Couple of valve shims wanted

[KevR]

Do you know that they're case hardened rather than through hardened then?

Nope, just making poorly-researched assumptions as usual!
But in the absence of a definitive answer I'd be inclined to err on the safe side. I would also be very surprised if you could keep the two surfaces parallel if holding the shim to grinding wheel by hand.

[Brian]

Here we go....Knife and Fork method I have used, and proved successful in the past.

This provides a relatively parallel grinding face as the shim is free to rotate.

Nut of Suitable size, Bolt, Mole Grips or similar, Gloves, Eye protection, Pillar Drill and Grinding Wheel.

Place nut on grinding wheel, drop in shim, screw in bolt till end of bolt touches shim.

Hold nut with grips, gloves and eye protection on, switch on grinder, then gently and slowly rotate nut to start the grinding process.

Turn off grinder wait till wheel stops then measure the shim thickness.

Repeat till the required thickness is obtained.

I have found that the initial grind takes a while indicating that the shims are case hardened.

Fit with the ground surface up wards, on the face of the bucket.

Good luck.