Fresh ground chuck - mmmmm tasty

[John in CA]

Just got done grinding in a mag chuck for the first time, the fine pole electromagnet chuck on our Boyar-Schultz Challenger 618 at work. It came out great and I just wanted to thank all the regular contributors here for all the terrific information I was able to glean which helped me to do this with relatively few problems. In fact the only difficulty I ran into I'll share with you, you might get a kick out of it...

I had taken a few passes with good results, but still had a few more to go to grind the low spots all the way out of the middle of the chuck. Out of an overabundance of caution, this being my first rodeo grinding a chuck in, after each pass I'd attach an indicator to the wheel guard and indicate the fresh ground portion of the table, to make sure I was seeing what I wanted to see. I was getting good, repeatable results, until one morning I came in, took a pass of about .0003" deep, then put the indicator on and the damn thing read like diamond plate. Dressed the wheel, took another pass, same deal. Frustrated, I decided to walk away for awhile, collect my thoughts and decide how to proceed. I started another job I had on my bench, a one-off lathe part. I was indicating it in on the four jaw on my lathe, which sits not too far from the grinder, when the needle on my DTI started dancing all over the place. I'm sitting there going WTF, and I notice the needle fluctuations are oddly rythmic. That's when the noise registered in my brain.....
KA-CHUNK, KA-CHUNK, KA-CHUNK.....
The Trumpf CNC laser/punch press right next door to the grinder area was embossing some stainless parts and sending little mini earthquakes through the whole floor of the shop, and throwing my poor mag chuck mercilessly into the wheel as I ground. I don't know how I didn't realize it sooner; I've got my ear pretty well tuned for when things go wrong in the shop, but I guess the sounds of normal operation just sorta blend into nothing. And through freakish coincidence, I had been indicating the chuck, both times, while they had been loading the press with material. I waited till they were done with the run they were on, made another couple passes, problem solved. Live and learn, eh?

Anyway, thanks again, guys. I now have a chuck suitable for a couple tool grinding jobs I've got coming up, and I probably couldn't have done it without the information I'd gotten from here.

[chrisfournier]

I too would like to thank those who posted information on this topic. I finally ground the mag chuck on my little Chevalier 612 this past Friday after gaining the confidence to do so by reading here on PM.

The chuck is small and fortunately it was not out by very much < .0006 in one small area but <.0003 for the most part. I realise that there was room for improvement given that this is a surface grinder after all.

Two light albeit tedious passes and the surface is as good as I require. Using an infrared temp guage I made sure that the chuck temp didn't get too warm. I prepared the chuck face with dyekem prior to beginning the process and it was interesting to see where the chuck was low and also to watch how the wheel ground from the cutting corner back to sparking out as it was traversed across the chuck.

I now have a grinder that I can try refining my technique with. I am interested in the "favorites thread" that discusses deeper cuts with fine traverse feeds for optimal surface grinding.

[cash]

One thing about indicating your magnet in to see if you have done a good job of grinding it. If your machine has vee ways or vee and a flat way this is not a good indication of your work. As your table recriprocates it actually rides on the oil film in between your ways.

If you have a smaller machine with the ball bearing ways I believe then an indicator would be a pretty good way of checking. Or a machine with linear guide ways.

The best way to check to see how your machine is running is grind some test blocks.

An indicator will give you some idea but actually grinding is the best way.

[chrisfournier]

While not an expert in this field I have to agree that on my small grinder with v-ways that a test grind will be required to see if I've done a decent job of chuck truing.

When I pump the one shot lube system on my 612 I believe that the chuck to wheel distance is reduced albeit a small amount and for how long the fresh shot of oil affects a stable set up I don't really know. I suppose that the lubed v-ways are really always a changing value as far as the chuck/grinding wheel distance goes. This is why my grinder is only useful for "decent" work. Much of what I do is grind valve shims which is suited to my machine because the chuck travel required is small and the amount of grinding required is minimal. I lube the ways at the start of the job, run them in and then begin to grind; I believe that this gives the most "stable" set up for the task. Larger jobs will require a wheel truing and way lubing break between material removal sweeps.

[winger]

You may want to get isolator pads for the machine.The same pattern will show up on the workpiece and the machine bearings will also deteriorate due to vibration. The brand we use is Vibrodynamics.
Couldn't even read a .0001 indicator before installing these. You will need to know the weight of your machine and the normal workpiece weight.

[Davis In SC]

One shop building near me was once used to run, repair and rebuild punch presses. The press area has a floor made of 4X4's stood on end, in a bed of sand... Former owner said it absorbed all the vibration, so the shop machines were not affected..

[John in CA]

Originally Posted by cash

The best way to check to see how your machine is running is grind some test blocks.

An indicator will give you some idea but actually grinding is the best way.

Thanks, Cash, I had this written down on the little procedure sheet I stuck in my spiral notebook, but completely spaced it.

Winger- I'll look in to those isolator pads; don't want to have to schedule every darn grinding job I get around what the press happens to be doing.

[easymike29]

Originally Posted by cash

.

The best way to check to see how your machine is running is grind some test blocks.
An indicator will give you some idea but actually grinding is the best way.

Keep in mind that grinding test blocks or using an indicator will only tell you how accurately the chuck has been ground but will NOT tell you anything about flatness.

Gene