Uprading my PM-25MV mill to PM-835S. Anyone have this mill?

Pcmaker

Pcmaker

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I think I'll be upgrading my PM-25MV mill next year to a knee type mill. I generally work on 1018 mild steel, but I want to work on harder materials such as hardened steels like stainless, etc... I almost never work with aluminum.

I haven't decided what to get yet. This is what I have:

PM-25MV Milling Machine – Precision Matthews Machinery Co.

www.precisionmatthews.com www.precisionmatthews.com

I'm leaning towards buying the most affordable knee mill by Precision Matthews, which is the PM-835S. Too bad I do not see any videos on Youtube about it.

PM-835S Milling Machine – Precision Matthews Machinery Co.

www.precisionmatthews.com www.precisionmatthews.com

I keep hearing there's a huge difference between bench type mills and knee mills when it comes to rigidity. The next mill I buy, I'll opt to get DRO already installed and X axis, as well as Z axis power feed. Maybe I"ll add Y axis power later on.

I want to know you guys' take on it. This mill seemingly has a smaller footprint than the other knee mills that they have. How much of a difference is there between this knee mill and the best bench mill they have at PM?

Here are the specs:

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I can't give you a personal review as I haven't used one. I can say that I was seriously looking at it when I found a Bridgeport locally. You might also contact local machinery dealers if you are looking for new. I have seen some listed from a local shop from a couple of different brands. I think PM still had them beat on price for similar features though.

A couple of things I use every time I use the mill. X power feed. Seriously, unless I'm drilling, I use it for just about everything. Awesome for things like face mills and fly cutting.

My ghetto Z power feed (a cordless drill with a 3D printed adapter). So nice when moving the knee more than a couple of turns. A real Z feed would be nice, but I'm not convinced it's $400 nice.. :)

DRO. You already said that you want one, but even if you have to do your own install for budget reasons, so nice to have. I bet the PM unit has useful instructions. I had to fiddle for a while to get the bolt circle to work on mine.

VFD. Not absolutely required, but it's nice to be able to tweak the speed more than the pulleys allow. The description says single phase, but it might be worth asking about 3 phase even if you have to get your own VFD. I can usually leave the belt alone and use the VFD and the back gear to do all the speed changes.
 
ttabbal said:
I can't give you a personal review as I haven't used one. I can say that I was seriously looking at it when I found a Bridgeport locally. You might also contact local machinery dealers if you are looking for new. I have seen some listed from a local shop from a couple of different brands. I think PM still had them beat on price for similar features though.

A couple of things I use every time I use the mill. X power feed. Seriously, unless I'm drilling, I use it for just about everything. Awesome for things like face mills and fly cutting.

My ghetto Z power feed (a cordless drill with a 3D printed adapter). So nice when moving the knee more than a couple of turns. A real Z feed would be nice, but I'm not convinced it's $400 nice.. :)

DRO. You already said that you want one, but even if you have to do your own install for budget reasons, so nice to have. I bet the PM unit has useful instructions. I had to fiddle for a while to get the bolt circle to work on mine.

VFD. Not absolutely required, but it's nice to be able to tweak the speed more than the pulleys allow. The description says single phase, but it might be worth asking about 3 phase even if you have to get your own VFD. I can usually leave the belt alone and use the VFD and the back gear to do all the speed changes.
Click to expand...

I upgraded from an HF Sieg mill to a PM-835S with 3-axis DRO and 3 power feeds and it is great.

The Z-Axis feed could have probably forgone without much pain, but I like having it.
The DRO is great.

I added a power drawbar. Really tricky if you want it to work wherever the quill is.
I added a quill DRO (not Mitutoyo, are you kidding?)
I upgraded from a single phase to 3-phase so I could implement a Fuji VFD and the speed control is excellent. Anyone want a spare 3HP PM single phase motor?

Quill power feed I never missed until I had it.
Using the TTS system for many, but not all tools.
The accuracy is superb and with a decent vise (Kurt of course) life is also great.

I would love to know how others have implemented a tach. It is tricky.
 
yeah, I just noticed there's no tachometer. There's no dial to change the speeds? You have to change the belt every time you want to speed up or slow down?
 
Pcmaker said:
yeah, I just noticed there's no tachometer. There's no dial to change the speeds? You have to change the belt every time you want to speed up or slow down?
Click to expand...

Not familiar with that machine, but changing belts to set speeds is quite common.
 
My guess is you’d find the PM835 more rigid than the PM25, but I for one do not subscribe to the idea that just because the 835 is a knee mill that this means it’s more rigid than a bench top mill. Lots of factors come together to contribute to mill rigidity. I refer you to my posting Here where I document my own experience moving from an RF45 benchtop mill to the PM935 knee mill:
www.hobby-machinist.com

833T & 1340GT Questions

I agree with a lot of what’s been said here: Replace the belt on the 1340 with a Gates Tri-power. I would stick with Dorian (my choice) or Aloris for the quick change tool post rather than trying to save a few dollars on an off-brand alternative. Avoid the Dorian “First time buyers...
www.hobby-machinist.com www.hobby-machinist.com
 
davidpbest said:
My guess is you’d find the PM835 more rigid than the PM25, but I for one do not subscribe to the idea that just because the 835 is a knee mill that this means it’s more rigid than a bench top mill. Lots of factors come together to contribute to mill rigidity. I refer you to my posting Here where I document my own experience moving from an RF45 benchtop mill to the PM935 knee mill:
www.hobby-machinist.com

833T & 1340GT Questions

I agree with a lot of what’s been said here: Replace the belt on the 1340 with a Gates Tri-power. I would stick with Dorian (my choice) or Aloris for the quick change tool post rather than trying to save a few dollars on an off-brand alternative. Avoid the Dorian “First time buyers...
www.hobby-machinist.com www.hobby-machinist.com
Click to expand...
Given that the PM835 weighs roughly 5 times what the PM25 weighs and only slightly larger travels, I would wager it is a safe bet that the PM835 is substancially more rigid than the PM25. Now comparing two machines of similar weight, it might be more questionable as to which is more rigid, but with such a huge difference in weight and size, there is no question which is the sturdier machine.
 
I'm also looking at the PM940M, which is their heaviest bench top milling machine.
 
I’d put my money on the 940 being more rigid for the reasons stated in my previous post. If you have never experienced a J-head, you might want to check that out and experience it since quite a change from a geared head machine (look into how the back gear and power downfeed work).
 
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