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How to correct a bandsaw

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Forum topic by Evol posted 01-18-2011 06:47 AM 760 views 0 times favorited 5 replies Add to Favorites Watch
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Evol

2 posts in 2146 days


01-18-2011 06:47 AM

Hi all,

I am currently working on a pair of solid body guitars. The body designs on these guitars require that I “bookmatch” several pieces for joining and lamination.

Wood types:
9.5×21 x 3/4 Hard Flame Maple (looking for a strong 1/4” after plaining)
8.5×21 x 3/4 Bubinga (looking for a strong 1/4” after plaining)
8.5×21 x 1 3/16 Padouk (looking for a strong 1/2” after plaining)

So a test cut showed the blade was cutting even on top and bottom. However as progress reached the center of the board, the blade suddenly appeared right out of the side of the board. The cut was tracking perfectly on the top and bottom. Upon inspection the board was scooped gradually starting 2” into the cut.

Neither of us has ever seen this before. We brought up the blade tension (approaching maximum) and ran another small piece (cherry) it also scooped.

Is there an adjustment we can make to avoid this? This is only the second use of the blade, so it should be plenty sharp. His saw is a Delta 14 bandsaw Model #28 475x (with a 6” throat expander)

I appreciate your help!


5 replies so far

View Nomad62's profile

Nomad62

726 posts in 2418 days


#1 posted 01-18-2011 06:58 PM

The only thing my experience could help with is that perhaps you are feeding the wood thru too quickly. Blade tension will not keep the blade from twisting under a push, and any dull teeth will greatly add to the problem. Try cleaning the blade with mineral spirits, a dirty blade will not cut correctly. Lastly, the blade will need to have 2-3 teeth in contact with the wood as it cuts; if your blade has too many teeth (7-8?) on the cutting surface it will cut poorly as well. Good luck.

-- Power tools put us ahead of the monkeys

View NBeener's profile

NBeener

4808 posts in 2634 days


#2 posted 01-18-2011 07:14 PM

I think Nomad62 hit the high points.

The other thing I would check: your upper and lower guides should be within a dollar bill’s thickness of your blade, and … just behind the gullets of your blade.

But … feed rate is probably your biggest issue.

One more thing: a blade tension “approaching maximum” could be a bad thing. Your coil spring is one of the main things that MAKES a band-saw what it is. If you’re TRULY close to maximum, you may have compressed ALL the spring out of the spring—not a good thing.

If your saw has an index to show how much tension a given width of blade should have on it … I’d use that as your guide—maybe going one thickness, or MOST of one thickness higher.

In other words, if you’re using a 3/8” blade, maybe set the tension half-way between 3/8” and 1/2”

And … on THAT note … you should be re-sawing with about the widest blade your saw can properly tension. For most 14” Taiwanese band saws, that’s probably a 1/2” blade, and—in that category—I like the Wood Slicer !

And … keep your upper guides no more than 1/2” ABOVE the wood you’re re-sawing.

-- -- Neil

View Loren's profile

Loren

8295 posts in 3108 days


#3 posted 01-18-2011 07:16 PM

I’ve seen this problem. First thought is a dull blade or not enough
tension.

Resawing boards for guitar plates is fussy work. I’d look at the luthier
forums to find out how other builders are managing with the Delta
14” saws. There’s an old article from Fine Woodworking about this
exact application. The guy built a tall fence of plexiglass and set his
metal guide blocks very close to the blade, used a very sharp blade
and (as I recall) really cranked up the tension.

I’m not a big advocate of cranking the tension to solve all bandsaw
problems, but a lot depends on the saw you’ve got.

You are using a 1/2” blade, right?

View NBeener's profile

NBeener

4808 posts in 2634 days


#4 posted 01-18-2011 07:16 PM

Loren: I like the way you think :-)

-- -- Neil

View Evol's profile

Evol

2 posts in 2146 days


#5 posted 01-19-2011 03:32 AM

Thanks all,

Some additional info…
it is a 1/2” blade though there were about 8 teeth in contact over the 9.5” of board, is this really a concern? more opinions?

I suppose the blade could have been resonated from the wood burning stove. While this is only the second use of the blade (according to the owner), it has been installed for over a year. I have acetone on hand… will this work for cleaning the blade?

Blade guides are set, checked and double checked… upper guide was set at approx 1/8” above upper surface of wood.

On blade tension: we had it set at about 60% load, we turned it up to about 90% load for the Cherry piece, still scooped.

Feed rate may have been to fast. I did not time it, but I would guess the 21” was cut in around 3 minutes.

I will also chek out the luthers forum… Honestly while I am sad that this expensive board is 1/2 waste, I am just glad no blood was shed… that blade just popped right out… never even heard of this before.

Main new questions…
1. more teeth on the cutting edge is bad?
2. higher tension is good?
3. feed rate in inches per minute?
4. Acetone to clean the blade?

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