Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old October 31st 03, 11:37 PM
Roy
 
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Default Info on how to make a chipper knife

Being that one of my knives on my chipper broke and I am a cheap son
of a bi%#@ i need to make one. Its approximately 1.25" x 3.75" x .250"
thick, with two 5/16" countersunk holes in it and a bevel of 37 deg
ground on one long edge.


For the time being I used a old but unused heavy duty mower blade
which was as hard as a leaf spring is, and cut it to size and have
been using it, but it does not quite hold up as good as the original
blades did, but its still useable.

The original is supposedly hardened to 58 rc. So what materials would
you recomend making this blade out of.? I don't really have a temp
controlled furnace, but I maya be able to acccess one, unless I can
get by on heating with a torch or in my crucible furnace.

Any info appreciated.


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Old November 1st 03, 02:38 AM
Beecrofter
 
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Default Info on how to make a chipper knife

Why not mill a step into a properly sized blank and braze in some carbide?
You ain't making veneer so it could be a few smaller pieces brazed in.
Only the edge needs to be hard.
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Old November 1st 03, 06:36 AM
JWDoyleJr
 
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Default Info on how to make a chipper knife


Being that one of my knives on my chipper broke and I am a cheap son
of a bi%#@ i need to make one. Its approximately 1.25" x 3.75" x .250"
thick, with two 5/16" countersunk holes in it and a bevel of 37 deg
ground on one long edge.


Roy,
I had a similar problem with a 10 HP Murray chipper-shredder. It had one
blade, 1.375 X 3.125 X 1/4 with two 5/16 countersink holes and a similar bevel.
This was a shi**y design. The blade was too short to begin with, allowing a
sliver of a green branch to slip by the inside end and wrap around the axle.
It was also of the wrong material. The original blade fractured through a bolt
hole, and a replacement was priced at about $24 + shipping cost.

I went to the farm store and bought the cheapest plowshare in stock for about
$7, and hacksawed out a blank and worked it from there -- mill, drill,
countersink, grind. I made my blade 3.625 long, and it works like a charm. No
fractures. No wraparound. And priced to please the cheapest son of a bi%#@
on earth. After some experience, I tried grinding more "clearance" in my
blade, and it literally sucks the branches in. (The original had to be force
fed.) And I have a lifetime supply of material for more blades.

Overall comment on this chipper: The chipper body and rotor do not have the
strength to take 10 HP. I have about a pound of weld on mine, repairing over a
foot of fatigue cracks and reattatching parts that were blown away. The
rotating flails were mounted on weakened pins which failed, with results
approximating an explosion.

Try the plowshares for a source of cheap, tough steel. They're designed for
fatigue strength and wear resistance. Milling it will test your skill and
vocabulary. Say carbide, and then have fun.
Pat
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Old November 1st 03, 02:27 PM
Roy
 
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Default Info on how to make a chipper knife

On 01 Nov 2003 06:36:33 GMT, (JWDoyleJr) wrote:

===
===Being that one of my knives on my chipper broke and I am a cheap son
===of a bi%#@ i need to make one. Its approximately 1.25" x 3.75" x .250"
===thick, with two 5/16" countersunk holes in it and a bevel of 37 deg
===ground on one long edge.
===
===
===Roy,
===I had a similar problem with a 10 HP Murray chipper-shredder. It had one
===blade, 1.375 X 3.125 X 1/4 with two 5/16 countersink holes and a similar bevel.
=== This was a shi**y design. The blade was too short to begin with, allowing a
===sliver of a green branch to slip by the inside end and wrap around the axle.
===It was also of the wrong material. The original blade fractured through a bolt
===hole, and a replacement was priced at about $24 + shipping cost.
===
===I went to the farm store and bought the cheapest plowshare in stock for about
===$7, and hacksawed out a blank and worked it from there -- mill, drill,
===countersink, grind. I made my blade 3.625 long, and it works like a charm. No
===fractures. No wraparound. And priced to please the cheapest son of a bi%#@
===on earth. After some experience, I tried grinding more "clearance" in my
===blade, and it literally sucks the branches in. (The original had to be force
===fed.) And I have a lifetime supply of material for more blades.
===
===Overall comment on this chipper: The chipper body and rotor do not have the
===strength to take 10 HP. I have about a pound of weld on mine, repairing over a
===foot of fatigue cracks and reattatching parts that were blown away. The
===rotating flails were mounted on weakened pins which failed, with results
===approximating an explosion.
===
===Try the plowshares for a source of cheap, tough steel. They're designed for
===fatigue strength and wear resistance. Milling it will test your skill and
===vocabulary. Say carbide, and then have fun.
===Pat



Yep, what you did is along the lines of what I was thinking, but I
used a heavy duty .300" thick mower blade tip that I acquired
somewhere. The blades on my JD mower seem to be holding a good edge
while used in sandy conditons, and are still pretty sharp, so thats
what led me to try a mower blade. Mine also broke off on one of thr
sections with a bolt hole, and the other section is cracked up to the
bolt hole and starting to propagate on the other side. I can see that
they need to be hard, but somehow I think they may be too hard, thus
making them fracture prone.

I like the idea of milling a step and brazing in some carbide........

I too am a cheap SOB (I did not get the name frugal machinist for
nothing, and have a hard time p[aying over $25.00 plus shipping and
handling for this small chipper knife, when I can vuy a 3" x 8" x
..375" thick knife for $22 that fits a commercial chipper unit. The
price just does not fit this item. If I had a way to cut and
countersink the bigger knife, it would be a item to make it out of as
well. Guess I will check the local farm supply for a plow share, as I
do know they are much harder than a lawn mower blade is.


Another thing I had considered was usuing z piece of this mower blade
and hard facing a couple of beads of hardface on it and then grinding
the edge, but that would propbably be more trouble than simply milling
a step and brazing in carbide, or milling out a plow share to fit.
Biggest problem is my countersink, but its doable.
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Old November 1st 03, 05:27 PM
Ted Edwards
 
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Default Info on how to make a chipper knife

Roy wrote:

Being that one of my knives on my chipper broke and I am a cheap son
of a bi%#@ i need to make one. Its approximately 1.25" x 3.75" x .250"
thick, with two 5/16" countersunk holes in it and a bevel of 37 deg
ground on one long edge.


I like the idea of milling a step and brazing in some carbide........


I don't like the carbide idea as carbides are brittle and chip easily.

I too am a cheap SOB


Not as cheap as me! ;-)

I would try the following: Cut the blade out of a piece of old (free)
leaf spring (plasma or O/A). Anneal, flatten, drill the holes and
roughly shape the edge. Build up the edge with Stellite #6 (TIG or
O/A). Grind the edge to finished shape and sharpen. You can then
harden and temper to purple for additional strength if you wish. The
heat won't affect the Stellite. You may have to sharpen it once after
some use as the Stellite work hardens.

BTW, I picked up a box of Stellite #6 TIG rods at a blow out sale at the
local welding shop. Stuff is expensive but that knife wouldn't take
even half a rod. I've made center punches for hot work out of tipped
re-bar scrap and even used it for some heat resistant electrical
contacts. Well worth having a few rods around.

I loaned a friend a cold chisel I made from a piece of 1" re-bar. I
forged it to shape with a very blunt square edge. I built up a bead of
#6 Stellite on the edge and ground to shape and sharpness. He wanted it
to clean off lumps of concrete left from knot holes in the forms. I
fully expected it to come back in pretty bad shape but I was curious to
see what would happen. Well, I found out! The edge was a little dulled
- not worth bothering to sharpen yet. No chips.

Ted




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Old November 1st 03, 09:05 PM
Jack Erbes
 
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Default Info on how to make a chipper knife

On Fri, 31 Oct 2003 23:37:36 GMT, (Roy) wrote:

Being that one of my knives on my chipper broke and I am a cheap son
of a bi%#@ i need to make one. Its approximately 1.25" x 3.75" x .250"
thick, with two 5/16" countersunk holes in it and a bevel of 37 deg
ground on one long edge.


For the time being I used a old but unused heavy duty mower blade
which was as hard as a leaf spring is, and cut it to size and have
been using it, but it does not quite hold up as good as the original
blades did, but its still useable.

The original is supposedly hardened to 58 rc. So what materials would
you recomend making this blade out of.? I don't really have a temp
controlled furnace, but I maya be able to acccess one, unless I can
get by on heating with a torch or in my crucible furnace.

Any info appreciated.


I'd try some 1/4 x 1-1/4" W-1 or O-1 flat bar (from MSC or Enco?).
Cut it to length, mill the bevel, drill and countersink the holes.
You should be able to harden those with an O/A torch.

That should get you a blade that is RC 63 (O-1) to 66 (W-1) or so, a
one, hour 500 degree temper should drop that to RC 58 or so. If you
only have a home oven, an hour at 400 will get it down to RC 61-62 or
so and that may work okay for a wood chipper.

You can get 9 blades our of a 36" piece of O-1 or W-1 which I would
guess at around $60 or so. Your time does not count when you're
working for yourself right? :)



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