Good quality (smooth) UHMW cut on PM66 table saw with power feeder - Page 3
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  1. #41
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    I think we are all pissing in the wind until we have a high def pic of the desired cut result. Guessing the total elimination of tooth marks is the goal. "Cutting" may not be the name for the process, at least not from what I have read so far.

    Stephen, making the blade wobble is a serious process of frustration. I have a set of those wobble washers, and have also used folded paper too. Stuff the paper to make the blade cut maybe 3/16 kerf while you turn it by hand. Power on and kerf is same as without paper. WTF? Blade at speed flatens out to cut same kerf as always. So you pack more parer in. At some loud nasty noise the blade seems to cut what you want, but very different from the kerf when rotated by hand. When you get to this point you are still going to get screwed. The kerf is rpm dependant. Faster it spins, narrower the kerf. How about this. You need to make some "egg crate" dividers. You set the wobble to cut the deep dado at the correct width. But you do this with a very shallow test cut. Yup, all is good. Sandwich 4-5 pieces and cut your first deep grooves. WTF, dovetail cuts? From a saw blade? As the blade slows down the centrifugal force is less so the blade straightens out and makes a wider cut. Does this at the deepest part of the cut. Once cut is done the blade spins thinner.

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  3. #42
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    Scruffy-

    Good description if the blade is large diameter in comparison to the collar diameter!

    I don't actually reccommend the process.

    But the few times i have used it, more or less like the described egg-crate problem, I have tended to use smaller dia blades than a "regular" blade for the TS. So this has usually been done on the tiny little Rockwell unisaw which normally only takes 10" blades, but has a 5/8" arbor. So skill-saw blades or blades even as small as 6" can be used.

    I recall once using a thickish (for the diameter) steel blade and dressing it as it ran to get the tops correct, then back filed relief without removing it for some production job.

    Usually it is better to accept a blade or dado stack close to the side, and then plane or sand the components to a snug fit. If a widebelt is used, even plywood is better fit this way.

    I use saw stacks on the tenoner cope head at times, and have used tape or paper to adjust a fit. Again, as you say, not ideal.

    Also again, for the OP's purpose I was in no way recommending it - merely wanted to see if it was an accident that worked on the old Grizzly machine. The arbors seem to generally be ok on the larger Chinese imports, more or less. But the saw collars often could use some refinement.

    smt

  4. #43
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    I have stepped away from the saw and have been working on other projects. The pictures I uploaded are from the highest res camera I have at the moment (my Iphone). When working with the Grizzly we definitely were "cutting" as we were running the blade forward and getting actual UHMW chips (more like fuzz). With our current setup running the blade backwards we are probably just melting through material.

    When starting this thread our arbor bearing seemed to be in good shape. Well it is going out now - the saw makes a terrible noise when slowing down and almost grinds to a stop. I am going to put a new arbor and arbor bearing on and see how we are cutting then. (maybe the new arbor/bearing will solve the problem)

    I have a lot of ongoing projects right now and a two week trip at the end of this month, I probably wont replace the arbor and bearing until early March. I will continue updating this thread.

    Thanks again!


    Quote Originally Posted by Scruffy887 View Post
    I think we are all pissing in the wind until we have a high def pic of the desired cut result. Guessing the total elimination of tooth marks is the goal. "Cutting" may not be the name for the process, at least not from what I have read so far.

    Stephen, making the blade wobble is a serious process of frustration. I have a set of those wobble washers, and have also used folded paper too. Stuff the paper to make the blade cut maybe 3/16 kerf while you turn it by hand. Power on and kerf is same as without paper. WTF? Blade at speed flatens out to cut same kerf as always. So you pack more parer in. At some loud nasty noise the blade seems to cut what you want, but very different from the kerf when rotated by hand. When you get to this point you are still going to get screwed. The kerf is rpm dependant. Faster it spins, narrower the kerf. How about this. You need to make some "egg crate" dividers. You set the wobble to cut the deep dado at the correct width. But you do this with a very shallow test cut. Yup, all is good. Sandwich 4-5 pieces and cut your first deep grooves. WTF, dovetail cuts? From a saw blade? As the blade slows down the centrifugal force is less so the blade straightens out and makes a wider cut. Does this at the deepest part of the cut. Once cut is done the blade spins thinner.
    Quote Originally Posted by stephen thomas View Post
    Scruffy-

    Good description if the blade is large diameter in comparison to the collar diameter!

    I don't actually reccommend the process.

    But the few times i have used it, more or less like the described egg-crate problem, I have tended to use smaller dia blades than a "regular" blade for the TS. So this has usually been done on the tiny little Rockwell unisaw which normally only takes 10" blades, but has a 5/8" arbor. So skill-saw blades or blades even as small as 6" can be used.

    I recall once using a thickish (for the diameter) steel blade and dressing it as it ran to get the tops correct, then back filed relief without removing it for some production job.

    Usually it is better to accept a blade or dado stack close to the side, and then plane or sand the components to a snug fit. If a widebelt is used, even plywood is better fit this way.

    I use saw stacks on the tenoner cope head at times, and have used tape or paper to adjust a fit. Again, as you say, not ideal.

    Also again, for the OP's purpose I was in no way recommending it - merely wanted to see if it was an accident that worked on the old Grizzly machine. The arbors seem to generally be ok on the larger Chinese imports, more or less. But the saw collars often could use some refinement.

    smt

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  6. #44
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    We've cut a fair amount of UHMW both on the beam saw and the router. 3" UHMW on a 15hp beamsaw requires a feed slower than most materials because it runs out of power. We run a lot of material through our Straight line rip saw using blades made for that application. Excellent cut quality. We use Leuco blades. SL rip blades are made with long teeth that have very little taper toward the center of the blade. That makes the teeth work like planers. It also means they take more power.

    Since running a power feed requires some tilt toward the fence, mounting it straddling the blade may be crowding the part that is not against the fence into the trailing edge of the blade.

    But first you need to go over the saw and make sure everything is precisely aligned. Powermatic is not a particularly high quality machine, it is Chinese! If all else fails buy a European saw, Martin?

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    OK, Time to update you all.

    We finally had our out of house tool repair guy, Steve come by and he has bad news.

    We ran through all of our troubleshooting and observations and Steve could not think of anything else to try.

    Steve thinks that because the saw is so old that part of the saw that holds the arbor bearing is just worn out ever so slightly and allows bearing and blade wobble.

    Our current MO is to continue running the saw backwards. It sounds terrible but the cut quality is great. We have been doing this for about 6 months now.

    Thanks again for all the insights and advice.

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    ^ Loctite the bearing outer in place using the high strength retainer grade, will stop any slight slop there with ease.

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    were both saws single phase? how old is the Powermatic? perhaps the bearings have a bit of wobble. is it possible to add a spring loaded thrust bearing on the back end of the shaft to preload the bearings? maybe even an out board support to instead push the shaft towards the motor. how about shaft diameter? if it is slightly smaller in diameter, maybe that is letting the blade cast around the shaft [just made up that term].

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    Is there a purpose-built saw available? Specifically for best finishes?

    If yes, what are the differences?

    My guesses are:

    Oversized arbor, perhaps 2-3 times the current diameter

    Three phase motor

    Flywheel, or oversized motor

    VFD to tune out resonances (noise equals vibration)

    If a belt drive, does it vibrate? Perhaps a Gilmer belt is better than V-belt?

    Heavyweight table to dampen resonance

    Kerf splitter wheel that rotates as it keeps kerf open, steadies the part being cut off.

    High performance removal of swarf. Vacuum, brushes, etc.

    Study the blade with a strobe, adjust the VFD to minimize vibration

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  13. #49
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    Steve, I am not sure about a purpose built saw for this, but I ran an older cnc panel saw alot at the old job and it had a 20hp main blade motor and swung a 16" dia blade. Center hub was app 4" diameter and the flange that held it all was app 7" diameter. Blade body was almost 1/8" thick and had a 3/16" kerf. It was driven by a 2.5" wide toothed belt, probably the gilmer that you mention. This was a horizontal beam saw, so when the material was moved into position, the 2 beams dropped to clamp the material in place, both sides of the cut. I don't recall the finish on any plastics as we did not co that but once or twice while I was there. I'd think that at that point it would be up to the blade type vs any other machine variables. I know that alot of the plastic vendors use a similar saw, but not sure what finish they are getting as they usually aren't worried about it.

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    Quote Originally Posted by surplusjohn View Post
    were both saws single phase? how old is the Powermatic? perhaps the bearings have a bit of wobble. is it possible to add a spring loaded thrust bearing on the back end of the shaft to preload the bearings? maybe even an out board support to instead push the shaft towards the motor. how about shaft diameter? if it is slightly smaller in diameter, maybe that is letting the blade cast around the shaft [just made up that term].
    Both saw are single phase. The Powermatic is about 40 years old. Arbor shaft diameter should be to spec as we replaced the arbor with the arbor bearing assembly.

    Quote Originally Posted by SteveBausch View Post
    Is there a purpose-built saw available? Specifically for best finishes?

    If yes, what are the differences?

    My guesses are:

    Oversized arbor, perhaps 2-3 times the current diameter

    Three phase motor

    Flywheel, or oversized motor

    VFD to tune out resonances (noise equals vibration)

    If a belt drive, does it vibrate? Perhaps a Gilmer belt is better than V-belt?

    Heavyweight table to dampen resonance

    Kerf splitter wheel that rotates as it keeps kerf open, steadies the part being cut off.

    High performance removal of swarf. Vacuum, brushes, etc.

    Study the blade with a strobe, adjust the VFD to minimize vibration
    As far as I know there is no saw built just for this purpose. Ones that exist are likely custom built. Two years ago we took a trip out to the midwest to tour our UHMW supplier and learn some of their processes that we were taking in house. All of their saws are set up the same as ours and are cabinet table saws. I am not sure the motor HP or whether they are 1 or 3 phase.




    The saw is working great cutting with the blade backwards. We are getting about 1/2-2/3 of the blade life and we will likely burn the motor out faster. This is the cost of getting good parts and we are OK with these issues for now.

    Our long term plan is to take our material and blades to our local machinery dealer, and try cutting on their floor models (likely a PM66 and some SawStop.) Our machine mechanic who is very competent and has helped us out of binds in the past thinks we are best putting this one out to pasture as it will likely be flawed like this for the rest of its life.

    Some of these suggestions are good, specifically the thrust washer idea and we may try some of them as we have some room to breathe.

    Thanks


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