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Puckdropper
03-18-2017, 07:33 AM
I've got a Jet 14" wood band saw with Powermatic Riser block that isn't running how I expect it to run. What happens is the blade "fishtails" in as it goes through the table. What I mean by that is part of the blade is moving side-to-side like it's being twisted.

Because of the fishtailing, the blade cuts a much wider kerf then it has to.

I have tried replacing the tires and recrowing the tires, and the wheels seem co-planer but it's not exactly easy to get a decent reading. Blade tension seems fine, it's about an E or F on the bottom string of a guitar, using the pluck method.

I'm wondering if the one wheel is at an angle to the other (a twist along the vertical plane) so as the blade comes 'round it's actually twisting. Think of a piece of paper held between your hands, with them at an angle to each other. Does it sound plausible that this is the cause? Is there a way to measure this enough to get close? It takes several minutes to detension the blade then undo the bolt holding the halves together and adjust the top. (I've already ground off one alignment pin to give me that freedom of movement.)

I'm open to suggestions, even a "that's normal for that saw" would let me put the tools away.

J Harp
03-18-2017, 07:51 AM
Are the guides properly adjusted? Many people suggest the thickness of a dollar bill clearance between the blade and the guide. The blade should contact the back bearing as soon as cutting pressure is applied.

Take the blade off and see if it is bent front to back, it could have been jammed and stretched out of shape. There could be sections of the blade which have been twisted. Sounds to me like the problem is a bad blade.

Lowery Racing
03-18-2017, 08:21 AM
I 2nd J Harp's reply, have you tried a new blade?

Puckdropper
03-18-2017, 08:38 AM
There are no guides on the saw right now, I took them off for diagnostic purposes.

I will try a new blade, but this one does look to be in good condition. However, I did post something yesterday about holding on to false assumptions...

tincture500
03-18-2017, 09:08 AM
Law the current blade on a level concrete floor or table on the back side of the blade. Then sighting to see if there are gaps between blade back and surface. This will expose kinks. Realty sounds like the blade is the source. Other thing to check is the drive belt. If it has a bump or lump, when this passes the puppy, it may cause a moment of greater tightness, causing a jump
Tom. I did stay at the Holiday inn 😁

Stepside
03-18-2017, 11:12 AM
If you remove the table you should be able to check if the wheels are co-planer with a long enough straight edge. Check the wheels in four or more places. Start with the right hand side of the wheels. The straight edge should touch in four places. Go closer to wheel center and check again and then check the left side of the wheels in two places. I would do this with the blade at proper tension.

It is possible the Riser block does not fit correctly. I have a 14 inch Jet with a Jet riser block that has no problems.

It would be wise to check the blade for issues before doing anything else.

Puckdropper
03-20-2017, 11:45 AM
The new blade was the last piece to the puzzle. I noticed it was leaving about 1/16" kerf on a test piece of 2x4, that's just about perfect. The finish was also smoother than it's ever been, so the tune up did some good.

It cuts a lot faster as well.

Thanks!