Blade flexing up in cut. Help

RPowers · November 13, 2015, 10:15:13 PM

I am having trouble with my blades bowing/flexing up in the center of wide cuts. I am using an LT28 with a 25hp engine and 4 degree WM blades. The problem is mostly in cuts 15" or wider. The lumber ends up cupped before it dries, which is very frustrating. I have made wide cuts in the past in hard woods such as post oak without the cupping, this is consistent even in wide Cherry which has always been a soft easy cut for me. I have checked the drive belt tension, its at 16#, and the rollers are both aligned. My mill has that red rubber blade tension "gauge", and I am having the problem even at significantly more tension than is recommended. Any ideas or experience with similar? Here is a pic of what I am dealing with.

dgdrls · November 13, 2015, 10:31:51 PM

No need to over-tension the band

How much set are you running on the teeth?
and have you had the same issue with with say a 7 Deg or 10 Deg bands

Dan

customsawyer · November 14, 2015, 03:08:57 AM

Sometimes new blades aren't right. Try a different box of blades.

LeeB · November 14, 2015, 05:07:43 AM

You might have to slow your feed speed just a tad. It's called a barrel cut, or at least that's what it's called on a vertical shop band saw. Comes from trying to make the blade eat too much at once.

Peter Drouin · November 14, 2015, 06:48:03 AM

Set on the blade is off. And a new box of blades is not always 100%. I have got a new box of blades and had to sharppen them before I use them.
Like now I get reg 7° mixed with turbo 7° in the same box. :

bandmiller2 · November 14, 2015, 07:08:37 AM

RP, sharp and set are always suspect but in your case it looks like that log has a lot of tension and is cupping after the board is cut. Try a different log preferably a different species. Frank C.

RPowers · November 14, 2015, 01:29:06 PM

Thanks for the replies.

I am using ReSharp service so it is woodmizer's people in MO doing the sharp and set. I only have 4 degree right now. I think I might try some 7's next order.

I have tried feeding faster and slower and still get the "barrel cut".

FrankC, if you look at the straightedge in my picture you can see that the curve is also on the top of the cant, not just in the board.

Peter, one of my last boxes of ReSharp blades was almost unusable. It was as if they didnt grind the teeth much at all, the tips were still rounded from the previous use wearing the set corner off. Cut terrible. If the problem show's up again I'll call them, I wonder if someone just set the machine wrong.

terrifictimbersllc · November 14, 2015, 01:50:24 PM

What kind of wood is it?

If that happened on my mill I would think the blade wasn't sharp. I cut a lot of very old timbers usually some kind of sappy pine, with 4 degree bands, and when doing so that's how I tell the blade needs changing, by putting a straightedge across the width of the cut. Alternatively on wide hardwoods I am either using 4 or 7's. In knotty wood it's easy to tell a dull blade by feeling over the knots. When there's no knots, any deviation from flat detected with a straightedge, means the blade needs to be changed to cut that width of wood.

Use a 10x hand lens look at the tip of each tooth, if there is any rounding of the tips its easy to see the blade has lost its initial sharpness. If your resharp blades have any rounding of tips I would say something. Can also see by naked eye if there is any light reflecting (shiny), off the outside edge of the tooth.

dgdrls · November 14, 2015, 04:43:15 PM

terrificT I'm interested in knowing what the set is on the bands you run,
Rpowers can you check the set on one of your bands and compare it to what TTLLC runs?

Dan

terrifictimbersllc · November 14, 2015, 05:39:22 PM

Quote from: dgdrls on November 14, 2015, 04:43:15 PM
terrificT I'm interested in knowing what the set is on the bands you run,
Rpowers can you check the set on one of your bands and compare it to what TTLLC runs?

Dan

Generally 25-26 thousandths on both 4s and 7s. I still use some 9s and the target for those is 20 thousandths, those are for sawing frozen smaller logs. I've had no trouble with 7s set at 26 thousandths sawing frozen logs.

drobertson · November 14, 2015, 05:56:09 PM

24 to 26 as said, automated ed is not always locked in as some mention, they just put up with it,, resharp can be a pain, and I mean the pro's

RPowers · November 14, 2015, 10:35:36 PM

I have had this happen in everything from cherry to red oak to post oak.

I don't have any way to measure set. I've just been trusting resharp to send me properly set blades back. I put a new Resharp blade on and the problem lessened by about 50%. I am thinking they need to grind more into the profile and set them after, or I need to buy new blades.

beenthere · November 14, 2015, 10:43:34 PM

Look closely at your mill to see if either the guide rollers are reaching the teeth to remove set, or the blade going around the large wheels are not taking the set out...

BrentRobinson · November 15, 2015, 01:19:19 AM

Can you find anyone to sharpen and set locally? I find new blades are never as good as our local saw filer can get them. Absolutely no comparison. I always seem to have trouble with shipped blades pulling up or down or doing the wave and then when they come back they cut true as anything. Handle with care doesn't seem to mean much.

bandmiller2 · November 15, 2015, 07:03:45 AM

As Beenthere suggested I would do a complete mill alignment according to your WM manual. Put a new band on and try it. Sometimes things happen on a band mill that defy explanation, every log is different, some resist our best efforts. Frank C.

YellowHammer · November 15, 2015, 08:28:49 AM

If this is happening routinly and consistently in many species, then I would suggest checking band alignment to see if it's parallel to the bed with the clip on alignment tool. It may be slanting up and causing the climbing, and the guide rollers are restraining it.

Uneven set will also cause this. Or improper sharpening as well. Use a cheap magnifying glass such as an "opticscope" found at any drugstore for about $20 and take a good hard look at the teeth.

It can also happen if sawing too slow and packing sawdust on the side of the band. 4° bands usually cut very straight, but have a tendency to pack sawdust. If you see lots of fine flour sawdust packed on the boards, that could also be a problem.

RPowers · November 15, 2015, 09:02:58 AM

Thank you all for the input. I will go over the mill with a complete alignment soon and see if that helps.

I haven't found any local service who will do blades, the few guys who do just do their own. Can't blame them.
RP

Ga Mtn Man · November 15, 2015, 09:35:35 AM

Contact FF member Cutting Edge about sharpening your blades.

RPowers · November 30, 2015, 08:14:09 PM

So I took everyone's advice and checked all that I can check on the mill. I also ordered two 9 degree and two turbo 7's to try against the ReSharp 4's. I did a complete alignment on the mill, everything within 1/32", put on two new B57 belts, checked drive belt tension (at 15.5#), and threw a 14" RO butt log on along with a new ReSharp blade. Set the blade tension exactly at the edge of the washer per book spec and took a slab off. Cut was chattery and aweful, the blade climbed over 1/4" in the first 4 inches of the cut and left drag marks the whole way like I'd hit a nail. Took blade off and checked it, it had a tooth sheared off from a nail before I sent it back to Resharp, but I figured if they didn't reject it then it wouldnt mess with the cut quality when I got it back. Wrong on this one.

Put on the top blade from a new box of Resharp 4's, set the tension up a turn (middle of the washer), and cut again. The cut quality was better, but the blade still climbed 3/16" in the beginning of the cut and had over 1/16" of "barrel" across the cut.

I finished slabbing the log into a 10x9 cant, then grabbed a fresh Resharp blade and took a board off the top.
This time the rise was only 1/8" in the first two inches, still with 1/16" of cup/barrel across the board. Better, but still bad for a fresh blade on only 10" of knot-free fresh Red Oak.
I put the 9 degree on and made a cut - less than 1/16" of rise and dead-flat across the board. Tried a Turbo 7 with the same result. I cut 3 cuts each with the 9's and 7's, and two with the Resharp 4. Consistently I had a 1/8" plus climb in the first 3" of the cut with the 4's, and the blade stayed there till the end of the cant then dropped after it exited to the original set height. Also, the cut was very slightly wavy, a 24" straight-edge showed definite high spots and low spots down the board, just under 1/16". Both the other blades, brand new, showed a dead-flat cut against the straight-edge, but they on some cuts did rise 1/16" in the first 2" of the cut. Some cuts they didnt.

My conclusion is that there is an obvious issue with either the sharpening or setting on the 4 degree blades I just got back from Resharp. They aren't as sharp as a new blade, or at least they aren't cutting with a new blade. Maybe this is to be expected, but I assumed that a reset and grind on a factory profile would get a "factory" sharp back on them.

Since even the brand new blades showed a tendency to rise a slight amount as well, what on my mill's alignment is causing that? Do I need more down pressure on the rollers? More tension on blade? tilt the rollers 1/16" down using the BGAT? I'm stumped.

RP

gww · November 30, 2015, 08:27:45 PM

I should let other more experiance people answer and am not trying to send you on a wild goose chase. My homemade mill acts simular. I always considered that it was probly a track alighment issue, maby not being level side to side in the beginning of the track where the cutting head sits. It has been good enough for my uses that lazyness has kept me from trying to get it better. I also used to wonder if hardness of the log ends from not cutting when felled could have some affect. I am sure wood mizer owners will have better imput. I would be curious of your fix if you ever narrow it down.
Good luck
gww

Kbeitz · November 30, 2015, 08:28:03 PM

I had this problem early this year. I was about ready to pull my hair out.
It turned out that my throttle got out of adjustment. I was running about
200 rpm slower than normal. It was an easy fix after I found the problem.

POSTON WIDEHEAD · November 30, 2015, 08:45:43 PM

Sometimes when I'm sawing W I D E (15 - 20 plus wide ) Red Oak or White Oak I literally slow my forward speed down to a creep.
I have a 29 hp engine.
But like Jake said it may be in the blade. If the problem is my blade I can slow the cut down and get a good straight cut.

dustyhat · November 30, 2015, 09:06:05 PM

I believe i read in in one of the magazines that cooks saw puts out about what causes this and the cure. but i could be wrong it could have been another outfit.

RPowers · November 30, 2015, 10:01:41 PM

Quote from: POSTONLT40HD on November 30, 2015, 08:45:43 PM
Sometimes when I'm sawing W I D E (15 - 20 plus wide ) Red Oak or White Oak I literally slow my forward speed down to a creep.
I have a 29 hp engine.
But like Jake said it may be in the blade. If the problem is my blade I can slow the cut down and get a good straight cut.

Poston,

What blades are you running in that oak? I have found that slowing down in wide cuts will make my drive belt scream, even at 16#. Maybe these 4 degree blades pack too much dust at slow rates and bind the blade up?

POSTON WIDEHEAD · November 30, 2015, 10:51:05 PM

Quote from: RPowers on November 30, 2015, 10:01:41 PM
Quote from: POSTONLT40HD on November 30, 2015, 08:45:43 PM
Sometimes when I'm sawing W I D E (15 - 20 plus wide ) Red Oak or White Oak I literally slow my forward speed down to a creep.
I have a 29 hp engine.
But like Jake said it may be in the blade. If the problem is my blade I can slow the cut down and get a good straight cut.
Poston,

What blades are you running in that oak? I have found that slowing down in wide cuts will make my drive belt scream, even at 16#. Maybe these 4 degree blades pack too much dust at slow rates and bind the blade up?

I always use a 4 degree.
My engine is always running at full throttle....29 hp.....wide open.
I just slow the head down moving the blade into the log.
Your belt should not be screaming if the throttle is wide open and your sawing slow.
My blade tension is always set at 2800-3000 PSI.
My belt tension is set at 15-18 pounds.

What is your blade tension?

Also keep this in mind. If I want a 2 inch slab for a table top, I saw my slabs at 3 inches. A thicker slab with weight on it while air drying will not cup very much if any. When the slab is dry 2 years later, I can re-saw the slab down to 2 inches. I lay my stickers 12 -16 inches apart between slabs while drying. Re-sawing is the beauty of having your own sawmill.