't seem to work for me because it always looks like it is wobbling. Maybe I am just not looking at the right thing. The wood was very dry and the blade is 6tpi. I wouldn't say it is dull, but it is probably not sharp. I do own a 1/2" 3tpi blade. I will just us that free hand from now on.

Thanks

[David Rose]

Stefan, you have figured on what to do on your question, but you still will want tension somewhere in the right area to avoid other problems. Unless things are being forced out of alignment, that sounds like a very loose blade. I can't use the TW "flutter method" for tensioning my Delta either. Does your saw have any sort of tension gauge? They usually aren't very accurate as the springs get weak with age, but it can be a starting point. With TW blades my 3(?) year old Delta will tension 1/2" blades well set for 3/8" blades. I do release the tension after every daily (well... most :( ) use.

David


Thanks for the advise everyone. Blades and blade tensioning has just been a mystery for me. I have purchased the Timberwolf blades and tried to tension it according to the instructions. It says to tension until there is no wobble, then just one more turn. That method just doesn't seem to work for me because it always looks like it is wobbling. Maybe I am just not looking at the right thing. The wood was very dry and the blade is 6tpi. I wouldn't say it is dull, but it is probably not sharp. I do own a 1/2" 3tpi blade. I will just us that free hand from now on.

Thanks

[John Preston]

I made my own circle jig, and end up remaking it every time I use it, but one thing I've had problems with that would also cause your problem is putting the center of the circle in front of the blade or behind the blade. When it is in either of these locations, it side loads and twists the blade, and with my 1" blade and 2.5 hp motor, it starts whining and my blade guides start moaning, then about the time the smoke starts pouring out of the kerf, I figure I must be doing something wrong.

I put my center right even with the teeth of the blade, and what do you know, it works like a champ.