PM's Mills

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Geswearf

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I've been wondering about what PM's mill descriptions really mean. They describe the 748VT as an ultra precision mill, but a similar machine (roughly the same size), say the 727 mill gets no such accolades. Or for about the same money as the 728VT, consider the 30MV or the 932V (both of which are heavier, more powerful and have larger capacities. Yes, I've read that machine tools made in Taiwan are better than Chinese made machines, but what exactly does this mean?

Members of this forum have posted about buying other PM mills than the 728 (most of which seem to be Chinese in origin) but nobody has said their PMxxxV is only good for machining +/- 0.01. For the sake of this discussion, lets ignore standard accessories/features that kick the 728's price up, or design differences such as the placement and ease of use to raise and lower the head.

How much better a machine is the 728? Can this be quantified? Sure, this mill can be upgraded by installing $1000 screws, but lets talk about the basic machine. I'd rather compare it to machines that are roughly the same capacity and weight - it makes no sense to me to try to compare a 728VT to a 932V.

I'm trying to make some sense of PM's offerings because (as I've said in other posts) I'm thinking about buying one of their smaller mills.
 
A cursory look at the 728VT specs suggests some answers beyond the usual mainland Chinese complaints:

"Super Precise Way Grinding Matched with Highly Skilled Precision Fitting and Scraping of Matching Way Surfaces and Gibs" - you won't find this claim elsewhere.

"Thrust Bearings in leadscrew ends"

"Ultra Precision Spindle, with Triple Bearing Support. Deep Groove Ball, and Angular Contact Bearings " - my guess is the bearings are NSK or similar from Japan. R8 spindle taper tolerances on the lower cost Chinese machines are a common complaint.

"5 Year Warranty" - the others are 3-year.

Have you asked PM to detail the differences?
 
I do wish that PM's machine descriptions were a more quantitative than qualitative, less bragging and more numbers (for example TIR). There used to be a mill comparison pdf, but I can't find it on the site right now, but it was somewhat incomplete as it was.
 
@davidpbest, I've read the PM descriptions and what you quoted is not news, however, how does this translate into the quality of the end product? If not hand scraping the ways does not yield any benefits that folks here have seen using PM's other mills, why do that? If it does give better machining results, quantify them, please.

@braddr, exactly. the comparison chart is woefully incomplete. I've gotten more info reading the machine description, but again, no way to judge the difference between the quality of the machines.

@Nutfarmer, I want to learn as much as I can by asking questions from guys who use these machines, not (yet) from Matt at PM.

As I mentioned, there are differences that I've gleaned by reading threads. For example, some of their mills have the head elevation crank situated low on the side of the post, making it easier to reach than the 728's* crank at the post top. Not sure if they would point this out to me in a phone call, and PM does not have a show room. I live about 2 hours away from them and have called to ask if I could stop by and look at some of their mills. They offered to uncrate any machine I wanted to see (the fellow on the phone was very nice) and set it up, but I do not feel comfortable asking them to do that to several different machines. It may yet come down to that if an accessible side crank makes a power feed for Z unneeded.
 
Geswearf said:
but nobody has said their PMxxxV is only good for machining +/- 0.01.
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No machine tool for sale today won’t hold .001”. Asking for that level of detail is akin to asking a car dealer to point out that all the cars have steering wheels.

The wild card here is the hands at the controls. Without hard stops, I doubt many of us are capable of repeating to .001” anyways.

If you need greater precision then .001”, then you need to start looking at surface grinders.

Most professionals I’ve met get by just fine with equipment that’s been hard used by uncaring and random operators for decades. Hobbyists ought to relax a little probably.
 
I guess this would be the forum to request specific machine information from owners, I'm sure owners will be happy to answer questions, and post photos. I own a 940m. for one - i'd have to have a power feed for the 'Z' - I couldn't imagine cranking that heavy head up and down all the time... Another tidbit about the 940 - it's heavy, about 1000lbs. makes it a chore to have to move.
 
I don’t own any PM products so you can dismiss my comments if you like.

Asking questions and reading this forum will get you most of the way towards answering the questions you asked in this thread.

In general, all machines built in Taiwan will be better fit and finish than China. Quantifying how much more accurate they are is probably beyond what any manufacturer or reseller is capable of doing. There are just too many variables including the biggest one, the operator.

PM has been a forum sponsor since before I joined here and from what I’ve seen has earned the reputation they have. People here do great work with both their Taiwan built and mainland machines. Also with tools from other suppliers.

Mostly your decision should come down to your expectations. If you want a supplier who supports what they sell then PM will probably not disappoint. If you value a higher standard of workmanship then go for Taiwan built.

However, if you desire perfection from the machine itself you may be disappointed no mater what you get. Precision is something to work towards, not something you can buy. There’s a reason drawings have tolerances called out, and although getting closer is good it’s not always worthwhile.

Good luck in your pursuits here, no matter what your passion you’ll find someone on the forum who shares it.

Cheers,

John
 
@jwmay, I've been using a harbor fright mill that might on a good day be good to a thou. There are a number of things wrong with it, and were I to keep it, the whole tool would have to be torn down, examined, and worn parts replaced. Any mill on the market today would do for me, however, i'm calling their bluff...so to speak. I want to know what they mean by 'ultra precision' and what @davidpbest calls FUD fighting words (whatever that acronym stands for). I'd call their description laced in technobabble or ad-speak. It's meaningless verbiage when they could have said exactly how the 728 is better than the other mills they sell. Give me a good comparison, please. They don't have a showroom. Why should I buy their mill and be disappointed by something that does not meet expectations or is difficult to use (like the top mounted Z axis wheel on the 728*) when I can ask you guys here and get good answers to my questions.

I'm not tall, and reaching in and up to adjust the tool head (Z axis) will cost me an additional $400. A power drawbar adds almost a thou. Tell me, honestly, do you think PM will say, "Unless you mount this mill lower than our pedestal mounting, or are over 6' tall, reaching the top handwheel will be difficult at best". This feature alone might be a deal breaker for me. I don't know, because I don't have enough info yet.

@hotrats - thank you. That's exactly why I am here and not on other forums. And I appreciate the pointer on your 940's weight. I have sort of ruled out the 940 because of its weight and size. I'd have to move it down 4 stairs into my basement (low ceiling, too) and unloading it would be a task that is difficult at best.
matthewsx said:
1. Asking questions and reading this forum will get you most of the way towards answering the questions you asked in this thread.

2. In general, all machines built in Taiwan will be better fit and finish than China. Quantifying how much more accurate they are is probably beyond what any manufacturer or reseller is capable of doing. There are just too many variables including the biggest one, the operator.

3. PM has been a forum sponsor since before I joined here and from what I’ve seen has earned the reputation they have. People here do great work with both their Taiwan built and mainland machines. Also with tools from other suppliers.

4. Mostly your decision should come down to your expectations. If you want a supplier who supports what they sell then PM will probably not disappoint. If you value a higher standard of workmanship then go for Taiwan built.

5. However, if you desire perfection from the machine itself you may be disappointed no mater what you get. Precision is something to work towards, not something you can buy. There’s a reason drawings have tolerances called out, and although getting closer is good it’s not always worthwhile.

6. Good luck in your pursuits here, no matter what your passion you’ll find someone on the forum who shares it.
Click to expand...
1. Exactly - as I said to hotrats
2. I understand and have read that in many places. I tend to react badly to technobabble and suspect the purveyor is not being forthcoming. Yes, my personal problem.
3. I was wowed by Matt's responses here to the guy who had a badly machined spindle - his public participation has pushed me away from Grizzly and to PM (also their proximity to me...I can pick up what I buy and save a bundle).
4. I'm trying to get a realistic picture of what the machines are before I buy one. If PM had several set up in their showroom it would be easy...and I'd probably have fewer q's for you guys here. Their not so detailed comparison page doesn't help. At least you can usually drive a car before you buy it.
5. I don't. A gunsmith friend once told me his mill was sloppy and you had to know how to use it - take up slack before you begin cutting - if you wanted good results. I know its the guy behind the tool that gets the good or bad results.
6. Thanks. That's why I've been struggling since March to get confirmed on this website. An email problem that I've not yet figured out but that's another story.

*Not even sure if its the 728 that has this feature, my Excel spreadsheet comparing the mills and features is not open right now. As pointed out, the 940 might be what I'm talking about.
 
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