Diving Blade Issues

Axe Handle Hound · October 09, 2011, 09:41:07 AM

First post here on FF, but I've been following the forum for quite some time and have learned a lot. I have a homemade bandsaw mill that I'm having a diving blade issue with. Based on what I read in previous posts I'm fairly certain it's related to blade tension, but thought I would see if folks on the forum agreed. I had been running a Woodmizer blade (150"X1.25"X0.035") on the sawmill cutting seasoned white oak and it was working just great. When the blade dulled I took it off and put on a new Cooks Duratooth (150"X1.25"X0.042") and instantly had problems. The second the blade cut into the cant it started to dive at a severe angle and did not come up. I checked the blade to see if it was dull, but it wasn't. I don't have a set gauge, but it appears to have good set. I checked for dirt, stone, metal in the log and didn't find any so I backed the blade out and checked everything on the mill. I adjusted the blade guides so they and the blade were parallel to the bed and tried a different, brand new Cooks blade. Exact same result. The blade dives down in the cant and stays there. At this point the only thing I can think is that the thicker band isn't getting enough tension, but I'm hoping people here will chime in with their thoughts. I have the mill tension device maxed out so if that's the issue I may be out of luck.

paul case · October 09, 2011, 09:51:37 AM

welcome to the forestry forum.

how is your bandwheel alignment?

what kind of guides do you have? the thicker blade could cause some problems there if ther happens to be a groove worn in the guides from the thinner blades.

pc

barbender · October 09, 2011, 10:25:55 AM

Mu first guess would be what you suspected, not getting enough tension on the thicker band. But that should only cause minor waving/diving. I had a similar issue with some dead standing red oak I was sawing once. I was using Simonds Red Streaks, new out of the box, and they were all over the place. I tried everything, finally got some WM blades, problem solved. :

Magicman · October 09, 2011, 10:27:03 AM

First, Welcome to the Forestry Forum, Axe Handle Hound. Your statement about having "the mill tension device maxed out" is interesting, but not knowing "how much" tension you have is concerning. Maxed out may not be enough for the different blades.

You did not mention if the hook angle was the same on the Cooks blades. ?? I would want to throw a different species log on the sawmill and give it a try. Also, put the dull WM blade back on just to see what happens.

Any pictures in your Gallery should be posted.

Axe Handle Hound · October 09, 2011, 10:55:27 AM

Thanks for the replies everyone. Since I posted this morning I went back out and studied the mill some more and with a little rework found a way to get more tension on the band, but I also found out that tightening the blade more actually causes the entire carriage to flex so that the blade teeth ride proud of the left bandwheel, but are still on the crown of the right bandwheel (as viewed from behind the saw). I tried running the blade with the additional tension again, but it still wants to dive so I'm guessing that this saw just isn't able to create enough tension on the blade. I also noticed that when I look at the blade the teeth are set different then what I would have expected. Two teeth are set down, than one up, two down, one up. Does this sound normal for bandmill blades? I am used to working with handsaws and vertical bandsaws where each tooth is set opposite of the one before it.

Magicman- Sorry about not posting the photos. I tried numerous times to get them to post in the message, but something in the FF application causes an error and closes down my Internet Explorer and I wasn't able to figure out how to solve it.

Magicman · October 09, 2011, 12:09:45 PM

If I am following you about the blade tooth set, I do not see how they could saw properly.

There is a very good photo posting video/tutorial here on the forum. I would watch it and then give it another try. My comment was about the purpose of the gallery being a place for posted pictures only, not a personal album.

WH_Conley · October 09, 2011, 12:28:40 PM

I agree with MM. If I understand the set, 2 teeth down and one up, it can not straight. One side of the blade is doing twice as much work. All the blades I have ever tried were set 1 tooth up, one tooth down, one tooth straight. Might give Cook's a call they are a reputable company. If it is a blade issue on their end they will want to know about it. If it is on your end, handling, they will be able to help too. I too would try the dull blade just for the heck of it.

ladylake · October 09, 2011, 12:51:23 PM

Right, the way it's set will pull the blade down. Something went wrong with the setting. steve

Banjo picker · October 09, 2011, 05:02:15 PM

If somethig aint broke...don't fix it...You said the Woodmizer blade was cutting great...buy some more like them....Tim

eastberkshirecustoms · October 09, 2011, 08:34:15 PM

Are you sure your guide wheels aren't taking the set out of the teeth? The wheels look much wider than the blades. Also, how much deflection do you have? To me it looks like very little. You should have about 1/4". If increasing tension makes the blade wander or walk off the wheels, you may need to re-align them, toe and caster. Also, in your third photo, it appears that your carriage is flexing or bowed upward from the blade tension. Is this an optical illusion? If not you may need to 'beef' her up a little.

rbarshaw · October 09, 2011, 08:54:55 PM

In your first pic. I see cracks in the wood that run parallel to the blade dive, that indicates a path for the blade to follow if anything is wrong with the mill. In your 2nd pic the teeth of the blade look like they are rideing on the guide wheels, if that is the case they will have the set knocked out of them. Are the different blades used the same width? Also the set on the teeth should be left, center, right, and then repeat all around the blade, if they are not like this prior to mounting on the bandmill then they are set wrong, if it happens after mounting on the mill then something on the mill is changing the set.

T Welsh · October 09, 2011, 08:57:46 PM

Looking at your photos and seeing the blade guides or wheels and then you said tension and white oak, your mill will not give you good results! things I see wrong, 1. blade guide wheels need to be real not rubber wheels. 2. tension needs to be high 2500 to 3000 PSI range for hard wood! 3. your cutting white oak it takes sharp blades to even go through it let alone cut straight , go back to wooodmizer blades and cut your loses, I have taken a new resharpen blade out of the box,made one cut and taken it right off because it wouldnt cut straight. go backwards to get a grip on what went wrong and go from there! Tim

Satamax · October 09, 2011, 09:07:59 PM

One thing i've learn't with bandsaw, if it doesn't cut nice, and everything else is set as it should be. 99% of the time it's blade set or sharpening which is at fault, set being the usual problem. blade thickness is also important imho. And width too.

5quarter · October 09, 2011, 09:18:50 PM

I don't think tension is your problem. Cooks blades have a very agressive hook angle and a little more set than most. I bet your guides and or band wheels are knocking some (but not all) of the set out of the inside of the band. That would cause it to pull down and stay down. I can't imagine the tooth pattern you describe is correct. you should have left cutter, right cutter, raker etc... It would require a special setter to achieve the pattern you describe. You need to contact Cooksaw ...they will be able to pinpoint the trouble. also, show them a close up shot of your blade, or better yet, send it back. They will most certainly make it right. Best of luck. Nice saw, by the way. please give us the specs on it.

Magicman · October 09, 2011, 09:28:36 PM

I see that we now have pictures. ;) Do you have another "new & unused" Cooks blade. If so, how are the teeth set? Are they alternating left, center, right, etc. or as you stated above?

There are several things going on with your sawmill that could possibly cause your problem, but the blade tooth issue needs to be addressed first. In your OP you stated that you were sawing OK until you changed to a new blade. In that case, the blade was the only thing that was changes, thus the prime suspect.

Teeth contacting the blade guide will absolutely remove the set and cause the blade to wonder.

Satamax · October 10, 2011, 03:59:22 AM

Huh guys.

Am i daft?

Look at this.

Don't anybody see two cracks parallel to the cut below. Ok, growth rings being round, it shouldn't go all the way across. But it's strange to see it's parallel, same curve and seems to go horizontal after that.

Couldn't it be that he started his cut in a crack and this pulled his saw down. Or the tree was originaly bent, and path of least resistance was there. just an idea. Even then, it should not do this. But who am i to say!

kelLOGg · October 10, 2011, 05:56:50 AM

Quote from: T Welsh on October 09, 2011, 08:57:46 PM
1. blade guide wheels need to be real not rubber wheels. Tim

Also, the guide wheels appear to have a crown on them. That will let the blade flex too easily. I think Cookssaw can fix your problem.
Bob

GF · October 10, 2011, 08:56:30 AM

Not sure but it looks like the blade guide has the same angle as the blade as it has dived down, or it may be just the picture. I would put a dial indicator on the blade guide and see how much play it may have. You may try putting a 36" straight edge on the blade also to see if its level with the deck by measuring both ends. I build a small jig to clamp my straight edge to the blade.

GF

Axe Handle Hound · October 10, 2011, 09:06:30 AM

Thanks for all the continued help on this guys. To answer some of the questions/observations so far:

-Yes, the guide wheels are polyurethane casters with ball bearing backups to prevent the blade from walking back off the wheels. The casters have been ground down on the lead edge near the teeth so that they don't actually contact the teeth at all. The need for that modification became clear in a big hurry after the mill was built so I don't think the guides are knocking set off the teeth, but I would love to upgrade to a new set from Cooks.

-The parallel cracks in the wood are an interesting observation that I had not made until you guys pointed it out. It very well could be that the blade is just trying to follow the grain because I don't have enough tension on it to keep it from diving. This tree was definitely not growing straight when I cut it down. I also spent some time studying the mill yesterday and I think that eastberkshire customs is right that I don't have enough deflection in the blade. I know we had originally build more deflection into the mill, but it could be that under tension the carriage is flexing so that the deflection is lost. I also agree that we need to strengthen the frame on this thing. I don't like the fact that it comes out of square under tension.

-The troubling thing is that as much of a Frankenstein as this mill is, it had been cutting this same log beautifully with a Woodmizer blade only moments before so I have to believe the blade itself is the main source of my problem. In addition to the tension issue could it be that this mill just doesn't have the power (13hp) to run the aggressive set/tooth angle that 5quarter mentioned? If so, would that increase the chances that the blade would want to follow the direction of the grain? I may have to take TWelsh's advice and just cut my losses.

Magicman- thanks for the hint about the upload tutorial!

ely · October 10, 2011, 09:13:46 AM

if the mill was cutting fine before the blade change i believe the problem lies with the blade. maybe just that its a different blade. not a bad blade but a blade that has not been adjusted to the saw yet.

something to consider is i have seen here recently is different lenghts of bands that are supposedly the same lenght. my dad always ran his spring tension on his lt 40 at a certain point, then with some new bands he found the old setting was not near enough tension.

Axe Handle Hound · October 11, 2011, 02:55:40 PM

Update- I talked with the folks at Cooks Saw and they feel certain that the issue is being caused by the blade not being flat. Apparently this issue is more common on shorter band lengths and is exacerbated by the smaller diameter band wheels typically found on home made mills. They gave me the conbact name/number for a person about 40 minutes from my house who owns a blade roller and recommended I ask him to flatten the blades and try again. Guess I'll have to give it a try...maybe it will do the trick.

beenthere · October 11, 2011, 03:08:15 PM

QuoteWhen the blade dulled I took it off and put on a new Cooks Duratooth (150"X1.25"X0.042") and instantly had problems.

So they are saying that they shipped you a blade that was not flat?

What did they say about the tooth set that you described?

Wish you well.

Banjo picker · October 11, 2011, 04:56:20 PM

I have got one of the Cooks rollers, but if they sent me blades that wouldn't cut..they would get them back ....I wouldn't try to fix them....Thats if they came that way out of the box....Tim

Banjo picker · October 11, 2011, 05:10:25 PM

I forgot something....think of that..But back on post 14 MM asked if you had any other new cooks blades that had not been on the mill...In my mind once you put it on a mill all bets are off, but if you have a new one you can check to see if it needs rolling..Lay a flat piece of metal across the blade and it sould be nearly flat with very little light going under the piece of metal....you could also know that the mill had not knocked or messed up the set in any way....

I have never used their Dura Tooth, but I just got a new box of the Silva Chrome
1 1/2" .050's and they cut fine....Tim

Axe Handle Hound · October 11, 2011, 06:37:22 PM

They actually did tell me that the bands weren't flat. They said they spot check their bands for flatness before they ship them out, but they aren't able to check them all. In all honesty, I'm not convinced that the issue is blade flatness, but I'm definitely going to check like Banjo picker described when I get home. I'm also going to re-check the tooth set on the blade that I tried and also on the remaining brand new band that I've never run. It could be that my eyes just fooled me into seeing something I wasn't or maybe the set was affected by something on the mill that I haven't found yet.

Axe Handle Hound · October 11, 2011, 08:42:29 PM

I think I found it....while checking the blade for flatness I discovered one of my caster-guide bearings had a flat spot. They should look like this one with plenty of clearance above the teeth:

But the idle wheel side bearing looked like this:

Looks like my guide bearing got jammed and the topside of the blade chewed into the polyurethane and I would assume, dulled the teeth. I didn't notice it because the guide wheel stopped with the chewed side down whenever I stopped the mill. If the topside got dulled the blade would tend to pull itself down into the cant right? If so, it looks like I need to do a little repair on the mill and get my blades resharpened.

Magicman · October 11, 2011, 08:47:36 PM

And get some steel roller guides. ;)

GF · October 11, 2011, 09:09:14 PM

Also if the blade builds up any heat its going to more than likely cause the polyurethane to get soft also.

GF

ladylake · October 12, 2011, 06:21:54 AM

I'll agree, get some steel guide wheels and adjust to 1/4" down pressure, can't tell for sure but it doesn't look like you have much down pressure . Dry white oak likes a 7 or 4 * blade, I can't cut straight with a 10* or over either. Steve

redbeard · October 12, 2011, 10:36:31 PM

If you wanted to keep using your wheel mounts you could get by with some of cooks after market parts like there 1/2''or 3/4 zert bolts and some steel guide rollers. looks like they would fit those caster wheel brackets. Only problem is how do you plumb them they need to be squared and leveled with the blade or you get friction that causes the flat spots.

Axe Handle Hound · October 13, 2011, 09:52:21 PM

Redbeard- that's exactly what I've been thinking of doing, but you hit the problem right on the head. I'm going to have to do some modifications to get the existing caster brackets low enough so that the smaller diameter steel guide bearings provide downpressure and are level with the blade. I haven't ordered the the steel guide bearings yet so I'm not sure how I'm going to make it happen, but I'm hoping it it won't be too bad.

CooksSaw · October 14, 2011, 12:28:51 PM

Axe,

Once you get your guides worked out and if you still have issues with the blades give us a call we'll get some new blades coming to you.
You can either call and ask for me or Tim Cook toll free at 1-800-473-4804 or feel free to email me at james@cookssaw.com

Take care,
James

Axe Handle Hound · October 14, 2011, 12:45:25 PM

Quote from: CooksSaw on October 14, 2011, 12:28:51 PM
Axe,

Once you get your guides worked out and if you still have issues with the blades give us a call we'll get some new blades coming to you.
You can either call and ask for me or Tim Cook toll free at 1-800-473-4804 or feel free to email me at james@cookssaw.com

Take care,
James

Thanks James. I really appreciate the great customer service. I'm pretty confident that once I get this issue sorted out and the blades resharpened they'll cut great.