Originally Posted by Diesel911

In the Fuel Injection shop I worked in (5 years) when used 500 grit lapping compound for our hand lapping plates and our Automatic Lapping Plate machine 99.9% of our lapping of Fuel Injection Pump Parts and Injector part was done with 500 grit.

We used 1200 grit for our nozzle re-regrinding operation to lap the Injector Pintel seats and on sticky Injector Pintels and Plunger and Barrels (IP Elements).

That shop was in business for 30 years until the owner died. I can't imagine that in all that time he was using the wrong grit lapping compound!

I would prefer not to use the plate of Glass as a Lapping Plate but so far I have always been out bid on Ebay for a real lapping plate.
Also the lapping plates do not have to be grooved and some plates have a grooved side and a flat side; both can be used.

I have lapped 3 (10 Mercedes injectors and 6 Volvo injectors) sets of injectors on the Glass Plate and none of them have leaked.