Sharpening chipper blades

I have a small Sears chipper/shredder that will handle about a three
inch diameter branch. I just re sharpened the (2) chipping blades to
a 45 degree angle and now the thing seems very "grabby" when I feed in
a branch. That is, it wants to yank the branch into the blades rather
than letting me feed in the branch gradually so the motor (5hp)
doesn't bog down.
The unit is old to the point that the blades have been sharpened
several times over the years so I don't now what the official blade
angle should be.
Any suggestions to make this thing less grabby?
Thanks,
Errol Groff
Instructor, Manufacturing Technology
H.H. Ellis Technical High School
613 Upper Maple Street
Danielson, CT 06239
New England Model Engineering Society
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Reply to
Errol Groff
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Snub as you would a drill for brass.
Reply to
Simon Schnizzard
Hi. If this unit is like my OLD one, it is like a lawn mower with two rotating blades on the ned of the vertical shaft. You had sharpened only one half of the cutting mechanism. The other half of the cutting system needs to be sharpened or repaired. On my old unit, the blades used part of the housing as the other half of the cutting scheme. They were so worn that the blades just pulled the branches into the slots and beat them to pieces.
My solution was to fabricate plates that matched the original clearance for the rotating blades and screwed/bolted the plates over the original housing parts. It took several tries to get the new plates correct, but that allowed the machine to be useful for several more years.
The engine shaft cutting blades could also be turned so the second side could be used for cutting. I suppose you have already done this. Or am I way off base on the type of machine you are using?
Paul
Reply to
co_farmer
Paul:
This unit has a horizontal shaft engine and there is no mating pieces such as you describe. Thanks however for the response.
Errol
Reply to
Errol Groff
35 degrees Steve
Reply to
Steve Lusardi
This is a red contraption with a big round housing? Those were made by MTD. Mine has been welded back together so many times due to fatigue cracking it is a big mess. The problem is the blades get farther away from the funnel as they are sharpened, and the bottom of the funnel or chute gets bent massively, too. You get long strips of bark that pull stuff in when the get wrapped around the wheel. I had to un-bend the chute and build it up a bit with the welder to keep that gap small. You want it to cut like scissors between the blade and chute, not smash stuff hanging over the edge. Building the blade up by putting a shim under it ought to work, too. I've also thought of buying something like Stellite tool blanks and brazing them onto the cutting edge to both build it back up to the original dimension as well as make them a lot harder. I got a Bibb "Tung Carb" hardfacing unit and applied some carbide facing to the blades and it definitely helps them retain their edge longer.
I think the original profile was a lot more acute than 45 degrees, you may have removed more material and made the gap bigger that way.
Jon
Reply to
Jon Elson
I'm pretty sure this is an MTD, I know Sears sold them for some time, may still sell them. If you take the intake chute off, there is a lip at the bottom of the chute that gets pretty close to the blades. It gets bent down over time from the force applied to the branches. That definitely increases the "pull" on the branch, and probably the hammering effect on your hands, too!
Jon
Reply to
Jon Elson
Thanks Jon and all:
I will gake the chute of on Wed. afternoon and take a look at the innards. I will try taking a coupld of photos and post them to a web page for further comment.
Errol
Reply to
Errol Groff

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