touching up knives in the chipper

[imagineero]

Thought this worth posting up. I've always used the bandit knifesaver tool, but it's pretty crappy honestly. It makes a small difference but doesn't really do much. Couple weeks ago I decided to have a go with a dremel, I've got one of the small rechargeable dremel stylus tools, the shorter pistol grip style 7.2v one not the longer 10.8v straight style tool. For my machine the longer straight tool would be too big to get into the machine. The 7.2V tool is small enough that I can sharpen both blades on my 250XP without needing to move anything. I used the grinding stone number 8193 and it did a pretty good job of redeeming the otherwise ****** slightly chipped edges of the blades in about 5 passes. I sharpen the blades from both sides as per bandit recommendations, not just a single sided blade.

I find that blades still do ok when slightly blunt on most material, but you need super sharp blades on stuff like cypress pine or small thin hedge like material or it just comes out real twiggy. Touching the blades up with the dremel brought the blades back to producing good chip from stringy stuff. It takes about 6 minutes to do all 4 blades. You could use any stone, but try to use a large diameter stone or you'll leave divits in the blades if you stop for a moment.

 

[blades]

I am sure bandit means both knife edges, grinding on the beveled side only, not both sides of the same edge- just for some clarification. Grinding on the beveled side and the flat side is a very poor practice and will cause feed problems. Never let your knives get a rounded edge. That puts and unbelievable stress on components as well as increases your fuel consumption considerably.

 

[imagineero]

You might want to read the manual again. The knife saver kit comes with a flat file and a double edged knife sharpener. They recommend turning the single bevelled blades into a slightly double bevelled blade right out of the box - extends the life of the knives apparently, then maintaining that double bevel with the double sided knife sharpener tool. I'll dig the manual out and scan it for you if I have some time this week.

I use the blades as single bevel out of the box and keep them touched up with the knife sharpener tool. As the tool becomes less effective I put a back bevel on the blade. Straight out of the box the single bevel blades are too aggressive, and can pull material through stopped feed rollers. Some guys actually blunt them a little out of the box for safety reasons.

 

[Pelorus]

Putting a back bevel on the blades just makes them wear out faster, imo, and makes them harder (take more passes on a knife grinder) to sharpen properly.
The fellow who sharpens my knifes doesn't want me to back bevel them. So I quit using that knife sharpener thing.
If sharp knifes are pulling material through the stopped feed roller(s), mebbe you should check the spring pressure on them?

 

[capetrees]

Manufacturer sharpens mine to factory spec. I'll never use an aftermarket blade and I'll never attempt to sharpen my own. Blades threw on an old machine and man is it hairy.

 

[imagineero]

Your OEM knives are aftermarket. As far as I know there isn't a commercial grade chipper manufacturer in the world that also makes their own knives. Bandit OEM used to be simmonds, but zenith was half the price and just as good. So now bandit supplies zenith knives as OEM. Factory spec for bandit knives is to put a back bevel on them with a file.

 

[imagineero]

Putting a back bevel on the blades just makes them wear out faster, imo, and makes them harder (take more passes on a knife grinder) to sharpen properly.
The fellow who sharpens my knifes doesn't want me to back bevel them. So I quit using that knife sharpener thing.
If sharp knifes are pulling material through the stopped feed roller(s), mebbe you should check the spring pressure on them?

Yeah I agree you're reducing the number of times a knife can be commercially sharpened by putting a back bevel on it, maybe only once or twice if you're back bevelling. But you're also extending the hours the knife can be run for, esentially getting the same life out of the knife and saving the cost of a sharpening. New set of knives runs about $280 here in aus for a bandit 250xp, a sharpening is about $100. You might get 2 sharpenings out of a set of knives, or 1 if you're back beveling and touching them up.

I haven't had a problem with fresh knives pulling material through the rollers on my machine, but its been a problem for a few guys I've spoken to on newer bandit drums, 1590/1890. My springs probably have too much pressure on them.

 

[NYTREECLIMBER]

We've have 3Vermeer 1800XL's and all of them will pull wood past the feed wheels, only when the blades are new thought. It has happened since day one, and I find that slowing the feed wheels down helps but does not eliminate it from happening. We generally get 3-4 sharpening's out of the knives


Character is who you are when no one is looking

 

[imagineero]

I think it's a problem that seems more prevalent with drums than disks. I've operated 1800XL's, and they aren't a favorite of mine though they're a real bargain and can be had for very little money in aus. My 250XP cost more than some 1800XLs. It's the best value for money 18" chipper out there. I'm not a fan of the vertical rollers, and the consistency of the chip ins't brilliant but it's hard to complain for the money.

The auto feed combined with the vertical rollers reminds me of those old western movie carnivals, with the wooden dummies. You'd punch them and they'd spin round and slap you in the back of the head. That auto feed has a mind of its own, when it's had enough of a bite and wants to spit ot back out for another taste it moves in feet not in inches.

 

[NYTREECLIMBER]

I think it's a problem that seems more prevalent with drums than disks. I've operated 1800XL's, and they aren't a favorite of mine though they're a real bargain and can be had for very little money in aus. My 250XP cost more than some 1800XLs. It's the best value for money 18" chipper out there. I'm not a fan of the vertical rollers, and the consistency of the chip ins't brilliant but it's hard to complain for the money.

The auto feed combined with the vertical rollers reminds me of those old western movie carnivals, with the wooden dummies. You'd punch them and they'd spin round and slap you in the back of the head. That auto feed has a mind of its own, when it's had enough of a bite and wants to spit ot back out for another taste it moves in feet not in inches.[/ disc chippers definitely make nicer chips but drum are better suited for processing larger material. As far as the vertical feed wheels, I think they are great. I used bandits 250's for years and can say IMHO the vermeer is a better all around machine,so long as there is a cummins diesel in it.


Character is who you are when no one is looking

 

[imagineero]

That's what I said alright ;-)

 

[NYTREECLIMBER]

Somehow my post merged with your post, strange


Character is who you are when no one is looking

 

[DR. P. Proteus]

My take is that when re-sharpening after the bevel is sharpened then you de-burr the backside adequately and that's it. If you are just and only touching up with some kind of touch up tool a back bevel is OK because you can't change the shape and dynamics of the knife with a touch up blade AND a small hand filed back-bevel on a knife that has been cut true on a machine is good. It is not good to keep hand filing and using touch up tools because after awhile you end up back-beveling the tip of the cutting surface to far away from its original position which will start to strain things and have other adverse effects.

 

[blades]

My take is that when re-sharpening after the bevel is sharpened then you de-burr the backside adequately and that's it. If you are just and only touching up with some kind of touch up tool a back bevel is OK because you can't change the shape and dynamics of the knife with a touch up blade AND a small hand filed back-bevel on a knife that has been cut true on a machine is good. It is not good to keep hand filing and using touch up tools because after awhile you end up back-beveling the tip of the cutting surface to far away from its original position which will start to strain things and have other adverse effects.

Exactly!!!!!

 

[derwoodii]

I'm much the same i run my drill with fine stone lots & cooling lube along the edge it get them back good to go sharp edge and will do so 2 maybe 3 times before it self become a waste of time as the whole blade face needs to be professionally ground clean again

 

[derwoodii]

What kind of machine are the knives ground on in a shop?

supe dupa flat bedded water cooled grinders that rubb away the knife edge face to set ideal angle new sharpened knifes are so sweet and yet so dicey to handle need to glove up and move slow but you wont/dont feel the slice if mistake made.

 

[CalTreeEquip]

I have talked to Bandit dealers and techs about the whole back bevel thing. I have been told its not necessary. It looks good on paper but that's it. They do not bevel the blades when they install them so what does that tell you. Furthermore, I don't believe any of the other manufactures suggest you do it.
As for hand grinding you blades in place, I don't think its good. These blades are so easy to change why would anyone cheap out on that part. When you change them your inspecting them and the bolts as well. Bolts do fail, blades do crack and if you're going to catch that before it happens you need to pull the blades.

 

[CalTreeEquip]

I do use an AccuSharp to touchup blades sometime. It will put a little bevel on the blades but nothing like is recommended in the manual. If that's not good enough to put an edge on the blades then its time to pull them.

 

[blades]

I grind the chipper blades at my shop commercially. I use a 54" traveling head grinder full coolant flow on knives. I grind them as matched sets. It amazes me how far people will let them go before pulling them, I will try to get some pictures up later today. The amount of stress imparted on your drums or flywheel and related parts from poor condition blades is the #1 cause of bearing, drive shaft failures in chippers. The blade angle varies mfg-mfg, generally about 32-40 deg. not all that super critical. Most double edged blades have a minimum length from the center line of the mounting holes to the edge. Un matched blade pairs will impart an imbalance as well causing vibration that will tear things apart. Also please be aware that there have been problems reported about bolt failures- chi-com mfg grade 8.

 

[jefflovstrom]

We change out the bolts on every 3 blade changes.
Jeff