Band blade drag sharpener

[RetiredTech]

  Hey guys, saw milling is still very new to me and I'm just sawing for myself. I've been toying with the idea of building a drag style band sharpener. I've seen a bunch of videos on the web and read about some on the forum here. I've also read a bunch of the sharpening posts. I see some sharpeners go down the face of the tooth, clean out the gullet, and grind up the back side of the blade. Others go down the face of the tooth, clean out the gullet then lift up without grinding the back of the tooth. Even production sharpeners are built both ways.
  I understand the need to clean the gullet out. But what are the pros and cons of grinding the back of the tooth? It would seem to me that grinding the back of the tooth would be a waste of material from the hardened tooth. If your only removing a few thousandths of an inch on each sharpening and then only getting 3-5 sharpenings on a blade I don't see how it would change the shape of the blade enough to matter. In my mind the most it would do is create a small amount of extra room in the gullet to carry the sawdust out.  

[barbender]

 When your tooth dulls, it is because the whole tip of the tooth is eroding, not just the face. If you just grind the face, you end up with a rounded tip with a sharp face. Grinding the back gives you a square, chisel shaped edge.

Designing a sharpener with he cam movements intrigues me, but I'll never get around to it😊 If I were to build one now, it would be with the shaped CBN wheels, where the grinding wheel comes down and hits the whole profile in one touch, instead of a drag type. Actually, you could accomplish both on the same machine with just a different cam.

I've considered getting a profiled CBN wheel for my Cooks drag sharpener, and modifying the cam to work with shaped CBN wheel. MAYBE I'll get around to that one some day😊

PS drag sharpeners are fussy, imo. I think the term ,"learning curve" may have originated from trying to get the grinding wheel shaped and the machine adjusted right to grind the gullet and back of the tooth correctly😁

[RetiredTech]

  I looked at the CBN wheel sharpeners too. I have a very old Craftsman radial arm saw I was going to convert. But I think the drag sharpener will be a better fit for me right now. I'm buying small batches of bands. 5 at a time so far. I want to try several different brands and tooth configurations to see what works best on my mill. That would probably require multiple CBN wheels which isn't in the old budget at this time. I could cut a cam for each batch of blades for just a little time.
 

[Magicman]

Your question about only sharpening the tooth face would be equivalent to sharpening a dull knife blade on only one side.  
 

[barbender]

 Knowing now what I didn't know then😊 I wouldn't mess around with different blade profiles much. Woodmizer 10° have always cut just fine for me, and that is a somewhat standard blade profile that other manufacturers make as well. I run the Woodmizer 7/39 Turbo blades now. They allow a faster feed rate but you need a little more horsepower for them.

 All I have now are the 7°, for everything I saw. 

 A RAS based CBN sharpener should work quite well, and be very simple.

 Dod I mention that drag sharpeners are very fussy?😊

 I always remember something someone used to say on here, when folks would start going on about this blade profile or that being the only way to go-

 "Sharpen and set carry the mail" -Frank C. 

[RetiredTech]

Having never sharpened a bandsaw bade before I assumed that when you sharpen the front it would straighten the tip up too. I knew you guys could set me straight. I've got the grind motor and the gear reduction motor already. If it all falls through there's still the old Craftsman saw to fall back on. I have 5 of the woodmizer 10° blades. But I haven't run the mill since they came in.

[beenthere]

 I'm buying small batches of bands. 5 at a time so far. I want to try several different brands and tooth configurations to see what works best on my mill. 

Seems to me this approach will lead to a lot of frustration, as there are way too many variables that cannot be controlled to "see what works best". Far too few different blades in your "batches" to draw any helpful conclusions. 
If experimenting, try to cut your variables down to just one, or two at most.  And every log will be different which is a variable that can't be controlled. 

[Magicman]

I agree with the above.  I sawed well over 1MM board feet with 10° blades before I switched totally to Turbo7°.  During that time I tried blades from other manufacturers, as well as 4°, 7°, & 9°.  The proper set will probably affect your sawing performance more than the tooth profile.

My recommendation is always to avoid "chasing blades".

[RetiredTech]

 OK, So I probably need to settle on 10° or 7° blades and just go from there. The sharpener project is something I can work on during cold rainy days inside.

 My band speed is too high at full throttle. I think it is shortening the blade life. I really don't know for sure since I've only used two blades and the second one was ruined by the metal side stop. When I get to saw again I'm going to throttle it down and see if the little diesel still has the torque to do the job. If not I've got to change the pulley configuration. I knew the drive pulley was too small going in but couldn't find one like I wanted. I can't change the one on the engine as it's a flange mounted pulley bolted directly to the flywheel. Something will turn up. It always does.

 I expect to cut mostly pine for a while as we have a lot of trees dying right now. I do have one pecan and one Black Locust to process before I can start on the pine.

(Nothing to do with Sawmills)
 Primitive weapon season opened for us this morning and I was blessed to harvest a nice sized doe. She's in the cooler chilling down now.

[barbender]

There are formulas (there's one in the Forum Extras Toolbox) for figuring out your blade speed. A bit over 5000fpm is fairly standard, I believe my Woodmizer LT40 with a 40hp diesel spins my blade faster- approaching 6500fpm to cut faster with the additional power.

[JoshNZ]

I would nudge you in the direction of picking a profile (or two, or three, if you have to..) and getting CBN wheels for them and building your sharpener around that.

Especially for a diy build, it removes many of the variables and does a better job without the whole process of chasing stone profile and cams shapes etc.

Be cool to see how you do it in any case, keep us posted with plenty of pics ^^

[KenMac]

 Hey guys, saw milling is still very new to me and I'm just sawing for myself. I've been toying with the idea of building a drag style band sharpener. I've seen a bunch of videos on the web and read about some on the forum here. I've also read a bunch of the sharpening posts. I see some sharpeners go down the face of the tooth, clean out the gullet, and grind up the back side of the blade. Others go down the face of the tooth, clean out the gullet then lift up without grinding the back of the tooth. Even production sharpeners are built both ways.
 I understand the need to clean the gullet out. But what are the pros and cons of grinding the back of the tooth? It would seem to me that grinding the back of the tooth would be a waste of material from the hardened tooth. If your only removing a few thousandths of an inch on each sharpening and then only getting 3-5 sharpenings on a blade I don't see how it would change the shape of the blade enough to matter. In my mind the most it would do is create a small amount of extra room in the gullet to carry the sawdust out.  

According to Tim Cook you sharpen the back of the tooth to assure that all teeth are the same height and, consequently all working equally while cutting.

[RetiredTech]

  Thanks Ken, now that I think about it that makes perfect since. It's like flattening a handsaw blade before you sharpen it.
 
Barbender,
  This is the site I used to check my band speed.  Band speed 
Assuming an engine speed of 3600rpm my band speed is just over 7000fpm Even if the old diesel isn't producing 3600rpm it's still too high. If I can drop rpm down to around 2800 or a little less I should be in a good range. Hopefully she'll still produce enough torque. If not I'll need to change the gearing ratio. It cuts fine but leaves a lot of very fine sawdust in the cut. When I visited MM the sawdust that did remain in the cut from his WM was much more granular. The engine is a small 3 cylinder Kubota diesel. The pulley mounted on the flywheel is 4 1/4" diameter. The pulley on the band wheel is 12" diameter and the band wheels are 21" diameter. I remember when I was building the mill I wanted a 16" pulley but didn't have one available. Instead of waiting for the 16" I found a 12" and forged ahead with it. I think I should have waited.

Josh,
  The CBN sharpener would be much easier to build and I may end up with one when it's all done. However, the drag sharpener is going to happen first. If it fails I have a backup plan. A CBN wheel mounted to an old Craftsman radial arm saw, a blade guide and a lever advance. Easy-peasy. But I still need to scratch this "Rube Goldberg" itch first.

[JoshNZ]

We'll look forward to your progress pics! 

[barbender]

 RT, that diesel should be governed in the 2800-3000 rpm range if I'm not mistaken. I'd try to find the specs for that engine and see what the governed rpms are. Lowering your engine speed to get the right blade spade is not the right way to go about it. I'd ust get the right size pulley and be done with it.

 You have too many variables to assume that the fine sawdust left in the cut is due to the blade speed. Fine dust is more likely from a dull blade, and when the blade is dull the fine dust it makes spills out of the gullet. 
 

[RetiredTech]

  I'm really not sure about the little diesel. It was another freebee. This mill was built mostly from my scrap iron pile. The engine is a Kubota D662. It came on what was left of an old garden tractor/lawn mower. What little data I was able to find on it is contradictory in hp. It  lists it as a 12.7hp at 3600 rpm but then goes on to say it's Max hp is 19.2 @3600 rpm. It's supposed to have a " Centrifugal ball mechanical governor" but doesn't say that top rpm is governed less than the rated 3600rpm. I've just assumed the hp is somewhere between the two maybe 16hp and wide open throttle was near 3600rpm. I don't have anyway to measure the engine rpm.
  Changing the pulley is not as easy as just bolting on a new one. In order to mount the pulley behind the trailer tire I had to use a cut down 8" trailer wheel mounted to the back side of the axle hub and weld the the pulley to it. Remember, scrap iron. I can build another one and will probably order one in the near future. Extra torque is always nice. MORE POWER hohoho. Now that the mill is running and producing lumber my wife is beginning to see the benefit and doesn't mind me spending a little money on it here and there.
  She was dead set against a mill in the beginning. That's what prompted the cheapo build instead of buying a mill in the first place. Gotta keep Moma happy you know. When I read through Gww's build from some old exercise equipment I knew I could make it work, mostly with what I had on hand. It's been a fun project and I've learned a lot along the way. All the help I've gotten here has been great and no body has criticized my rinkydink mill all. Everyone just seems to accept it for what it is and try to help me make it better.

[Magicman]

All the help I've gotten here has been great and no body has criticized my rinkydink mill all. Everyone just seems to accept it for what it is and try to help me make it better.

Actually, that is the Forestry Forum way!! 

[RetiredTech]

  Hey guys, I value your opinions greatly. I didn't mean to change this thread into another one about my mill. If you'd like to continue the discussion of Engine speed / sawdust size I've posted some sawdust photos on the original mill thread here DIY Scrap Iron Bandsaw Mill.

  I'll get some photos up here about the Drag Sharpener. For starters this is a hunk of Cedar I salvaged from a log my uncle tried to burn up. I remember this tree when it was planted at the corner of my Grandparents house. I want to use it as the sharper base. The other side is actually better, but the photo didn't turn out.

[Magicman]

That hunk of salvaged ERC is destined to become a treasure. 

[RetiredTech]

  I don't know about a treasure, but I'll always remember that little Cedar tree and Grandma's when I see it. We cut it down to size ran it through a planer and put some polyurethane on it to seal it. Here's the top side of it. Complete with scorch marks.
 



This is the Vevor Chainsaw Sharpener I plan to use for the project and the little 30rpm gear reduction motor that will drive the band advance. Both have been delivered. We'll see what else I need as the project moves along. I see rain in the forecast so it may sooner than I thought.

[Magicman]

I see rain in the forecast so it may sooner than I thought.

I surely hope that your forecast is also my forecast.  I would git nekkid and do a rain dance if I thought that it would help. 

[LeeB]

Please don't. And if you do pictures are forbidden. 

[barbender]

 Lynn won't do anything without pictures😂

[beenthere]

Think we read about MM doing that once before. As he was streaking by an old couple at the old-folks home, one turned to the other and said "wasn't that MM running by, and what was he wearing"??

The other responded "I don't know, but it needed ironing!"

[RAYAR]

... the little 30rpm gear reduction motor that will drive the band advance.

I have a custom built drag sharpener and the band advance seems to run at about 11 rpm +- and that's a bit on the slow side. I think somewhere in the 15 to 20 rpm range would be ideal. It's going to be interesting to see that running at 30 rpm. Just my 2 cents worth. Time will tell. Hoping to see a video.