I have my own valve grinder but rarely use it anymore. The shop that does my work uses a grinder that incorporates a V block to hold the valve stem. The valve will always run true regarldes of how many times you place it in the machine because the end f the stem rests against the block. You can't get that sort of repeatablity with a collect type grinder.
They even check new valves to make sure they're straight. This machine is like the difference between a valve seat grinder and a valve seat cutter. Not that these old machines can't do the job but uniformity suffers by comparison.
