keeping the bandsaw blade clean

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  • #775862
    Barry B
    Participant

    i’ve been resawing a lot of pine and it gums up the blade. i have to remove the blade and spray it down with simple green to remove the buildup.
    a search on the internet finds suggestions ranging from PAM (cooking spray) to chainsaw bar and sprocket oil.
    does anyone have a favorite that won’t degrade the tires or result in blade slippage and reduces buildup?

    thanks and regards

    Barry

    #775934
    Larry Geib
    Participant

    Barry,

    Keeping the blade clean is more than finding a magical spray or oil to stop buildup, though lubrication does help. I don’t think it matters much which lubricant you use as long as it stays on the blade. That one reason you have seen chain saw bar oil mentioned. It sticks to metal well for a relatively long time ( in the minutes time scale).
    Several factors come into play, such as the type of wood and wetness of it you are cutting, the blade pattern, type, and size, the surface feet per minute the blade is geared to, the extraction and blade cleaning during running, etc. IMO the main cause of resin buildup is heat. Bear with me.

    With your case using pine, there are some special considerations. Use a 3-4 TPI count. It will clear the wood from the kerf faster. Use a skip tooth pattern.
    The resin buildup isn’t all due to actually cutting the pine. If you run at a high sfpm you can cut quicker, but it’s at the expense of an increase in heat buildup, all things being equal. Things that run fast get hotter from friction, which in turn causes the resin in the pine sawdust to melt and get gummy. You can reduce the heat by running slower and by lubricating, but also by having an airflow over the blade. Proper extraction of sawdust is best done with a high airflow volume and speed right under the cutting area. Extractors that just suck from an enclosed large volume space aren’t as effective. There are videos on the webs on setting up your extractor to do that. Rob Cosman shows an easy conversion here:

    A bonus of this system is that the high velocity/ high volume cools the blade.

    The lubricating oil I use is just mineral oil with a small amount of Bar oil added to make it stick better to the steel. Modern bar oil is just canola oil based, so it isn’t toxic. It’s the same formula I use for my rag in a can, so it’s nothing magical. I just run the blade backwards by hand while holding the Rag in a can against the wheel, but any method will work.
    I use urethane tires and haven’t perceived any harm to the tires in the couple decades I have used them. I can’t speak to other types of tires. One consideration is that the blade will slip on old, glazed over tires. That is another source of heat from friction.

    As to speed ( sfpm — surface feet per minute of the blade) it depends a bit on the size of your bandsaw. The blade needs a chance to cool before it engages the wood on the next rotation, so small bandsaws need to run a bit slower to allow that to happen. If you run fast, the blade has less time to cool before it has to cut again. I’d also run a bit slower on pine, since it is so easy to cut with a sharp blade. There are charts on the internet to match blade speed to saw size, but the lower end of the scale is maybe 2600 sfpm for a small (12”) saw and around 4000 sfpm for an 18” saw. Large Industrial saws run faster. (A couple hundred sfpm +- is of little consequence)

    Again, the faster speeds require more cleaning. It’s part of the trade off to cutting faster. My saw is a 14” saw and I run most cuts at 2600 sfpm partially because the saw runs smoother at lower speeds . Casting tolerances weren’t as tight in 1920 as they are now. I’m not in an industrial setting anymore, so the slower cutting rate doesn’t bother me. It’s still way faster than hand work. Smooth cuts are more important to me.

    And in addition to a high speed airflow over the blade I’d consider a strategically placed brush to wipe the lower tire and keep sawdust from collecting on it. Less sawdust constantly contacting a warm blade means less resin to transfer to the blade. You’ll find methods of doing this on the webs, as well as commercial add on systems. Even so, clean the lower tire from time to time.

    And tuning the blade helps a lot. Only using sharp blades reduces heat buildup. Dull blades are less efficient, and that also leads to heat buildup.
    And in addition to sfpm or the blade, there is the speed at which you feed the wood through the saw. Working slower will allow the sawdust to clear the kerf better, which also reduces friction.

    Setting the blade guides properly also helps. Many people set the guides too tight, another source of heat and friction. The blade should not contact anything when it’s not actually cutting.

    Consider cool blocks or other low friction guides. My saw is an antique and was designed for guides made of oily woods like cocobolo or lignum vitae infused with pertolatum. It works quite well and is quieter than steel or ball bearing guides. Actually any infused porous hardwood works.

    And get high quality blades. They will be set more uniformly which eases friction and gives a smoother cut. I stone my blades when I install them in the saw the first time. It’s as easy as lightly holding a fine stone or diamond paddle against each side of the blade wile MANUALLY turning the blade backwards one Rotation of the blade for each side. DO NOT HAVE THE POWER CONNECTED WHEN YOU DO THIS. ITS A HAND POWERED PROCEEDURE. Also stone the back edge of the saw blade where it contacts the thrust guide for less friction and longer blade life.

    Hope that helps.

    • This reply was modified 1 month, 3 weeks ago by Larry Geib.
    #776063
    Barry B
    Participant

    Hi Larry,

    Thanks for the reply. You gave some good insights. I went over my saw (14″ Rikon) and gave the tires a good cleaning, vacuumed all the residual dust, checked that the lower wheel brush was still adjusted correctly and that the guide bearings were adjusted correctly. I only use 3-4 TPI skip tooth blades and they are still sharp. I use a shopvac with the most CFM i could find (and afford) with a cyclone separator as my dust collector.

    I’m pretty sure the main culprit in this case is the wood (construction grade pine with a lot of small resinous knots). I will try using the ‘rag in a can’ oiler and see if that helps. I should be cleaning the blade after each sawing session (it’s just normal maintenance, but easy to overlook!)

    Thanks and regards

    Barry

    #776486
    Colin Scowen
    Participant

    I have a second hand band saw, 20 or so years old, only had the large port on the back for dust extraction, so doesn’t fit with my Dyson / cyclone system. I am currently building an auxiliary table for it, and I decided that rather than use a single piece for the table, I would use two full size pieces, and have some smaller pieces sandwiched between them. This allows me to also mount a dust extraction nozzle in to the back of the table, in line with the blade. The inner layer sets a channel between the hole for the blade, and the hole for the dust adapter. The (hopefully) attached picture should help to visualise it. The sandwiched table comes out of the cauls today, then I need to mount the front and rear bracing and the dust adapter. Should be ready for a test run by the weekend.

    Colin, Czech Rep.

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