Why off center

C Craft

C Craft

Well-Known Member
Have you ever notice when you grind something with a drill/drill press turning the object tends to be off center! FOR EXAMPLE: Lets say you have a center punch and the point gets a little mushroomed.

So you chuck it up in your drill or drill press and you grind/file the new point.:3:

Then when you can't seem to punch consistent starter dimples. :les:

You turn the newly ground center punch up and look at the point and dad-blameit the point is off center!:mad:

I always thought maybe it was wobble in the drills chuck, but I have tried this with a new drill and same effect. I have locked the grinding/filing apparatus down and same effect, off center!

Some days when the Sun and the Moon align and Jupiter is....................... well, some days I can hit center better by eyeball!

I have one center punch that was very cheap and I litterly ground it down till it's almost dangerous to use now, trying to come up with a solution to make the newly ground point center better!!

So my question is WHY , and what can be done to make it center better???? I don't have a lathe, so there has to be a solution to whip this problem short of buying one!!!

Please don't try to tell me that I am the only one who has ever experienced this, cause I ain't gonna buy the pile of dog stuff!!:s12205:
 
Really, it's because we're trying to do something outside the limits of the tools. It gets off center because of flex and give that may not be visible by eye when it's spinning. It starts out minor and perpetuates and gets exponentially worse the more it turns.

You can turn something pretty round but you have to figure out a way to lock your workpiece up pretty solid. If your drill press had a tailstock like a lathe does to hold the other end of the workpiece, you'd have it made. There is either some flex or wobble (or both) in your drill press chuck and in the case of smaller items being turned, in the item itself. Same goes for a file or something locked down to file or grind with.
 
Try this.

Chuck the punch in the drill press and turn it on. Instead of trying to file it while turning, use a dremel tool with a fine grinding wheel. Hold the dremel parallel with the drill press table and very gently grind the point to desired sharpness and angle. Basically, you're grinding the point the same way a valve grinder grinds the angles on engine valves.

Hope this helps.

-Kurt
 
My advice is to chuck it up in a cordless drill, then take it to your belt grinder (a slack area). I often have people come in the shop and ask why I have 3-4 cordless drills in holders near the grinder.....its because I use the heck outta them, from little jobs like you mentioned, to finsishing out damascus pen barrels, or anything else that needs a concentric radius.
 
Thanks everybody for the advice!

John, I kind of figured it was because it was play, in the setup, (even if I didn't want to admit it)!!!!

Kurt, I will have to try the dremmel trick, that one I don't remember ever trying.

Ed, I recently tried one on the slack area of a belt and it did a lot better. Might have even done better than that if I wasn't being cheap and trying to get everything out of a very wore put belt!:what!:

I should know better than that from my carpenter days. I got an old work horse of 4 x24 belt sander and I learned a long time ago when a belt is wore out it only good for two things, polishing and screwing up what ever you are trying to do with it!!

You we need a shop tips thread!!!! I got a couple of good ones!
 
I'm with you in this :)
Consider i made my disk grinder from scratch and imagine the pita to get the disk round hacking it while spinning, using an angle grinder by hands. I started with a bandsaw and a plate of steel to have the first round to work with.
Then the key was to barely touch it with the angle grinder.....no other way than minimize the pressure......yes, lot of time involved, but the wobble due to off-center had been reduced to usable range
 
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