Double bit geometry

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Square_peg

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I'm thinking about changing the bit geometry of this 4# Stiletto double bit. I think I'd like it to be a little straighter, to have a little less curve to it. I've seen DB's with even more curve than this and others that were much straighter.

How does the bit geometry effect the way the axe cuts? Is a straighter or rounder bit advantageous for certain applications or types of wood? I'm guessing this is a Young's Pattern axe. I think the tips have been worn down and filed back, changing the geometry.

Would you reshape this head if it was yours? What shape do you prefer in a DB? Why?

Stiletto6.jpg
 
Straight bits don't bite as deep, yet chop faster through logs due to the more even and level cut--you don't make tons of fine chips that way, just big ones, as the whole edge bites across the plane of the log. Hence the rolling cut used by competition cutters with their heavily curved racing axes--it completes the line of the cut in the same way as regular chopping with a straight-edged bit does. Just be aware that that's a lot of steel to remove, which will affect the angle at which you're able to sharpen the bit without hitting the eye.
 
The perpendicular lines are just reference points. They demonstrate that the upper tips have been worn/filed back short of the lower tips. I'm thinking about taking the edge back about 1/3 of the way to the reference lines and maybe aligning the tips.
 
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Hey Pegs, I frequently straighten up my bits. My favorite doubles are my Kelly Perfect western patterns. They have very straight bits and chop like beasts. I also like that the toes are not swept up like on a swamper because they are not as vulnerable to damage.
 
Hi Peg...Your first pic had me a bit worried. Two things I dislike are: Filing a lot of steel away from a used axe, and an axe with a flat face. Your second pic seems more acceptable to me. If she were mine I would take any gaps or chips out of the face then take a little from the cheeks (if necessary).

Any axe will easily cut through wood that is smaller than the width of the axe face, but I love the way a round face
'leads in' to a big log.

regards...Frank
 
Thanks for the input guys. Weighing in at 4# this is a 'big log' axe. I guess I need to mull this over a bit before I proceed. It's interesting to read the different perspectives of respected axe men.

The cheeks on this one are a little fat to begin with so I'm probably going to doing some filing on those anyway. I think I should try to retain much of the mass of this axe since I already have a lighter 3.5# DB and a cruiser which I'm guessing is about 2.5#.
 
I usually take a sharpie and shade all of the area of the edge that I want to remove. Then I stare at it awhile and make any adjustments. I try not to get too extreme with it.
 
That's a good attitude Matt. I often see axes in 'second hand' shops or clearing sales that have had the guts ground out of them. I suppose the seller thinks that potential buyers see them as being sharp. Never met a man who can pick up filings from the work-shop floor and stick them back on an axe.

regards...Frank.
 
Frank-New Zealand said:
That's a good attitude Matt. I often see axes in 'second hand' shops or clearing sales that have had the guts ground out of them. I suppose the seller thinks that potential buyers see them as being sharp. Never met a man who can pick up filings from the work-shop floor and stick them back on an axe.

regards...Frank.
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Wiser words rarely spoken! :thumbup:
 
mattyak said:
....... similar to the board stretcher that the new guy on the crew was sent to find in the tool van.
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It's usually kept next to the sky hook. Check there.

But back on topic, to me this axe looks funny with the toe being short of the heel. It makes it look worn out. The toes have obviously been worn or chipped and ground back. It would look fresher to me if the heel was taken back at least perpendicular to the toe and if the radius of the bit were a little larger.

Also, if I do grind it back do you think the resulting edge would be softer than the original edge was? Assume that I never overheat the edge in the grinding/shaping process. Will the metal 1/4" back from the original edge be less hard than the original edge was? Should I re-harden and temper the edge if I do this?
 
Peg, I'm glad you asked this question. I've been holding off on reshaping more than moderately on a couple of heads that I have. Im curious as to how much reshaping an axe can handle before it is detrimental to the temper.

I once watched a new guy spend 20 min digging through that damn van. Ha. Skyhook! Boardstretcher! HaHa
 
Same Peg...I often come across axes with heel or toe worn unevenly. It never looks right. I have often wondered if it is steel hardness or user sharpening. More likely user sharpening. Just like some guys can never get their saw chains equal.

That DB of yours doesn't look too bad though. In fact it looks pretty good.

regards...Frank
 
mattyak said:
I'm curious as to how much reshaping an axe can handle before it is detrimental to the temper.
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That's what I wonder about, too. Judging by the dark line on my axe the temper appears to go quite a ways past the edge. But to be scientific a fellow would need to do a Rockwell test on the original edge and a second test on the edge once it has been ground back. I suppose I could do a file test on the existing edge and a 2nd file test after filing the edge back. Then I'd have an idea whether or not it needed re-hardening. I wish I had a Rockwell tester.
frown.gif
 
We need Kentucky to jump in on this. Here's my VERY cloudy understanding of what I've read:

Axes will generally be forged from a "deep hardening" or "medium hardening" steel. So the hardening should have reached all the way through working section of your bit with little variation in hardness assuming the HT was done well.

Hopefully, Kentucky will see this and jump in to correct or clarify what I just said...
 
I've started reshaping this axe and cleaning it up a bit. First thing I discovered is that the metal turns very hard just at the temper line. I took a file to the top edge of the axe to clean up some hammer marks. As soon as I got away from the eye and into the temper I could feel the difference right away. So I know that this thing is hard all the way back to the end of the temper line. And it's damn hard. Only my freshest highest quality files will cut it.

I did the reshaping of the bit with a grinder - don't freak out - I didn't effect the temper. I'm careful. I used a low speed with a coarse wheel and kept my finger on the edge close to the wheel as a constant test for heat. I dipped it as soon as it got uncomfortably hot. Never saw temper colors come up.

Stiletto2.jpg


Once the bit was reshaped I switched to files to thin the edge and cheeks. WHAT A BUGGER! This thing is hard as hell! My Heller Multi-Kut files which eat other axes could just barely cut this thing. Any cheap or slightly worn files are useless on it.

If the stamp on this axe was fresher I'd make it a wall hanger. But with the stamp pitted I'm figuring this for a user. And it will be a helluva user.

Stiletto4_001.jpg


I've also done some work on the haft. I found a pretty decent DB haft at a local hardware store. It has a nice straight vertical grain. I had to thin it a bit with a spoke shave and I've turned it into an octagon. I'll post pics once it's assembled.
 
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