Grinding a straight/taper on a long pin

One of the big PITA things is trying to get a nice straight grind on a long pin. I've been through the shimming routine and hated it.

Here is an easy solution to the problem. I have two 3/4" plates bolted together in a tripod fashion. Two widely spaced 1/4" bolts with a common flat washer between the two plates on the back rail end, as per the following pics.

An overall view.



Showing the two hinge point bolts.



Shows an indicator mounted to the bottom plate to adjust taper.




Showing the third leg of the tripod, a jack screw and a pull down screw.



This arrangement works like an 11" sine plate setup with no gage blocks, making it very easy to very accurately adjust out an unwanted taper, or to create a small taper.

grinding long skinny pins

Hello RJ:
I've had excellent success grinding long skinny pins by supporting them with a steady rest at the outboard end.
I've used two methods:
The first uses a single, sprung contact pad from directly underneath with a sine bar under the spin fixture, much like your compensation mechanism.
The sine bar is adjusted with screws rather than gauge blocks, and compensates for the upward force created by the spring.
The second uses two sprung contact pads at 120 degrees from vertical, also supporting the pin from underneath.
The second method allows the grinding of skinnier pins without having the wheel destroyed with workpiece vibration, and reduces the deflection of the pin from the steadyrest pressure considerably.
Have you tried this technique?
Cheers

Marcus

implmex said:

Hello RJ:
I've had excellent success grinding long skinny pins by supporting them with a steady rest at the outboard end.
I've used two methods:
The first uses a single, sprung contact pad from directly underneath with a sine bar under the spin fixture, much like your compensation mechanism.
The sine bar is adjusted with screws rather than gauge blocks, and compensates for the upward force created by the spring.
The second uses two sprung contact pads at 120 degrees from vertical, also supporting the pin from underneath.
The second method allows the grinding of skinnier pins without having the wheel destroyed with workpiece vibration, and reduces the deflection of the pin from the steadyrest pressure considerably.
Have you tried this technique?
Cheers

Marcus

Click to expand...

Hi Marcus.

Pictures, or a sketch, if you have them would be nice. It's difficult for me to get what I would consider a true pic of your examples. It sounds like it could work well. I've tried what I think are at least similar methods with mixed success. I find that when you grind past the steady rest the dimensional change is not helpful. A follow rest behind the grind point can work, but is more difficult to set up.

I manually support the outboard end with a pencil or similar semi-hard item while grinding. The pins in my pics are just under 3/8" so they are pretty stiff and I get a size less than 1 micron differential in the length. I made a video of this but when I tested the link it was pretty slow loading and playing, even with my DSL. One of these days I'll put it in here when I can figure how to make it work well.

The pins shown get a slight taper ground on the tips, and it's just a matter of less than a minute to set the taper.

The main point of this idea is the adjustable base. I use this system even for large diameter pieces that need no support but need to be dead true. I have a Mahr Supramess 20 millionths indicator that I gage sizes with, and using this base I can easily get size straightness within less than one graduation.

edit: One thing I forgot to mention is that a fixed steadyrest can affect roundness and geometric straightness of the part, producing a bananna shaped cylinder. Using a manual damper/support as I do doesn't do that. It does take practice tho.

Hey RJ how about a picture of the finished product.

You said taper but the marks on the pin suggest to me that you intend to grind a wedge on that pin.

Also I could see what looks like a tripod in the background of one picture but it doesn't seem to have any connection with the fixture holding the pin and resting on the magnetic chuck.

That fixture looks like it will made that surface grinder into a cylindrical grinder so I imagine you could grind a wedge or a taper?