Surface Grinder Question

Using 4" wheels my choices are very limited. I have a 36, 60 & 100 grit wheels. J and H hardness I think.Pretty sure the table is moving up due to less wear on the ways at the far ends. And no coolant as my chuck is electric. My parts never get hot just barely warm if anything. Remember my chuck is very small so I can only grind very small parts. I stated above my chuck was 4x6 but actually it's a 3x5.
So here is a senario i'm dealing with. A guy at work asked me to grind a parallel. It was corroded so he wanted it cleaned up. It is six inches and fairly think. After grinding the center is .003" larger than the ends. Both ends are exactly the same dimension. I place it diagonally across the chuck. I tried placing a shim under the center. Realize now you can't do that as the part will rock to one end. Any suggestions on that?
 
I am using Vactra #2 (ISO 68) on the ways and slides, and Mobil DTE light (ISO 32) on the shafts and gears, John. I typically use 46 (and sometimes 60) grit wheels in H to J hardness, open structure types. They seem to work best for me. I often use a fast and deeper cross feed dress of the wheel for roughing and a fine feed dress for finishing, just as you say. It helps. I have some fine grit wheels, but I need to get much better at the basics before trying them. An issue I need to address is that I am grinding dry or with a light coat of cutting oil on the work. I have a mister that I could use, it works fine, but have not tried it yet. I am not set up for flood coolant at all, and I also don't want the mess. It seems coolant helps a lot with surface grinding, by what I have read. Don't get me wrong, it is a very nice grinder acquired from an equally nice guy. ;) I think most of the issues are with the inexperienced operator, who mostly needs a lot more practice...
 
ddickey said:
Using 4" wheels my choices are very limited. I have a 36, 60 & 100 grit wheels. J and H hardness I think.Pretty sure the table is moving up due to less wear on the ways at the far ends. And no coolant as my chuck is electric. My parts never get hot just barely warm if anything. Remember my chuck is very small so I can only grind very small parts. I stated above my chuck was 4x6 but actually it's a 3x5.
So here is a senario i'm dealing with. A guy at work asked me to grind a parallel. It was corroded so he wanted it cleaned up. It is six inches and fairly think. After grinding the center is .003" larger than the ends. Both ends are exactly the same dimension. I place it diagonally across the chuck. I tried placing a shim under the center. Realize now you can't do that as the part will rock to one end. Any suggestions on that?
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That is a large taper over a short distance on a small machine, Duane. You are probably looking at scraping the machine in to get it to the proper geometry and flatness. The chuck could also be part of the problem. How does it test for flatness? Previous owners were likely grinding small parts on the middle of the chuck, which concentrates the wear on that area alone. That is how I read it, anyway...
 
By the way I'm using spindle oil for the ways Velocite 10.
The taper is not gradual either, it is quite abrupt. I wonder if the magnet has something to do with it. Sucking it down in the middle part then rebounds up when the chuck gets turn off. IDK maybe that doesn't make sense.
Today I ground the part of the table that the chuck is bolted to, the bottom of the chuck and finally the top of the chuck. This was after my first measurements. I redid them and they were marginally better at best.
Checking for flatness, isn't that what I did when I put the precision parallel on and swept it with a DTI?
Yes on the scraping, eventually it would be nice to do.
 
ddickey said:
By the way I'm using spindle oil for the ways Velocite 10.
The taper is not gradual either, it is quite abrupt. I wonder if the magnet has something to do with it. Sucking it down in the middle part then rebounds up when the chuck gets turn off. IDK maybe that doesn't make sense.
Today I ground the part of the table that the chuck is bolted to, the bottom of the chuck and finally the top of the chuck. This was after my first measurements. I redid them and they were marginally better at best.
Checking for flatness, isn't that what I did when I put the precision parallel on and swept it with a DTI?
Yes on the scraping, eventually it would be nice to do.
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Velocite 10 is a very thin spindle oil, not a way oil. If that is what the manufacturer recommends, then fine. Otherwise, I would use way oil. "Precision" parallels are often not so flat, especially when they lay down flat instead of on edge. Test them separately, without and with the magnet on.
It is very common for mag chucks to get a low spot in the middle. They are made of soft metal, have grinding grit to wear them, and are not used properly by working all parts of the chuck equally.
There may be something wrong mechanically with the table travel. Take it apart and look at things carefully. It is an easy job on most surface grinders to take the table off.
 
Doubleeboy said:
If I was having problems grinding I would make sure I was using an open structure, soft wheel like and H, and grit of 46. In my admittedly limited experience the open structure type wheels which look like swiss cheese, give the waste material a place to go and get out of the way if the the coolant or mist or air doesn't evacuate them. By having a cleaner surface there is less recently cut grit in the way to get ground again. When that grit gets reground it heats, causing local heating of part, further causing part to swell, causing a bigger bite being taken by wheel, causing more heat, on and on. Once that scenario starts and it happens frequently for a novice the downward spiral has begun and its almost impossible to get off that train without stopping , retruing wheel, and making technique changes. As cheap as wheels that don't say Norton on them are, I would make sure I had a 46H in open structure handy. It is my go to wheel for most anything with iron in it, no matter how hard or soft. Learning to grind as Bob and others have pointed out is a process, few people master it quickly. If you are not running flood coolant or a boat load of mist you are making the learning dramatically more difficult. On the rare chance I get to see an old pro grind dry they always seem to have a 46 grit wheel with open structure.

michael
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Sorry, Michael, I somehow missed your post. I also use open structure 46H as my go to wheel, and all the wheels I have are Norton, Radiac, or other good USA made wheels. I need all the help I can get... The 46H wheel on a 7" grinder seems to be the sweet spot on steel. I suppose you might get a better mirror finish by using finer wheels, but then other problems come up. I am still working on achieving work that is consistently flat, with no wheel hop or other surface imperfections. Sometimes I can get it, sometimes not...

I really need to get my mister system hooked up and working. I think that will make a big improvement in my work.
 
Bob, I am not an experienced enough grinder to do flat work for accuracy of dimension and surface finish on large objects by grinding dry. It seems to me that smaller work is easier to work dry as long as its not super thin. I tried many times to surface a 8" x 4" x .5" piece of 1018 with near success grinding dry until that moment when the burn would start. It took me a while to realize that as the wheel dulled, the cutting was generating more heat, even taking a cut of just a few tenths, the heat would build up, part would swell maybe only a tenth or so, but voila, in starts the bigger cut, generating more heat and the cycle has started. Running flood or mist keeps that nasty cycle from starting in the first place. At least that is my take on it. Something as small as a 123 blocks with holes in them is a lot easier place to start working dry, the holes seem to help with cooling and a place for grit to go besides loading up the wheel. Any more when I look for wheels, I want to see them first hand or at least photos. Those nice big holes indicative of an open structure struck me as odd and wrong at first, now I realize they are a novices best friend, cool running.

I just last night got set up for flood, finally bit the bullet and paid the price for coolant surround for my Chevalier. Have the sealant drying right now, should be in use tomorrow. I should have bought a grinder years ago, the learning is slow, but I enjoy the challenge.
 
Doubleeboy said:
Bob, I am not an experienced enough grinder to do flat work for accuracy of dimension and surface finish on large objects by grinding dry. It seems to me that smaller work is easier to work dry as long as its not super thin. I tried many times to surface a 8" x 4" x .5" piece of 1018 with near success grinding dry until that moment when the burn would start. It took me a while to realize that as the wheel dulled, the cutting was generating more heat, even taking a cut of just a few tenths, the heat would build up, part would swell maybe only a tenth or so, but voila, in starts the bigger cut, generating more heat and the cycle has started. Running flood or mist keeps that nasty cycle from starting in the first place. At least that is my take on it. Something as small as a 123 blocks with holes in them is a lot easier place to start working dry, the holes seem to help with cooling and a place for grit to go besides loading up the wheel. Any more when I look for wheels, I want to see them first hand or at least photos. Those nice big holes indicative of an open structure struck me as odd and wrong at first, now I realize they are a novices best friend, cool running.

I just last night got set up for flood, finally bit the bullet and paid the price for coolant surround for my Chevalier. Have the sealant drying right now, should be in use tomorrow. I should have bought a grinder years ago, the learning is slow, but I enjoy the challenge.
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Agreed, Michael. I was able to get a 5x11" electromagnetic chuck flat within .0003" over the entire surface, but it took lots of time and I did use both Crisco and cutting oil to try to help. With my 6x18" permanent magnet chuck, the closest I have been able to get over the entire plate is more like .0008", and that is after several tries, all cut dry with very light cuts and multiple dressing toward the end. Heat is definitely part of the issue. Dressing the wheel often and again before and during the finish work is definitely part of the answer on large parts. I suppose flood coolant also helps to keep the wheel from loading up. We'll get there eventually. I am a lot more comfortable around the machine, and do small jobs that come out just fine, but nice, big, flat, shiny parts -- all at the same time -- are still a goal I am working to achieve. Right now it is "pick any one" or more accurately "settle for any one." It is definitely not as easy as it looks in a YouTube video done by a pro. Fairly simple machine, big learning curve...
 
ddickey said:
What do you mean when you say "go beyond then back"?
Mine has a gear and rack. I took the rack off and put the table back on and moved it by hand thinking the rack was interfering. Same results.
The problem with the four block test the magnetic part of the chuck is only about 2" wide.
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As I said the belt drive table, those at the end of travel have a tendency to lift the table a bit at the end of travel . Rack drives can lift too if at the end it's stopped quickly at the ends.
 
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