Chipper Chipper Blade Sharpening

Jibber · Oct 3, 2005

I have a Bearcat 70554 PTO driven chipper/shredder (new this summer). Today I cranked it up for the second time. Both Times I have used it, I've had a fairly good pile of tree limbs, branches and such to chip. Most of the stuff I chip is blowdowns.. dead stuff. Although I'd say about 20% is green.

Bearcat says when the unit stops self feeding then the blades need sharpened. It seems that this happens pretty quickly. The first time chipping there was a noticeable drop in self feeding after about two hours. Today it was more like an hour. I did sharpen the blades after the first use.

Bearcat advises to mix green and dead stuff to keep the blades cooler. Because I'm chipping mostly dead stuff I try to keep it slow so that the blades don't get too hot. But it still seems that they dull rather quickly.

My question.. for those of you with chippers, how often do you sharpen the chipper blades? Am I expecting too much from the blades? I don't need it to rip things out of my hands, but I don't like to have to push limbs in to get them to chip either. (I had enough of that with my old sears gas powered chipper).

CTyler · Oct 3, 2005

I have a Jinma 6" chipper but it has a feed roller to pull stuff. The manual, if I remember correctly, said to sharpen the blades after 8 hours. Or if the chips are more like shards instead of chips they need sharpened.

I've chipped many yards and they are still ok. Really small stuff comes out kinda funky but 2-3"+ stuff is chipped up ok.

I'd think they should/would last quite a bit longer than what your getting.

Jibber · Oct 3, 2005

It's a pain to turn or replace them too. You've got to pull an access cover (two bolts) then a swinging baffle plate (two bolts) then the screen (two hard to get at bolts) then two bolts per blade (4).

Each blade has two edges.. you can turn them once.. then sharpen both edges the next time round. Replacement blades are EXPENSIVE too. So you can't keep 3 sets lying around waiting to be used.

I live in the woods.. so every storm feeds the pile and I have to chip at least 2 or three times a year.

Even with the blades obviously dulled (some self feeding, but you have to push the big stuff) it does a pretty good job of chipping all but the little stuff.

cisco · Oct 3, 2005

OK, guess I'll stop complaining. I've a DR unit (literature says it takes up to 4", but I think 3" of hardwood is the limit, and I've more pto power, 29.5hp, than it needs). The instructions say sharpen every 10 hours, and that seems about right although all that happens is a gradual transition from fine chips to shards of wood after 10-12 hours. Yup, changing out blades is a pain.

escavader · Oct 3, 2005

With my salsco,and sharp knifes the wood will suck right in by gravity,When the knifes start getting dull it seems to want to stop at the crotchs AND I HAVE TO HELP IT,,this is when i know its time to change
ALAN

Cliff_Johns · Oct 3, 2005

Chipper blades should not be sharpened with a regular grinder, though you may already know that. They are higher grade high speed steel so they get sharper, but will soften if they get too hot.

They should be sharpened on a wet wheel, or by hand on a stone (diamond if you don't want to stand there too long). Don't sharpen them the way you would mower blades or something like that. If you do, they will not hold an edge and will dull quickly.

Cliff

jeffinsgf · Oct 3, 2005

( Chipper blades should not be sharpened with a regular grinder, though you may already know that. They are higher grade high speed steel so they get sharper, but will soften if they get too hot.

They should be sharpened on a wet wheel, or by hand on a stone (diamond if you don't want to stand there too long). Don't sharpen them the way you would mower blades or something like that. If you do, they will not hold an edge and will dull quickly.

Cliff )

Since there are some machinery dealers here that jump in when the subject warrants, I'm going to put in a shameless plug on this thread.

Cliff is right. Heat from a dry grinder will destroy a chipper blade. Same story for bench tools (hand chisels and plane irons). My "day job" is demonstrating and selling the TORMEK Water Cooled Sharpening System The planer blade attachment does a superb job of guiding a chipper blade on the grinder.

VA_Joe · Oct 3, 2005

Looks nice but pricey. Tough to justify unless one was in the sharpening business. How many (or what percentage) of units do you sell to hmeowners?

jeffinsgf · Oct 3, 2005

( ... (or what percentage) of units do you sell to hmeowners? )

About 85% of our buyers are hobbyist woodworkers. 10% professional woodworkers (lots of piano and violin builders) and the rest are professional sharpening shops. It all depends on your point of view. Lots of my customers would look at tractor prices and make a comment similar to yours.

VA_Joe · Oct 3, 2005

Makes sense - a set of good chisels or blades is not cheap. A serious woodworker would probably have one of these.

Joe

vjcunr · Oct 3, 2005

I have the same chipper, but made by Woods. I have about 10 to 15 hours on the first set of blades and they still self feed, but I can tell they are starting to getting dull. I have only been chipping wet pine and fir, and I noticed the wheel is getting clogged up with pitch and pine tar. I've thought about taking the chipper off the tractor, removing the blades and cleaning the wheel. Can you tell me how long it takes to remove and reinstall the blades? I was going to sharpen them by hand on a flat wet stone. There are no chips or dings in them. Does this work?
Thanks

Cliff_Johns · Oct 3, 2005

( I was going to sharpen them by hand on a flat wet stone. There are no chips or dings in them. Does this work? )

Note that chipper blades don't have a hollow grind or a secondary bevel. This means that your wet wheel must be flat, that is, you sharpen it on the side of the wheel. This also means that of you use a whet stone, you have to take metal off the whole edge, not just the last 32nd or 16th inch (a secondary bevel). So, if you're willing to stand there for a while, you can sharpen them by hand. That's how I've done mine (even though I have a slow wet wheel grinder that would yeild a hollow grind).

But I have a diamond flat and it takes off the metal pretty quick, then I hone it with regular Japenese water stones.

Cliff

vjcunr · Oct 3, 2005

Thanks Cliff,
Do you have any suggestions for removing the pine tar?

jeffinsgf · Oct 4, 2005

( Note that chipper blades don't have a hollow grind or a secondary bevel. This means that your wet wheel must be flat, that is, you sharpen it on the side of the wheel. This also means that of you use a whet stone, you have to take metal off the whole edge, not just the last 32nd or 16th inch (a secondary bevel). So, if you're willing to stand there for a while, you can sharpen them by hand. That's how I've done mine (even though I have a slow wet wheel grinder that would yeild a hollow grind).

But I have a diamond flat and it takes off the metal pretty quick, then I hone it with regular Japenese water stones.

Cliff)

What wet wheel are you talking about, Cliff? Your argument against hollow grinding is valid for a small diameter wheel (4 or 6 inch), but the hollow from a large diameter wheel (8 to 10 inch) is inconsequential on a chipper blade.

Cliff_Johns · Oct 4, 2005

( What wet wheel are you talking about, Cliff? Your argument against hollow grinding is valid for a small diameter wheel (4 or 6 inch), but the hollow from a large diameter wheel (8 to 10 inch) is inconsequential on a chipper blade. )

Well, I have a 10" wet wheel and don't use it for the chipper. There are two reasons. First, they take an incredible beating and even at 10" the wheel makes the edge thinner. Second, it changes the shape of the blade and modifies the dynamics of the blade on the chip and on the log. The chippers are designed to work optimally for a specific angle with no hollow grinding. It's the same reason I don't hollow grind jointer or planer blades -- though for some of the smaller hobby ones it would work just fine. If I wanted a grinder for this type of blade, I would get a wheel that lays flat and turns (I think Makita still makes a popular one).

Just my opinion. I suppose there would be a point in wheel size where I would consider the hollow grind to be inconsequential, probably around 20" for that thickness of blade.

Cliff

jeffinsgf · Oct 4, 2005

I suppose if I got out a high school geometry book I could calculate how much curve we are talking about, but if your blades are close to the same as mine (1/4" thick more or less), I would guess that the arc from a 10" stone would be under .001" You'll have a hard time convincing me that would be significant. If you want to do them by hand, be my guest. But I think that the readers should know that there is more than one way to remove the epidermis of a feline. /forums/images/graemlins/cool.gif

Cliff_Johns · Oct 4, 2005

( Thanks Cliff,
Do you have any suggestions for removing the pine tar?
)

Formula 409.

If it's old and hard, carborator cleaner (careful, it's flamable and will remove paint etc)

It's old and burned and really bad, spray on oven cleaner and let it sit for a while before
using a stiff toothbrush or a brass brush.

Mineral spirits can also work.

In general, the best thing is to remove it before it sets up. If you chip green pine, clean the chipper before you put it away.

Cliff

Cliff_Johns · Oct 4, 2005

You're probably right about the change in shape of the blade using a large wheel. It changes the angle by a degree (+or-), which doesn't sound like much and the shape being cupped slightly doesn't sound like much. If you get blades like this sharpened professionally, they will come back flat, and they come that way sharpened from the factory, but it does seem like a tiny difference.

Cliff

jeffinsgf · Oct 4, 2005

I promise this is my last swing at this dead horse. /forums/images/graemlins/grin.gif

( ... It changes the angle by a degree (+or-), which doesn't sound like much... )

Absolutely no reason that it should change the angle. 45 degrees is 45 degrees regardless of whether it is flat ground or hollow ground. Now, the angle is measured against the chord of the two points of the arc, but if that arc is less than .001" deep, the angle as measured - let's say at the chord at the middle of the blade - would be a few seconds of a degree off of 45. If you were aiming a rocket at the moon, it might mean something. On a chipper blade, I doubt it.

( .... If you get blades like this sharpened professionally, they will come back flat, and they come that way sharpened from the factory, but it does seem like a tiny difference.

Cliff )

It depends on what professional you send them to. Most sharpening shops would throw a chipper blade on a high speed BelSaw SharpAll, with a 6 inch diameter silicon carbide wheel that hasn't been dressed in 5 years and burn off a quarter inch of your blade (not cut off -- burn off) and cut a significant hollow in your blade (because of the small diameter). It would be that rare gem of a professional that would grind a chipper blade on a surface grinder or cup wheel which would yield a theoretically perfectly flat bevel. As far as new blades being flat ground, you're probably right. They probably jig up a surface grinder to do a couple hundred at a time. That would be an economy of scale issue rather than a preferred shape issue.

I am not trying to be argumentative (though it seems like I am doing a good job of it /forums/images/graemlins/smirk.gif), but I have had to explain the difference between flat ground, deep hollow ground, and shallow hollow ground edges in my industry for 20 years. It just comes natural.

Jibber · Oct 4, 2005

Actually, your Woods unit is made by Bear Cat. It IS the same unit.. diffo paint job.

It takes about a half hour to get the thing apart and remove all the blades.. Much longer to grind them all. Each blade is double edged so you can just swap them around the first time.. second time you have to grind.

I use a Delta sharpening center which has a flat turntable like wetstone. It's faster than hand grinding.. but still takes some time. Because you are grinding on a flat, turning stone with a constant supply of water.. it's safe to use on tempered tool steel. But the blades are super hard.. so it's not a fast process.