Spinning on bearings - concentricity measurement

[royinidaho]

Need a hand. I have no idea of what I am talking about.

I heard a term kind of like 'spinning on bearings.'

Have no idea of what that is. . . but I think I want to give it a shot.

The quest is to measure bullet run out by running the bullet on roller bearings and indicating on several different points.

Somebody must have done this at one time or another?

Any hints would be appreciated.

 

[Trickymissfit]

Need a hand. I have no idea of what I am talking about.

I heard a term kind of like 'spinning on bearings.'

Have no idea of what that is. . . but I think I want to give it a shot.

The quest is to measure bullet run out by running the bullet on roller bearings and indicating on several different points.

Somebody must have done this at one time or another?

Any hints would be appreciated.

rotating a case on ball bearings is just one way to measuring a case runout. I built one that used ball bearings, but later determined it was a comprimise at best. I came to this conclusion due to the contact made between the case and the outter race of the ball bearings, and then I also took into thought that a typical ball bearing has a certain amount of lateral end play. I did modify that setup with a ground sleeve that was shink fit to the bearing OD. I now use a ball bearing setup, but with precision steel bearing balls that do not rotate.

The first gauge I built used two .50" ground dowl pins in steel blocks. The steel blocks sat on three points (never use four points). Worked very well once I had all the bugs worked out of it, and must have made two dozen of them for friends in need. The second one was with the ball bearings, and later adding the steel rings to the O.D. of the bearings.

Later I went with the steel balls, and probably made three or four before I decided on the needed spacing. The setup I use now is very simple, and will work on any case from .38 Special to .300 Weatherby mag.
gary

 

[J E Custom]

Need a hand. I have no idea of what I am talking about.

I heard a term kind of like 'spinning on bearings.'

Have no idea of what that is. . . but I think I want to give it a shot.

The quest is to measure bullet run out by running the bullet on roller bearings and indicating on several different points.

Somebody must have done this at one time or another?

Any hints would be appreciated.

Roy.

I built several and found them lacking in usefulness as designed. So I decided to use one
that used 4 threaded pillars with a single ball bearing in each one. It worked very well.

Mine worked like the Sinclair gauge (part # 09150) but was not near as nice.

Look at the Sinclair concentricity gauge and you can see how to build one if you want to.

Hope this helps.

J E CUSTOM