Drum diameter for serrations

[CDH]

Tie breaker time, help me out guys.

Background: I have a guy that wants me to put in serrations for the first 2" or so on a fillet knife. The knife is already finished...so I'm not about to wrap sandpaper around a dowel and put them in by hand. I'm not that masochistic! As much as I dislike serrated blades, for fish cleaning it is actually pretty useful and I might just have to offer it as a standard eventually...people keep asking for it. I have said no many times, but this will be the 4th blade this guy has bought from me, so it's hard to turn him away!

So I have my Dremel and a hopefully steady enough hand. I have sanding drums for it that measure about .35" OD and I have chain saw sharpening grinder bits of various (5/32" comes to mind) diameters.

I tested both on the back of an old hacksaw blade and I could make an argument for either. The smaller grooves are a heck of a lot harder to keep evenly spaced but seem to bite better and would seem likely to saw through the spine of a fish better.

What size do you use/recommend, bigger or smaller???

 

[bhyde]

From a customer standpoint, I personally would prefer the smaller serrations. Probably more useful in the long run.
As a machinist myself, I would say to make the serrations fit the blade and the style if that makes sense. For example, I find myself using the machine to break the edges of the parts I build with a 45deg cutter. If the part is smaller, I will generally only break the edge .005 and graduate as the size of the part grows. If the part fits in a 1.5 in cube, it gets .005.. 4 in cube .01....after that, .015 max unless otherwise specified.
Now the fillet knife typically does intricate work, so I would think that smaller serrations would be a great fit


Bill

 

[lukus]

I vote for the smaller also.

Might be easier to strap the dremel down and move the knife. Pipe clamps or something similar, just fix the dremel down tight. Then you've got both hands to hold the blade. Even better, clamp a block of wood down at the end of the handle so the knife can't move back, then move the block up the distance of the serrations for each new serration.

 

[artmichalek]

I vote for the smaller also.

Might be easier to strap the dremel down and move the knife. Pipe clamps or something similar, just fix the dremel down tight. Then you've got both hands to hold the blade. Even better, clamp a block of wood down at the end of the handle so the knife can't move back, then move the block up the distance of the serrations for each new serration.

Even better would be to strap the dremel up vertically like a drill press over a smooth surface. Clamp the blade into a small drill press vise between a pair of angled wood blocks. Lay out the serration spacing with a fine tipped felt pen on the back side of the blade, then just slide the vise around to bring the blade up to the drum.

 

[kungfumo]

Like the above poster said I would chuck the bit up in the drill press real slow and put the blade in a macinest vice and run the drill press down on the blade, that would make a nice and even seration