Hi Swede and others.
Your point about heat traveling to the thinnest cross section is very true.
Any time a graver shows any blue heat color from the grinder, watch out.
You can expect some sudden and major point failures and the disastrous slip that usually accompanies this.
When hogging off excess metal on a bench grinder, expect to spend as much time with the blade in the cooling water as you spend with it in the short contacts with the wheel.
Because the engraving blanks we use have a very small cross sectional area to begin with, they overheat extremely quickly.
Do not try to move the graver from the wheel to the water without interim cooling.
Before you can reach the water, the heat will move from the body of the graver and concentrate in the thinner section towards the tip you are shaping and overheat it.
To avoid this problem have a WET PAPER towel in your hand and draw the blade back into it while moving it quickly to the water.
ALLWAYS use paper, NEVER CLOTH around a grinding wheel to avoid the wheel from grabbing it and dragging your hand into the wheel. NEVER wear GLOVES.
Cool the blade fully before returning it to the wheel for another short grinding session.
As the blade gets thinner it is necessary to use very short contact time with the wheel and even more time in the coolant.
Using a slow turning tool like the Power Hone with a coarse 100 grit diamond lap may take slightly longer.
That’s debatable, but it does avoid heat problems for sure as Andrew and Scott suggest.
Please excuse me, I know this is all “old hat” to the machinists and established engravers but it might be some help to our newer friends.
Txtwang, also pardon me for butting into your original post.
John B.
Your point about heat traveling to the thinnest cross section is very true.
Any time a graver shows any blue heat color from the grinder, watch out.
You can expect some sudden and major point failures and the disastrous slip that usually accompanies this.
When hogging off excess metal on a bench grinder, expect to spend as much time with the blade in the cooling water as you spend with it in the short contacts with the wheel.
Because the engraving blanks we use have a very small cross sectional area to begin with, they overheat extremely quickly.
Do not try to move the graver from the wheel to the water without interim cooling.
Before you can reach the water, the heat will move from the body of the graver and concentrate in the thinner section towards the tip you are shaping and overheat it.
To avoid this problem have a WET PAPER towel in your hand and draw the blade back into it while moving it quickly to the water.
ALLWAYS use paper, NEVER CLOTH around a grinding wheel to avoid the wheel from grabbing it and dragging your hand into the wheel. NEVER wear GLOVES.
Cool the blade fully before returning it to the wheel for another short grinding session.
As the blade gets thinner it is necessary to use very short contact time with the wheel and even more time in the coolant.
Using a slow turning tool like the Power Hone with a coarse 100 grit diamond lap may take slightly longer.
That’s debatable, but it does avoid heat problems for sure as Andrew and Scott suggest.
Please excuse me, I know this is all “old hat” to the machinists and established engravers but it might be some help to our newer friends.
Txtwang, also pardon me for butting into your original post.
John B.
