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Sharpening a Bi-Metal blade with my BMST50

Started by booman, June 19, 2024, 03:13:41 PM

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booman

After a lot of fiddling I have managed to sharpen a 4 degree and a 9 degree blade with my BMST50.   They are not perfect but they work.  So, I tried to sharpen a 7/39 degree blade (Bi-Metal).  After it eating my lunch for a while I finally called Woodmizer support.  He said, "Ah, the bi-metal blade".   When they are made, there is some fusing of 2 different metals and this causes the blade to be a few thousandths of an inch off between teeth.  One might be exactly 7/8", the next 7/8 + .002", the next 7/8 - .002".   That is what I was experiencing.  I kept trying to adjust the sharpener and never could get it right.  So, you need to get it close for the first round and then go around again until the teeth are all properly spaced.  Make sure to set the angle of the motor to the adjustment template that comes with the sharpener.  15 degrees.  Anyone else experience this?  Solid little sharpener once you get it dialed in. 
2019 LT15G25WIDE, 2013 LT35HDG25, Stihl MS880 with 59" bar with Alaskan sawmill attachment.  John Deere 5045 tractor with forks, bucket and grapple.  Many chainsaws.

fluidpowerpro

I'm no expert but I don't think what the tech told you makes any sense. I would think they would start with a blank band and then put in the profile after. The material the band is made of should not cause any difference in tooth spacing...in my opinion.
Change is hard....
Especially when a jar full of it falls off the top shelf and hits your head!

terrifictimbersllc

If the sharpener indexes with a pusher in the gullet why would the slightly irregular spacing matter?

Probably not related but I have two 10/30 bimetal blades that  are 195" and have 222 teeth. All my other 7/39.5 195" double hard and silver tip blades have 223 teeth.
DJ Hoover, Terrific Timbers LLC,  Mystic CT Woodmizer Million Board Foot Club member. 2019 LT70 Super Wide 55 Yanmar,  LogRite fetching arch, WM BMS250 sharpener/BMT250 setter.  2001 F350 7.3L PSD 6 spd manual ZF 4x4 Crew Cab Long Bed

booman

My original question was if anyone else has experienced this?
2019 LT15G25WIDE, 2013 LT35HDG25, Stihl MS880 with 59" bar with Alaskan sawmill attachment.  John Deere 5045 tractor with forks, bucket and grapple.  Many chainsaws.

MattM

I don't have a BMST 50 but it should be the same as a BMS250 as they're both CBN sharpeners. 

Alot of times new blade will have some differences between teeth. I always start right before the weld (the 250 has auto shutoff, so I put my magnet on the weld itself).

Set the machine, with the grind wheel turned off, so that it just barely scrapes the face of the tooth and just touches the back of the next tooth.

Make sure to move the blade forward everytime you adjust something.

When it seems good then turn on your CBN wheel and let it sllllloooowwwly touch a tooth with the oil turned off. Make sure you watch the face and gullet and make sure your not taking too much off... It'll burn the tip of you do.

If it all is good turn on your oil and sharpen the blade. 

Once the machine starts never.... Ever.... Ever make as adjustments. Otherwise the teeth will be slightly different from each other and setting them will be a pain.
LT35HDG25

Stephen1

I do not think I have experienced what you are talking about. Is that sharpener a CBNor a drag sharpener?
 I have sharpened hundreds and just run them and sharpen the same as the others, silver tips, dbl hards and even carbides with the diamond stone. Start it gently, and go around 2 XS.
I ran Bi metals for over a  year and still have some. They are more expensive hurts my wallet more when they hit metal. I also found they were really only good for 2-3 sharpening before they were junk and didn't cut as nice.  What Dennis TT says about the # of teeth is correct. They are always out by 1 and I sharpen a lot of Norwood blades for people and have to be careful as they are always out by 1 tooth. Make sure to never go past the start on the setter. Ask me how I know :veryangry:
IDRY Vacum Kiln, LT40HDWide, BMS250 sharpener/setter 742b Bobcat, TCM forklift, Sthil 026,038, 461. 1952 TEA Fergusan Tractor

booman

The BMST50 does use a CBN wheel.   I do start with the wheel settled into the gullet.  Try a few dry before turning the oil on.  It just seems to work good for one or two teeth and then will hit the back angle only or even catch the tip of the tooth.  I am making sure to push the blade fully.  Seems to constantly change.  Do I just grind all of that until the wheel makes equal contact throughout the gullet?
2019 LT15G25WIDE, 2013 LT35HDG25, Stihl MS880 with 59" bar with Alaskan sawmill attachment.  John Deere 5045 tractor with forks, bucket and grapple.  Many chainsaws.

Stephen1

I set the wheel dry and stopped as Matte describes but I am at least 10 teethe away from the weld. I then turn on the oil and wheel and run it, I hold the head as I lower it grinding to ensure it doesn't grind too deep, and keep lifting the head until there are no sparks So a light grind. It takes 2 teeth movement to see the results of an adjustment. I really like to hear the double tap. I'm looking for shiny teeth all thru the gullet. Use a thick sharpie to mark all thru the gullet,  if that will help. You will see what the grinder did or didn't take off.  I also find the wheels have a wobble you can't see and it will it touch all it needs to touch.
IDRY Vacum Kiln, LT40HDWide, BMS250 sharpener/setter 742b Bobcat, TCM forklift, Sthil 026,038, 461. 1952 TEA Fergusan Tractor

booman

Stephen1, are you not grinding down to the stop?  Just light taps?   I have been trying to set it so I grind down to the stop but the gullets are slightly different heights or depths. 
2019 LT15G25WIDE, 2013 LT35HDG25, Stihl MS880 with 59" bar with Alaskan sawmill attachment.  John Deere 5045 tractor with forks, bucket and grapple.  Many chainsaws.

booman

Ok, Woodmizer makes their own blades like Doublehard and others.  They sharpen them before sending out to customers.  Bi-Metal  is made for them by someone else.  When this company stamps out the gullet, the metal is so hard it deforms it slightly, lengthwise, thousandths of an inch.   Woodmizer does not sharpen these before sending out.  Also, if anyone needs to resharpen one of these blades, just the face of the tooth is sufficient.  I think I can handle that.
2019 LT15G25WIDE, 2013 LT35HDG25, Stihl MS880 with 59" bar with Alaskan sawmill attachment.  John Deere 5045 tractor with forks, bucket and grapple.  Many chainsaws.

terrifictimbersllc

I always paint about 15 teeth of every blade with red lay out die. The face and whole gullet should be bright after grinding, no red should remain. When you use this method, you can spot check as you are  sharpening blades, but it is also visible in a flat pack of 10 to 15 of these blades when some of them still have red on them that way you can keep tabs on your sharpening. 
DJ Hoover, Terrific Timbers LLC,  Mystic CT Woodmizer Million Board Foot Club member. 2019 LT70 Super Wide 55 Yanmar,  LogRite fetching arch, WM BMS250 sharpener/BMT250 setter.  2001 F350 7.3L PSD 6 spd manual ZF 4x4 Crew Cab Long Bed

booman

t timber, does this work on the Bi-Metal?
2019 LT15G25WIDE, 2013 LT35HDG25, Stihl MS880 with 59" bar with Alaskan sawmill attachment.  John Deere 5045 tractor with forks, bucket and grapple.  Many chainsaws.

Stephen1

Quote from: booman on June 21, 2024, 10:53:04 AMStephen1, are you not grinding down to the stop?  Just light taps?  I have been trying to set it so I grind down to the stop but the gullets are slightly different heights or depths. 
Of course, I just hold the head on the 1st startup of the oil/wheel, to make sure the blade is not too high. eventually by grinding twice the wheel will touch everything. 
IDRY Vacum Kiln, LT40HDWide, BMS250 sharpener/setter 742b Bobcat, TCM forklift, Sthil 026,038, 461. 1952 TEA Fergusan Tractor

terrifictimbersllc

Quote from: booman on June 21, 2024, 06:21:51 PMt timber, does this work on the Bi-Metal?
meaning the red layout dye sticking to bimetal blade? sure. it evaporates very quickly for me within a few seconds, and stays on unground areas even after passing through the oil. 
DJ Hoover, Terrific Timbers LLC,  Mystic CT Woodmizer Million Board Foot Club member. 2019 LT70 Super Wide 55 Yanmar,  LogRite fetching arch, WM BMS250 sharpener/BMT250 setter.  2001 F350 7.3L PSD 6 spd manual ZF 4x4 Crew Cab Long Bed

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