Of a 10degree 34mm blade (~1.35"), to make perfect flat cuts in knotty english oak 950mm (~37") wide?
I was pretty happy with the results - I think the waves are shallower than the warping that may occur during drying, 1-2mm max and flat for most of log, but I still wonder if it could be better. Where do you draw the line at acceptable quality from a flexible band?
Would a 4 degree blade likely resolve this? More tension?
Was my first day sawing for a customer, cypress for first half of day which we breezed through. English oak the second half which didn't go as well. The loader driver dropped a ~1T log on my wheel/edge of bed from a few feet up. Wrecked the rim, bent the mills legs etc. Crap happens. Wasn't hugely disappointed with the cut quality anyway but I'd like to dial it in as best I can.
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I would sure think so. If that were knotty white oak and your mill were the LT40 Super 42HP I used to have, a doublehard (Woodmizer) 1-1/4 4/32 045 band would cut flatter than an equivalent doublehard 10/30 band.
I would expect flat cuts from my mill. 10 is a good all round blade for a small horse power mill. I had to change to a 9 to saw Ash and Sugar maple on my old 24 hourse onan.
Check drive belt tension is a big cause of wavey cuts.
And here i thought we were gonna talk about getting the band back together.
;D
There you go fixed it for you Mike lol...
My sharpening guy wasn't really interested in backing off the rake angle on my blades. I wondered about trying to adjust one with a chainsaw grinder.
Drive belt tension is same as it always has been but I have no idea how to tell if it's slipping. The saws note while in the cut doesn't change
I use 10 degrees on pine, cypress, cedar, poplar, sweetgum .. 4 degrees on oaks, hickory works good for me.
It looks like, in the photo, that you are packing sawdust? I'm also seeing what appear to be band rub streaks across the face of the log?
Smooth cuts are the end desired result, but sawdust residue are a valuable diagnosis tool, and it will tell a lot about the mill and band combination, and how it is performing in a log.
I just can't conclusively tell from the photos.
Packed sawdust is when the cut is too slow, or too wide for the sawdust to create and stay in suspension with the air in the gullet, and be efficiently ejected from the cut. This had a lot to do with the tooth angle, the gullet (which acts as a recirculating or swirl zone for the air suspended sawdust), the set (which controls air flow, sawdust amount, and saw kerf), the sawing speed, and the amount of band lubricant used.
If the sawdust falls out of suspension in the air in the gullet of the band, generally due to sawing too slow, it will pack under the body of the band as it moves forward, and if the amount of packed sawdust is greater than the set, it will force the band up and cause waves. If the packed sawdust under the band in the kerf is a lot, it will create a black steak in the sawdust where the metal of the body of the band is actually wearing off and showing up in the sawdust, packed on the board, creating a bluish gray streak.
Other than that, I would think a 7° would be better in a 30 inch walnut log.
The key to flat sawing with the proper band is to be able to cut as fast as the hp of the mill, not the band, will let you. Faster cutting means cooler sawing in the band because the moisture of the log acts as a coolant, better sawdust ejection, and better gullet suspension. As a general rule, if you are not sawing on the top end of the power band, ie. where the engine is loaded up at full power, then the band is controlling the cutting, and it means the band is not optimal. Ideally, you should be able to saw at full speed and full power, deep into the governor, and cut straight. If the drive belt is loose, it won't let you get there.
You sound like you'd be a handy guy to have around for a day YH haha.
I didn't think to look closely at the sawdust but definitely saw both packing and metal streaks. What do I change when I see it if I can't change width or tooth angle since I can't change either at present?
I got the butt end of the oak up on the mill today, with great difficulty since the loader wouldn't lift it, about a meter wide anyway. I put a brand new blade on it and got perfect flat cuts right up until about the last 6 cuts where I had a piece of wire to go through for the last of them. Was my last band (since my 4th and 5th spare were welded too short by supplier =/) so I just kept going and got pretty darn flat cuts anyway, bit of ramping up at the start and not a great surface but couldnt knock it for the same band hitting metal 6 times. I was pretty happy with how it went today.
I'm definitely not loading engine up. It's 22hp I think if I did load it up in 1m oak it'd misbehave. Are you suggesting in say 400mm wide cypress I should be pushing as fast as the engine would cope? It slips through logs like that really well but could go a lot faster before bogging. I think I've found I start getting worse results if I do that.
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Those old logs will dull up a blade fast. Steve
Thanks for that excellent post @YellowHammer (https://forestryforum.com/board/index.php?action=profile;u=11488)
Does gravity offer much benefit toward ejecting sawdust in a vertical oriented bandsaw?
I'm not sure with a vertical bandsaw, but intuitively, I would say it would actually be a better orientation, as gravity and sawdust ejection would be working toe=gether, and flow in the direction of the cut.
The characteristics of the band is such an important driver, not being able to experiment with band profiles, set, thickness etc will make it hard to change things.
Certainly, alignment is also crucial, and the band needs to be dead straight with the mill bed, because if there is the slightest angle it will try to lift like an airplane wing. We are not talking "kind of" aligned, but dead on. The roller guides must also be perfectly aligned, which can be problematic as they wear with a taper. A quick way to check is to clip two of the band alignment tools to the band, one near the idle side blade guide, one near the drive side and sight down them from a perpendicular angle and make sure the are both perfectly parallel with each other.
With a 22 hp motor and logs that wide, of most any species, yes, you should be able to cut dead flat, until the engine bogs (don't let it bog, not good). If you can't saw that fast, that is a symptom of a band that is controlling the cut, not the engine, assuming the drive belt is tight. Of course, sometimes its a user's call to slow down when getting into a knot or some other issue, but generally, you should be able to cut at the limit of the engine horsepower on a routine basis.
I use a drive belt tension tool to make adjustments to my drive belt, but most time I can tell when it gets loose beause I can't load up the engine and change its pitch.
When I had my LT15, with a 15 hp engine, I used 7° doublehards and cut pretty slow, because it only had a little bit of engine power. When I got my diesel LT-40 I was able to use the exact same bands and cut about 3 or 4 times as fast, straight as an arrow. Years later, when I had a WM annual alignment done, we went through everything and dialed the mill in perfect. At the conclusion, I loaded some logs and started burning through them, way up in the engine power band, and the WM tech just started loading his tools in the truck, saying he knew he was done when I could make a saw grunt like that and still cut dead flat wood. All this was done with the same style band, the engine horsepower and alignment was just allowing me to cut faster and still be flat.
With my LT70, with even more horsepower, I have found a band that lets me run to the high end of its power band, and can cut flat at the maximum hp the engine can deliver.
Thats another reason its so important to have a clean and shiny band, any crud or sap will cause the band to deflect and ruin the chances of a full power cut.
Full power, high speed cuts aren't just for production. Everything works better when cutting faster. For example, if the sawdust is being ejected from the cut like its supposed to, there is not enough sawdust left on the board to scrape off. So one less step to do. I haven't scraped sawdust in years, I don't even own a scraper anymore. If I ever get excessive sawdust, I don't reach for the scraper, I look for something wrong with the mill or the band.
I got a few of my bands back from the saw doctor this week, he's done one at 12 degrees which is what he said he has been doing them all at. He did the other 2 at 4 degrees and didn't get around to the rest but I needed them now so picked up the three.
Saw another new problem yesterday while sawing 900mm wide cants, bone dry (i.e. sitting in milled blocks like that for a couple of decades). With the 12 degree blade sharpened blade, and a brand new 10 degree blade, I experienced what I could only describe as tool chatter. Or blade chatter. The blade started squealing much like a cutter tool does on a lathe when you're getting chatter, and I got the same spiral pattern you'd get on a lathe, at the points where it happened on the wood.
Switched to the 4 degree blade and it disappeared. I think I'm going to get all of the blades reground to 4 degrees, I know this isn't a great test for general sawing but that one problem in particular went away, nice cut flats with it and I didn't notice a huge decrease in cutting speed anyway. In fact while cutting some of the thinner stuff I did quite happily push the engine until it was loaded right up and got great cuts. Very hard to read sawdust with a dry cant as it all just blows away when you remove the slab.
Quote from: JoshNZ on September 08, 2020, 06:51:18 PMI did quite happily push the engine until it was loaded right up and got great cuts. Very hard to read sawdust with a dry cant as it all just blows away when you remove the slab.
Actually, those are two very positive outcomes. You are loading the the engine getting the horsepower it has, and the best sawdust is the sawdust that blows off with no effort. No more scraping sawdust is definitely "taking steps to save steps." :D
I don't think I could have done anything to get sawdust that wouldn't blow away this stuff was just so bone dry. Obviously had been milled into its big cants for decades.
I've got an elm to try tomorrow. Not very wide but will be interesting to see if I can load the engine up in them with 4 degree bands and get a flat cut.