Help with surface grinder wheel selection

It is well known to be difficult to grind soft metals like copper and aluminmum. When doing it commercially they use automatic dressers that dress the wheel constantly. Not something to try at home as a newbie. Soft steels will grind OK, just use a coarser soft wheel with an open structure for less problems with the grinding. Grandpop's wheel suggestions are good for ordinary steels.
 
I've heard that you use a softer wheels for harder metals and harder wheels for softer metals. Is that generally true? EDIT: Nevermind. I see that you posted that up above Bob. :)
 
Last edited:
While .0002-.0005 passes are good for finish work, it depends how big a piece you are grinding and how much material you need to remove. It is not unheard of to take .002-.005 passes when you may have .010-.015 to remove. Just allow time between passes for the material to cool down.

Part of having limited wheel selection means you need to use them differently depending on size of piece and depth of cut. For example, if you want to take a heavy cut, then slow down the l-r table travel speed. That would make the wheel last more like a harder one would. Light finish cuts keep the l-r table travel a little faster to mimic a softer wheel. For reference the hardness is the letter after the grit size (G,H ,I ,J , K, L).
 
While .0002-.0005 passes are good for finish work, it depends how big a piece you are grinding and how much material you need to remove. It is not unheard of to take .002-.005 passes when you may have .010-.015 to remove. Just allow time between passes for the material to cool down.

Part of having limited wheel selection means you need to use them differently depending on size of piece and depth of cut. For example, if you want to take a heavy cut, then slow down the l-r table travel speed. That would make the wheel last more like a harder one would. Light finish cuts keep the l-r table travel a little faster to mimic a softer wheel. For reference the hardness is the letter after the grit size (G,H ,I ,J , K, L).
It makes a lot of sense to use deeper cuts with smaller step overs for removing material. It makes the wheel work like it is supposed to, with rough grinding happening at first contact, gradually decreasing to minimum spark out at the other side of the wheel, which stays nearly pristine. That makes for better surface finishes, less chance of burning the metal, and better control of producing a flat and even surface. Since reading about this concept I have been trying it, with quite good results, at least for a mainly self taught rookie...

However, you still need to be careful to not put heat into the metal faster than it can escape. If you have problems with burn marks and warping, try to do a better job of getting the heat out of the metal. Use wheels that will not hold on to lots of swarf, dress them often, and use flood or mist coolant where it makes sense.
 
Last edited:
It makes the wheel work like it is supposed to, with rough grinding happening at first contact, gradually decreasing to minimum spark out at the other side of the wheel, which stays nearly pristine.

For this reason is it good practice, when shooting for the best finish and size, to only do the grinding in one direction only (feed wise not travel wise) so the trailing edge of the wheel is always "finishing" the grinding passes? This is how I finished up dusting my magnet and it seemed to work well, but I'm not sure if the technique was necessary (but it made sense to me). When I was "roughing" I cut in both directions, then dressed the wheel to finish.

Ted
 
When I was "roughing" I cut in both directions, then dressed the wheel to finish.
You can use both sides of the wheel, but the roughing work damages and loads the wheel with swarf more deeply than you might guess. It will take quite a bit of dressing to get back down to a pristine surface capable of fine finishing on sides that have been used for roughing. I do not find it takes much time or effort to move back to the one side for doing all the work. At least that is what I have been doing lately, and I think it makes a noticeable difference in the results I get. Try it out and see for yourself...

Another issue might be the actual width of the wheel. My surface grinder holds a maximum wheel width of 1/2". If you are using a wider wheel, I think you will be able to have more latitude in technique because the extra wheel width gives more finishing area.
 
Bob, thanks for the info. So, it sounds like you typically use one side only, for both roughing and finishing. I do think this makes sense, especially for those like you and me who only have 1/2" wide wheels.

Thanks,
Ted
 
When I grind the chuck I always start at the front edge (closest to operator) and work my way to the back. Most of my finish grinding is done the same way (f-b). Roughing I will use both sides of the wheel, as it seems like it gets less loaded with 2 wear spots rather than doing it all one way and getting heavily loaded on one side.

We used to grind to ± .00005 (50 millionths) for several production tool details. We did most of the rougher grinding on one direction, but when you got down to those last cuts we always went over the piece front - back, let it cool, cranked the table back to the front and cut same way again without touching the downfeed, let it cool, then crank table back to front again and go over again without touching the downfeed. Just trying to make sure there was absolutely nothing left to remove before going and measuring. Often if you put a pencil line on the part you could take it off with little/no sparks.

In my home shop I don't worry about multiple passes at same setting; one final pass with a sharp wheel is generally good to ± .0001/.0002.
 
When I grind the chuck I always start at the front edge (closest to operator) and work my way to the back. Most of my finish grinding is done the same way (f-b). Roughing I will use both sides of the wheel, as it seems like it gets less loaded with 2 wear spots rather than doing it all one way and getting heavily loaded on one side.

We used to grind to ± .00005 (50 millionths) for several production tool details. We did most of the rougher grinding on one direction, but when you got down to those last cuts we always went over the piece front - back, let it cool, cranked the table back to the front and cut same way again without touching the downfeed, let it cool, then crank table back to front again and go over again without touching the downfeed. Just trying to make sure there was absolutely nothing left to remove before going and measuring. Often if you put a pencil line on the part you could take it off with little/no sparks.

In my home shop I don't worry about multiple passes at same setting; one final pass with a sharp wheel is generally good to ± .0001/.0002.

Did you find there was any difference in finish/size feeding from front to back vs back to front? Physically, there are slightly different forces on the spindle, either pushing into it or pulling away. Or, did you do it for visual reasons so you can see the finish better? Or other reason?

I know the best way is for all us grinding newbies to try different approaches ourselves, on our own machine, but if we can learn something from someone else I'm all for it! :)

Thanks,
Ted
 
I was not worried about the spindle effects, they were usually in good shape. I mostly did the front to back as there was some wear in the machine ways and tables did not move same in each direction; would lift a little bit one way. You could clearly see this with an indicator on the table as you cranked it in and out (especially near the ends of the travels). Most guys just threw up their hands and said couldn't work that tight on that machine. Where I worked during my apprenticeship all 8 of the machines had wear, so was taught that method as a way to get better tolerances out of a worn machine. I always seemed to be able to meet tighter tolerances than most of the others on the worn machines, and that carried over to each shop I worked in.

My home shop Boyar Shultz does definitely have some wear. From the wear patterns on the ways it also looks like it has the classic Boyar Shultz twist in the table (or saddle) issues. With hardened steel liners under the table I am not going to try to scrape it in, I just grind the best I can to try to minimize the issues.

For the 50 millionths work, we had Mitsui roller table machines - VERY sweet! Even though they were about a dozen years old and used full time evry day they had very minimal wear. Not sure it made any difference on them which way I went, just following my standard practice. I REALLY wanted one for my home shop, but just couldn't justify the cost (about 5x-8x the Boyar cost).
 
Back
Top