Hammer out bevels in San Mai

[Greenberg Woods]

Hey guys, im getting back into some forging before i leave for college, and im getting some blue and white san mai billets "thank you phorizt," and i had a few questions about hammering out bevels, both in general and with san mai

so here goes

Keeping the blade straight: Yes, i learned about pre curving the blade to help keep the bevels straight, but how do you tell how much? I know some of it is just intuition, but is there a general rule of thumb? For every inch the bevel is brought out the spine curves X degrees from the normal?

Keeping the blade hot: Obviously you dont want to hit cold steel, especially blade stock, and with thin bevels the steel cools even more quickly. I have seen some smiths pick up the stock between every blow, while others dont. What are your feelings on this?

San mai bevels: As i said, im getting some billets that are blue and white cores with low carbon sheathing. I am reciving them around 1.4 inches wide, but i need at least 2 for my chef knives. Should i profile then bevel? Or the other way around?

Will the fact that the outside will move more easily than the core, given the massive difference in carbon content, effect the process? How can i compensate?

Thanks a bunch your time guys!

 

[Bill Burke]

you can work the distal taper in as you form the bevels to help control the curving. most importantly is to not let the curve get away from you then try and straighten all at once or you will almost certainly mess up.

 

[Stacy E. Apelt - Bladesmith]

The number one thing to keep in mind when working san-mai is to keep the core centered. Regularly grind the edge smooth on 120 grit and dip in the FC tank. Check the black line and adjust as needed. Once it gets too far off center, the final blade will be very different from side to side. Some wobble and difference is inevitable, but minimize it as much as possible in forging.

I prefer to grind in the distal taper, working from side to side and dipping in FC until the core starts showing on both sides at the tip. I then fine tune the core placement in the taper and leave just about 1/4" of core showing on both sides. The core should now be centered along the edge fairly well if it was right to start with. Watch the core at the edge as you grind the bevels and adjust as needed before it is too late. Grind the edge and dip in FC often. Done in this order, the san-mai should end up even on bother sides....more or less.