Yesterday went so smooth that we were able to really get some of the very critical tasked out of the way. Of course I will explain those in a bit more detail later.
Below we started the rough grinding. You start we a very coarse 2"x72" 60 grit belt, you do all your rough work and grind to the parallel we spoke of in the earlier post. The key is to get both sides as even as possible. If one side is different then the other it could cause the blade to warp in heat treat.
Constantly checking and measuring ensures that you get as close to perfect as possible. As you can see in this picture the the contact (Grinding wheel) is very small. I have contact wheels from 2" to 14" the larger the wheel the flatter the hollow grind will be. In this case I choose a 6" wheel which will produce a very deep hollow grind.
Having some fun and grinding the blade with my eyes closed, please don't try this at home.....ha ha
All the holes are polished with scraps of belts, so they have a nice smooth finish.
After taking measurements and satisfied that things look good and ready for heat treat. We decided to do just that since we had time to get it done. I like to finish my grinding after heat treat as the steel responds much better, its much harder and the grinds are nice and crisp.
Before heat treat we decided to take nice group shot of bad ass things
The Heat Treat Station
The knives are completely cleaned of any residue, then placed in the kiln edge up. Close the door, turn it on and it heats up to 1500 degrees. The first cycle is called "Normalizing" what happens is the knives are heated to 1500 degrees but they do not get quench in oil, they are removed and allowed to cool. What happens is it refines the grains in the steel you can do this several times before you do the final hardening quench. So in a nutshell it produces a better grain structure and stronger knife.
I opened the door for a quick view of the "Heat Miser" at work.
The blades removed from the normalizing stage and allowed to cool, this also gives you a chance to check and ensure they are straight and straight they are.
Back in the oven edge up, back up to 1500 degrees for 8 minutes. With fire proof gloves and metal tongs the first blade is grabbed at 6 minutes and plunged into the quench oil. The quench oil takes the blades from 1500 degrees down to 800 to 900 degrees in about a minute, in two minutes you can handle them with your bare hands.
At this point you have a very small window to check for any warping that may occurred, in the picture abouve you see a press I carefully use that to make minor corrections. To much pressure and the blade with snap......and yes I have snapped a few and it really sucks.
The blades after the quench, they have a soul, they are hard and ready to tempered.
The blades at this point are very hard....brittle would be a good term. If left in this state they would break under hard use or even dropped on the floor. So they go through whats called a "Temper cycle. Which consist of 400 degrees for one hour two times.
I check them with whats called a "Rockwell Tester" very expensive devise but it's worth every penny. The rockwell tester has a diamond that penetrates the steel via a dial it tells you how hard the steel is. In this case it read Hardness Rockwell "C" scale or HRc 58-59
Stay tuned for more action