chipper/mulcher blades

I regularly use a friends "red roo" mulcher and wish to put a set of new blades on it for him.

My problem is that it is quite an old machine and the blades are no longer available at an acceptable price (anyware from $500 t0 $800 for two blades).

The original blades are single edge and a cross section that tapers from 3/8inch at the front down to 1/8inch at the trailing edge. What I have in mind is to try to find a parralel double edged blade of the same size etc. Can anyone see a problem with this ? - the blade being equidistant from the anvil as it passes rather than tapering away, after all that is how others must work.

Denn

Got a picture? Is it the cutting edge or the back of the blade that tapers away from the anvil?

I am surprised at the cost, have you tried Hugans in Osborne park, they cut knives to order and may be able to help?

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Originally Posted by Burnsy

Got a picture? Is it the cutting edge or the back of the blade that tapers away from the anvil?

I am surprised at the cost, have you tried Hugans in Osborne park, they cut knives to order and may be able to help?

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Sorry I didn't put up a pic' this morning, I just had too much on - anyhow here is what I have. The top of the blade would travel past the anvil whilst the chips would travel underneath and through a hole in the flywheel/disc - this means that the bottom of the blade would travel parallel to the anvil at a distance equal to the thickness of the blade.

Hughans would make some up exactly the same at around $320 per blade ($640 for two of them).

One company in Sydney still have some originals but at $440 plus postage I prefer to find another solution


Denn

I think you could use a flat blade but you may have to change the bevel on the cutting face or modify the drum or disc to get the right angle to the anvil.
I made my own blades for a McQuarie drum and a Bandit disc out of spring steel. I made them from new spring steel them heated the back of the cutting face (just the outside 1/2") to just dull red and dunped in sump oil. If to hot they become brittle and the blade chips. A friend got some one to make some for him and they said you had to harden the lot not just the edge or they would crack. But theirs cracked though the bolt holes were as mine lasted very well.

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Originally Posted by glenn k

I think you could use a flat blade but you may have to change the bevel on the cutting face or modify the drum or disc to get the right angle to the anvil.
I made my own blades for a McQuarie drum and a Bandit disc out of spring steel. I made them from new spring steel them heated the back of the cutting face (just the outside 1/2") to just dull red and dunped in sump oil. If to hot they become brittle and the blade chips. A friend got some one to make some for him and they said you had to harden the lot not just the edge or they would crack. But theirs cracked though the bolt holes were as mine lasted very well.

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Thanks Glen, yes the more I think about it the more I am convinced that the flat blades will do the job. As for the bevel, It would be the same in relation to the bottom of the blade in the pic'.

Unfortunately I am not equipped to do the job myself but I am sure a simple flat blade could be made much cheaper than something with the original cross section. However that is now going to have to wait untill Tuesday, after the long weekend.

Denn

I have a wood chipper with similar shaped blades, I was thinking about making a new set as well.

Been wondering about the taper, why it's there. Is it to give clearance on the back of the blade after the cutting edge, same as a drill bit needs the clearance?

I know the chipper blade is a bit more brutal than a drill bit, but it is a cutting edge all the same.

I'll be interested to know how you go anyway.

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Originally Posted by Ironwood

I have a wood chipper with similar shaped blades, I was thinking about making a new set as well.

Been wondering about the taper, why it's there. Is it to give clearance on the back of the blade after the cutting edge, same as a drill bit needs the clearance?

I know the chipper blade is a bit more brutal than a drill bit, but it is a cutting edge all the same.

I'll be interested to know how you go anyway.

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I am beginning to think that it may have originally been as you suggest - to allow clearance; if so then I wonder, is it really nescessary? as few mulchers these days have tapered blades.

The blades on my friends mulcher always seem to develop cracks on the thin side of the taper - the weakest part. So a parrallel blade would also benefit from being equally strong on both sides of the holes.

My current plan is to buy the appropriate steel (probably from Bohler steel), have a friend do the machining, then I have to find a heat treatment specialist. Does anyone in Perth have any recomendations re the heat treatment people.


Denn

Denn spring steel is a fraction of the price of chipper steel. I bought a GMC cut off wheel to cut them up then drilled the holes (not easy need a very slow drill or milling machine) then bolted them on to a piece of angle iron set this way ^then cut a 45 deg edge with the cut off wheel. The cheap rough chinese wheels work better because the edges break off and stay sharp and don't work harden the steel otherwise it doesn't cut. I then put an angled plate on the bench grinder with a stop to line them up and grind with a white stone then harden. This gives a slightly hollow ground blade so its easy to touch up by hand. One set of blades would pay for the tools.
I made about 10 sets same size run them all; then re-hardfaced the anvil with tool steel re sharpend all the blades and reset for anther run. I bought ~6 set of blades and zero anvils in 20 years.

Wow! I paid $970 for my 13 hp chipper mulcher, delivered.

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Originally Posted by glenn k

Denn spring steel is a fraction of the price of chipper steel. I bought a GMC cut off wheel to cut them up then drilled the holes (not easy need a very slow drill or milling machine) then bolted them on to a piece of angle iron set this way ^then cut a 45 deg edge with the cut off wheel. The cheap rough chinese wheels work better because the edges break off and stay sharp and don't work harden the steel otherwise it doesn't cut. I then put an angled plate on the bench grinder with a stop to line them up and grind with a white stone then harden. This gives a slightly hollow ground blade so its easy to touch up by hand. One set of blades would pay for the tools.
I made about 10 sets same size run them all; then re-hardfaced the anvil with tool steel re sharpend all the blades and reset for anther run. I bought ~6 set of blades and zero anvils in 20 years.

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I have a friend that will do the machining for me, so thing now is to decide on the steel to use. and the heat treatment (spring steel sounds promising).

Today is a public holiday so it will have to wait untill tomorrow.

Also I have I have found another couple of problems with the machine - caused by my friend not being mechanically savvy. Thankfully though they are easier to solve than the blades.

Denn

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Originally Posted by damian

Wow! I paid $970 for my 13 hp chipper mulcher, delivered.

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Don't just leave it at that - tell us more.

Size?

Make?

How long ago?

Etc Etc

Denn