Brian Dougherty

Stress concentrations are a very real engineering concern, but as you say, it is nearly impossible to make a perfectly sharp inside corner. For knifemakers, the question becomes, "How much of a radius is necessary for a knife to do its job?" I'm a sparkey so I didn't take that many mechanical engineering classes, and the last one I had was darn near 30 years ago. Take the following with a truck-load of salt. The stress concentration factor is a function of the geometry of the joint. The fillet required on a large notch needs to have a larger radius than on a small no

Looking good. If you are really feeling guilty, and need someone to send it to, I'll volunteer

Looking good Rob. Amazingly straight to my eyes! As I visualize (fantasize?) the quench operation on long blades, one thing that seems like it will be difficult is the transition from horizontal to vertical without letting the balde bend under its own weight. I assume you grabbed the tang with some tongs and supported the middle with a stick somehow? How did it go?

Thanks Jerrod. I've come back and read through this a few times with some time in between to digest. I've been tempering 1075 folder springs at 550F. I haven't seen any break (yet) and am now wondering if it is just luck, or if it is because the 1075 I have is clean enough to not fall into the "one step temper embrittlement" trap. The max S is 0.05% and max P is 0.04%, but as you say, the mill probably tries to run below that. What do you think?

Looking good! Thanks for sharing the learning process on the engraving with us.

You're getting all kinds of mileage out of those 20mm shell casings. They certainly bring a neat material and talking point into the knife. The leather decoration is great. I've never thought about going at it with a wood burning iron. I'm assuming the leather was completely dry when you did? In the pics it looks like it might still be damp, but I wouldn't think that would work out well.

Should be a pretty easy "Drop in" replacement for an appropriate PID controller.

My approach is similar. I get things set to where the spring is nearly flush in all 3 positions with a few thou (~0.1mm) extra to allow me to grind everything perfectly flush once the center pin hole is in position. Then I clamp the spring to one liner in position with the blade open. Next I pull the blade off, and measure from the belly edge of the liner to the spring so I can calculate what my new target for this dimension is once I put in the pre-load. Then I slide the tip of the spring towards the belly about 30 thou (~0.75mm) and reclamp it. Once I check that the dimension

One of the tricks is getting the spring flush with the scales in all 3 positions. (Open,Closed, and Half-locked if you do that) I start by fitting the open position so that the others leave the spring a bit proud, and then file/grind away carefully on the tang to tweak the other positions.

cut it up into elbow patches for all your tweed sport coats

Nice. I've used my lathe for a lot of strange things, but never to power a transfer pump I'll have to remember that one...

Hopefully I didn't steer you the wrong way on the temperature Gerhard. Here is a pic that shows one of my springs. You can see how much it is relieved (thinned down) in the area where it flexes. I can say with absolute certainty that if I try to close one without that relief, it will snap the spring. (Yes, I had to learn that lesson twice)

I should look at my notes when I can get back to them to make sure, but I believe I have been tempering the 1075 springs at 550F. (Roughly 290C)

Cool! Go Faye go!

The people around me know that I don't take myself very seriously, and that I'll do just about anything to make others smile. My organization shuts down for the year this afternoon, and I thought this might give our employees a chuckle. (My raging Yoda Christmas sweater and Santa hat today are also having that effect) I tend to unplug every year for a couple of weeks about this time. Before I go dark I wanted to wish a Merry Christmas to those of you who celebrate it, and wish warmth, happiness, and success in your endeavors to those of you who don't. See y'all in