Harig 612 Reassembly - Table Flatness Measurement

[jwweathers]

Sweeping the table by indicating the chuck top off the headstock ( wheel spindle head) might check/show zero-zero but that does not prove the machine will grind a flat part. Checking for bed way condition only a flatness test proves that the fresh ground chuck is truly flat and assures that grinder will grind a long pat flat. *It is different than sweeping the chuck and different from the set gauge blocks on the chuck.
If the chuck after grinding has a slight concave or convex top then sweeping may check dead true but the chuck out of flatness will make a ground part out of flat.
It is good/best to inspect the set pad for flatness and check the chuck top for flatness not with sweeping but with s near true flatness gauge of some sort.
Note that I said the three or four gauge block test is a rough test/ the same as sweeping the chuck is a rough test.
I have seen some of the best name grinders with having this condition and it makes grinding high precision parts a confusing nightmare because grinder hands have difficulty figuring out why part-error occurs.

Appreciate you taking the time to walk me through it. I need all the help I can get. I think I understand now (takes me a min or two…). I will follow your suggestions regarding indicating off a parallel to try and narrow in on the source of the error.

Thanks!
Jeff

 

[michiganbuck]

It is best to flatness check a machine before grinding the chuck or the set pad, because will have to grind the chuck and set pad again after you fix the bed ways.

 

[stephen thomas]

I will follow your suggestions regarding indicating off a parallel to try and narrow in on the source of the error.

No intention to be rude, you probably already know this-
"parallel" here means a substantial qualified tool, ground or scraped flat and truly parallel. Should have some width to it, though does not necessarily have to be a box parallel.

Not a general work set up or vise parallel of the 1/8 or 1/4 x 6 or so type.

Your grinder does seem to be in good shape - good luck with it!
smt

 

[jwweathers]

No intention to be rude, you probably already know this-
"parallel" here means a substantial qualified tool, ground or scraped flat and truly parallel. Should have some width to it, though does not necessarily have to be a box parallel.

Not a general work set up or vise parallel of the 1/8 or 1/4 x 6 or so type.

Your grinder does seem to be in good shape - good luck with it!
smt

No offense taken at all. It is best to assume that I don't know something. I have a granite parallel that I think should do the trick.

Thanks!
Jeff

 

[michiganbuck]

QT Op ( I have a granite parallel that I think should do the trick.)
Agree for the length of that parallel straightness might be good.

looking at the scraped oil ways being much the same for the length cam often give a .0002 or so, rough appraisal of flatness.
Finding more wear to the middle of long travel ways may suggest that someone overtightened the chuck hold-downs. Perhaps reducing the accuracy from day one.
Tighten hold-downs with from the elbow swing/rotate your arm(forearm). not pull from your shoulder and body weight.

An old-timer surface grinder machine with fresh scraped ways is likely a better machine than anyone can buy nowadays.
Fresh plastic ways can be as good as iron. but not as long-lasting.

IF I designed a SG it would be good for 20 years but expensive enough that nobody would buy it.
QT:
Your grinder does seem to be in good shape - good luck with it!
smt

I agree it looks very nice and in good shape from here.