Tuning Up a Bandsaw

      Bandsaws for resawing lumber need some careful attention to get and stay in tune. July 3, 2008

Question
I recently purchased a Hitachi cb75 for res-awing koa and other tropical woods and from the beginning I have been having a problem with the blades. Maybe it is not a problem but a nature of the machine. This machine is not altered in any way and I am using the stock guide blocks that were supplied. It seems as if what it happening is that the blade sets up some sort of frequency vibration in the cut and removes a lot more material than it should. It also leaves a pronounced wobbly cut pattern. It generally only does this during the first 1-2 inches of the cut and will straighten out on its own. Some blades I have used are better than others; although some will not cut smooth for 5-6 inches and will occasionally do this "dance" further down the cut seemingly with no reason at all. I mostly re-saw koa into 3/16ths or 5/32nds. Most stock is 4 to 10 inches wide and 21-36 inches long.

The only way I can minimize this is to crank the tension down all the way but then I see blade tracking problems after re-sawing for a couple of hours and turning off the machine for a few minutes to take a break , upon restarting the machine the blade will wander out of tracking about 1/4 inch and then slowly return to its original setting. Once, after the blade I was using had about 12 hours on it, I restarted the machine and the blade came off the machine and cut through the blade guard before I could shut it off. It destroyed the blade and was quite scary. Has anyone else experienced these problems and if so are there any remedies?

Forum Responses
(Solid Wood Machining Forum)
From contributor P:
What size blade are you using? I have a 3" rip blade on mine.



From contributor H:
The Hitachi was designed to run only with their own 3" blade unless you have their bearing guide add-on for narrower blades. I say "their own blade" because pretty much no one else will make a 3" blade for a 16" diameter wheel saw.

If you aren't using the Hitachi 3" Stellite tipped blade (either every tooth or every other tooth tipped) give that a try. Very expensive blade though. These are touchy saws. They can work really well for the money but can also be frustrating machines.



From the original questioner:
Thanks for the reply, I am using the Hitachi 3" Stellite tipped blade. I have seen the add-on bearing guide for the narrow blades and thought about modifying it to work with the 3 incher to see if that would help. But so far it just seems as if the machine, the way it is built will not allow me to tighten the blade enough.


From contributor H:
The main thing I learned after selling my old Hitachi is that you don't need a 2" to 3" blade to re-saw. If you can lay your hands on the smaller bearing sets, then try running a Lenox Woodmaster B blade. I wish I'd known that when I had the old Hitachi as I did have the bearing set but never put it on the saw.


From contributor Y:
I have been using my Hitachi for 16 years - through thick and thin. I bought it used (the model I have was last made in 1984) and it came with blade guides for both the 3" wide Stellite blades and guides for standard blades, down to 1/4". I stopped buying the wide blades years ago and switched to 3/4" and 1/2" blades exclusively - I can get 5 Lennox bimetal blades for the cost of one Stellite blade.

The saw has to be set up properly - it took me a long time to adjust it correctly. Also, Stellite blades will cut for a long time after they are dull, just not well. That might account for the rippling you are seeing.



From the original questioner:
The cost off the blade is not an issue for me, as the person I exclusively re-saw for buys his own Hitachi blades and only uses them for around 10 hours of saw time, before changing the blade out. He is very particular and has done a lot of re-sawing himself but he swears that the Hitachi blade produces the best cut for him. I do not have a lot of experience re-sawing and am just learning along the way. He has seen this wobbly cutting on other saws that he has used even with brand new blades but he has never seen the blade come off the machine in all the years that he has been re-sawing.

My machine and the others that he has used have the 3 horse motor on it, and he thinks that the wobbly cut may be due to the machine being slightly under powered for what we are doing but it makes no sense to me because the saw will cut wobbly more it seems when we are cutting narrower pieces. This leads me to think tension or guides. You can actually watch the blade as its cutting and as it enters the cut for the first inch or two it will wander all over the place and make a high pitched screaming sound while the blade is vibrating when you take the cut piece and turn it so you can see the cut and take a speed square and draw a line across the rippled portion of the cut each ripple is exactly the same distance apart as the tip of the blade. I am stumped as to why this is happening but am more worried about the tracking issue than anything else. Any help or suggestions would be very helpful.



From contributor H:
It would probably be a good idea to check wheel alignment and tires. Use a straight edge and some blocks to make sure the upper and lower wheels are in the same plane. There are some bandsaw tuneup guides out there that can explain this further.

If I remember correctly the tire on the top wheel of the Hitachi is flat as versus crowned as on most band saws. Check this out as well. If you've developed an overly tall center crown in the tire then that might result in no front edge support for the blade, and subsequently, drift in the lead edge. Band saws are tricky beasts. It doesn't take much for them to get all out of whack.



From the original questioner:
I looked at the machine and the top wheel is crowned and the bottom is flat. This machine is brand new I have only had it for about two months. I would not think that the wheels are out of alignment from the factory unless it was dropped in shipping. The pallet it was on was slightly damaged but it looked more like a forklift stabbing incident than a drop.

The only other thing that seems kind of weird is that without a blade on it the upper wheel seems to have a lot of play. Not in the bearing but in the tracking linkage. On the tracking knob shaft there is a collar that is held in place by a roll pin that rests against a frame piece. That is where the play is like there should be a shim or washer under the collar. I do not know if this makes any sense, perhaps I should be talking to Hitachi but they have not responded to emails I have sent them trying to figure this out by going through tech support.



From contributor H:
I didn't realize it was a new machine. Don't assume the wheels are correctly aligned from the factory. I rarely buy any machine that is "right" out of the box anymore. When the blade is tensioned there should be no tracking play in the upper wheel that you can move by hand. Blade tension will keep it pulled downward. Sorry about thinking the upper wheel might have been flat, I just didn't remember correctly.

Make sure your plastic blade guides are pressing the full width of the blade, spaced away about the thickness of a folded piece of paper on each side. Make sure your blade teeth are just in front of the upper tire. If I remember correctly those wheels are about 3" deep.
I would not bother emailing Hitachi tech support. See if you can get them on the phone. You could also have a bad blade. I believe band saw blades are supposed to be a tad longer along the back edge to put more tension on the front edge.



From contributor V:
Yeah, I might suspect a bad blade too. I think your tracking accident where the blade cut the housing is a separate issue. Always spin the wheels by hand while adjusting tension and tracking before you switch the power on.


From the original questioner:
Since I started this discussion I have learned a lot about these saws. The most important thing I learned is that for the most part these saws are a pain in the butt. They cut really good sometimes but other times not so good. I learned that I can spend close to an hour to set it up for a production run and get it to cut absolutely flawlessly (I'm talking about only a few thousands of an inch thickness variation measured with a micrometer between 6 points on the finished board) for a day’s worth of cutting. I can then walk away from the saw for sometimes weeks on end and not touch it at all, come back, and it will not cut well at all, sometimes I de-tension the blade, sometimes I do no. It does not seem to matter.

I have learned that the better the drying and stabilizing process the better the saw cuts. If you have a good moisture meter you will probably be able to nail down the suppliers that get it and the ones that don't. Also check for case hardening in the wood that you are getting (most good meters will only measure in about 3/4 of an inch, so take a few cuts and measure again.) I also learned that the relative humidity, temperature and wind speed (open air shop) all make a difference.

Most guitar makers (Gibson, ect.) all re-saw in a controlled environment of around 50% relative humidity, living in Hawaii I do not have this option as the relative humidity is around 90%, although I try to only cut guitar parts when it drops below 70%. I seem to have better results when I do this. I only have to cut this good for one particular customer. So for the most part I really like this saw for the power and speed that it has.

The only issue really is the wobbly cut it makes as you are starting in on a cut and sometimes randomly during a cut. I am fairly sure that it is because the saw really needs a five horse motor to cut well, or it is a nature of the beast thing with the wide thin blade. I have three questions. Tom, do you get a very pronounced wobble to the 3 inch blade as you are starting a cut that leaves an "s" shaped pattern in the wood? The pattern should match the t.p.i. of the blade? Contributor H - do you know the kerf of the Lennox blades that you use? This saw is driving me nuts and I am open to new ideas about re-sawing! Also, do these Lennox blades work on the Hitachi cb75 or are you running these on a different saw?



From contributor B:
I haven't measured, but I'd say the kerf on the Woodmaster blades is somewhere around 1/16" to 3/32" - much heavier than the Hitachi 3". The 1/2" (2 tpi) and 3/4" spacing versions I use are designed for rough cutting as versus the Hitachi which is designed for minimal kerf finish cutting.

I've tried 2" blades but they don't seem to work as smoothly as the 1" blades. I wish I had thought to try narrower blades on the Hitachi as I had the complete smaller blade bearing sets. I was thoroughly convinced that re-sawing required a very wide blade though. I suspect that if I had tried a 1" blade on it I never would have sold it and bought the Laguna Resaw Master.

The Resaw Master is a decent saw, but it took a long time and a lot of parts replacements from Laguna to get it going properly. It is only an 18" wheel though (granted that's larger than the 16" Hitachi wheels) and I don't think I'd ever get another re-saw smaller than 20" - I'd prefer a 24". We do not get full life out of the blades before we get stress cracking. I've tried just about everything to fix this but have become convinced it is the small diameter wheel. Other than that the saw works adequately well. We typically cut 6" to 10" poplar, oak, cherry, mahogany, pine etc.



From the original questioner:
To contributor H: I am assuming that you are using a Laguna saw with Lennox blades. Have you ever tried the Laguna re-saw blades? They have a 1inch carbide blade that sounds like it may come close to the cut quality of the 3 inch Hitachi blade. Also I watched the drift master fence video they have and that looks very tempting!


The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor R:
Could the wobbly cut pattern have anything to do with the initial feed speed of the material into the band when it begins to enter the wood? I recently re-programmed a large resaw for a reduced speed when the wood enters the band. The feedworks speeds up to production speed for the rest of the cut. The old experienced sawyer believed if it could be done that it should be helpful in band life and due to the dryer nature of the end of the material and start angles, help get the band on started on the right track.



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