bandmill blade questions

[chainsaw_louie]

Made some progress...

Cleaned off what appeared to be a combination of pitch and rust, with a light touch of an orbital sander , only the blade body , didn't sand the tips.  Discovered the WoodMizer M4XM label after cleaning the blade.

Next, put the blade back on the Woodlandmills sharpener and played with the settings until I got it to grind the back of the tooth all the way up to the cutting edge.  I discovered that the pusher was set up to push the current tooth, I changed it to push on the 1 ahead , the on-deck tooth. This gave me the control needed to reach the back of the teeth all the way up.

I'm hoping that these sharp, square corners are going to make a big difference in how much the blade gets pushed around by knots etc resulting in wavy cuts or straight.

I did notice a bit of blueing on the tips from the heat of grinding , not every tooth, hard to control and not do that. 

I

[Bradm]

I've been sharpening bands, blades, and cutters for 20+ years and here's my thoughts on what I'm seeing in your pictures.

Top image looks like you have a negative hook angle.  In my experience, this is what I have seen when a customer brings in bands for sharpening and they say "bands aren't cutting".  This is caused by excessive wear on both the corner and side of the grinding wheel that contacts the tooth face.

If I increase the size of the bottom image, though I lose resolution, it really appears that the grinding wheel has the same shape to it that I think I'm seeing in the gullet.  I would recommend trying either a new grinding wheel or reducing the diameter of the one on the grinder until the side of the wheel is straight (probably close to 1/2" so if you need a radius rather than a sharp corner, put one back on afterwards).

Edit - formatting.

[chainsaw_louie]

Good point , I'll check the hook angle with a square and angle measuring tool.

[OnParr]

Great job. I am a newbie on here, but have that sharpener and setter.

When setting the teeth, bend them a few thou more than you want the final set to be as the teeth spring back a bit. On mine where I have the gauge measuring the tooth from I get 39-41 thou when I set the tooth, and then it is 21-24 when I just touch the gauge to the tooth. I may be pushing on the tip of the tooth where there is maximum spring in the tooth.

With the sharpener, watch the left edge of the grinding wheel. It will wear and not cut to your desired angle. Try and measure the angle on the face of the tooth every 3-4 bands and you will likely see they are closer to straight up and down than having the positive attack angle. You will just need to dress the wheel a bit. You can also upgrade it to the cbn wheel so that you no longer need to worry about dressing the wheel.

If you wanted to try to grind the entire tooth profile, Woodland mills sells multiple cams that are better fits for specific tooth shapes.

[barbender]

I find it is really hard to not blue the teeth tips with a drag grinder. Just take the lightest grind that you can. 

There are a few problems with heavy grinds. First, with a vitrified stone wheel, it wears your wheel really quickly, to the point that it might not make it around a blade before it is worn down and changed your grind.

If you grind your gullets heavy, it can cause cracks to start. In my experience, blades air harden if you overheat them, and if that happens in the gullet they will start to crack. 

[customsawyer]

Made some progress...

Cleaned off what appeared to be a combination of pitch and rust, with a light touch of an orbital sander , only the blade body , didn't sand the tips.  Discovered the WoodMizer M4XM label after cleaning the blade.

Next, put the blade back on the Woodlandmills sharpener and played with the settings until I got it to grind the back of the tooth all the way up to the cutting edge.  I discovered that the pusher was set up to push the current tooth, I changed it to push on the 1 ahead , the on-deck tooth. This gave me the control needed to reach the back of the teeth all the way up.

I'm hoping that these sharp, square corners are going to make a big difference in how much the blade gets pushed around by knots etc resulting in wavy cuts or straight.

I did notice a bit of blueing on the tips from the heat of grinding , not every tooth, hard to control and not do that.

I

In the fourth picture here, the upper left tip of the tooth doesn't look like it has been touched by the grinder yet. It might be the angle of the picture, as I've never seen it shaped like that. The point I'm trying to make, is that's the corner where the blade engages the wood, on each of the set teeth. The teeth that are set the opposite it's the out side corner. Make sure you are grinding those little corners. It doesn't take much time to just send that blade around again and clean up all the little corners. 

[chainsaw_louie]

"The teeth that are set the opposite it's the other corner. Make sure you are grinding those little corners. It doesn't take much time to just send that blade around again and clean up all the little corners. "

@customsawyer,  thanks , I fully agree , the corners must be ground square and proud as per the micro photos posted by Yellowhammer.  One more pass and I should be able to hit all the tips fully. I was trying to go lightly and not cause overheating and blueing of the steel, resulting in losing the steel's temper and hardening. This  seems to be happening on some of the teeth as in the 4th picture.

@OnParr , re cams from Woolandmills to grind the entire profile , this seems like a good idea , have you used them? The sell 4 specific model of cams for different blades:
- Woodmizer Silver tip
- General purpose
- Ripper 37
- Kasco woodmax

I'll have to call and see which cam profile would be the closest for these WMzr blades I have.  One pass to do the entire profile is definitely better than the multiple pass method I'm experimenting with here.

Wlndmills cams:
https://woodlandmills.com/blade-profile-cam/

[YellowHammer]

On my drag grinder, I was never able to get satisfactory results in one pass, it always took two.  Also, if the band clamp is not tight enough, the wheel pressing down on the face of the tooth will minutely push the band backward as it is grinding, and decrease the hook angle.  So sometimes a heavy cut will not have the same hook angle as a lighter cut.  Also, a heavy cut will "de-profile" the stone faster.

Both the shape of the cam and the shape of the stone will effect the profile, and I found that over time, the stone wanted to develop its own profile and instead of fighting and changing that, I modified the cam.

Modifying the cam is pretty easy to do, and I was able to buy generic cams and match every profile I had.  However, I eventually just ground to one generic profile for 95% percent of my sawing, and no matter what band brand I bought, they all became that over time.

Grinding bands is very fiddly at first, and that is why so few people can do it well.  However, once you get the hang of it, it will become second nature and you will be able to easily know and hear when the the whole process is dead on, and yes, a well sharpened and set band will cut noticeably better than even a new one, so there is a reward for getting it right.  

[chainsaw_louie]

Regarding my hook angle as mentioned by Bradm and Yellowhammer, it seems there is indeed a problem here .  I don't have a negative angle but it's sure not 9 degrees either. I'll have to see about the band slipping during the face grinding. Also I need to check if this Woodlndmills RS8 grinder's angle values are accurate. 

As for being able to grind the entire profile in one pass, at this point I'd agree that it's not going to be possible with this grinder. Because of the mechanics involved in grinding a  corner (back-side & face of tooth) , I can't yet see how to do this except with two passes and two settings. 

Two groups of three settings are needed, one for grinding the face & gullet and a second group of settings for the back/top of teeth:
- pusher-advancer,
- depth of cut,
- "stop-plate" for hitting tooth back/top

I can see that recording these settings and switching between the two will be necessary.
This is probably the compromise of this sharpener that more expensive units have somehow resolved .


Picture of my current grind angle and a line drawing of 9 degrees, for comparison.

[SawyerTed]

Woodmizer has a blade hook angle gauge.  I'm very far away from mine right now so a photo isn't possible .  

It's a multi-sided sheet metal negative template that is used mostly for identifying the blade.  They are quite precise. Eventually you'll be able to look at them and tell.  

It would be helpful in diagnosing your angle variation, if there is one.  You could eliminate the drawing.  

I'm sure other manufacturers have something similar. 

[Gere Flewelling]

From my experience with sharpening, I have rarely ever seen a time when my drag sharpener will grind an entire face of a tooth in a single pass. It is only possible with a CBN style grinder. I have accumulated 12 cams for my drag style grinder. Most of which I have customized to fit specific tooth profiles from many manufacturers. I always plan on a second pass to even up the back of the tooth. I modify the cams to touch all of the gullet on either the first pass or the second pass. I personally don't think it is critical to shine up the entire gullet every time, but as I sharpen for others I find customers buy into the theory that the entire gullet must be ground to eliminate microscopic cracks. It's important to keep customers happy. I do believe it is important to verify accurate set and adjust every time a band is serviced. Often times wood dull bands will be close but metal struck bands will be all over the place. I have found that with the exception of the .055" bands, .025" is the maximum set to use. Over that it requires more power to saw, cause's vibration, and eventually will cause band to break. I have one customer who monitors his band breakage very closely and through experimentation we determined this number to be consistently accurate. I use this theory with all my customers and have had good success. Sharpened 850 bands last year and on track to reach 1,000 this year. Sharpening is not for everyone, but it makes a good retirement income for me.

[Magicman]

Here is the Blade Gauge that Ted was describing above.  I painted the 10° White, 4° Green, and the 7° Red.  It also has  9° and something else.  The section of blade is Turbo 7°, or sometime described as 7-39. 

I do not use any of the above since I standardized to the Turbo 7.

[barbender]

Yep, all Turbo 7 for me too. I like to keep it simple. Then WM had to come out with the 747 and also call it Turbo👎

[Magicman]

Yes I agree.  That additional use of the Turbo word with the 747 could be confusing, and to me was wrongly used.  They shoulda just named it the 747 Jet.

I have not and will not try the 747.  I am sure that they will cut but that is hanging a mighty pointy tooth tip out there which will surely dull more quickly but at least it is cutting rather than scraping such as the 4° does.

That being said, I sawed over 1MM bf with 10° blades which I suppose have the pointiest tooth tips of all.  I tried the standard 7° blades but the deep sawdust carrying gullets in the 7T's win the prize, for me anyway.

[Bradm]

Woodmizer has a blade hook angle gauge.  I'm very far away from mine right now so a photo isn't possible . 

Angle gauge is good, but if the wheel has worn an angle on the face the gauge won't expose it.

@chainsaw_louie , can you provide a picture of the grinding wheel as it's currently setup on the grinder?

[chainsaw_louie]

Today I tested the blade that I've been using to learn the sharpening process with the Woodlandmills tools.  Following the suggestions , I've:
  - cleaned the gunk off the blade and gotten down to bare metal
  - gave it a spin on the  sharpener at 9 degrees, grinding face & gullet
  - then another 2 spins until all the back/top of teeth were ground
  - set the teeth to .020 then per suggestion,  re-set to .026 +- .002

The results were pretty good.  I sliced up a cant of ash and the cuts were quite smooth and mostly straight,  much less wave than I've had in the past.  But on the 2nd log the blade suddenly snapped which given that it was quite sharp was surprising to me . This left me with more questions:
  - was the set of .026 +- .002 creating too much drag, heat, tension on the blade in ash?
  - the tensioner was set to 2400 psi, possibly too much for a used blade with 5x(?) sharpenings ?

Wondering as blades are reused , can reducing the psi on the tension-er prevent breakage without affecting the cut?

At $25 for a new blade, my time and effort to resharpen isn't cost effective but hopefully I'll get better and faster at this.  I fully understand why folks dont bother with sharpening.  I'm discovering that with this type of sharpener, it takes a lot of attention to detail to make a blade sharp and set to within thousandths of an inch.  I'm sort of surprised that the mfg's instruction manuals don't go into more detail about actually sharpening a blade but perhaps if they did, it would scare customers away. For example, to set a tooth, I squeeze the handle to snug the blade to the anvil but not touch the tooth, then to increase the set the handle is squeezed more until the set is too far but the tooth springs back and hopefully hits the target set or lower in which case a second squeeze of the handles will nudge the tooth to the correct set.  Opps , over-set ? ,  pull the blade backwards and use pliers to bend the tooth backwards , push the tooth back into position, measure and set, repeat, repeat. It's definitely got a learning curve and is part art and part science.

Test of sharpened blade , it snapped soon after this, @&#* !

[SawyerTed]

Woodmizer has a blade hook angle gauge.  I'm very far away from mine right now so a photo isn't possible .

Angle gauge is good, but if the wheel has worn an angle on the face the gauge won't expose it.

@chainsaw_louie , can you provide a picture of the grinding wheel as it's currently setup on the grinder?

My experience differs.  The guage fits the blade profile very precisely.  If the way a blade is ground differs, the variation is very apparent and easily seen.  

[Magicman]

I would not blame the blade breaking on anything that you did or did not do.  All blades will eventually break because they will only go around the blade wheels so many times.  Chances are that if you examine that blade closely, you will find some partial breaks.

[SawyerTed]

+1 in Magicman's comment.  An occasional blade breaking is usually from blade fatigue over multiple sharpenings.  Look close at the break.  

A series of broken blades might be indicative of some other problem, like the heel of the blade riding the flange on the guides.  I wouldn't go there until something points there.  Sawing as much as you did says it's probably cracks in the blade not a mill related problem. 

Your set is within the range.  

[Ben Cut-wright]

Wondering as blades are reused , can reducing the psi on the tension-er prevent breakage without affecting the cut?

  I'm discovering that with this type of sharpener, it takes a lot of attention to detail to make a blade sharp and set to within thousandths of an inch. 

I'm sort of surprised that the mfg's instruction manuals don't go into more detail about actually sharpening a blade but perhaps if they did, it would scare customers away.

 It's definitely got a learning curve and is part art and part science.

Fiddling with band tension to remove *flutter is sufficient and usually will result in less than MFG strain recommendations. I'd stick with specified tension for now.

It does take attention to detail and constant monitoring until every aspect of the procedure results in repeated sharp correct profile blades.

You are correct that it is art and science, more-so with the drag sharpener than the CBN.  Correct grind wheel profile and proper machine setting will *ultimately result in grinding the entire blade profile in a single pass though. 

Wheel profile can be thought of as another 'just as important setting'.  A change in wheel profile must be made hand in hand with machine setting.  Take too much off the wheel and the machine setting might be radical or made impossible to profile the entire surface.  Initial wheel profile should be done a little at a time combined with minute and careful machine settings.  It's rare to adjust one without a need to make accommodating adjustment of the other.

Starting at the face of the tooth *without actually grinding/honing is my first step.  Then I get the depth of the gullet setting somewhere near the bottom of the gullet.  From there you can judge where the stone needs to be shaped.  Eventually ALL the *adjustments will result in slight sparks off the entire surface.  If not.....either the blade profile doesn't match the cam or the stone...or further adjustments are needed.

My preference is for a few thou deeper gullet which requires less material removed from the *bottom left of the wheel.  This means I gotta take a tiny bit more off the angle of the wheel on the right side....and... drop the depth stop adjustment on the machine. 

The above are small examples of fine tuning that will result in complete grind in a single pass. May not be the *first pass on a blade profile or when using a new stone.  Your photos show a course grind surface and bluing.  Both indicate too much material was being removed too fast.  Slow the rate or grind/hone less.  Personally my patience is sated by grinding less and speeding up the rate.

Accurate manual setting will become second nature after hours of practice!  Well, maybe it took me longer than that. Ha.  Different blades require more or less over-set to get where they need to be.  First few teeth will tell you what you need to know afa as over-set.  Dead set accuracy isn't necessary and nearly impossible so cut yourself some slack there.  Within three thou is what I shoot for and have the dial indicator set for that range. 

[barbender]

I still wouldn't call the sawing results "good" with that blade. There's a lot of waves. I can see marks from an incorrectly set tooth as well. I don't say this to pick on your sharpening, only to point out that you shouldn't accept substandard results.

I am totally unfamiliar with your setting machine, but here is my experience with mine- I get it set up, which is tedious. But once it is in the correct range, I run the blade around without looking at individual teeth. Mine doesn't have dial indicators on it anyways, but I only check teeth to make sure an adjustment hasn't moved or something. My setter gives very good results like this. I think if you are individually setting each tooth while watching  a dial indicator, you'll go crazy!

Get it adjusted to plus or minus .002 of your target, then just run the band around without looking at the dial. 

[trimguy]

" Both the shape of the cam and the shape of the stone will effect the profile, and I found that over time, the stone wanted to develop its own profile and instead of fighting and changing that, I modified the cam. "



These are obviously 2 different profiles. @YellowHammer the left corner of my grinding wheel wears off before I get around the blade and gives me the rounding at the bottom of the tooth instead of a "corner " is this what you are referring to when you say don't fight the grindstone ?

[Bradm]

Woodmizer has a blade hook angle gauge.  I'm very far away from mine right now so a photo isn't possible .

Angle gauge is good, but if the wheel has worn an angle on the face the gauge won't expose it.

@chainsaw_louie , can you provide a picture of the grinding wheel as it's currently setup on the grinder?

My experience differs.  The guage fits the blade profile very precisely.  If the way a blade is ground differs, the variation is very apparent and easily seen. 

I wasn't clear and I do agree with what you said here.  What I should have said was that the gauge won't show a worn wheel without first grinding the blade and I want to know what my wheel profile is before I start grinding.

[chainsaw_louie]

I still wouldn't call the sawing results "good" with that blade. There's a lot of waves. I can see marks from an incorrectly set tooth as well. I don't say this to pick on your sharpening, only to point out that you shouldn't accept substandard results.

I am totally unfamiliar with your setting machine, but here is my experience with mine- I get it set up, which is tedious. But once it is in the correct range, I run the blade around without looking at individual teeth. Mine doesn't have dial indicators on it anyways, but I only check teeth to make sure an adjustment hasn't moved or something. My setter gives very good results like this. I think if you are individually setting each tooth while watching  a dial indicator, you'll go crazy!

Get it adjusted to plus or minus .002 of your target, then just run the band around without looking at the dial.

Point taken , I should have said "better"  but as you point out , there are definite visible waves and nobody wants that.

You guys have been great with all the helpful comments as I try and get my hands around sharp blade issue.  It should have been obvious but its now clear that when lumber output is increased via hydraulics & power feed systems,  consumable , straight cutting blades are now my bottleneck. I intend to press on and see how much I can accomplish with this WlndMill RS8 & setter but its hard not to get discouraged when I look at the more expensive grinders.

There is a fella on Youtube that uses a pedestal grinder with a shaped stone and in the manner of a CBN grinder, manually feeds each tooth/gullet into the wheel.  His speed is quite fast , not sure about his accuracy though .

[barbender]

With a profiled CBN wheel made for dry grinding, it probably wouldn't be too hard to build an accurate grinder using a miter saw or something. But your blades would still have to be clean to index accurately.