Playing with the single bevel...

[SlowBowinMO]

I've been working with single bevels a bit lately, thanks to the work of Dr. Ashby.  

I'm a long time fan of the Grizzly, but you don't have to shoot Grizzlies to benefit from the single bevel.

Here's a Wolverine 160 I converted to a true single bevel with a file.  I've got several of these in my quiver this year.  Since the Wolverine is not a laminated head, it's very easy to convert to true single bevel.  I made mine left bevel since I shoot mostly left helical feathers.  I only lost 1/16" of cutting diameter and 15 grains  of weight.

   

I added a Grizzly tip as I do with almost all my heads.  They spin in my broadhead target just like a Grizzly, but to the left.

[Jaeger]

Have you perforated anything with it yet?

[SlowBowinMO]

Here's a Magnus 1 that I converted, also left bevel.  These are a laminated head, and I find it easier to modify them to what is best described as a "3/4 single bevel".

   


If you felt so inclined you could take them all the way to full single, but a 3/4 conversion is pretty easy to do.  I only lose 1/8" cutting diameter on these, and they still spin to the left in the target, although not quite as quickly.  I would have to believe I'm getting at least some of the benefit of the single bevel even with the 3/4 conversion.

[OzarkRamblr]

I did the same thing with the last batch of 190 Ribteks I got.

They are as dull as can be when delivered but they do have a slight grind on the blade. I was wondering if I'd get the same benefit by sharpening like a Grizzly so I gave it a try. I put a right hand bevel on them & they seem to penetrate really well. Unfortunately I havn't gotten the chance to test them real world yet.

[SlowBowinMO]

Jaeger, no such luck!  I've had a couple of opportunities I've failed to make good on.  

[Jaeger]

Ok, I'm guilty of not keeping up with Ashby's latest work. I've kind of glazed over this single bevel stuff.
Both edges are sharpened, correct? But only on 1 side. Hence the right hand/left hand bevel. Until just now for some reason I thought only 1 edge of the broadhead was sharpened.

[Jaeger]

I just went and actually read some of this stuff. Some days I'm just not too bright!

I just ordered some Grizzlys and adapters from you. I'll try to put them to work in the late season.

[SlowBowinMO]

Yep, you've got it.  They're sharpened on both sides but the bevel is on one side, which creates rotation.

I suspect they fly better too as long as they match your fletching, but that's a whole new can of worms!

[Michael Peschek]

I shoot the Magnus I broadhead and was thinking of trying out the single bevel. What do you mean by a 3/4 conversion?

I am also confused of how to achieve the single bevel, you bevel the one side to 25 degrees but how do you sharpen the other side without beveling it?

[SlowBowinMO]

By 3/4 bevel I mean I've not converted it all the way down.  The Magnus I and most traditional heads these days are triple laminated in the tip.  That creates a lot of strength, but it also creates a significant bevel in that area.  To take all of that off would require a lot of file work and would significantly alter the head I think.

To get the 3/4, I simply file one side until I've achieved a single bevel on the trailing rear portion of the head.  If you look at the picture closely, you can still see some of the bevel on the off side remaining on the laminated tip...but it's significantly reduced.  That's why I'm referring to it as a 3/4 for lack of a better term.  It still creates spin just like a true single bevel (like the Grizzly or the Wolverine pictured above) but not quite as much.

All I'm doing to create this is clamping the head in a vise and filing one side, in this case the left side to match left wing fletching, until I have achieved the single bevel on the rear.  Then I flip the head over and repeat.  I finish by carefully putting a small Grizzly tip on so the head will spin true (the process messes with the tip a little) and I'm done.

[Michael Peschek]

Thanks! I played with one when I first saw the report and was wondering what to do about the tip but now it makes sense.

[Sharpster]

SlowBow,
I'm also a huge fan of Dr. Ashby's work. The bowhunting community as a whole owes this man a debt of gratitude that we will never be able to repay.

I'm glad to see that you shortened the tip on the Wolverine. Those are famous for folding over on impact. Nice work!

As for the 3/4 single bevel I'm not sure that you'll get the full advantage of a true single bevel cutting edge like that. I'm sure that the broadhead will rotate as it penatrates but, if you re-read Ed's report on single bevel broadheads you'll notice that the rotation is not the only advantage. There is a second significant advantage that a single bevel has over a double bevel head. Ed calls it "Machanical Advantage" or "MA" and it relates to how easilly the blade is able to slice soft tissue. It took me a while to fully grasp the concept but a single bevel edge is far more likely to slice through the tiny capilaries in soft tissue than a double bevel of the same relative sharpness because of the thinner edge of the single bevel.

A true single bevel blade ground at 25 degrees has a total bevel of 25 degrees but, a double bevel broadhead ground at the same 25 degrees on each side has a total bevel of 50 degrees. The double bevel is a much thicker wedge shape and because of this the double bevel is more likely to permit soft tissue fibers to deflect away from the cutting edge where the narrower single bevel will cleanly slice the same fibers. The result will be more blood on the ground with a true single bevel, all other factors being equal.

I'm not saying your 3/4 single wont perform well, I'm sure it will. I just wanted to point out the other, less talked about advantage of single bevel broadheads. Let us know how your heads do in the real thing.

-Sharps

[SlowBowinMO]

Sharpster I think you're absolutely right.  It is unbelievable how scary sharp they get isn't it?    

I agree I don't think the Magnus is getting the full benefit, but I am able to get the trailing 2/3 of the blade wicked single bevel sharp, and they do rotate some as well, so I'm thinking I have probably at least made an improvement.

I've tried to field test these a little better but unfortunately I've not done my part.  

[oops sorry]

I am new to this so please forgive an ignorant question. Has anyone made broadheads with helical twist blades? Sort of "left wing" arrow BOTH blade and fletch?

[SlowBowinMO]

Oops, there have been/are a few over the years.  They've mostly been replaceable blade type heads like the Kolpin Twister, GKF Deadhead and I believe Rocky is making one also.  The old Serpentine heads and I'm sure some others I'm forgetting go way back as well, but all of those heads are quite a bit different than what I'm talking about above.  None of those heads are single beveled, they create twist by blade alignment which is different altogether.  The Ashby reports can explain the advantages of the single bevel far better than I can.

[Sharpster]

Oh yea, I almost forgot, For those of you who like Steelforce broadheads- They will make single bevel broadheads at your request. No extra charge and only one week of lead time.

I don't have the phone # right here but I'm sure you can find it on their website.

-Sharps