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Basic Surface Grinding- What my Son and I used to do a first part.

countryguy

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#1
Most of all- The son and I are new to so many parts of being hobby machinists! He is in School for product design and Mfr. We have some decent CNC skills built up... but that manual surface grinder- , No computers, Dials, no screens = a bit intimidating.

Mostly we just needed some basic instruction and overall equipment how to's. This Vid collection was really well done and got us knowing the basics and using w/ some confidence.
Please note- Upgraded video 2. Titles are similar on 1 and 2.

 
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Bob Korves

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#2
For such a simple machine, I have found that a surface grinder has a long learning curve for doing truly good work with it. It is pretty easy to make lots of sparks, but to make a nice, shiny, and accurate part is not at all trivial. Of course, it might be easier with a brand new top quality machine than with my 1946 Brown & Sharpe that I am still dialing in little by little. Actually, it is not so much the machine as it is the operator... :(
 

rgray

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#3
Don has a more powerful machine than I do. Both mine have 1hp driving the spindle.
So on his "do it fast vid" where he takes .008 at once, that really don't work for me.
I did find his videos very informative though.
 

benmychree

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#5
That .008 pass is quite excessive, cross feed must have been very little and would result in breakdown of the edge of the wheel; on the 12 X 36 Thompson grinder that I had before retiring, with (I think) 5 hp on the spindle, I'd generally take no more than a few thou per pass, although with at least An inch of cross feed. On my present B&S Micromaster, I take no more than a couple of thou per pass, again with perhaps half the width of the wheel in cross feed.
 

Bob Korves

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#6
There are two main methods to surface grinding. The most common one uses a light feed of not more than a few thou, along with a fairly large step over per pass. The other method uses a deep cut with a small step over. The cuts might be .020" deep, but only a few thou step over per pass. The claimed benefit to the second system is that the wheel is mostly cutting on the side, which gets heavily worn, but the opposite side of the wheel does little work, so it tends to retain it's diameter better. That gives flatter results with just one pass across the work.

Edit: That is all book learning. I have only tried the first system, so far...
 

benmychree

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#7
There are two main methods to surface grinding. The most common one uses a light feed of not more than a few thou, along with a fairly large step over per pass. The other method uses a deep cut with a small step over. The cuts might be .020" deep, but only a few thou step over per pass. The claimed benefit to the second system is that the wheel is mostly cutting on the side, which gets heavily worn, but the opposite side of the wheel does little work, so it tends to retain it's diameter better. That gives flatter results with just one pass across the work.

Edit: That is all book learning. I have only tried the first system, so far...
I'd think that method #2 would generate more local heat, causing distortion; I guess I never read THAT book!
 

4gsr

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#8
Taking a plunge cuts more than a couple of thousandths could be detrimental to the spindle bearings. Especially if the wheel is not redressed often when plunge grinding.
 

countryguy

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#9
Guys, Thanks so much for all the comments back. We have the bridgeport 815. 1 HP. Anything over .005 really drags it down too. But, I will say that we were able to make a part that was so flat and smooth that it seems to ring and stick to our flats. (so the kid thinks). I need to read more about ringing. That is really cool!

ps- did you see the comment that when looking thru a gap, a few tens turns the light blue? that is really fun to learn.

Later all.
JJ
 

countryguy

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#10
btw- our Mag chuck is pretty worn. Shallows from about 2" out from the edge which looks new and hardly used. Walker Magnetic. Now I'll need to run a few more test jobs for my own skills, then I will take a run on it.
 

Bob Korves

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#12
btw- our Mag chuck is pretty worn. Shallows from about 2" out from the edge which looks new and hardly used. Walker Magnetic. Now I'll need to run a few more test jobs for my own skills, then I will take a run on it.
It is a tough deal that after you get a surface grinder cleaned up and ready to do to work, the first real job is to grind the chuck, which is a difficult job to do well, and is quite possible to mess it up badly. It took me weeks of studying and reading before gaining enough courage to start the job. I first ground the table flat, it was out quite a bit. Then I ground the bottom of the chuck to get it flat and also to improve the geometry of it a bit. Then the top. I have two mag chucks, and did the smaller (about 5+ by 11+ inches) first. I was able to get it within .0003" over the entire surface, which I am happy with. Then I went on to the 6 x 18" chuck, and after three attempts, the best I have achieved is .001" over the extent of the chuck. I think the bottom of the chuck is also not quite flat and I need to go there again to get a better result without the chuck moving against the table. I have done quite a few small projects with it as it is, and they turned out fine, but I will not be satisfied until is is correct.
 
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4gsr

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#13
Replace 'Anonymous' with 'Bob'.

Sorry Bob, the devil made me do it!

Another thing that helps, is to keep a few different wheel types on hand for the different materials and hardnesses you may need to grind.
I got lucky a few years ago on picking up some Radiac grinding wheels at a heavily discounted price for free. I don't recall the exact grade or wheel type, they have a pinkish color to them. They are a 46 grit, kind of a wheel for most types of grinding. I find it to work good on medium to higher heat treated materials in the 20 to 62 HRC range. But for lower hardness materials, it don't do as good. Still gives a good finish. Just loads the wheel much more. I keep a couple of finer grit wheels for when a much finer finish is needed, too. And I've yet hooked up and used my coolant system on my SG! I'm to the point of doing so.
 
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