Ball bearing center

[Gordon]

I have this ball bearing center which got too close the the tool bit. I would like to regrind the point but I cannot figure out how to get it apart. There is no hole through from the back and the front seal or shield does not appear to be easily removed. Some centers appear to have a front shield with spanner wrench pin holes but this is just flat. The option is to put it in the headstock and find some way to keep the point from turning while it is being ground. Any ideas?

 

[kf2qd]

You don't take it apart. You need a proper fixture to preload the bearing and mount it by the morse taper and then regrind it.
Send it out and have it reground.

 

[RM-MN]

In my area of the US, a new MT3 center like that ranges in price from $10 to $30. Buy a new one. Regrinding will likely cost much more.

 

[Gordon]

OK I will try to regrind it in the headstock and if that does not work I will just buy a new one. I should be able to cobble up something to keep it from rotating.

 

[Scott_M]

Hi Gordon
2 Hose clamps a a piece of sheet metal bent to go underneath both clamps should hold it from turning.
Before doing that I would hold it in a 4 jaw and dial it in to make sure the body and point run concentric, then clamp the 2 together.

Just an idea.

Scott

 

[Richard Carlstedt]

You can also mount it in the Lathe Headstock OR Tailstock- NO power needed
and use a rubber O ring around the straight section of the center.
Drive the O ring with a Dremal tool and that will spin the center and you can rework there, or even grind it . Wash the straight section with lacquer thinner first,, no oily surface allowed
Rich

 

[Chiptosser]

Remove the face sheald off the center and the cap off the rear of the shank. The bearings have to come out the front. There also could be a nut and a threaded portion in the end of the taper. You have to figure how yours is made. A new center with a longer center step is what you are looking for?

 

[awake]

I wonder if this was pressed together, and thus is held together by press fits. If you could heat up the outside (including the bearing) and cool the center spindle, maybe it would come apart without needing persuasion. Not sure how to achieve that, other than perhaps heating up the whole thing (giving a good heat soak), then dipping the nose in a bath of alcohol + dry ice, or something like that. Not sure what the thermal shock would do to it ...

Another thought, though likely more trouble than it is worth - drill a hole through the center of the MT3 shank (assuming it is not too hard to drill) up to the area where the center spindle should be. Thread a portion of this hole, then screw in a bolt with a spacer to put pressure on the back side of the spindle.

Honestly, I have doubts about either of these ideas working, but ... just brainstorming ...

 

[djc]

Drive the O ring with a Dremel tool and that will spin the center...

What is a reasonable estimate for the minimum speed that a Dremel would spin the centre at?

How does this speed compare to the speed items are spun in a traditional cylindrical grinder?

Would it be one, two or three orders of magnitude different?

I suspect a cordless drill could be a better option for this task.

 

[Richard Carlstedt]

The tool used does not matter, any rotary source can be used.
The speed is determined by the pulley or rod being held to drive the belt. The surface area of the driven diameter is 3-4 times greater than the point being reworked , so the forces are favorable. I would estimate that 3,000 RPM max for the center would be appropriate to allow remachining or grinding
Rich