Chipper blade snapped

[htb]

7 minutes ago, PeteB said:

Sure nothing bad went through to start it off? Was the infeed speed too high and the blade was being asked to par off too much in one bite? 

I 'ring' blades before fitting them, my old arboreater used a few blades and we learnt after a similar failure to check before fitting. A dull ring and that set was put aside!

Old skool tech, but it works.

[tonytree]

3 hours ago, Mick Dempsey said:

Stuff happens, it’s a pretty violent process.

 

No damage to the anvils?

I haven’t had a good look and taken them out but they seem fine and there isn’t any play in the flywheel bearing so that’s good. 
 

2 hours ago, PeteB said:

Sure nothing bad went through to start it off? Was the infeed speed too high and the blade was being asked to par off too much in one bite? 

I 'ring' blades before fitting them, my old arboreater used a few blades and we learnt after a similar failure to check before fitting. A dull ring and that set was put aside!

I’m positive nothing went through beforehand hand as for the roller speed It wasn’t set high. I’ve never heard of that method so I’ll definitely be trying it next time. 
 

 

3 hours ago, Stubby said:

Take the broken bits to a tool room and get them tested on a Rockwell hardness tester . Check that result against the spec . Looking at the fracture I would say that was at least 62 Rockwell C .

Don’t mean to sound ignorant but where would I find the spec the blades Rockwell hardness should be?

 

Do you have a rough idea on what Rockwell the should be?

 

thanks 

Edited June 14, 2020 by tonytree

[PeteB]

Rockwell is  just a measure of hardness and with hardness comes brittle. Tto hard and things shatter, too soft and the edge goes off really fast. A test would be expensive and even if they are too hard, the damage is done. Hopefully, not other damage has been done to the blade bed, bolt hole or the rest of the machine. Check shear bars, bearings and the 'wrap' or chipper casing. There may be a hydraulic  tank which is part of the casing and you don't want that punctured! I doubt that it is covered by warranty.....

[Stubby]

7 hours ago, PeteB said:

Rockwell is  just a measure of hardness and with hardness comes brittle. Tto hard and things shatter, too soft and the edge goes off really fast. A test would be expensive and even if they are too hard, the damage is done. Hopefully, not other damage has been done to the blade bed, bolt hole or the rest of the machine. Check shear bars, bearings and the 'wrap' or chipper casing. There may be a hydraulic  tank which is part of the casing and you don't want that punctured! I doubt that it is covered by warranty.....

I never considered a Rockwell test to be expensive as it only takes about 30 seconds .  Place component on the flat surface of the tester , lower the diamond point onto the component , wait a few seconds till the dial/readout stops moving and read off the result .

[PeteB]

3 minutes ago, Stubby said:

I never considered a Rockwell test to be expensive as it only takes about 30 seconds .  Place component on the flat surface of the tester , lower the diamond point onto the component , wait a few seconds till the dial/readout stops moving and read off the result .

True enough, but add professional fees for the report, the time sending them off and all else and for what end? If they are within specified limits, what is the gain? The chances that they are wrong are slim and one cannot be sure that something in the material chipped did not start the damaged? To be honest, I'd chalk it up to experience  and walk on.

[aspenarb]

2 hours ago, PeteB said:

True enough, but add professional fees for the report, the time sending them off and all else and for what end? If they are within specified limits, what is the gain? The chances that they are wrong are slim and one cannot be sure that something in the material chipped did not start the damaged? To be honest, I'd chalk it up to experience  and walk on.

I have had failures in aftermarket blades and sent them back to the seller for analysis, on both occasions they have been lost or misplaced and despite chasing them up never had an explanation or refund. On both occasions the knives exploded through the chute and thank god there were no injuries. For this reason alone I will only by genuine blades, not saying it can’t happen to genuine blades but I have never seen a failure in one.

 

Bob.

Edited June 15, 2020 by aspenarb

[jmac]

Do you get your torque wrench calibrated? Do you put it back to zero after use? If you dont it could be miles off as it stretches the spring over time (or so I was told anyway). I bought a new torque wrench after I found this out. 

[Stubby]

1 hour ago, PeteB said:

True enough, but add professional fees for the report, the time sending them off and all else and for what end? If they are within specified limits, what is the gain? The chances that they are wrong are slim and one cannot be sure that something in the material chipped did not start the damaged? To be honest, I'd chalk it up to experience  and walk on.

If . its all if isn't it ?  If they are not to spec  you would have some come back surely ?  You are probably right in saying chalk it up and walk on but if there were a bad batch ......

Edited June 15, 2020 by Stubby

[Khriss]

Try dressing it with a file which is hardener than the blade 'should' be , if it just rings off n don't remove metal, that's too hard fr a chipper blade. K

[PeteB]

27 minutes ago, Stubby said:

If . its all if isn't it ?  If they are not to spec  you would have some come back surely ?  You are probably right in saying chalk it up and walk on but if there were a bad 

I reckon we make over 5000kg of blades per year and don't ever recall any bad batches. Goodwill?, yes, I have given a number of free sets away, I don't recall any on an accusation of being too hard, just goodwill or thanks for a favour done like the use a machine for an hour etc....

 

I did get told that batches of blades are made from a known type of steel, machined to tolerance then heat treated to a set standard. There a number per batch that are tested as part of that suppliers routine quality control and CE compliance certificate. I've seen some very good (and very cheap) copies too, but would never advocate using them.