Blade "diving" into the log

50 Acre Jim · March 09, 2018, 04:44:14 PM

I had 9 blades re-sharpened by a fellow here in town. Never used his service before so I didn't know much about him, just that a few guys use his service and they say the blades are better than new ones.

OK, cut a bunch of Black Walnut with one of the blades and it worked swell. Put on another one to cut a 28" White Oak and 2" into the cut the blade started to dive into the log. I backed the blade out and started looking for a problem. Sawmill was level, eveything else checked out OK so I tried a few more times. Same result.

Replaced the blade with a brand new factory blade and it cut like butter. Not sure what happened to the blade he sharpened but it's certainly acting strange and is basically unusable. I thought maybe it was just the White Oak causing the problem so I used the unstable blade on a 10" Poplar and it wouldn't even cut that without heading toward the center of the log.

Anyone have any ideas? Is it possible to put an incorrect pitch or taper or sometlhing on a blade when it's being re-sharpened?

Thanks in advance for any help.

Jim

Kbeitz · March 09, 2018, 04:53:33 PM

Check the set.

50 Acre Jim · March 09, 2018, 05:13:31 PM

What does that mean Kbeitz?

Kbeitz · March 09, 2018, 05:18:14 PM

Check the set of your band. It will dive like crazy with little or no set.

50 Acre Jim · March 09, 2018, 05:26:44 PM

Let's pretend like I have no idea of how to check the set of my band. And if that were the case, how would I do that?

Kbeitz · March 09, 2018, 05:29:37 PM

You can use a caliper.

50 Acre Jim · March 09, 2018, 05:40:43 PM

OK, I understand now. Thank you Keibtz!

Magicman · March 09, 2018, 07:07:21 PM

When I bought my sawmill I had no idea how/where I would get my blades resharpened. I was referred a guy that owned an LT40 and sharpened blades for others as well as himself.

Long story short, one of his blades took a dive similar to yours in a relatively small SYP log. Also, I was having to make a 30 mile round trip twice to deliver and retrieve the blades.

That is when I decided to use Wood-Mizer Resharp. That happened 16 years ago and the rest of the story is history.

Peter Drouin · March 09, 2018, 07:10:58 PM

If your blade is level from front to back then your blade has more set on the outside face then the inside.
Wood Mizer sells a gage gizmo to check the set.
Wood Mizer will only sharpen their blades.

Magicman · March 09, 2018, 10:05:38 PM

Some WM Resharp centers have relaxed this a bit but there are some mfg/profiles that they will not resharpen. Call your resharp center before shipping them other mfg blades.

dgdrls · March 10, 2018, 08:30:51 AM

Hi 50 Acre Jim,

FF supporters, Cook's sawmill has some good reading on bands

The Bottom Line about Sawing Straight - Part 1

lots of good info here and more links on the right side of the page.

best
D

Kbeitz · March 10, 2018, 02:26:05 PM

Quote from: dgdrls on March 10, 2018, 08:30:51 AM
Hi 50 Acre Jim,

FF supporters, Cook's sawmill has some good reading on bands

The Bottom Line about Sawing Straight - Part 1

lots of good info here and more links on the right side of the page.

best
D

Very good reading... But I got a question...

Tim states...

I looked over all the pieces and saw that the blades with the crack of daylight dish on the inside ran very good and the blades that were dished on the log side would not cut at all without diving....

But nowhere does no say if the dish is facing up or down.
Can anyone help with this? Concave or convex ?

terrifictimbersllc · March 10, 2018, 04:06:08 PM

I would interpret "dished" or "dish" as the face that is concave. Because he calls it "crack of daylight dish". Also because our usual view of a dish is the side we're eating out of.

So Dish on the inside would mean concave on the inside of the band.
Dish on the log side would be concave on the outside of the band facing the log.

Kbeitz · March 10, 2018, 05:11:11 PM

I was kinda thinking that because you would thing after running for a while that the band would take shape of the wheel. But then he said...

I looked over all the pieces and saw that the blades with the crack of daylight dish on the inside ran very good and the blades that were dished on the log side would not cut at all without diving.

Does this mean that after running your bands for a while they will dish away from the wheel?

I have an English wheel. If I want to cup something it goes with the crown not away from it.

Kbeitz · March 10, 2018, 05:41:31 PM

I watched some utube videos on rolling a band saw blade. It looks like they are trying to cup the inside of the band. That makes no sense to me. Why does the saw mill not cup the band with all the pressure pushing on the inside of the band to match the shape of the wheel. How can it cup the other way? I'm lost.

Also if you'r band is diving I would think all the bands teeth would be leaning down not up. So rolling the band would make the teeth point more up and that would fix the problem. So what I'm not understanding is how the band can cup the wrong way just from running on the mill.

This post says they cup down...

Cupping Band Blades...Too much Tension? in Sawmills and Milling

Cutting Edge · March 11, 2018, 06:59:41 AM

To help the OP (50 Acre Jim)-

There is a chance that the blades you got resharpened were not done correctly. The fact that a new blade performed in an acceptable manner after trying the ones that were serviced would somewhat lead a person to assume this is the case. One or more things could have attributed to the problems you were/are experiencing. This is also one of those times a person has to make such assumptions based on the information provided.

Walnut saws relatively easy compared to White Oak. You also shared the White Oak was 28" dia. That's starting to get into pretty wide cuts with not much blade support from the "guides", regardless of species. The fact is was W. Oak probably didn't help the situation. Having blades best suited for your machine and what you're sawing makes a big difference too.

Because of your HP and description of your sawing situation, you may look at getting some 4 deg. blades.

Take a good hard look at your ceramic guides. The effects of the guides themselves can/will play a role in poor blade performance. The heat generated from the friction (guides contacting the blade) and also the literal damage to the blade body itself from the guides "scrubbing" both the sides and the back edge of the blade. A blade that performed acceptable when new, may have damage that no amount of sharpening will ever correct.

Also check and make sure your blade is dead parallel to the bunks. This is critical, even more so than sawmills running a roller guide system. You may even contact Norwood about upgrading to roller guides. By far, one of the best investments you can make to improve both your lumber quality and blade longevity/performance, IMO.

Hope this helps you out.

Kbeitz,

Blade curvature has little bearing in the OP's case because of the guide system. Since the bandwheels themselves provide the foundation of support for the blade while in the cut, the ceramic guides are mostly a static fitment that guard against extreme deviation. BUT, it can can have an impact and play a role in poor performance and product produced. The process for servicing such blades is handled somewhat differently because of this.

Roller guide system, different case. TerrificTimbers is correct as to his summary.

The reasons for addressing/correcting curvature is a process NOT done on an English wheel. Similar influence on the steel, but far more precise and controlled.

Kbeitz · March 11, 2018, 10:01:11 AM

Quote from: Cutting Edge on March 11, 2018, 06:59:41 AMThe reasons for addressing/correcting curvature is a process NOT done on an English wheel. Similar influence on the steel, but far more precise and controlled.

I was not even wanting to try rolling my blades with my English wheel. What I was saying was when I roll
a piece of steel with my English wheel it follows the crown of the wheels. So I would think the crown of a
bandsaw wheel would after running for a while would put a curvature in the band to match the curvature of
saws band wheel. But from what I get from reading everything the curve is going away from the wheel. How can
this happen?

Revival Sawmill · March 11, 2018, 10:13:37 AM

Quote from: Kbeitz on March 10, 2018, 05:41:31 PM
I watched some utube videos on rolling a band saw blade. It looks like they are trying to cup the inside of the band. That makes no sense to me. Why does the saw mill not cup the band with all the pressure pushing on the inside of the band to match the shape of the wheel. How can it cup the other way? I'm lost.

Also if you'r band is diving I would think all the bands teeth would be leaning down not up. So rolling the band would make the teeth point more up and that would fix the problem. So what I'm not understanding is how the band can cup the wrong way just from running on the mill.

This post says they cup down...

Cupping Band Blades...Too much Tension? in Sawmills and Milling

The cooks guys talk about anticlastic curvature in some of their literature/videos - If you look for those articles, it may clear things up for you? I'd guess it has something to do with the spring tension of steel and the alignment of various positions on the surface of the steel band; as it goes around the crowned wheels, it does cup the 'expected' direction (cup on the inside), but as it comes off the wheel that cupping means that the center of the band is actually longer (around the length of the band) than the back or front of the band... that extra length has to 'go' somewhere, but it can't cup to the inside for some reason - either the tension, or heat buildup, or something about the steel makes it pop back the other way? I don't have that answer.

Pabene · March 11, 2018, 01:57:53 PM

The "anticlastic curvature" describes what is going on when a band is bent. You will see that effect when band of any material are bent. It has nothing to do with the wheel surface material but the radius for the wheel. Smaller wheel means harder effect. The band will always "cup" out from the wheel. If you would check a blade, with many hours in the saw, you will see the cup also when the blade is under tension and also all the way around the wheel. Check with a ruler cross over the blade outside and you will see it is concave.
An easy and clear way to see the effect is to bend a rubber band. Let say you have a 1/4" thick and 1" wide band, rubber, plastic or other homogen material, bend it to different radius and you will see the effect of anticlastic curvature.
The steel in the blade will "remember" more and more of the "maltreatment" on the wheel in the mill and it ends up in more and more cup.
I am sure it would be possible to run the blade on the mill, with the teeth backwards, and that way run it back to flat.

Kbeitz · March 11, 2018, 06:25:04 PM

Thanks to all... Learned again something new on this forum.
Time to make a band roller.

Peter Drouin · March 11, 2018, 06:36:38 PM

Kbeitz, With 1¼ wide blade you won't need a roller, The blade will junk wore out and broke by then. :D :D

Kbeitz · March 11, 2018, 08:54:27 PM

Quote from: Peter Drouin on March 11, 2018, 06:36:38 PM
Kbeitz, With 1¼ wide blade you won't need a roller, The blade will junk wore out and broke by then. :D :D

Thanks...
I also think by adding more set gets around having to roll you'r blades. It gives more clearance for the curve of the blade so it does not touch the log and push you off track.

Peter Drouin · March 11, 2018, 09:39:56 PM

More set works very well for me.

50 Acre Jim · March 13, 2018, 07:51:47 PM

Quote
To help the OP (50 Acre Jim)-

There is a chance that the blades you got resharpened were not done correctly. The fact that a new blade performed in an acceptable manner after trying the ones that were serviced would somewhat lead a person to assume this is the case. One or more things could have attributed to the problems you were/are experiencing. This is also one of those times a person has to make such assumptions based on the information provided.

Walnut saws relatively easy compared to White Oak. You also shared the White Oak was 28" dia. That's starting to get into pretty wide cuts with not much blade support from the "guides", regardless of species. The fact is was W. Oak probably didn't help the situation. Having blades best suited for your machine and what you're sawing makes a big difference too.

Because of your HP and description of your sawing situation, you may look at getting some 4 deg. blades.

Take a good hard look at your ceramic guides. The effects of the guides themselves can/will play a role in poor blade performance. The heat generated from the friction (guides contacting the blade) and also the literal damage to the blade body itself from the guides "scrubbing" both the sides and the back edge of the blade. A blade that performed acceptable when new, may have damage that no amount of sharpening will ever correct.

Also check and make sure your blade is dead parallel to the bunks. This is critical, even more so than sawmills running a roller guide system. You may even contact Norwood about upgrading to roller guides. By far, one of the best investments you can make to improve both your lumber quality and blade longevity/performance, IMO.

Hope this helps you out.

Thank you Cutting Edge,

The mill is level, the blade is "dead level" to the bunks, and I had just upgraded to roller guides. I have cut White Oak this diameter before and this experience was not what I expected. :-)

I agree 100% with the need to use 4* blades instead of the 9* I was using. But that being said, the blade was diving so deep, and so quickly, that there was over a 1" gap between the bandsaw blade and the right roller by the time I had gone a few inches.

I switched blades again yesterday to cut a few 4x4's and the saw ran great. Albeit, it wasn't White Oak but still, the saw ran as expected and that made for a good day.

Thank you, everyone, for taking the time to help me. It is truly appreciated!

Jim