Thread: Dremel Technique

One day I lost a beautiful (and rare) 6/8th + W&B special with a killer smile… the dermal picked up traction, went around the spine to the other side and snapped the blade… I guess I should have made one of those “blade rests” everyone talks about… instead one holding it in my hands... nor very smart.
So now I use a small "home built" buffer with lots of torque, medium hard 3" felt wheel, Simichrome polish, 700 RPM (seven hundred), moderate pressure... blade rarely ever gets hot to the touch.

Everyone says overheating is bad. Why? What happens to the metal if it gets too hot?

Just curious.

Originally Posted by JetHed

Everyone says overheating is bad. Why? What happens to the metal if it gets too hot?

Just curious.

well, you can change the temper of the blade...meaning it will get too soft to hold a good edge.
This is a chart that demonstrates...the specifics of course depend on the steel composition.
Temper Colors and Steel Hardness : anvilfire.com

Honestly though, I think 1000rpm on a bench buffer about the same than 5000 on a dremel. What matters isn't rpm, but edge speed for heat buildup and speed of work. Increase the radius/diameter by 2 times, and the diameter increased by 2x. And therefore the edge speed at the same RPM increases by the same multiple.

I have yet to really try a dremel on my razors though...busy trying to learn the art of the straight razor shave...ok...I really haven't sent by razor to be honed yet...but soon.

Originally Posted by MetalAndy

well, you can change the temper of the blade...meaning it will get too soft to hold a good edge.
This is a chart that demonstrates...the specifics of course depend on the steel composition.
Temper Colors and Steel Hardness : anvilfire.com

Honestly though, I think 1000rpm on a bench buffer about the same than 5000 on a dremel. What matters isn't rpm, but edge speed for heat buildup and speed of work. Increase the radius/diameter by 2 times, and the diameter increased by 2x. And therefore the edge speed at the same RPM increases by the same multiple.

I have yet to really try a dremel on my razors though...busy trying to learn the art of the straight razor shave...ok...I really haven't sent by razor to be honed yet...but soon.

Personally I find it hard to believe that you could (or at least would) heat a razor to a point where you'd change its temper while holding it in your hand against a cloth wheel. The steel would have to be glowing cherry red and the wheel would be charring and smoking if not in flames. Having said that, I will say there is a safety issue when the steel is too hot to maintain a firm grip. Also the thin edge will certainly deform because of thermal expansion while the thicker center will not (certainly not as much) and this will place much stress into the blade and can cause cracks to propogate.

Regarding the calculation of size/RPM differences between bench wheels and Dremel type things, calculate circumference by multlying the diameter of the wheel by PI (3.14). An eight inch wheel has a circumference of 25.12 inches. That means for each revolution, 25 inches of wheel are passing on your razor. At Lynns bench with 1800 RPM the razor is under 45,216 inches of wheel/minute. That is dragging the wheel along your razor at about 43 miles per hour. For a 1 inch wheel on the Dremel, that is 3.14 inches per revolution, times 6000 rpm is 18,840 inches of wheel/minute. This means the Dremel is putting the wheel along your steel at only about 18 mph. Who'd a thunk it?

If the razor gets whipped out of your hand at 43 mph, it is going to do damage to something, hopefully it won't be you.

Brad

My dremel technique:

Step #1: Don my lucky Spiderman PJs

Step #2: Always wear goggles

Step #3: Whip dremel out of it's sheath and hold it above my head (at 3,000RPM) whilst yelling "In the end there can be only one!" and then lay hands upon the nearest Double Arrow and hack a few thumbnotches in it

Thanks Brad for doing the math. Quite interesting.

@Brad: Actually, steel transfers heat pretty slowly. If you hold a dremel on the blade while holding the tang, you can heat it beyond temper heat before the tang even gets warm.

I just use a dremel with small felt wheels @7000 rpm and chromium oxide buffing compound. I know an 8" buffer wheel would be much faster, but them things scare me to death.

Originally Posted by Bruno

@Brad: Actually, steel transfers heat pretty slowly. If you hold a dremel on the blade while holding the tang, you can heat it beyond temper heat before the tang even gets warm.

Oh sure but try that with an ancient Egyptian copper razor and see how long you can hold onto it.