Looking for Sanford MG-612 Surface Grinder owners

kevin said:
Next step is to grind in the table and mag chuck.
Click to expand...
After we purchase and clean up our often old and neglected surface grinders, the usual next step is to grind in the table and both sides of the mag chuck. It is also about the most difficult job we can attempt on a surface grinder, and is often attempted by those with enough skill to get the machine up and running, but with essentially no surface grinding experience at all. Been there, done that.

It probably makes the most sense to not get too hopeful of what you will achieve the first time you try it -- while pushing for perfection. We also need to have learned how to properly dress and true the correct type of grinding wheel, and need to have a good coolant system before trying it. The last thing we need is knowing and accepting when all is not well when testing our results as we proceed. Been there, disappointed and wanting to keep grinding until it is right. It won't happen. Until the machine is correct geometrically, table and carriage gliding smoothly on flat ways, the correct type of wheel mounted and dressed properly for the job, and the operator using the correct methods, it will probably not come out well. Don't keep grinding hoping things will get better. Stop, regroup, test things some more, study how real surface grinder pros approach the job, and if things do not get better, STOP, and look in the nearest mirror at the real problem behind the failures. Making sparks on a surface grinder is very easy. Making things flat, smooth, parallel, and with a good surface finish over the entire table and both sides of the chuck takes real skill and knowledge. There is no magic to it, and it is not trivial.

Consider it good enough for the time being and go on to making smaller and less critical parts as nicely as you can, to a very high standard of size, flatness, parallelism, and surface finish (all at the same time!) to get real world practice on expendable pieces. Aim for perfection. That can be done on a less than perfect chuck. After doing plenty of smaller jobs, and you feel better about achieving predictable results, go back to the table and chuck and give them a dust grind with everything as good as it can be. It will likely go much better, and will not remove much material while doing it.

Another cause of poor results is tightening the chuck too tight to the table. Yes, they are perhaps half inch bolts and nuts, but they only need to be a smidgen more than finger tight, or you will warp the table and the chuck, sometimes creating real, permanent damage. If I twist hard with my fingers, I can loosen my chuck hold down nuts. Yes, the table stays put. Then do lots of accurate measuring and planning before grinding in those large surfaces. Success will come with time and practice and knowledge. With the correct attitude, it can all be fun and useful.
Edit: My table and chuck are still not where I want them to be... ;)
 
Ok. The Williams wrench came today. The nut came off the end of the spindle. Left hand threads. That’s what I was expecting. The Sopko puller easily removed the wheel adapter. No rust on the spindle nose. Looks brand new. I measured it. 1” on the big end, .700” on the small end. 1.312” length. My calculator is telling me that the taper is 2.7439” per 12”. That seems like a really odd size. I used a dial caliper to take the measurements. The taper length was measured with the depth attachment on the caliper.
I might just send the adapter to Sopko for them to verify my numbers.

56B5E25B-63DF-4706-B65D-0316D5D2437F.jpeg

CC285345-7481-430F-9298-9BA912215944.jpeg
 
Bob -

I appreciate the good advice. I seriously considered not grinding in the table and chuck, but I decided to go ahead with it because the machine had been neglected for some time. Fortunately the machine was stored in a (relatively dry) pole barn, but there was some rust on the chuck fence (which was also improperly mounted), and nothing has been cleaned for a good while, so there was a considerable crust of hardened grinding sludge. Worst of all, the surface of the chuck is pretty rough - I don't think the previous owner ever ground it in.

I'll certainly take your advice and be cautious, and take my time. I feel that if I can do even a moderately good job, it will be an improvement.
 
Andy Pullen said:
Ok. The Williams wrench came today. The nut came off the end of the spindle. Left hand threads. That’s what I was expecting. The Sopko puller easily removed the wheel adapter. No rust on the spindle nose. Looks brand new. I measured it. 1” on the big end, .700” on the small end. 1.312” length. My calculator is telling me that the taper is 2.7439” per 12”. That seems like a really odd size. I used a dial caliper to take the measurements. The taper length was measured with the depth attachment on the caliper.
I might just send the adapter to Sopko for them to verify my numbers.
Click to expand...
Are you measuring the length of the tapered surface or the center line length of the taper?
 
Andy -

Your taper measurements are similar to mine - allowing for measurement errors I am guessing that we have the same taper (approx TPF = 2.7). If you decide to send your adapter to Sopko, I'll be interested to see what number they come up with.

FYI Sopko told me that if I sent them my adapter to inspect, they would only need it for 1 day, and I would get it back pretty quickly. They gave me a ballpark figure for a custom item of about $450 (note this ballpark figure is without looking at my adapter, so the actual number could be more or less). I had it in the back of my mind that if I could find other Sanford owners with the same TPF, we could maybe get together and do a larger order, on the assumption that Sopko could make 5 or 10 cheaper per adapter than if they just set up for a one off. However, I have not asked Sopko if this is in fact the case.
 
Bob Korves said:
Are you measuring the length of the tapered surface or the center line length of the taper?
Click to expand...

I’m measuring the taper from the small shoulder on the large end to the face of the small end as close to parallel to the centerline as I can.
 
Can't answer for Andy, but I made my measurements per the diagram below from Sopko, where length L is measured along the centerline.

taper-diagram.png
 
kevin said:
projectnut -

Great information on the bearings, I have added it to my web page.

That finish looks pretty good to me. Very creative use of a blade balancer. I do not have a balancer yet, and looking at the prices on them I'll probably end up making one; right now I'm just winging it.

So far I am happy with the results I am getting. I checked my test piece (surfaced on two sides) on my surface plate, and the sides were parallel all over to within a two tenths. Not bad, I think, for a machine that has not yet been tuned up, and with a very used wheel.

I finally got around to removing my mag chuck from the table, so I could get them both cleaned up. I did a lot of online research on mag chucks, and I have saved the best links here:

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

Once I had the chuck cleaned up, I found a serial number on it:
View attachment 270201

From my research I found the following "facts" which may or may not be correct:
  1. Older Walker chucks (and maybe all older mag chucks) are oil filled.
  2. Newer ceramic magnet chucks are not oil filled (typically a specific grease is recommended by the manufacturer)
  3. Oil filled chucks can "stiffen up" if they are kept upright for a long time; flip them over to allow the oil to lubricate the magnets - this may help the mechanism work more easily
  4. Chucks may lose oil if the seals around the on/off handle are worn. Some chucks have an oil fill hole. For oil, 90W (non-detergent) or way oil is recommended.
  5. Weak magnetic chucks: This may be due to wear in the internal cam mechanism or related parts. Opening up the chuck and repairing this may rescue the chuck.
My chuck has an oil fill hole (I think). There is an open threaded hole on one end; I didn't think it would hurt to squirt a little Vactra-2 into the hole. I also flipped the chuck upside down and worked the on/off handle a few times; it seemed to help. I closed up the oil (?) hole with a screw to keep crud out.

An alternate explanation for the "oil hole": Some chucks have an adjustment screw to stop the internal mechanism from sliding past the optimal position. There could have been an adjustment screw in the hole at one time.

Finally got some new wheels in. Next step is to grind in the table and mag chuck.
Click to expand...

I would agree with at least statements 1 and 4. I have 2 permanent magnet chucks. A Walker 6" x 10", and a Brown & Sharpe 5" x 10". Both are oil filled and both have oil ports on the bottom. At least in the Brown & Sharpe the oil level is above the pivot point of the handle. When I first got it the chuck was low on oil. When I added some it started to leak at the handle so I had to replace the seals. I had to disassemble it to replace the seals so I cleaned the interior and put in the proper amount of oil before putting it back together. I was surprised how full the cavity was. Even with the chuck in the upright position the handle and cam mechanism are still covered.

I originally purchased the Brown & Sharpe to use on my vertical mill to cut down horizontal mill arbor spacers. I reground both sides at the local technical college when I was using their machines to determine which would be the best fit for my shop. I have not had holding problems with either chuck. Statement #5 sounds reasonable, but as mentioned both my chucks are working fine. On larger parts I generally put a piece of paper between the part and the chuck to make removing the part easier. Without the paper the parts often stick to the chuck and have to be slid toward the operator to overcome the wringing effect of the smooth surfaces. I have scratched the chuck on occasion, but the paper eliminates that problem.

When grinding smaller parts I of the use magnetic parallels like this:

https://www.ebay.com/itm/Universal-...519292?hash=item3d69a66bbc:g:Gb8AAOSwqN5bJ~gK

Often times the parts are small enough they only span one or two magnet lines on the chuck so I use the parallels to increase the number of lines of magnetism passing through to the part. Each line of magnetism through the blocks is weaker than those directly on the chuck, but the increased number of lines through the part holds it more securely.
 
I ran across some instructions sheets from Walkeron installing/grinding magnetic chucks, which I have added to my web page of surface grinder references ( https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/my-surface-grinder---2 ), or you can find it here:

https://drive.google.com/file/d/1BXqRw-9YIyDaATXkFzvsJ806N8fnx01w/view?usp=sharing

I also ran across a statement on the Walker Magnetics site stating that 90 weight gear oil should be used in their magnetic chucks (at least those that use oil!).

I might have added an item 6 to my list, but I have my doubts about it: A person on a knife-making forum ( http://www.sablade.com/forums/showthread.php?2230-Magnetic-chuck-maintenance ) makes this claim: "A magnetic chuck needs to be left in the “on” position permanently while not in use. Cover the entire top surface of the chuck with a suitable magnetic material (sheet metal works well), to ensure that the chuck is “working” all the time. 24/7, 365." I've never seen this opinion any where else. True or false?

I've tried to find "official" (from the manufacturer) magnetic chuck maintenance information online, without success.
 
You must log in or register to reply here.
Back
Top