Die grinder “scraping”

[AndySomogyi]

I’ve been experimenting “scraping” different metals with a die grinder, metals where you can’t use a scraper. I’m interested in building new equipment.

This is a scrap chunk of cast stainless steel.

I’m experimenting with different techniques of holding the grinder. So far, best I’ve come up with is a 3” finer grit cut off wheel, where I smooth the edge first on a silicon carbide bench grinder. I’ve also tried sanding disks and a cut off wheel works better in that it produces more uniform scrape marks. With a bit of practice, I’ve gotten each individual grind mark to about 0.0002 depth.

It requires a LOT of concentration, and being extremely delicate. I had to feather the air so the disk isn’t spinning all that fast.

This part is after a hour or so of experimenting, started with a rough saw chunk, get it roughly flat with an angle grinder then switch to die grinder. I’d like to be able to get to about 40 PPI, not quite there yet.

Oddly enough the hardest thing I’m finding is seeing the damned blue. I’m using Permatex Prussian blue and If I lay it down thinner, it’s so faint I can’t see anything, but thicker and it smears the whole thing. Really need a better ink. IDK, maybe it’s the lighting??? Or that I’m trying to ink stainless?

Anyways, what I’ve found is it requires an extremely light touch, just dance over the spots. Once I get a repeatable technique, I might make a video.

 

[Nutfarmer]

The canode inks will show up better. A good carbide scraper will cut anything I have ever wanted to scrape. Never thought of trying a die grinder. I guess what ever works. Let us know how things turn out.

 

[Bob Korves]

A hand or power scraper can take off a tenth or two easily and consistently after some training and practice. Having not tried a die grinder for the job, my guess is that it would be more difficult to get the depth of cut you want consistently, and it seems to me that the divots would be easy to make like divots when using one. But, practice makes perfect. I would like to see some careful "scraping" done with a die grinder and check it out with a tenths indicator for depth, to see just how consistent it is.

 

[benmychree]

Using a different color for a background can make spots easier to see; use a very light application of canode yellow, and use a dark canode color for spotting. Prussian blue is the least best for that sort of work.

 

[AndySomogyi]

A hand or power scraper can take off a tenth or two easily and consistently after some training and practice. Having not tried a die grinder for the job, my guess is that it would be more difficult to get the depth of cut you want consistently, and it seems to me that the divots would be easy to make like divots when using one. But, practice makes perfect. I would like to see some careful "scraping" done with a die grinder and check it out with a tenths indicator for depth, to see just how consistent it is.

I’m getting about 1-3 tenths depth per cut, but I did have to work at dressing the wheel so it’s very smooth.

Also have to feather the rpm a lot, and be very deliberate and careful with cuts.

It’s a lot like using a scalpel, you have to be careful, definitely can’t rock and roll like I’ve seen a lot of power scraper users go at it.

 

[AndySomogyi]

The canode inks will show up better. A good carbide scraper will cut anything I have ever wanted to scrape. Never thought of trying a die grinder. I guess what ever works. Let us know how things turn out.

Many materials, especially stainless work harden, and can’t really use the standard really high negative rake scraper blades. I haven’t tried it, but I understand carbide scrapers won’t work on hardened steels.

But yeah, I’m an engineer, and in my world, only thing that matters is if it works or not. If it’s flat, and surface roughness is within spec, that’s what matters.

I’ll have to try to get ahold of that Cannode.

 

[Jeff.64]

I think you might find this interesting.

While looking for the above, I found these.

 

[AndySomogyi]

I think you might find this interesting.

While looking for the above, I found these.

Thanks, I’ve seen the way grinding one, but the tool steel one is new to me.

I’m using A LOT lower rpm than them, I rarely make sparks.

I’ll have to measure the difference in cuts of high vs low speed.

A Dremel might also work, I’ll have to try that too and report how it compares to a cut off wheel.

 

[Ulma Doctor]

The reference surface will wear at an accelerated rate due to the introduction of grit from the grinding wheel if great care is not taken .

 

[AndySomogyi]

The reference surface will wear at an accelerated rate due to the introduction of grit from the grinding wheel if great care is not taken .

Hmm, not sure...

Silicon carbide won't really bond with ferrous metals, but I'll have to take a sample into work and give it a look under the electron microscope.