Chipper Chipper Blade Sharpening

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.