FITCHBURG 12" CHUCK AND DUCK

[DOGHILL]

This is my first post but I have spent lots of time reading on this site. Thank you to everyone who contribute their knowledge to the community.

I need some advice on a 12" Fitchburg Chuck and Duck...First off, this thing is a beast. I have owned it for about 5 years and chipped tons of trees and branches. Over time it has become less efficient to the point that it actually takes work to feed branches into the machine. I end up jamming the branch into the drum so it will catch. Not ideal if you are familiar with these machines. I have determined that the likely cause of the slow change is that the blade clearances are way too big. Manuals call for pretty tight clearances (found these from old posts) but not sure how to achieve these tight tolerances. Goal clearances posted elsewhere are feed plate clearance of .065"-.070" and bed knife clearance of .004"-.006". The spring loaded feed plate currently is about 3/4" from the blades and not further adjustable (#32 in attached patent photo). I can adjust the bed knife up and down to achieve proper clearances (#36 in attached patent photo). The only way I see to achieve all recommended clearances is to adjust my blades out (#44 in attached patent photo). If I do this, quite a bit of the blade will be above the drum. Any pictures I see of drums, the blades look pretty flush. Even in the patent photo they are shown pretty flush. Should I adjust the knives out and try it? How much above the drum is too much? Any input from others would be greatly appreciated.

I also know that sharp knives are very important. All of my knives feel sharp and are with defects. I do admit that I have no idea how sharp new knives are though.

 

[old CB]

I operated a Woodchuck 12 for years--similar setup to yours, and the behavior is the same as what you are dealing with. If there's too much gap, performance is lousy and you must push material into the machine. The gap between knives and anvil should be no more than the thickness of a dime. Knives must be super sharp to perform right. Just like a chainsaw, when knife edge is any less than razor sharp performance drops off.

On my machine I had to have the anvil machined on occasion to restore a sharp, square edge. When it was the least bit rounded, performance went down.

I would not be afraid to adjust your knives out to get the required gap.

 

[DOGHILL]

I operated a Woodchuck 12 for years--similar setup to yours, and the behavior is the same as what you are dealing with. If there's too much gap, performance is lousy and you must push material into the machine. The gap between knives and anvil should be no more than the thickness of a dime. Knives must be super sharp to perform right. Just like a chainsaw, when knife edge is any less than razor sharp performance drops off.

On my machine I had to have the anvil machined on occasion to restore a sharp, square edge. When it was the least bit rounded, performance went down.

I would not be afraid to adjust your knives out to get the required gap.

Thank you for the quick response.

My anvil, although has an angle still present, is not at all sharp. It is also not completely flat/square. Outside edges slightly higher than middle from wear. This is likely contributing to my situation. Interestingly, looks like the anvil can be flipped although the other side is much more concave and clearly used previously. Will need to find a machine shop willing to do the necessary work.

I noticed a typo in my original post, my blades are WITHOUT defects...anyways sharp enough to cut my finger when messing around with this thing but I would not say as sharp as a freshly sharpened chainsaw blade. Will need to have some work done there too.

I am going to adjust my blades out a bit to improve the clearance, not sure I will be able to get things to the recommended specs but I would suspect anything closer than I have right now would be an improvement.

 

[Steve-Maine]

Make sure the anvil is perfectly 90 degrees best to take to a shop that do chipper knives and have all done at same time. Good Luck. Was my first chipper with Hercules 4 cy flathead. Finally could afford a 12 Disc Vermeer chipper with Perkins Diesel with auto feed.

 

[DOGHILL]

Just so the information is out there for others to reference, I did a google search of all the patent numbers I could find on my machine. The diagram above was one of them but the bed knife is shown to be 90 degrees. The attached file shows the knife with an angle (which I believe is the model I own since the bed knife had an angle on it).