Surface Grinding

A small step over helps a lot for a good surface finish and a flat surface. It makes almost all the metal removal take place on the leading corner of the wheel, with the rest of the wheel width evening it up and sparking it out while staying mostly clean and pristine.
 
Unless someone has changed out the handwheel for the vertical feed it should have graduations of .0005". I have the exact same machine and it's fully capable of grinding to the tolerance you're looking for. In fact one of the first jobs I did when I purchased the machine was grind some shims for a differential.
One thing to check for before trusting the scale on the down feed is the gear ratio. When I first got my machine I was having trouble hitting tolerances. Everything seemed to be thicker than the scale indicated That's when I found that along the way someone had changed the bevel gear ratio on the spindle elevation. The machine originally came with a 3:1 ratio, which coincides nicely with the graduations on the handle. Mine has a 4:1 ratio which equates to .00041 for each graduation on the wheel. Here are a couple pictures of my machine.



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You are correct. The resolution is 0.0005" for the vertical axis. Also about the 4:1 gear ratio. Mine is 3:1 as required. when I first got the machine I rebuilt it with parts from Mcmaster. Mcmaster had almost everything. It seams this machine is put together with all standard off the shelf hardware. I got both the rack and pinion from Mcmaster and all the wheel handles and new oil cups. I had to find the spindle bearings elsewhere. Mcmaster also had bevel gears but not in 3:1 ratio. They did have a set that I could have used but I believe it was either 4:1 or 2:1

IMG_20190320_210542349.jpg
 
The surface plate concept seems to be the way to go. I tried going this with a mag base covered with a steel plate over the magnet but the plate was not ground smooth enough and the setup was just too unstable to get repeatable results. Grizzly has small 6" x 8" granite plate for ~$25.00. I think I may pick one up.

IMG_20190320_194905386.jpg
 
So results of my trials today with the practice washer were successful after about 3 tries. My last 2 attempts were withing 0.0001" on average. Biggest concern is the out off parallel condition of 0.0002" The attached file shows several attempts to get to a target value. Target values are highlighted in green. Error from target is highlighted in yellow. During the second trial I ran dry on coolant and it did take a toll on the results. After that things did turn out well. I did find that I could remove the washer from the chuck, measure clean off the chuck and washer good and continue to grind as if I never removed the part. I couldn't possibly do that prior to grinding the chuck.
 

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  • Grinding trials.xls
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Mercedes, for first time grinding, you got terrific results. As your skills improve, and when you are familiar with the quirks of the machine, you will do better. Good grinder hands take about 10 years to reach their potential. It's not all in the machine.
 
Dabbler said:
Mercedes, for first time grinding, you got terrific results. As your skills improve, and when you are familiar with the quirks of the machine, you will do better. Good grinder hands take about 10 years to reach their potential. It's not all in the machine.
Click to expand...

Thanks Dabbler. I had the grinder for about 10 years now but this was the first time I had to grind to a real dimension. What I lack in experience I make up for in time and patience. So far it only takes me about 3 hours to grind a washer.
 
This weekend I finally did the job on the real shim. Shim was about 2 times the diameter and 1/2 the thickness but I still managed 0.00015". Thank you to everyone.
 
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