# Die grinder “scraping”



## AndySomogyi (Sep 15, 2020)

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.


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## Nutfarmer (Sep 15, 2020)

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.


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## Bob Korves (Sep 15, 2020)

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.


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## benmychree (Sep 15, 2020)

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.


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## AndySomogyi (Sep 15, 2020)

Bob Korves said:


> 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.


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## AndySomogyi (Sep 16, 2020)

Nutfarmer said:


> 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.


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## Jeff.64 (Sep 16, 2020)

I think you might find this interesting.







While looking for the above, I found these.


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## AndySomogyi (Sep 16, 2020)

Jeff.64 said:


> I think you might find this interesting.
> 
> 
> 
> ...



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.


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## Ulma Doctor (Sep 16, 2020)

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 .


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## AndySomogyi (Sep 16, 2020)

Ulma Doctor said:


> 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.


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## Richard King 2 (Sep 20, 2020)

I have been grinding hardened ways for several years.  I am the one who told Chris German on Practical Mach and he did a vertical mill with hardened ways.  Then he made this one ---->  ttps://www.youtube.com/watch?time_continue=18&v=YXLk0mJOwJM&feature=emb_title

Andy, in My professional opinion.  Leaving those dep gouges look bad to a professional machine builder, machine rebuilder or a machinist.   I also have used a belt sander to grind down worn wide ways so it looks like they were surface ground.   Also use the 2 color like Ben said.  Toss that Permatex away and buy some Dykem High Spot, Carbonnel or Canode.


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## ericc (Sep 21, 2020)

Those "gouges" do not look much more than 0.0001" deep.  This represents a significant improvement over much of what I've seen on Youtube.
,
Often, when someone thinks about (maybe in a fit of anger) taking a grinder to the ways of a lathe, they are dealing with ridges 0.025" deep.  If I read the complaints correctly, this is "25 thousandths".  Can a misstep of 0.0001" ruin something that is already so far off?  Maybe so, because then the carriage could get stuck at the low spot?  But so much material has to be removed that a 0.0001" slip might not be so bad.  I have seen worse stuff on Youtube.  Sometimes, it is just interesting to see something new which kind of works.  It may not be suitable for industry, but it may be intriguing nonetheless.  For example, I got curious and wondered if anybody could do a DCEN TIG weld on aluminum with pure argon.  Not much on Youtube.  So, I tried it out and it worked.  Not well.  Certainly not well enough for industry.  But it was strong, and there were no inclusions.  I'd have appreciated it if someone put this up on Youtube, just to look at for entertainment, not necessarily to build a career out of.


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## AndySomogyi (Sep 29, 2020)

So this was an experiment on my part to determine the feasibility of a technique.

I’m absolutely certain many have used a grinder for scraping, but it’s *not documented* anywhere, and in my background (science), if it’s not documented, it doesn’t exist.

Anyways, never did this before, and on my first try, after about an hour of messing around, the depth of the scratches is about 0.0005” and average surface flatness is about 0.0001. 

Compare that to this disaster. I bought my Grizzly mill USED (another mistake), and the bonehead I got it from removed the way wipers to install a DRO, and all sorts of chips got in the ways and destroyed them. When I bought it, I didn’t know to look for that, I’m not a machinist or machine repairman. 

So used it for few months and decided to take it apart. Basically I was thinking just clean it out and stone the bottom way. Doesn’t need to be perfect, just needs to work.

The bottom of the saddle here is a complete disaster from the factory. It was clearly worked with an angle grinder and it’s out of flat by about 0.015”! Yeah, the big dips here are almost fifteen thousands deep.

So yeah, I think my little hour of just goofing off with a die grinder Is about an order of magnitude better than this disaster.

Anyways, I think I’ll use the die grinder to get this saddle within 0.001 flatness, and give it a finish with my little hand scraper.

Again, this mill doesn’t need to be perfect, just needs to work well enough to make some parts.


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## Eddyde (Sep 29, 2020)

AndySomogyi said:


> So this was an experiment on my part to determine the feasibility of a technique.
> 
> I’m absolutely certain many have used a grinder for scraping, but it’s *not documented* anywhere, and in my background (science), if it’s not documented, it doesn’t exist.
> 
> ...


Andy, I be happy to watch your videos on YouTube "Professional" or not it's all about the journey of learning and making something better than it was.


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## Ianagos (Sep 29, 2020)

Well I’m the guy that made the video on scraping the tool steel. 

I found that my grinder marks were much shallower than a typical scrape mark. I started by using lower rpm but found that the high rpm gave a much smoother surface finish and was still very easy to control.

If I really tried I could get it to within .0001” on the surface.

I did it as an experiment as well and figured I’d document it. I have decided I will not be resurfaceing my ways with this technique but I would consider it on your machine.

My ways are 4” wide and about 30” long x2 só a huge surface area to grind. I just did not want to get into that as once i replace the turcite it will probably be good enough.


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## Richard King 2 (Sep 30, 2020)

I'm not condemning the grinding of ways, I have been grinding ways for 45 or so years.  In soft ways to get them close and then scrape them,  I did a 100" Blanchard Grinder that was worn .100" and it was easier and cheaper to grind it with a 6" electric angle grinder then it was to rig it out and have it planned.  When I was an apprentice 45 years ago my Dad rebuilt a 6" Lucas Boring Bar Machine that had hardened bed ways 12" W x 15' L and we used belt sanders to sand or grind the ways using emery cloth belts for the same reasons.  I helped another rebuilder in Richmond VA.  We used a  6" electric angle grinders on 8" wide x 10' steel ways on a 500 ton extrusion press that was worn 5/16"  The press made aluminum windows and they used carbon to hold the semi molten ingots and it acted like lapping compound with the grease lubrication.  There was 4 of us grinding over the Thanksgiving holiday and we wore out 2 grinders, we worked 18 hour days 2 guys inside the machine for an hour and then switched, as one group ground the other group rested. 

I told Chris German (CG Precision)  and the readers on  PM forum 6 years ago these stories and one when I taught a scraping class at Gloyes Gear https://www.cloyes.com/tech-center/ down in Paris, Arkansas that had a hardened bed slant bed lathe that was in the center of a 100 machine factory and they would have had to shut down production to move the machine and send it to be ground down at Commerce Grinding in Dallas TX.  So I showed them how to use 2" snap in grinding disks on a air angle grinder.  Instead of scraping we hand ground it.   I would bet that people watch CG Precision on You Tube  after he learned the technique from me where  Chris German grinds a hardened bed of a small vertical mill. 




What we did was use a 60 grit disk to get it roughed in and progressively finer grinding disks and a final step of using a cast iron lap plate we made out of a 1" x 2" x 4" with diamond milled shapes in it and diamond lapping compound until it looked like a new as if it had been ground.   So as I say I'm not debating hand grinding ways should not be done.  What I mentioned in my other post was the appearance.  If someone wants to let the ground ways look bad with scratches as seen in the photo's so be it.  I like to teach in my professional opinion, to make it look like it was done on a way grinder or surface grinder or a scraped surface as Chris German shows.


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