Started by Robert.schade, November 28, 2023, 05:27:44 PM
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Quote from: moodnacreek on November 29, 2023, 08:26:04 AMSo if all the saws do it... where they all hammered by the same guy? Probably not the saws. Turn the mandrel by hand with a dial indicator rubbing the outer contact area of the tight collar. Should not be more than .002 wobble. Something out of balance on the mandrel or drive can do this or something loose. Does it flutter at slow speed when coasting down to a stop? How about cold versus been run for awhile. How about if the guides are pulled back so they don,t touch the saw. I had 3 saws do this and they were all bent from big slabs hitting them. When did this start and what happened to cause it?
Quote from: DanielW on November 29, 2023, 03:18:07 PMsnip
Quote All my saws come from one guy hammering.
Quote from: DanielW on November 29, 2023, 03:18:07 PMDialing the collar would be the first step. It's a little hard to tell from the video, but that looks like an unusually thin-gauge saw. Not the typical 7/8 or 8/9 you see on conventional headrigs. We've done a few circular headrigs with thin-gauge saws, sometimes with carbide brazed teeth. It's possible to get them to work, but always a bit of a struggle. Until you go with a full guide system (water-oil pressurized guides), those thin saws can be hard to stabilize. If it's a conventional hammerman doing the tensioning, he might not be familiar with how strugglesome these ones can be to get right. Is that flutter happening after it's cut a few boards, or is it like that right from the get-go? If you collars are ok and it's like that (or gets worse) after cutting, it looks like a tension problem.The hammering/tensioning of a saw is primarily to counteract the strain when the saw enters the cut: The rim stretches due to cutting forces. The metal is still within its elastic zone so you don't get permanent deformation, but it certainly does stretch. A smaller (much smaller) proportion of the tensioning is to counteract the centrifugal forces from running at speed, but these forces are minimal compared to the cut forces. Back in the day, folks assumed the centrifugal force was the primary concern, but this isn't true. The hammerman needs to apply residual stresses to counteract the cutting stretch and make sure the plate stays in-plane. Speed and feed make a difference in hammering: Higher rpm with the same feed will result in less rim strain. Lower rpm with faster feed will result in higher rim strain. Gullets improperly sized can lead to a boat-load of strain (and many other problems). A lot of hammermen only ask for RPM and right/left hand, because feed rate often doesn't vary too much in most headrigs. There are several exceptions however: One exception is sharp-chain and canter systems which can really boogey. Another exception is the old handset farmer mills like the Belsaws which have a very slow feed rate. Good hammermen will take these factors into account in addition to RPM.When you get into thinner gauge saw plates and different teeth, the conventional rules go out the window. Brazed teeth don't impart the same stresses in the rim that conventional inserted shanks do (this is important if you're running conventional inserted teeth - make sure you have a full set of shanks. Some folks remove every other bit to save power on slower feeding units, but you need to still have the shanks and dummy bits in there). Smaller tooth pitch and gullets will really change the rim stresses. Some of the thin kerf units really wind up the RPM vs. feed ratio, which may lower the rim stretch when in the cut, but exacerbate the centrifugal strain. When you get into thinner plates, getting rid of any ridges is much more critical. All hammermen get rid of ridges/lumps, but few get it absolutely perfect. It's no fault of theirs: most of the time it's not necessary to get it 100% perfect. You can put a fair pit of hammering/rolling into a thicker plate to account for high cutting stresses before you start influencing its free-running condition. With a thinner plate, every little bit of tension you add is going to influence the free-running condition to some degree. It takes a good hammerman and a lot of trial/error to account for all these factors in an unconventional saw plate.So: Start with dialing the collars, but if that all looks good, let us know a few more spec's: Plate thickness, RPM, tooth type/profile, collar condition/profile/taper, who/how it was tensioned, etc.Also, after you shut down (assuming you're able to cut with it), feel the saw. See if it's hot towards the rim, hot towards the eye, hot all over, or not hot at all. That'll tell you a lot about how the tension's behaving.Good luck with it. I hate circle headrigs next to clearing belts like you have there. A tiny bit of wobble and suddenly you've hit the belt frame and send shrapnel everywhere. If you don't have a rear guide on there to prevent contact with the belt when the saw goes snaky, you should really add one. Just make sure it doesn't influence the saw during normal operation - set it a good 1/8" away from the saw's nominal running position. Because it's not there to guide the saw it doesn't have to be phenolic - you can use UHMW (or even wood).As a final note: It doesn't hurt to put a tach on the arbor. You'd be surprised at what a little belt slip can do, or what can happen if some maintenance chap on night shift swapped out one of the belt sheaves to one that was 'almost' the same size.
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