Pm727 Questions

S

sfsteel

Forum Guest
Register Today
Hi everybody,

Hobby-Machinist.com rookie here :eagerness:

I’m looking into purchasing the PM-727, and I see a lot of members here own this machine. I have a few questions.

1). PM-727v versus PM-727m... is the variable speed worth the extra money? I havent seen any complaints about lack RPM control on the standard 727m model. Am I overlooking something that is highly beneficial about the variable speed model?

2). My research shows that it’s popular to mod geared machines over to belts (particularly with the G0704). Never the other way around. The 727 has a six speed gearbox, which I do not want to modify. How are the gear boxes on these machines? Does anybody have any gripes with noise or gear switching?

Thanks in advance!

Patrick
 
Hi Patrick,

My last bench top mill had a 3Hp BLDC variable speed motor with a 3 speed gearbox to cover a speed range of 50-3000RPM. Variable speed allows you to change speed on the fly and dial in a specific speed for the work conditions. It makes it much easier to get the optimal speed and feed. Trying to achieve this with just a 6 speed gearbox w/o variable speed is cumbersome and the speed steps are very large. Given the choice and nominal cost difference, variable speed is the way to go. You need the six speed gearbox to give you the power band for each variable speed range which I would estimate would be 40-100%. As you decrease the variable speed down you loose Hp.

The main reason for a belt conversion is noise (which I have not heard as an issue with the 727V) and increase spindle speed. You are getting a mill with a 1 Hp motor, so you need the gearing steps or multiple pulley steps to provide the mechanical ratio within the operating range of the variable speed motor. Most people that convert to belt drive use two steps and use a larger motor, otherwise the performance will suffer. Conversion to a belt drive is usually done on conversion to a CNC machine where you they are spinning the spindle at much higher speeds using a small bit. Converting a PM-727V to a belt drive would compromise the machine significantly if using it only for manual milling. You would also be spending a lot more money unnecessarily converting a PM-727V to belt drive vs. buying a PM-30MV which comes with a 2 speed belt drive with a 2Hp motor.

Both the PM-727V and PM-30MV, offer an optimal milling package in my opinion for their size and price. If you need a smaller footprint and/or only have 120V go with the PM-727V, if you want belt drive and have 220V go with the PM-30MV. Size matters, but as far as travel (X, Y, Z) the 30MV gives a bit more X travel, but otherwise they are very similar in this category. If you have 220V, the PM-30MV would be my recommendation. Be aware that the cost of equipping your mill (vise, chucks, end mills, etc.) can easily be the same cost as the mill itself.
Mark
 
Many folks converted the G0704 to belt drive to eliminate the plastic gears in the drive train. I did the same to a early PM25 for the same reason. Having said that:

I much prefer variable speed machines, primarily for the reasons Mark explains above. The ability to 'dial in' the rpm can improve surface finish and prolong tool life.

I have a preference for BLDC motors over A/C motors. Better efficiency and power across the rpm range. A/C motors have a narrower power band so require gearing to provide a broader spindle rpm range while keeping the motor in or near it's optimum power/torque range. A BLDC motor is basically a 3-phase motor that is driven/stepped by DC electronics (similar to a A/C powered VFD and 3-phase motor combination).
 
I have been very satisfied with my 727m. I agree with Bill and Tom above about the variable speed and think if it were in my budget i would go that way. The v model was not available when i bought mine. I'm two years in as far as ownership and the gearbox has been no issue, the one issue i did have with the motor was taken care of by Matt quicker and easier then i ever would have imagined. Another words Very Satisfied.
 
The website does not specify the motor type. So I'm assuming it's A/C?

BTW, I'm not planning to convert to CNC.

I would love to get the PM-30MV, however I don't have 220 in my shop. I may need to investigate running a new line of power out there though. For an extra $50 I get more girth, bigger table, significant X axis travel, and a brushless/belt setup.

I started out thinking I was going to purchase the G0704 -> Pm25mv -> PM-727m -> PM-727v -> and now the PM-30MV.

Funny how that happens...
 
I started out thinking I was going to purchase the G0704 -> Pm25mv -> PM-727m -> PM-727v -> and now the PM-30MV.

Funny how that happens...

Ha! I started with a Sherline, then a cheap chinese table-top, then a LMS, then a early PM25, then a 9x40 Charter Oak, and then on to my current 935TS. There won't be any more... ;)
 
Last edited:
Sounds like my lathe decision tree.. HF mini-lathe > grizzly 10x > PM1022 > PM1030 > PM1127. I also considered trying for the PM1236, but I think the wife would have used it to make decorations from my bones after killing me. :)
 
It looks like my buddy, who is a commercial electrician, is going to help me route a dedicated 240 line to my shop, so the 30mv is looking more and more attractive
 
It looks like my buddy, who is a commercial electrician, is going to help me route a dedicated 240 line to my shop, so the 30mv is looking more and more attractive

When I bought my PM25, I REALLY wanted the PM30, but Matt discontinued selling the Weiss-based PM30 (and PM25) because of quality issues. Years later he comes out with a new and improved PM25 and PM30, but I had already moved on to a larger machine.

My timing over the years has never been that great. If I had just sat on my hands for about 6 years or so, I could now have a PM949TV and a PM1440GT sitting in my garage. But how was I supposed to know? Oh well, coulda, woulda, shoulda... ;)
 
Back
Top