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  1. #16
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    Double posted.
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  3. #17
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    The concern I have with sharpening the front of the tooth is that you can easily alter the rake angle. I touch up the back of the tooth. This preserves the rake, and creates a clean, sharp tooth.

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

  4. #18
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    Quote Originally Posted by derekcohen View Post
    The concern I have with sharpening the front of the tooth is that you can easily alter the rake angle. I touch up the back of the tooth. This preserves the rake, and creates a clean, sharp tooth.

    Regards from Perth

    Derek
    However, as Paul has pointed out, with extended use and repeated sharpenings the bottom of the gullet will eventually need to be ground out to remove the micro-cracking that develops there.

    IIRC (?), that is more of an issue with larger blades with fewer TPI running on higher tensions than with smaller blades with higher TPI.

    BTW, given its primary purpose, the chainsaw sharpener method is more suited to larger BS blades. The abrasive discs available for them go no finer than 3.2mm, so 4TPI would perhaps be about as fine as it would go without the risk of grinding into adjacent teeth.

    Grinding out the gullets could be done manually with a Dremel and an appropriate sized stone, but BigA's method allows the gullets to be done in a more controlled way when that is eventually needed.
    Stay sharp and stay safe!

    Neil



  5. #19
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    Quote Originally Posted by derekcohen View Post
    The concern I have with sharpening the front of the tooth is that you can easily alter the rake angle. I touch up the back of the tooth. This preserves the rake, and creates a clean, sharp tooth.

    Regards from Perth

    Derek
    Derek

    I can see that given the tools you have, sharpening the back of the tooth might be easier. However by sharpening the back of the tooth you are automatically changing the rake, because the face of the tooth is curved and not straight as in a handsaw for example. You can tackle this problem by each time you sharpen increasing the depth of the gullet by either a chainsaw file, or other round file or one of the grinding stones set in a Dremel or similar machine. If you increase the gullet depth in the same direction the rake will stay the same. As mentioned before by Neil (and myself) this will remove the stress cracks that develop in the gullet and is a necessity for blade longevity.

    The bandsaw sharpening machines use a thin grinding disc that has to be shaped (using a granite stone) to a tight radius on the top and a shallow radius on the lower side. As the disc descends it "kisses" the front of the tooth (it need only just nick the very top of the tooth, but grinds harder as it reaches the gullet and progressively lifts up towards the back of the gullet. The pawl acts to advance the blade during this process.

    However, they are not set up for small teeth (maybe 2 or 3TPI minimum?). My saws were either 3/4" pitch, 1" or 1½" pitch. The principle is the same with more numerous teeth. I would not be concerned about deepening the gullets too much. That will just assist sawdust clearance and by the time the gullet is too deep and weakens the blade, you need a new blade anyway.

    Dinasaw.jpg

    The Dinasaw people used to have a video that showed the action, but on their site the video is not there for the moment.

    One other comment is that a small amount of efficiency is lost every time a blade is sharpened no matter how well it is done.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  6. #20
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    Bandsaw blades are harder than chainsaw chain where the cutting edge is provided by a very thin fine grained hard chrome coating on the outside of the cutter. While sharpening the the chain the sharpener doesn't actual sharpen the Cr coating so much as break it off forming the cutting edge. If the teeth were made of the solid Cr they would wear the grinder wheel very quickly
    The sharpeners main job is thus to shape the cutter (side and top plate cutting angles).

    It depends how often you use a chainsaw sharpener but the ceramic wheels do wear and lose their shape so they need dressing which further wears the wheel. The wheels are cheap but I found it a PITA dealing with all this, which is one reason I still hand sharpen chainsaws chains.

    If you want to get fancy and have lots off spare $$$$ then CBN and diamond wheels are available for chainsaw sharpeners.
    eg 4" CBN Grinding Wheels

    The Dinasaw bandsaw blade sharpener we have at the timber yard came with a 4mm thceramic wheel but we never used in and and instead purchased a 1/4" thick CBN wheel. Its a custom wheel so it was also not cheap but it sharpened the dozen or so 1TPI bimetal blades many dozens of times each before it ran out of puff. The Dinasaw grinder is limited to 3TPI using the 3mm thin wheel.

    If you are only doing the odd BS blade then there are steel cutting diamonds wheels for angle grinder with a thin kerf - I have one with a 1.6mm kerf. I have no idea how long it would last but it may enable higher TPI blades to be touched up with a CS sharpener.

  7. #21
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    Quote Originally Posted by Bushmiller View Post
    The Dinasaw people used to have a video that showed the action, but on their site the video is not there for the moment.
    Close up of the Dinasaw Automatic Bandsaw Blade Sharpener - YouTube
    Stay sharp and stay safe!

    Neil



  8. #22
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    Quote Originally Posted by BobL View Post

    If you want to get fancy and have lots off spare $$$$ then CBN and diamond wheels are available for chainsaw sharpeners.
    eg 4" CBN Grinding Wheels
    The OD and bore diameters of the wheels for the CS grinder that I have (Swartz) is not commonly available, viz...

    Disc size: 145 x 22.3 x 3.2mm

    There are what I consider to be reasonably priced diamond wheels for them, however, the issue with these resin matrix bonded diamond wheels is that they come with a chain tooth profile and are not readily re-dressed to your preferred grinding profile for BS blades. I know from occasionally attempting to re-dress my 200mm resin bonded matrix diamond grinding wheel that this is not readily achieved.
    Stay sharp and stay safe!

    Neil



  9. #23
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    Quote Originally Posted by NeilS View Post
    However, as Paul has pointed out, with extended use and repeated sharpenings the bottom of the gullet will eventually need to be ground out to remove the micro-cracking that develops there.

    ...
    The 10 or 12mm bimetal blades I use for general cutting are sharpened about 5 times before I toss them. The amount of steel removed is possibly 1.5-2mm in all. The gullet is reduced by this amount. I have not noticed any negative effects. Ditto the set. There is no need to reset the teeth.

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

  10. #24
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    Quote Originally Posted by Bushmiller View Post
    Derek

    I can see that given the tools you have, sharpening the back of the tooth might be easier. However by sharpening the back of the tooth you are automatically changing the rake, because the face of the tooth is curved and not straight as in a handsaw for example. ....
    Regards
    Paul

    Paul, I agree with you in theory. It is just that, in practice, if the rake is altered by touching up the rear of the tooth, it is insignificant to affect the performance of the blade.

    This is not just my experience - I did not invent this method - there are many experienced bandsaw users who are happy with this.

    I am not meaning to come across as contradictory or to sell a different method, just to point out that the back-of-tooth method is a viable alternative.

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

  11. #25
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    Yet another way of doing things with the Swarts Tools sharpener. Thanks Neil for the idea.

    After changing the knurled knob on the chain backstop to allow a bit more clearance for the motor, I found that I just had to set everything to zero and and it would simply eat a band saw blade! I just need to moderate my settings and touch a little bit and I will be able to just take a scrape off the tooth. (And how much fun can you have doing a 3TPI blade off an 18inch bandsaw, rather than the 1 TPI!)

    I sharpened a few saw chains first and I think it will do the job there too. My only experience with an electric sharpener before this was an Ozito out at the Heritage Village. It seemed to do a square cut on the tooth, whereas this one, with the 10 degree tilt seems to do as good a job as a file. It can rip the metal off a chain saw tooth too. The saw chain uses one side of the stone and the band saw uses the other so that is a plus.

    Cheers,
    Alister.
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  12. #26
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    Sorry, I didn't think that that first post had gone through. Completely missed the second page!

    Thanks,
    Alister.

  13. #27
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    Thanks Neil for the link.

    That model is an upmarket version. All the blades I have "set" in "threes." Set left, set right and straight. That machine is set up to sharpen with a bevel on the left and right sets and is an automatic. That one is quite a lot of dollars. My machine is a manual crank and cuts each tooth at 90° irrespective of set. My memory is that even over twenty five years ago my machine, which was a base model, was around $1600

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  14. #28
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    Quote Originally Posted by derekcohen View Post
    Paul, I agree with you in theory. It is just that, in practice, if the rake is altered by touching up the rear of the tooth, it is insignificant to affect the performance of the blade.

    This is not just my experience - I did not invent this method - there are many experienced bandsaw users who are happy with this.

    I am not meaning to come across as contradictory or to sell a different method, just to point out that the back-of-tooth method is a viable alternative.

    Regards from Perth

    Derek
    Derek

    That's quite all right. I expect you need to do many sharpenings to see and feel much difference. If the technique of filing the back only was carried out without deepening the gullet, two things would occur. Firstly, and very obviously, there would be next to no gullet and a dearth of sawdust removal, but secondly the rake would have changed from perhaps 8° to zero°: Then I suggest some difference would be noticed. If you are able to maintain the original profile the band should perform as originally intended.

    The other thing I might mention is that the way I was shown to decrease the number of teeth. Hold on to the thought despite it sounding a little "criminal." Every other tooth on, in my case the 3/4 pitch blade, was slightly lowered so it became a scraper tooth. This can only be achieved on a band that is set left/right/straight. That was how I achieved a 1½ pitch blade. We know that for ripping small logs on the bandsaw larger teeth are better and it may be a way to convert a blade for ripping (only if there is the three way set.)

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  15. #29
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    While I'm at it maybe I'll split some hairs
    It all depends on the angle of the touch ups.

    The "rake" or hook is the angle shown between the blue solid and blue dotted lines
    The solid purple line is the original slope of the back of the tooth which together with the dotted purple line makes up the clearance angle
    Touching up the back of the tooth MAY affect the "pointiness" of the tooth which then determines depth penetration into the wood.

    If touch ups are done according to the red line (ie parallel with the solid purple line) the "pointiness" of the tooth stays the same and all that really end up changing very slightly is the depth of the gullet.

    If the touch up is done according to the green line the "pointiness" is reduced so the tooth will not penetrate as far into the wood.
    Presumably Derek (and Others touch up somewhere between the red and green lines?
    Screen Shot 2022-05-15 at 2.53.53 pm.png
    Touching up the front of the tooth by staying parallel to the original tooth front face is like touching up on the red line.

  16. #30
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    Quote Originally Posted by BobL View Post

    If the touch up is done according to the green line the "pointiness" is reduced so the tooth will not penetrate as far into the wood.
    Presumably Derek (and Others touch up somewhere between the red and green lines?
    Screen Shot 2022-05-15 at 2.53.53 pm.png
    Touching up the front of the tooth by staying parallel to the original tooth front face is like touching up on the red line.
    Thanks, Bob. That diagram is helpful for this discussion.

    Looking back at my OP the closeups photos of the teeth before and after grinding show that my grind angle is closer to the red line than the green in Bob's diagram.

    The grind wheel only just kissed the back of the tooth to remove the small worn area that can be seen on the back (top) of the tooth in the first of those two closeups.

    There was minimal rounding over on the front of the tooth before grinding and therefore minimal removal of metal required from the front of the tooth to restore a sharp cutting tip.

    At least on the tooth profile of that blade, which is similar to Bob's diagram above, a considerable amount would have to be ground off the back of the tooth before it changed the rake angle... on my blade the angle near the top of the tooth is constant for about half the depth of the gullet.

    Although depth of cut will be lost with successive grindings on my blade, there is still a lot of life left in it if only that amount of tooth height is lost each time.

    On a different tooth profile lowering the tooth height by just a bit could have more impact on the rake angle, eg...

    Looking at the quite large gullet size in my 1TPI blade I don't anticipate that the removal of a small bit of tooth height each time is going to make a lot of difference to chip clearance with the depth of cut that it is being used for (max of 12").

    However, at some point I will grind out the bottom of the gullets as I understand (rightly or wrongly) that micro-cracks develop there that eventually result in the blade breaking.
    Stay sharp and stay safe!

    Neil



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