I am looking to purchase the Precision Matthews PM-728. I've been comparing it to the PM-30 and having second thoughts.
The PM-30 has a table size of 81/4" X 33" vs PM-728, 7" X 28"
The PM-30 weighs 530 lbs, vs PM-728 370lbs.
The PM-30 has a 2Hp Variable speed motor, vs 728 1Hp variable speed motor.
The PM-30 has precision ground ways vs PM-728 hand scraped.
My thinking is, more weight = more ridged and finer finish.
2Hp is better than 1Hp.
The oiling system I can do myself.
I plan on converting to CNC as time permits.
If it was me and it is that variant of the 728 you're looking at then that is what I'd get myself.
One selling point for me is: Cross Travel (Y Axis) 8.5' With Full Way Support, 10” to Travel Stop.
I have a version of the PM25 and my Y axis carriage overhangs a lot when fully forward. Can be a ***** to get the gib set right to stop the whole thing swaying.
When it comes to cnc you want as much way/gib support as possible in my view.
Then also 1: 4000rpm. 2: More weight. 3: Precision ground ways.
Yes it says only 1 hp but I can't see you having much trouble cutting most materials.
I like ways and the extra Y on the 728, I like everything else about the 30.
For a CNC conversion the spindle motors and VFD is going to get removed. So the specs don’t matter to me. The larger table and more weight from the 30 would seal the deal.
I was doing the same evaluation, but primarily for a CNC conversion, where I am interested in better precision than the average hobby conversion but still staying under the price of retail CNC machines. I opted for the 728 (I had started with the 30 as the original choice)
The power of the motor was certainly a consideration, but at least for the materials I wanted to cut most frequently (aluminum and brass/bronze with some mild steel), the spindle speed was more important. The default speed is 4300 rpm out of the box but if you look at the angular contact bearings that are included in the spindle, they are good for up to 10,000 rpm, so changing out the motor later does not require modding the spindle in most cases.
The run out on the spindle out of the box is around 2/10ths and the hand ground ways and additional supported length all add up for what seems to be a better starting point
PM-30 vs PM-728
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