Hello Dusty.
When I read Your message I remembered that in the thread and feed chart of my Emco Compact 8 the H has also the same meaning.
In the manual page it is legended as douille (entretoise) wich translated to english using google.translate.com results in sleeve (spacer).
You can see the manual’s page here:
Oh! By the way. When I bought my Emco lathe, made in Austria, all the chinese were still Maoist…
Just for fun, You can also see a true chinese poster from the seventies showing a large lathe and some chinese people admiring it.
Here:
Note: Sorry for the boxes and their shadows in the corners. I used them to prevent the poster from scrolling.
Best regards
Dias Costa