Looking for Sanford MG-612 Surface Grinder owners

[kevin]

It did occur to me that the column might be tilted slightly with respect to the ways on the base. I understand that the column should be exactly perpendicular to the crossfeed ways, and the wheel should be parallel to the longitudinal ways, but how do I go about measuring/determining this?

 

[Bob Korves]

It did occur to me that the column might be tilted slightly with respect to the ways on the base. I understand that the column should be exactly perpendicular to the crossfeed ways, and the wheel should be parallel to the longitudinal ways, but how do I go about measuring/determining this?

Start here:
http://www.hobby-machinist.com/threads/connelly-on-machine-tool-reconditioning.41802/
The chapter on surface grinders is the last one, chapter 30, page 482. It is based on, but does not repeat, the previous 29 chapters. You cannot do a truly successful job of getting a machine correct if you do not understand the theory, process, testing, and proving, all done properly and in the correct sequence...

 

[kevin]

Bob - thanks for a great reference; looks like a goldmine of information. I'll definitely be taking a look at it.

Any chance you also have a link to a book on surface grinding?

P.S.

Looks like that book has good information on scraping as well - something I'd like to try some day. So double thanks.

 

[Bob Korves]

Bob - thanks for a great reference; looks like a goldmine of information. I'll definitely be taking a look at it.

Any chance you also have a link to a book on surface grinding?

P.S.

Looks like that book has good information on scraping as well - something I'd like to try some day. So double thanks.

Glad if I might have been helpful, Kevin. Machine Tool Reconditioning is often called the bible of machine rebuilding and scraping. It is becoming dated since it is from 1955, and the illustrations are not so beautiful, but still, there is a ton of useful stuff in there. It is also not quick, easy, and light reading, having been written by a machine tool repairman, not by a seasoned author with strong communication skills. Still, it is highly useful to have as a reference guide. I have read it twice all the way through, and have read several portions multiple times more. I don't know of other literature on fairly modern surface grinder repair and reconditioning. There are some posts in various places on the internet where you can find the opinions of others, like here. This forum is great because it is interactive and people tend to care about each other here. Be careful to vet any information you get with multiple expert sources before trying anything that might cause you more work in the long run, or even ruining a machine.

Sorry, I do not know of a good book or articles on surface grinder operation, sometimes it seems to be a secret community out there. Hobby Machinist is a fine place to ask for advice. Try to vet your sources to those with lots of hands on hands on experience doing varied work. I do not fit into that category...

 

[projectnut]

There are several good books on grinding available. Most cover the fundamentals of multiple types like surface, cylindrical, centerless, and tool and cutter grinding. Unfortunately most are in textbook style and available only in paperback or hard cover versions.

I have this one: https://www.amazon.com/Grinding-Technology-S-F-Krar/dp/0827302088/ref=sr_1_2?s=books&ie=UTF8&qid=1530022181&sr=1-2&refinements=p_27:S.F.+Krar

It has about 45 pages on the basics of surface grinding. It's a good book, but I would look for it at either a public or engineering school library before making a purchase. The prices for these types of books seems to have risen considerably in the last few years. When I bought mine it was at an almost give away price of less than $25.00. I checked a couple online vendors today and most are asking $60.00 to $135.00 for a used copy. The newer versions are going for considerably more.

This is the least expensive 1994 edition I've found:
https://www.ebay.com/itm/Grinding-T...905630&hash=item21373080a3:g:UjsAAOSwmRFaX97Z
I haven't read or purchased it so I can't vouch for its contents

I have attempted to read Connelly's book on Machine Tool Reconditioning on several occasions. It's full of excellent information, but it's also a hard read.

Fortunately I have the inspection tools required for the process. I'm not sure I would have been interested in purchasing my grinder if I also had to purchase all the inspection tools at the same time. Most of my equipment was purchased used over the years from my former employer or local shops. The most expensive part by far would have been to purchase a 24" x 36" surface plate. I was lucky to find a Challenge brand one from a local shop. The plate was originally owned by my employer and sold to the shop when the company closed down it's machine shops. Rather than paying nearly $4,000.00 for a new one I was able to pick it up for what I would consider scrap prices. I have not had it recertified, but it's last certification was in 2016.

 

[projectnut]

I forgot to add in my last post I did get back to the used equipment dealer last weekend. I picked up the hub he had. Unfortunately it was the only one of that size. He did have some smaller ones, but I have no idea what machine they fit.

As for the one I did pick up it isn't identical to the one I have. This one has an ID of .656" on the small end and .998" on the large end. It will slide over the spindle, but doesn't seat back as far as the one that came with the machine.

I was considering ordering a slotted nut for the end of the spindle so I measured the threads. Apparently 1/2-13 left hand thread is a common size. Mine is 9/16-18 left hand. It looks like I'll be making some nuts if I want a spare, or happen to need one in the future.

 

[kevin]

projectnut - my spindle thread is also 9/16-18. I don't know if that is common to all Sanford MGs or not.

 

[kevin]

About books: I'm on a limited budget, so I try to find free-to-download books if at all possible. Our local library is part of Michigan's inter-library loan program, so I can borrow (for free) pretty much any book in any large Michigan library (I'll look for the book you cited).

Meanwhile, I found this book online:

Advanced Grinding Practice : [1915] Douglas T. Hamilton and Franklin D. Jones, 344 pages.

I'm listing that book, and any others I come across on my web page here:

https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/my-surface-grinder---2

For a list of good free book sources, look here:

https://sites.google.com/site/lagadoacademy/useful-links#booksfree

 

[kevin]

A brief update on my Sanford MG surface grinder:

As I mentioned earlier, I found that the table surface on my grinder had a "tilt" of about 3 thou; the magnetic chuck had a compensating tilt of 3 thou. After debating with myself as to whether to try to correct this, I decided to leave well enough alone for the time being and just clean up the surface of the magnetic chuck. I also made some new chuck clamps, as the old ones were basically hacked together by some previous owner (and also interfered somewhat with the handle for the magnetic chuck).

I'm the first to admit that this surface grind is not great - you can clearly see a periodic wheel bounce pattern (I don't have a wheel balancer yet). I should also note that the few large dings you see in the surface were not caused by me - they were there when I got the chuck. In fact the whole surface was pretty rough when I bought the machine - I don't think the previous owner ever ground it in.

Sitting on the chuck is a fixture plate I picked up at an estate sale. It had been milled flat by whoever made it, so I decided to surface grind it as a test piece. I ground both sides, and checked it on my surface plate; I found a variance over the entire surface of about 5 tenths. On the one hand, 5 tenth is not exactly super-duper for surface grinding, but considering that the piece was only my third attempt at surface grinding I'm happy with the result.

At this point I think I have the machine working well enough that I can now work on improving my technique, work on balancing and dressing the wheel, and just basically learning the fine art of surface grinding.



Here's are pictures of the new chuck clamps I made - that's the on/off handle for the magnetic chuck in the middle; the tightening bolt for the clamp is hidden under the handle.


Here's the other clamp, showing the hex bolt for tightening more clearly. It's hard to see in the pictur, but there is a gap under the hex nut of about 1/8" - not much but enough to clamp down the mag chuck. I also had to make two new T-nuts.

 

[Bob Korves]

Your table magically changed from .010" out to .003" out. I don't understand that, but it is moving in your favor! I think you are smart for doing what you did to get you to this point. Grinding in the table and the top and bottom of the chuck correctly are probably the most difficult and challenging jobs you can do on a surface grinder, and being a novice and not clearly understanding what works and what does not, doesn't help a bit. Just use it for a while, but do more than merely making sparks. Be self critical of everything you do, and spend spare time thinking and studying what the issues, problems, and solutions might be. You are already making parts more accurate than most milling machines ever do, so pat yourself on the back and celebrate!

Maybe we talked about it before, but do not tighten the chuck down tight. It should be just the slightest bit tighter than finger tight at the right end, and just finger tight at the left end. That way you will not warp the table, which is easy to do. Don't worry, the chuck will not move... Wait, your nuts are pretty small, use a wrench, but with perhaps a light pinky pull...

Grind some oddly shaped parts just for the experience of learning. You cannot grind a nice, shiny part if you cannot hold it safely and without clamping pressures that can make the part come out distorted.

Congratulations on your progress, Kevin. I am still a rookie, too, but making gains and becoming more consistently mediocre...