I need to reduce the OD of a steering pinion input shaft from 23 mm to 19 mm over a length of 25 mm. The measurement is not overly critical as the shaft will get 2 flats on it to fit into a clamp type U/J. The shaft is obviously some kind of hardened gear steel - a hacksaw will not touch it so I am guessing that none of my lathe tools will either. My thought is to put it in the lathe and with careful use of the angle grinder reduce the OD as required. I have got an independent grinding machine for tool sharpening but I cannot think of a way of holding the work piece so as to use that. Any other ideas welcomed. TIA.

Pretty sure I have seen what you describe done in industry.... Rotating part in jaws ground by sliding grinder.... Be very careful not to shatter the grinding wheel!

I would have thought that HSS would cut it at the right feed and speed, I've managed to cut some pretty hard stuff before with it, if not carbide tipped tools should do the job. You can get a tool post mounted grinder, but they are expensive and not really made for what you want to do.

Shooter

Ive done similar but fabricated a clamp for the grinder using an old disc guard, and the side handle point, and bolted it to the cross slide.

ETA take your time and take very small cuts to prevent the disc shattering.

[Edited on 15/9/15 by r1_pete]

Why not modify the original UJ?

You should be able to cut it with a carbide tipped tool, but you could also do what your saying too

I did a similar thing on a damaged bearing surface. I mounted the shaft in the four-jaw and mounted a Dremmel in the tool post. It took away the deep scoring and was accurate enough to get an undersized bearing to fit.

You could try with some carbide tools, or use a grinder.

I needed to make a groove deeper in a hardened part so I g-clamped a pneumatic die grinder with a cutoff wheel to the toolpost and used that, worked great.

A toolpost grinder is what you want. Fab up a bracket for the angle grinder to hold it solid on the toolpost. Mount the grinder so that it turns toward the workpiece, sparks go down and run the piece in reverse. Make sure you cover your lathe up when doing this as the swarf will turn quickly to grinding paste on all the moving surfaces!

Cheers
Stot

I managed to grind down the OD of a number of valve shims for my Benelli motorcycle using a hand held dremel and the shim held between two bits of silver steel bar. I went slowly and stopped regularly to measure progress and managed to get them all within 0.1mm which was more than adequate for a shim-under-bucket arrangement. It did take a long time, but as the correct sized parts are very difficult to find it was well worth the effort.

However, the shim was only a few mm thick, so it was easy to get a fairly consistent diameter. If you had to grind down a significant length to the same diameter than I suspect it would be much more difficult/impossible.

Make sure you protect the lathe from grinding dust as mentioned above. Grinding dust on the slideways and screw threads is a sure way to ruin a lathe.

why are you having to do this anyway, is it hitting an engine mount or something? Surely there is another solution rather than weakening your steering?

Hi Mr Whippy. I am using a GM Manta/Chevette rack. It comes in two versions one with a spider and rubber coupling on the pinion shaft and one without. I am merely converting a spider type to spiderless. No risk of weakening I think.

Taking inspiration from Stot I made up a simple 'U' bracket and clamped this directly to the cross feed table of my ML7. Works a treat. It will also enable me to machine the flats with a non rotating work piece. Brilliant! Thanks Stot.