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

There are +/-'s to each mill design, I think most people would not be able to detect the difference in routine machining. Anything will be a huge step-up from the PM-25. I prefer the knee mills overall, on my previous bench-top I started to get some sag in the head because of uneven where on the gibs over time. So if you go with a heavy benchtop I would recommend some form of counter weight system to offset the weight of the head. If you are looking at the PM-940, I would also look at the PM-833T. There is something to be said for weight and rigidity, so there is also the used market in a full size knee if you can find something in reasonable condition.

Putting a tach on these mills is not so difficult, I have made number of them, the current components listed in the document seem to work better than some of the previous ones with different hall sensors. The actual hall sensor is the same for the 8-12 mm barrel sensors. The design below is for the PM-935, but have also adapted it to the PM-949 and Bridgeport style machines. You can choose different tach enclosures depending on what you want. Using a LED light ring greatly diminishes shadows when used in conjunction with other lighting.
 

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mksj said:
There are +/-'s to each mill design, I think most people would not be able to detect the difference in routine machining. Anything will be a huge step-up from the PM-25. I prefer the knee mills overall, on my previous bench-top I started to get some sag in the head because of uneven where on the gibs over time. So if you go with a heavy benchtop I would recommend some form of counter weight system to offset the weight of the head. If you are looking at the PM-940, I would also look at the PM-833T. There is something to be said for weight and rigidity, so there is also the used market in a full size knee if you can find something in reasonable condition.

Putting a tach on these mills is not so difficult, I have made number of them, the current components listed in the document seem to work better than some of the previous ones with different hall sensors. The actual hall sensor is the same for the 8-12 mm barrel sensors. The design below is for the PM-935, but have also adapted it to the PM-949 and Bridgeport style machines. You can choose different tach enclosures depending on what you want. Using a LED light ring greatly diminishes shadows when used in conjunction with other lighting.
Click to expand...

Thanks. Great diagrams and advice.
 
So now, I've kind of narrowed it down to the 940M, 833T or the 835S

I shot PM a question of which machine is more ridgid and if the 833T has tighter tolerances especially in the nod. I don't want to have to shim it to get to .001 like I did with my PM25MV.
 
If I were you, I would rely more upon actual user views, and encourage you to visit shop owners and form your own direct impressions. I can’t emphasize enough the merits of an hour’s experience with the J-head in contrast to geared-head. And as far as tramming the head goes, I’d much prefer to tram the column on a benchtop mill once and forever than have to deal with nod and tilt of a ram-mounted J-head monthly.
 
Yeah, that's why I'm asking here first, but there's hardly any users here of these mills

Not exactly sure what a J head is
 
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Pcmaker said:
Not exactly sure what a J head is
Click to expand...

It's a type of bridgeport head. I believe it's the kind I have. Pulleys for speed adjustment. While a gear head is easier to adjust, it is also potentially louder. I've seen posts about converting them to belt drive for that reason. I haven't used a gear head, so I can't really compare. That said, moving the belt isn't that bad. Loosen the bolt (it has a built in lever) move the motor, move the belt, put it back. Takes less time to do it than I spent typing. And I don't bother to most of the time with the VFD.

As for tramming.. I only have to adjust it if I mess with it. I check it occasionally, and don't see any drift with a tenths indicator. Perhaps if I took heavier cuts the forces would be more likely to move it? Certainly I've never seen it 0.001 out unless I put it there.

It can be tough for a hobbyist to get time on a machine. Most shops wouldn't allow it out of concern for safety and machine damage. Another hobbyist might, but there aren't that many of us.
 
I'm leaning towards the PM-940M now. I sent Precision Matthews about the difference of ridgidity between the bench mill PM-940M and the knee mill PM-835S. If the difference is negligible, then I'll go for the PM-940M.
 
As to changing speeds::
I am a hobby machinist who has achieved some nice parts.
I generally use my mill at one of 2 speeds: slow and really slow.
The last time I change the speed was a bit over a month ago (30-40 parts ago).
The trick is using the same end mill diameters.
 
Just got a reply from PM tech and he recommends the PM-935 which is this. If I get it, I will go with the 935TV which has a variable speed drive in single phase. I'll also go for the X axis power feed and 3 axis DRO

front-left-1.jpg


PM-935TS/TV Milling Machines – Precision Matthews Machinery Co.

www.precisionmatthews.com www.precisionmatthews.com

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