Surface grinder issues, any experienced users around?

[Mark Hennebury]

Hi Tony,
You have never seen it happen; that makes it a little more mysterious.

I wasn't using any coolant, These were 1" square bar, parts from an old machine that i was just skimming on all four sides, purely cosmetic cleanup. I was only taking a few tenths of with each pass, and moving fast, so i don't think that it was heat, also it was randomly happening, and instantly, it wasn't a gradual lowering, it would just plow down over a stroke distance of 6-8". When i say " plow down" we are talking in relative terms, so it may have been an extra few tenths or more, before i caught it. which is still going to mess up a part that you were doing to spec. So this wasn't a gradual heating up and expanding without me noticing, this was instantly noticeable, and would make me jump. I will check the wheel fit on the shaft also
I have several indicators, and i will test manually.

I appreciate any and all opinions as it will help me investigate.
Thanks.

First off, are you using coolant of mist spray while grinding? Are you sure the head is actually dropping? The reason I ask is after over 25 yrs in machine shop, I've never seen that happen. I have seen grinding wheels suddenly dig in due to getting the work too hot where it warps slightly, or expands, making the wheel dig in even more. Make sure the wheels you are using are a good fit on the spindle. If you have access to an indicator, plunge type would be best in this situation, set it, and if you can operate manually, run the table back and forth a number of times, move down a few thousandths repeat, etc to see if it will drop while not actually grinding a workpiece, or if it hangs up at any point, then go from there.

[Bill Dufour]

Sounds like backlash to me. I think you crank down the head and it comes down except for a fraction at the end. With vibration it settles down that last little bit. After lowering the head you should crank it back up to remove any backlash. If the handwheel is unbalanced it may be rotating to move the handle down. My lathe cross slide did that when the gib was looser.
How much backlash do you have on the head adjustment wheel. How much rotation would cause the unexpected drop?

[michael langman]

What Tony describes is very common when grinding without coolant. Also if the part is not flat to begin with it could be moving into the wheel. But usually the wheel gets loaded and heats up then heating up the part. Some metals are problems to grind and the correct wheel for the type of metal is important.

[Bill Dufour]

I woulds post over at "Practical Machinist". you will get many experienced answers very soon. I would post i nthe General section for quickest response.
Bill D.

[Mark Hennebury]

Bill, i haven't been able to get onto the Practical Machinist website lately, so i posted on here. i keep getting an error; This site can’t provide a secure connection

[Tony Pisano]

There is also a site called hobby machinist you might want to check out.

[Bill George]

Or here > homeshopmachinist.net the Practical Machinst site hates hobbyists. They are all Pro machinists and you better believe it!!