Precision Grinding Machines

[TomB]

Is there a seperate thread on grinding machines? Not bench type units but the more complex surface, center or centerless grinding machines. Has anyone seen small scale home shop versions of any of these type machines? Has anyone considered home building machines for any of these operations?

My interest is mostly in center or centerless processes as I would like to be able to precison grind spools for hydraulic control valves. (Spools are typically hard while cylinders are soft.) Typical tolerances on diameter is in the .0002 inch range, but tighter is better.

Tom

[Andre' B]

I use one of these on a surface grinder.
http://www.unisonemail.com/pdf/dedtruunit.pdf
Handy for little parts.

[RICHARD ZASTROW]

Andre' B beat me to the Dedtru Unison. Also, you might look into a bit larger unit, Royal Master. A few used machines are available on line.

Dick Z

[TomB]

Thanks for the quick replies. I looked carefully at the Unison webpage and I’m not quite sure how those attachments work. Since they are for centerless grinding on a surface grinder and that requires ‘pinching’ the stock between two grinding wheels it looks to me like they are providing the feed grinder and depending upon the wheel in the surface grinder for the main cut. (That makes sense and it is why I asked about the three type grinders as a set. I was actually thinking that it would be possible to mount something like the Unison attachment so that it worked in conjunction with the left or right edge of a surface grinder wheel or use an attachment like a very small ‘lathe’ to spin the stock against the wheel while the grinder table moved the ‘lathe-like’ stock holder in the in-and-out direction.)

However, I’m not sure how the Unison attachment accomplishes the ‘pinch’. Sort of looks like the Unison attachment must be on the work table and aligned so that the surface grinder wheel comes down toward the feed wheel in the Unison. That would mean the stock rest is to the side of the stock and side thrust generated by the pinch holds the stock against the rest. Is that the case? As the part diameter approaches the final dimension it would be less ‘pinched’ so side thrust would tend toward zero. What else holds the stock against the rest? One configuration I’m imaging, and I’m not sure I’m correct, would mean that continuous feed grinding would put the stock between the wheels and feed it directly toward the support column of the surface grinder. Is that how it works? In centerless grinding there are two critical sets of dimensions: the relationship between the two wheels and the location of the stock rest. The stock rest must be located precisely with respect to the cutting wheel which would be the surface grinder wheel. But the stock rest is part of the Unison attachment so just how does it get located with respect to the surface grinder wheel?

The Royal Master machines look to be overkill for a home shop. I’m thinking in terms of basics, how to push stock consistently against a grinding wheel and they are showing me pictures of computer control displays. I guess I could imagine how one might put CNC control on the feed wheel motion toward or away from the cutting wheel and perhaps CNC control for the stock rest position and maybe even rotational speed control for the wheels, but it seems like it might be harder to write the CNC program than to set up a machine with indicators. What am I missing?

Finally, I’m assuming that because nobody mentioned an old thread that covered these topics this discussion must be new ground. Somehow that surprises me as I guessed that many people would have encountered the need for precise home shop grinding.


Thanks again to both AndreB and DaveZ.

Tom

[Andre' B]

If you go to page 3 of the PDF there is a drawing of the different setups, blow it up to about 400%.
For centerless work there is a second blade to keep the part from falling out.

Mostly I use the spring loaded pressure roller for grinding small diameter punch tips. Also kick the carbide blade off at an angle and dress an angle on the wheel and it works great for repointing dead centers.

Edit:
And the stock rest is on a slide that moves up and out for different part diameters.

[Mcgyver]

Originally Posted by TomB Is there a seperate thread on grinding machines? Not bench type units but the more complex surface, center or centerless grinding machines. Has anyone seen small scale home shop versions of any of these type machines? Has anyone considered home building machines for any of these operations? My interest is mostly in center or centerless processes as I would like to be able to precison grind spools for hydraulic control valves. (Spools are typically hard while cylinders are soft.) Typical tolerances on diameter is in the .0002 inch range, but tighter is better. Tom

if you need a small cylindrical grinder, look for a tool and cutter grinder with a motorized work head. then you'll also have a nice T&CG

Finally, I’m assuming that because nobody mentioned an old thread that covered these topics this discussion must be new ground. Somehow that surprises me as I guessed that many people would have encountered the need for precise home shop grinding.

lots do, me for one, but there's nothing very cnc about it. Look to Practical Machinist and Home Shop Machinist BBS and you will find more home shop grinder content

[PixMan]

Give a call to Doug Holley, owner of Sterling Gun Drill Company in Vermont. I visited there recently and he showed me a perfect machine for your application that he has up for sale....cheap. It's a Harig surface grinder that was converted to to being a dedicated DedTru centerless grinder. Nice condition, very compact and hardly used at all.

http://www.sterlinggundrills.com/

[TomB]

Thanks Pixman. I will followup with Mr. Holley tomorrow. I looked quickly at his web site and immediatily noticed the address. We are located about 30 miles appart and I go through N. Bennington very frequently.

Also thanks to Mcgyver. I've heard of the Practical Machinist and Home Shop Machinist BBS but I've never looked at them. (There is just not enough hours in the day.) However, latter today I will check them out.

Finally thanks to Andre_B. I had not looked in detail at the tiny figures you pointed out. When I did so I realized they do explain several things I was having to assume.

At this point this thread has done what I wanted. Pulled up some good leads to chase down and I'll probably stop posting and go do some more reading.

Tom