Can buffing or polishing overheat blade?

[MTHall720]

When I use my Dremel at 30,000 RPMs to polish a blade either using felt, cotton, or even a rubber material to which I usually apply green compound the blade gets hot. Any chance it could have any detrimental effect on the heat treat of the metal? Most of mine are CPM 154, D2, 1095, S30v, and AUS 6 or 8.
Thanks for any input

 

[Obsessed with Edges]

With a Dremel, I wouldn't worry too much about the blade, UNLESS you're lingering in only one spot near the edge for a long time. Thin steel at the edge heats up a lot faster. Just keep the wheel moving back/forth across the blade, and keep pressure LIGHT. Maybe touch the blade occasionally, to see how warm it's getting. If it feels kind of hot, just give it a few seconds to cool before another pass. The small contact area between the Dremel wheel and blade is also going to limit how fast the blade heats up.

30k rpm sounds fast, but isn't really all that fast, because the Dremel's wheel is so small. In terms of how much linear abrasive is moving across the blade per minute, it's not much faster than if you were using a bench buffer/grinder with 6" or 8" wheels at their typical speed (3450 rpm or less). See below:

For reference, I crunched the numbers for actual speed, in inches per minute of abrasive material moving across the object being polished. Compared the Dremel with 1" wheel @ 10k/20k/30k rpm, vs. a bench buffer with 6" and 8" wheels, at 1725/3450 rpm. At 30k rpm, the Dremel is only slightly faster than a bench buffer with 8" wheel @ 3450 rpm:

Dremel with 1" wheel (3.14" per revolution):
@ 10k rpm --> 31,400 inches per minute
@ 20k rpm --> 62,800 inches per minute
@ 30k rpm --> 94,200 inches per minute

Bench buffer with 6" wheel (18.85" per revolution):
@ 1725 rpm --> 32,515 inches per minute
@ 3450 rpm --> 65,031 inches per minute

Bench buffer with 8" wheel (25.13" per revolution):
@ 1725 rpm --> 43,354 inches per minute
@ 3450 rpm --> 86,708 inches per minute

Edit:
USE CAUTION if buffing synthetic handle materials like Delrin. That stuff will melt in a heartbeat under a buffing wheel, if you linger for more than a second. I'm betting you already know this, though.

 

[MTHall720]

Thanks very much my friend. I think I may have been lingering too long in one spot at a time and using too much pressure. I have learned the hard way about synthetic handles.

Have a great day

 

[gooeytek]

What about when using a buffing wheel on a bench grinder? I've polished some blades using a 6" buffing wheel with some compound and have gotten good results, but I am concerned that the blade does get quite hot, uncomfortable to the touch sometimes, and I dip it in some water then dry it off and make a few passes again. I'm not messing up the heat treat, am I?

 

[Obsessed with Edges]

What about when using a buffing wheel on a bench grinder? I've polished some blades using a 6" buffing wheel with some compound and have gotten good results, but I am concerned that the blade does get quite hot, uncomfortable to the touch sometimes, and I dip it in some water then dry it off and make a few passes again. I'm not messing up the heat treat, am I?

I don't use a bench grinder/buffer, but it seems like you're handling it OK. Dipping the blade in water periodically is what I see frequently recommended here by the experts who do this often. I doubt you have anything to worry about, regarding overheating the blade. Especially if the blade is only 'uncomfortable to the touch'. To really mess up the heat treat of the blade as a whole, I think you have to go in excess of ~400F degrees with most steels. I'd think that would be a little beyond uncomfortable, if you got it that hot.

The thin steel at the very cutting edge can obviously get very hot, very fast. But, if it's only that thin steel at the edge, that can be sharpened away fairly easily anyway. Sometimes even factory edges are somewhat 'soft' at the edge, likely from a little over-heating during the final buff/burr removal at the factory. The common 'fix' for that is to just re-sharpen the blade a couple or three times, and the edge works back into some healthy and harder steel.

 

[gooeytek]

Cool, thanks for the reassurance Dave. Here's what I did recently to my Rake after I removed the hump from the spine (also cooled the blade down often after every few passes on the grinder). It was a lot of fun, I might do this more often now that I know it's safe:

 

[Bigfattyt]

Pat special attention when you are anywhere near the tip.

At the tip, especially with power tools, you can burn the tip and the rest of the blade will only feel warm.