Sharpening Blades w/o hollow grinding them

[Furu]

I have searched to see if I can find a thread on this and have not.

When dealing with large thick brushcutter blades (Woods BB-720)and chipper blades how does one avoid a hollow ground profile when using a grinder that has a normal size wheel? I have only been able to do it with hand sharpening and would like to do it the more advanced and less labor intensive way.
The steel blades are 0.5 inches thick and are ground at a couple of different angles (different on chipper and brushcutter)

 

[smstonypoint]

I will be following this thread with interest.

I have no direct experience in sharpening chipper blades, but I am in the market for a chipper and have been doing some research on sharpening the blades. Two dealers have told me that proper sharpening requires some specialized equipment. Here's a thread that discusses some of the issues involved:http://www.tractorbynet.com/forums/attachments/66669-chipper-blade-sharpening.html.

Steve

 

[aczlan]

For a rotary cutter, I would use a angle grinder while the blades are on the deck.

Aaron Z

 

[banjodunn]

For a rotary cutter, I would use a angle grinder while the blades are on the deck.

Aaron Z

x2 or if access is difficult while on the mower then remove and grind them in a bench vice


Jon

 

[djradz]

Hand held angle grinder. 4-1/2" works OK, but for taking a lot of metal off such as on a brush (rotary) cutter, I'd use a 7" or 9" instead. These will all result in virtually no hollow ground.

 

[Bill Hoffman]

or perhaps, a belt sander/grinder. Flat platen, easy to get belts,
quick to use, and safe. Don't grind on the side of a round wheel.
It's a great way to explode the wheel.

 

[Jim Thompson]

What is the downside of hollow grinding bush hog rotary cutter blades? That is the way I always sharpen those on my Rhino bush hog. I think we had a discussion some time back regarding this. I do not grind the blades to a sharp edge. I leave an eighth to three sixteenths radius on the edge, which is I think what the book calls for.

Jim

 

[Furu]

Hollow grinding can result in a much sharper edge but also somewhat weakens the blade by thinning it. As you point out the manuals specify a method for sharpening. Flat grinding is one and the 1/16 to 3/32 edge is another on the brushcutter but the chipper wants an actual sharp edge flat grind. IAW the manual.

 

[RoMad]

When I sharpen my bush hog blades I do it with the blades on and use a 4" grinder. I hold the grinder somewhat flat. It would be really hard to do it with the grinder held at 90 degrees to the blades even if you wanted to. I suppose it might hollow grind the blades a little, but you can't see it with your naked eye. I also leave about a 3/32" to 1/8" land on the cutting edge.
One thing I do no matter what I am sharpening with my grinder is I never let it get so hot I can't hold my bare hand against it. I may be way off, but I don't see how you can change the temper in any blade if you don't let it get hot enough to burn your bare hand.