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View Full Version : How do I check out a surface grinder?



Your Old Dog
02-29-2008, 07:38 AM
What is the process for checking out a used surface grinder you are interested in buying for home use.

I'm assumng I'd take my magnetic stand indicator, attach to the head and then move the table full length to see if it's worn out.

Probably remove the grinding wheel and rotate the spindle and look for un-even indicator readings.

Also, what is the preferred wheel methode? Was a thread sometime back that mentioned how nice it was to have one type of wheel over another?

Is there much else that can screw you up if you miss it? I've been pretty lucky so far with my purchases and now don't want to by 800 pounds of scrap!!

I'm looking at a Harig Super612.

edited to add: I found the thread with the comment I was wondering about.


If you want to do really close work a surface or universal grinder is pretty much a given IMO. I sometimes wonder if the small one sold by Grizzly and others is worth the trouble. I know it is no Harig, but is it usable? But one thing I know is if I ever get one it is gonna have the table traverse wheel on the right side of machine.

So what's the deal there? Is the Harig's traverse wheel on the right?

JoeFin
02-29-2008, 10:02 AM
Attaching an indicator to the “Spindle Head” is the wrong thing to do.

Even a machine with a cross table worn like a bow can grind the chuck fairly flat again so it doesn’t tell you any thing about the condition of the ways. Placing the indicator on the “In-feed saddle” and moving the cross feed side to side while indicating the chuck will give you a better idea of the condition of the ways

Really, if the machine is still under power you want to hear it run, and at least for 10 – 20 minutes. Shut it off and feel the spindle for warmth... Then ask for balanced wheel, dress it and run a few passes across a good piece of stock. Might be best to bring a small piece of “Tool Steel” stock which will be fairly close to parallel to begin with, (don’t want to waste too much time taking out imperfections)

Run a few passes at .0006” down feed and then finish with 2 passes of .0002” Look at your finish, you’ll know more about what your getting into from that then any thing else

Spin Doctor
02-29-2008, 07:16 PM
Some Harig's have the table traverse wheel on the right side, some on the left. I suspect it was optional at one time. Now they are all left handed. In a lot of ways I find this "wrong". 1) Most people are right handed and when doing manual surface grinding you do more work with your hand that operates the table traverse. Would you rather do that with your dominant hand or not? 2) Sometimes you need to look from the right side of the table when approaching the work. It is a lot easier in my opinion if the table traverse hand wheel is closer to the side you are rather than on the left side. Most of my experience with manual surface grinders is with Harigs. Not the best in the world but certainly adequate for most things a SG is called upon to do. Except for a grinding vise and an angle plate all of the special built tools I made for myself were finsh ground on Harigs. Its a matter of knowing some tricks to overcome some flatness issues the machine or magnet might have Mitsui's are really nice, the Reed Prentice and Parker Majectic's look to be really nice too. We had a Jones and Shipman ID/OD grinder and if their SGs are of the same quality I sure would not refuse a free one. Boyer Shultz and Delta Toolmakers I can't comment on as I have never used one. Sharp's, its a Harig knock-off. Just not as smooth IMO. Powermatics, the two we had were the biggest P'sOS I have ever seen. The spindles were junk. The company bought two and neither one was usable. Powermatic sent a service man in and he knocked the spindle bearing out popping the inner race out of one of the bearings. He then wanted to put all of the balls back in and pop the bearing back together with a hammer. He had no idea what kind of bearings he was dealing with as he said he had never seen one before that. Plus the Powermatics had what to me is a no-no for a SG. They employed rack and pinion for the table traverse. Personally I would rather see a cable and drum ala Harig or a cog belt that that runs from one end of the table to the other passing over two idlers to dip down to run on the srpocket. Both of these systems do not suffer from the backlash problem that rack and pinions can have if too loose. Plus a rack and pinion if the machine has wear can have the table riding on the pinion rather than on the ways.Now for some of the special tools you need if you have a SG. First you need some magnetic parallels. These are poitioned on the magnet under the work. Their primary purpose is to allow a sacraficial surface that you can grind that you set your work on. And you grind them every single time you use them. They are long term disposable tooling. My first set started at an inch are now down to .900

Your Old Dog
02-29-2008, 07:45 PM
Thanks guys. This gives me a place to start. I would have not thought to check the bearing for heat.

Sparky_NY
02-29-2008, 08:45 PM
Thanks guys. This gives me a place to start. I would have not thought to check the bearing for heat.

Along with checking for heat, check for extreme smoothness, and sound. Any vibration shows in the finish.

Another point, run a finger along the ways to see if there is oil film. If there is a automatic oiler you want to make sure it has been working, if its manual at least you can tell it has been oiled.

BTW 99-1/2% of grinders are 3 phase, so it looks like you will be getting the rotophase project on the road also.

beckley23
02-29-2008, 10:23 PM
I was aways told to check a surface grinder, grind 5 discs 1 in each corner and one in the chuck center, then measure them. That's assuming the chuck surface is good.
Harry

Mark Hockett
03-01-2008, 02:03 AM
Adding to what everybody else has said, another fairly easy thing to visually inspect on smaller rack and pinion feed SF grinders is the ways. The table just sits on the saddle so it is easy to lift off, there is nothing but gravity holding it on. I would remove the table and turn it upside down to get a good visual inspection on it. Usually you can see the scrap marks over the full length of the ways, If not it might be worn out. The table should float on a film of oil so there should be almost no signs of wear. Also look for grooves, gouging and other problems caused by lack of oil or grinding particles getting on the ways.

My last grinder was a 8" x 24" DoAll Hydraulic that had very slight wear on the ways. The grinder was useless for anything other than very very small parts or just putting a decorative finish on stuff. That grinder did not have any scrap marks showing at the ends of the ways.