Travel (X, Y, Z) and Z axis height (table top to nose) becomes pretty important as you start to work on larger parts, in particular when you have the vice height, the part and then try to tap a part. Also the Y travel is often a limiting dimension on many bench top mills. The PM-833 and PM-840 have travel dimensions that are close to what you would have with a full size knee. QMT has a nice comparison sheet of their benchtop mills so one can compare the different models. I agree with David as too trying to squeeze such a wide operating RPM with a single speed belt drive, so more geared to higher RPM work. It should be OK for most work other than low speed (under ~200 RPM) with big drills and cutters. As far as material removal, one can use a rougher for rapid metal removal.
Per what Bill just posted, ead droop or nod, is where the head at the spindle end may lean slightly backwards due to wear and play in the gibs. The heads can be quite heavy, and over time you can get a bit uneven wear in the gibs, if you need accurate work I would lock the head and use the spindle. On benchtop mills vertical alignment of the column is not adjustable, other than shimming the column, on a J head knee mill the nod (front to back) of the head is adjustable.
I am SO glad I chose the opposite from you. I bought the 835S and swapped the motor for 3-phase and a VFD. It's a great machine with all the capacity and rigidity I need. When your "rigid" machine is out of tram and needs nodding, what do you do?Thanks again for all the help everyone. I've decided I don't need a larger knee type mill, and really the 932 may be a bit of overkill for me. I've narrowed it down to the PM30MV and the PM932M now. It looks like the 30 doesn't have power downfeed and the 932 doesn't come with the powered x-axis drive (or, I'm not seeing it on the website at least...). I like the idea of having a variable speed control and x-axis drive on the 30, and not sure I'll ever need the power downfeed on the 932.
Leaning towards the 30 at the moment, it's probably all the machine I'll ever need. I'll wake up one day soon with a decision I'm sure.
Thanks again for all the help everyone. I've decided I don't need a larger knee type mill, and really the 932 may be a bit of overkill for me. I've narrowed it down to the PM30MV and the PM932M now. It looks like the 30 doesn't have power downfeed and the 932 doesn't come with the powered x-axis drive (or, I'm not seeing it on the website at least...). I like the idea of having a variable speed control and x-axis drive on the 30, and not sure I'll ever need the power downfeed on the 932.
Leaning towards the 30 at the moment, it's probably all the machine I'll ever need. I'll wake up one day soon with a decision I'm sure.
Still haven't woken up one day with a decision, LOL...