3-Knife Trimming - what bevel angle?

[Stickman42]

We run a hand-fed Accutrim 3 knife trimmer (from Colter Petersen / Amatco) and have been experiencing more spine chipping than we'd like to see. We run a stack at a time, up to 4" in height. Running 1 book at a time doesn't have any substantial benefit.

In speaking with our knife sharpening service, I found out that our high speed steel knives have been getting sharpened to 20 degrees. We went to 19 and the problem didn't budge. We just tried a set of knives at 22 degrees and there is limited improvement. I requested our next set gets cut to 24 degrees.

Does anyone have any experience of success with this issue being related to the angle of the knives' bevel?

PS - our product is perfect bound books, usually 6" x 9", 300 or so pages on uncoated offset with a 10 pt. C1S cover, either UV or film lam. Our standard head and foot trim amount is 1/4" (if we go down to 1/8" trim there's no difference)

 

[Stickman42]

Update - we're now running with our knives sharpened at a 24 degree angle, and the results are astounding. Virtually no spine chipping or tearing to be found.

I know there's been a few other threads about this in the past, so maybe this will help someone else.

 

[AP90]

Update - we're now running with our knives sharpened at a 24 degree angle, and the results are astounding. Virtually no spine chipping or tearing to be found.

I know there's been a few other threads about this in the past, so maybe this will help someone else.

Glad it worked out for you! It's things like this that are always hard finding info on and usually ends up being a trail and error thing.

Side note on blade sharpening. We have a Challenge 20 and noticed that our blades didnt seem to come back as good as they used to from our local sharpener. They use all the high tech stuff, cnc, etc. I bought a knife sharpening kit with additional stones and metal sharpeners that could hold our 20" blades and decided to try it out. First blade came out DULLLLLLL. Then I figured out I was trying to actually create an angle and edge. It already had it on there, I just needed to get it back to a razor. Second blade I did I threw on the cutter and it went through like butta. I was amazed. Ill always have to take them back to the professionals at some point but its nice to know if something random happens I can sharpen a blade myself and have it going in no time.

 

[pippip]

Update - we're now running with our knives sharpened at a 24 degree angle, and the results are astounding. Virtually no spine chipping or tearing to be found.

I know there's been a few other threads about this in the past, so maybe this will help someone else.

Let us know how they wear with new angle compared to old

 

[Pennypicher]

Usually the steeper the blade the quicker it dulls but if thats what works you deal with it.