So I used the manual feed handle (fine) to lower the cutter. Then while I was still turning the handle, I slowly tightened the quill lock. It was kind of a simulation to see what happens when the cutter starts cutting and there is some pressure applied. I then release the lock and boom the quill goes down a good eight of an inch. You can clearly see it lower in one shot. So that would be the backlash in the fine feed? Or am I doing something wrong?
Not sure why you would use it that way but that would be expected as you are putting load on the leadscrew doing that. I don't use mine that way. When I plunge as if milling a deep slot, I plunge to depth using the fine feed, then lock the quill without turning the fine feed anymore after that. I only lock the quill when taking a roughing/heavier cut. Then when I get close to my final depth, I plunge, again with the fine feed & make the finish pass without locking. On light cuts like for finishing the quill does not move with fine feed engaged & the quill not locked, provided that the setup is proper, rigid, no chatter, no vibrations. And if for some case I do need to lock the quill hard for a finish pass, I'll compensate for the amount that it might move.
Depending on how far my quill is extended, if I lock the quill hard it will move (according to my quill DRO) a 1/2 thou to a thou. Then if I unlock it, it will move back roughly the same amount or 1/2 thou more. If I lightly lock the quill, most of the time the DRO does not indicate movement at all (in the Z axis anyway). So when I lock on a roughing pass, if it's a heavy cut I'll make sure the lock is firm, yes it might move a bit but it's a roughing cut so doesn't matter to me. Not really any different than my table, locking either axis will indicate movement on my DRO but not nearly as much as the quill, couple to few tenths.
These are the very first things I made with my PM45. Chip pan rails for my old bandsaw. I miscalculated at first & to the left you can see my first starting slot which I plunged & milled using the method I explained above without any problem, as well as finishing them off
Not really a good example but here I also did the same, I did not plunge all the way through & mill the slot in one pass, I plunged halfway, then plunged through on the next pass.
Just a couple of days ago I finished this adapter for my RT. I don't have counterbores so I milled the counterbores by plunging with an endmill. I plunged with the fine feed to depth, then backed out. They came out great.
To add & not that it matters, my PM45 is a power downfeed model and was from the batch just before the PM45s & PM932s were offered with quill DROs. The PDF model does not have the depth indicator. I used an 8" Mitu scale & I prefer mine this way.
Every type of machine will have their advantages & disadvantages, a "perfect" machine is expensive! That's just the nature of their design whether good or bad, I would say get to know your machine & don't expect it to do something it's not capable of. If you can't live with it, time to get a replacement. I've learned a lot about how my machines behave & function & compensate for the things I might not like. Although I would like a full size knee mill someday & a 14-16x lathe I'm still very happy with what I have now as they haven't let me down yet.
