The bubble jig, whats your angle?

Fred.Rowe

Fred.Rowe

Knifemaker / Craftsman / Service Provider
Joined
May 2, 2004
Messages
6,848
I took some pictures during the grinding process, to show the result of using the different bubbles on the jig.
I use three different bubbles. One gives me an approach angle of 11 degrees.
This is the angle between the belt surface and the blade blank.. I develop the cutting edge using this angle. Once I have the edge straight and true, I move up the blade blank using the 9 degree bubble. I am lessoning the angle, of approach, by two degrees, from 11 to 9. I grind at this angle till I intersect the edge that I produced with the 11 degree bubble. I then change to the 8 degree bubble reducing the angle of approach by one more degree. This moves the grind up the blade towards the spine. When the 8 degree grind intersects the edge, I remove the jig and use the now completely flat blade surface to finish the rough grind. I am now ready for heat treat.

If you have questions, don't hesitate too ask, Fred

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Alarion said:
Never thought of using a bubble level! ;)
Will try it.
Nice mini anvil, BTW. :D
Click to expand...

It takes a bit of effort to align the jig to fit your grinder set up. But once you have it, You can turn out grinds like the most accomplished pro.

Good luck, Fred
 
I'm curious about a part of this jig.

The cotter pin clamp, with the notches in it, that holds the blade is a piece of railroad/track, I believe. What is its correct name and where would I get one? Anyone got one to sell me (not a lot of surplus shops where I live)? I'm assuming it's springy. I'm also curious what the notches are used for, if anything?

Thanks

Syn
 
synthesist said:
I'm curious about a part of this jig.

The cotter pin clamp, with the notches in it, that holds the blade is a piece of railroad/track, I believe. What is its correct name and where would I get one? Anyone got one to sell me (not a lot of surplus shops where I live)? I'm assuming it's springy. I'm also curious what the notches are used for, if anything?

Thanks

Syn
Click to expand...
A friend, who works for CSX picked this one up for me. It is a large cotter key.
What the RXR term is I do not know.
The piece was too stiff and would not pull together, when the bolt was tightened. To relieve some of the stiffness I cut the slots with a right angle grinder. .The piece had been hardened. I kept water on the back as I ground the slots.
You can find more photos of this jig on my web site. Page 4 or 5 in the new knives gallery.

Fred
 
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