Hi all
Got an issue im hoping someone can shed some light on..
I'm at a customers to saw up some LARGE old eucalyptus (e.globulus or southern blue gum)
The timber is fairly dense hardwood but seems to be wreaking havoc on bands i'm throughing at it.
I can easily remove the sapwood but now hitting the hardwood in about 3 passes I end up with the pattern in the picture and bands that don't work.
(https://forestryforum.com/gallery/albums/userpics/29851/20130430_165903.jpg)
Its like the band rides up and then tension on the band goes down and it also burns and it passes along, the bands also come off dark and discoloured.
And you end up with a crown effect and humps and hollows..
At the end of today I did check the roller guides and find that the drive side was 5mm aiming high and the idle side was about 1mm down.
So it would have been putting a "twist" on the band I think.
I ran the last band I had on and it looked the same BUT it could have been wreaked by then.
I tried fresh sharp bands, and also one from a local sawdoctor/sharpener place.
My own band sharpen/set seem to work better...
I have a box of brand new bands, these don't have enough even set and go skywards immediately.
I will go out to the shed soon and see what the last band of the day might tell me about set, it still seems sharp, but I think the set has been taken out on one side.
I'm using woodmizer bands, 10deg 1.5"
I've talked to one of the other local mills running woodmizers who have a lot of experience, they just said that it seems to dull things fast and you need to be careful and have razor sharp bands.
Some of the quarters or tree sections will be maxing out the size of the mill so I really want to get this running well.
For those that like photos check out the size of the sticks by the fence...
(https://forestryforum.com/gallery/albums/userpics/29851/20130429_140320_1.jpg)
Cheers
Justin
Hey Justin,
Do you have bands with less hook angle like 7's or 4's??
I suspect the 10 deg bands may be too aggressive for that hard wood
Band tension is proper?
Best DGD
My guess would be more set and less hook angle.
It sounds like you are heating the bands up bad ! Water water ! Also you indicated your alighnment is out or was out ,but I would check that with a fine tooth comb ! If possable try and get a couple WM turbo 7's . What would concern me is why the heat build up and loss of band temper ??
Water did seem to improve things and take out some heat.
dgdrls - I have been avoiding buying other bands, but I think I might order up a couple of 7deg band tomorrow to give it a crack. (I only have a 10deg CBN wheel)
The log I've been dealing with that has shown the big issue is the butt end and I'm going into the butt end first, so I'm asking for trouble really..
Of note I have sawn frozen hardwoods before with 10deg bands, I had to go fairly slow but it did work ok.
I'm guessing a few of you have found the 7s rather good and fast however?
Or is it worth trying to go right for a 4 to have around for the really tough stuff? (I have more of this stuff coming up)
Slider - tried more set, seemed better perhaps
Oh and dgdrls yes, band is tight to begin with at the normal 2400psi... it just moves once the cutting begins...
Cheers
Justin
I think you need to align your mill, and especially your blade guides.
Howdy Justin ;D sorry to hear of your struggles man, I may be mistaking but it looks like from the picture you have hit something, rock, or otherwise, If the first cuts are good then this lead me to believe your alignment is ok, but not there to verify this,, I would get the lesser hook angles, 7's work good, start your cuts from the small end of the log, and make sure your drive belt is tensioned proper, your blade roller bearings are good, heat comes form many places, I did read a post a day ago, someone mentioned that the 1-1/2" blades were hitting the covers, might check this too,, I hate the struggles, you can find the culprit, remain calm ;D think of the end of the day,, david
Thanks for the encouragement David, its only taken one day to half mill one quarter of a log, so im not setting any records on this one!
Speaking of belt tension, does someone have a picture showing there drive belt "twisted" over on the top to see how far it twists?
mine I could almost twist so it was going vertical so I adjusted it so its about half of that now. (no I don't have a meter to set it right)
Cheers
Justin
No pic available justin, flip you auto clutch switch so that full tension in on the drive belt, then turn the key off, leaving the motor raised in the tension position. you should not be able to twist the drive belt to veritcle, at mid point between pulleys, Mine is set in the 45 degree range,, still cant figure where those saw marks are coming from, that looks weird to me, like a tooth is out or something, let us know, looks like a great job, definetly don't need slow down issues, aye? david
Thanks david, that's where my belt is now.
That's after 3? cuts I checked the band last night and all the set is being taken out of the band, or specificly mostly one side then it rides up.
I just talked to the NZ woodmizer agent, he said "run away" from that stuff! haha
He is sending me a stellite band to try otherwise he has no 7s or 4s in stock.
Cheers
Justin
QuoteI just talked to the NZ woodmizer agent, he said "run away" from that stuff! haha
I was going to be smart and post something to that effect :D
The carbides on the swing mills (etc) seem to handle it OK (with some extra sharpening maybe) but it's got a bit of a reputation with the band saw mills.
But the blade setup is probably the key. Blue Gum is pretty hard compared to most Nth American wood so the harder tips and a different angle would probably help.
Ian
If I am following you about the set being taken out, is there a chance that you have sharpened the bands enough that the top edge is contacting the roller guides and rolling the set out?
Justin I get that type of cut if I'm making full width cuts in dense wood. The wider your cut, the more everything needs to be dialed in correctly. As you move your movable guide out, you lose beam strength. High beam strength can overcome dull blade/poor set/overfeeding etc for awhile. But the more unsupported blade you have between the guides, the less beam strength the blade has, and it will begin to show in the cut. Couple that with sawing blue gum (about as hard as our hedgeapple I think) and I can imagine you'll get some ugly cuts. also, 10° is too high a hook angle for sawing the hard stuff. 7 or 8 degree should be fine (I use 8° or less and have sawn some pretty hard stuff). Do a thorough blade alignment on your saw, make sure your set is exactly right (even and not too much), your blades are deadly sharp, bump your tension up just a little and don't over feed. You'll be puttin those logs to bed in no time.
That's good lookin job, BTW.
First thing I noticed were the black pitch streaks and very close or slow sawing pattern. This is indicating too slow a feed rate and bands that are very hot, leaving burned pitch residue, the black streaks, on the cant. The black on the blade you are seeing is pitch buildup and burning caused by a too hot blade. Black hot pitch buildup is death to a blade, results in blade wander and an immediate and significant loss of tension during the cut, which is what you are seeing. It's counterintuitive but too slow sawing heats up blades worse than sawing fast. Use the blade pressure gauge as a temperature indicator, if you drop significant pressure during the cut, the blade is getting hot and damaged. The more you have to slow down, the hotter the blade gets and the more the blade pressure drops.
All this assumes the blades start sharp and are set correctly.
Since you can't saw any faster with the style blade you are using to keep it cool, you should change hook angles and/or set, which is exactly what you are doing 8) Also, I would upgrade my lube to a much more heavy duty formula, or go to an emulsion oil and water lube such as my favorite cotton picker spindle cleaner or similar product which is what I use when going through very hard wood.
I have burned and overheated blades in one bad pass on hard wood...I called those learning experiences, for sure. It takes the right blade, the right speed, and the right lube to get it right.
YH
7 degree blades, doc, don't use the ones you use for "radiator" pine. Let the lube pour right out of there, water and soap. Or try diesel fuel. Keep the blade tight and cool. Go slow and let the teeth do their cutting. I suspect that once you get it whittled down a little, it will go better. Are you sure you didn't hit metal? My blade makes those bulldozer tracks in oak, etc. after I hit a nail.
Ian - feel free to throw the insults :D
MM - Bands are new or first sharpened, so no, the rollers are not flattening them.
5quarter - Been through the alignment a few times, and good to hear your input, as I think its on track.. i.e less hook..
YellowHammer - Makes perfect sense, i.e I cant push fast enuf through the timber and it heats and causes the lack of tension and it all goes bad...
When I tried to push faster though I had the band pushing and bouncing on the guide arm like it could not chisel into the timber which I had not seen before, I should have taken a video, it was something else!
But that follows the thought of not being able to push through it fast enuf...
I have been using a lube which is water, a bit of dishwash liquid and washing machine powder, its been fine up till now...
Okra, that radiator pine cuts so easy though! :D
I am now awaiting a stellite band and will see how it goes, unfortunately its still a 10deg band.
Local woodmizer isn't getting a new shipment in for a couple of months so I either have to find another source of bands as airfreighting a box of 7deg bands would cost a few bux I think :(
Otherwise I asked the customer to put a few of the "limbs" and smaller bits on that I think wont have as much compression as the butt logs.
and also small end first to give me a more fighting chance :-\
Here's another picture with a new 'helper' keeping over watch :D
(https://forestryforum.com/gallery/albums/userpics/29851/20130501_172957.jpg)
Cheers all!
The butt flair your helper is perched on would even make me nervous :D
Something is going on in there, grain run out, tension and general weirdness for sure.
Have you tried Thode and see if they can help you with an alternate blade?
http://www.thode.co.nz/ (http://www.thode.co.nz/)
The manufacture various bands here in NZ, I think using rolls of Lennox material, but can do pretty much any size to order.
Ian
I don't envy you cutting something that hard with a bandmill. But as MM alluded to, I think the first thing you need to figure out is what is taking the set out of one side of your teeth.
Thanks Ian I will give them a buzz first thing tomorrow.
I kind of get the feeling after talking to another local mill and the WM NZ agent that most people just avoid this really old big stuff and just turn it into firewood hence why he doesn't stock the lower degree bands since no one chases this hard stuff - that's my take anyway...
The other local mill running a lt40 and 70 say they have cut this stuff before and with the same bands, but tweaked to an inch of there life....
I told the owner today that as long as he will let me I'm turning it into a personal mission now so I can figure it out and make it easily repeatable so if I came across some of this again I can produce something. (or run away screaming)
Nomad, yes sounds like a bit of a mill fault BUT, I can cut the softer sap wood off fine, and I put a bit of cypress firewood they had there and with my new "fine tune" I can slice it like butter (with a non destroyed band of course)....
Just for others interest, I have cut a few cube of hardwood that was frozen last winter which the machine in poorer tune and the same band setup and I made it through that ok. This stuff makes that frozen hardwood look easy peasy in my book!
I'm pretty convinced that I'm just trying to use the wrong cutting tool and need a less aggressive band to chew through it.
Its just now finding a new band I can get my fingers on.
I will report back how I get one with the smaller bits of the tree tomorrow anyway, unfortunately I wont get the stellite band for a day or two yet.
Cheers
Justin
I love the "helper's" attire. Long sleeves and barefooted. :D
Here is my opinion:
old hard wood needs 4° bands with the short teeth. The tooth length of the 7° is too long for the real hard stuff. I have sawn enough old dried out Osage logs to know what hard is.
I have yet to try a stellite band so I don't have an opinion on them yet.
I sometimes use 10 d stellite bands when I dont think the double hards will cut the mustard. they are superbly good,but they are expensive. good for 3-4 sharpens. cheers john
Well if that don't beat the band!
Justin, do you know what the Janka hardness is for that species? Or maybe Ian knows?
Okra...around 2100 I think. A good flooring wood.
Quote from: 5quarter on May 03, 2013, 01:26:52 AM
Okra...around 2100 I think. A good flooring wood.
Something around that, 2030 according to my book, but the faster growing NZ trees may not be quite that hard.
It can be a real pig to get dried though. E saligna is very similar, but behaves much better and makes good flooring. It's hard to tell them apart without a close examination of the leaves, flowers and seeds.
Ian
yes, give me the ASH type euc's anyday! - tend to get a fair amount of fastigata (brown barrel) and delegatensis (mountain ash) around here.
This stuff is good flooring wood for sure (which is what they want).
I'm going to end seal the cut boards for them and they have a good spot to stack to dry, as most euc's are very hard to dry correctly.
Small update...
After spending some time down at my other mates mill I've learnt a couple of things from them...
They have reverted there CBN grinders back to drag grinders and there bands are lasting A LONG time as there razor sharp compared to my CBN ones.
I've put an order to WM agent for a different cam to change my sharpener as well. - my CBN wheel is probably end of life anyway (not sure how to tell?)
They also bin the lubemizer setup and run a NZ made lube system, however it requires air so not quite ideal for a mobile guy like me...
I think I might get there old lubemizer as it will still beat my 'flood system' :D
stellite band arrived, so I will give it some more set and check and go attack that wood this weekend.
Cheers
Justin
Justin...there's no substitute for razor sharp bands. even after you get it all dialed in and the cutting is good, expect the bands to dull much quicker (ie, less BF per sharpening) in really hard wood as opposed to radatia pine, for example (I'm sure you know this, just a reminder :) ). take a bunch with you and change frequently. You should definitely get longer life from the stellite. Keep the RPMs up when you're in the cut. overfeeding and losing RPMs even for a few seconds can quickly heat the blade and ruin a cut. I'm anxious to hear how it turns out this weekend...work hard. ;)
ok, update on this problem...
Went and tried 3 bands today. (been a tad busy to get back to this customer, I wasn't expecting this job to spill over to this week >:()
The first two bands were 10deg with 0.025" set
One was sharpened by a local mill on there converted drag style setup and the other by myself with CBN wheel.
As expected the added set took the crowning out of the cuts and the waves got WAY better this bands were also sharper than I had before.
Very little if any of that nasty burning black marking...
The bands still got heated and probably caused the small amount of wave and I think my 'tap' lube system on one side of the blade is the last bit letting me down slightly.
I'm thinking I should just bite the bullet and order a proper lubemizer to A- save me filling the water/soap bottle all the time. and B - lube both sides of the blade properly, I would even get some of the local lube the other guys use (looks like good stuff)
Oh, the third band was a stellite one which I set to the above but didn't sharpen it first.
It powered through the middle of the log (splitting for 1/4 sawing) really well.
Haven't run it much at all but out of the box it seems pretty good.
Now what I find interesting is that the 10deg bands are obviously WRONG for this type of timber, but REALLY sharp with lots of set you can get by (I think)
I haven't found a local supplier with a band under 10deg (not that ive REALLY looked hard)
But I suspect, a 7deg or so running sharp and most of my troubled would disappear.
the good news for me is i've fine tuned my sharpening and setting skills a lot better, so i'm getting my other bands ready because next week i've got the entire week booked milling LOTs of eucalypts (softer younger ones) so I suspect I will power through them much better now :D
I tempted to try more set and see if it helps that last little bit, anyone think that's a good idea?
the sawdust was heavy on the board and fairly packed, so that would suggest more set I think?
Cheers
Justin
Justin...That's great news. 8) 8) I knew you'd figure it out. You can try a little more set, but remember that more set equals more sawdust, and a wider kerf means more HP needed to make the cut. also means you need wider, thicker bands to compensate for the added stress on the band body. I've used as much as .032" set, but it was cutting some wide, knotty, pitchy pine. Try .026" or .027" set and see if you hit the sweet spot.
More set may help keep the blade from rubbing on the packed sawdust, or you may have even more spillout. But either way it's still a problem. WM has a new 7° Blade out with a deeper gullet, similar to the Cooks SS profile that may clean that problem up.
The more you experiment in search of a better cut, the better sawyer you become. ;)
Thanks for the encouragement!
yes, I'm keen to try the new WM turbo bands but have to wait two months for them to get to NZ sadly.
I am running the lombardini diesel engine which is 35 odd horsepower I think, so it should have enuf grunt I think?
I'm using 1.5 by .45 bands so there are fairly tough I think.
Cheers
Justin