I Got Burnt!!

[brino]

I've not heard of a machine yet that can be bought for $2k (roughly) and "out of the box" hold a thou over it's working range. Not even close. You won't get that out of a worn/used machine either. I don't care where it's made. Brand new BPs don't even advertise one-thou tolerance, and no experienced machinist I know would expect that.

Bill, Thanks for the response!

I sure do NOT consider myself an "experienced machinist"; please help set my expectations, have you got any references?
The Bridgeport website and brochures seem tight lipped on any claims of accuracy, precision, repeatability.
This is why setting expectations is so difficult.

...and no, I would not expect that from used/worn machines, what I said (or tried to say) was that I expect a price/precision trade-off, the more I pay the more precise. For used machine I expect to pay less, and expect to get less precision due to wear, but at least my expectations may be met.

-brino

 

[chips&more]

And then the Imports have the audacity to say they are ISO certified! That tells me that being ISO certified is just a consumer buzz phrase trap…Dave

 

[toolman]

FWIW, ENCO has several on sale right now including the Rong Fu machines. I almost bought one used a couple of years ago before deciding to get a larger machine, but it was a nice little mill that ran really quite and smooth.

 

[joshua43214]

But how does a newbie set expectations properly? Their own and the suppliers.
Should a newbie not even consider a machine at this price-point, but be forced to pay double to have someone actually test/inspect it knowing that a newbie owner won't know how to evaluate or adjust/tweak it properly? What suppliers offer that "extra" service?
Should the supplier not sell to an inexperienced buyer?

-brino

The very legitimate gripe here is that CO charges far more for the same basic machine that any one else. My understanding is that the company changed hands in the last year or so. In the past, they justified the extra cost by doing all the finishing work here in America, and they have a truly massive work envelope. It looks like the new company is doing all the extra inspection in China now and not passing on the savings.

I do feel the OP's pain. I also tend to get anal retentive over details. I also understand that I would have to shell out >$40,000.00 for a mill that would make me happy. The buyer should always beware whether you are buying a lab grade mill, or a cheap import, and expectations should be set appropriately. There is no such thing as a "precision" Chinese machine, period. Once you accept this, life is much easier.

When I was looking for a mill, the CO was very high on my list. Further research found that people were having some issues with the mill not living up to advertised expectations. I went with a Precision Matthews in the end and my only regret is that I wish I had a bigger mill
It had an issue with the screw in the spindle, it has an imperfect pain job, it twists the column when I cut too deep, the quill is not reliable for deep boring with a boring head, and some other stuff. All minor, all with in my expectations. All for a good price from a good person.

-Josh

 

[coolidge]

Brino in my research before purchasing the CO mill I found complaints on many other brands of this type of mill regarding the ways binding. This can happen when the ways are ground on a taper or more commonly imo when the ways are tight at each end and loose in the middle. One of the reasons I chose the CO mill was because they were aware of this issue and have been working with the factory to address this for a while. This is because they sell CNC versions of this mill and if the ways are binding that's a huge problem. So I figured I would go with a company that is at least aware of the problem and dealing with it vs some other brand that may not care because the mill is just a manual mill.

It would be my guess this problem is a lot more common across brands, its just that most people don't go to the trouble of disassembling, cleaning, adjusting the ways to a close tolerance, and testing for it. You can't really check this with a hand wheel crank you have too much leverage. You need to slide the table and Y/Z saddles back and forth by hand after adjusting the gibs to a slight drag fit with the screw disengaged. The drag should be slight and consistent across the full travel of the axis. Any loose or tight spots will stick out like a sore thumb when you do this by hand, then you get the dial indicator out and confirm.

Maybe for most manual milling operations it doesn't matter but I was thinking of converting this mill to CNC which is why I specified this and checked it. Its worth noting that the ways on my first RongFu 45 mill I purchased maybe 8-9 years ago were so bad I ended up having it hauled to the scrap yard, I would not sell it to someone else it was that bad.

 

[coolidge]

But how does a newbie set expectations properly? Their own and the suppliers.
-brino

They visit the Hobby Machinist forum first!

 

[coolidge]

The very legitimate gripe here is that CO charges far more for the same basic machine that any one else.-Josh

For example? At $2,350 its actually less expensive than many mills in its class while offering a much larger work cube and is substantially beefed up in areas where competing mills are still weak and puny. I'd like to see 1-2 examples that compare that are less expensive. I'm not trying to pick a fight here, but I think we need to be fair to CO.

Here's something to consider and was another reason I chose to go with the CO mill. You really can't judge how massive this mill is until you see it in person. There's a reason Bill named his El Hefe. I have owned a RongFu 45 mill before, the CO 12z is much larger. My 29hp diesel Kubota tractor front end loader couldn't even lift the thing off the pallet to which I replied

Are there quality issues yes, is it over priced at $2,400 I say no. Just realize you are buying a $2,400 mill made in China not a knee mill costing 2-5 times the price.

 

[wrmiller]

Not picking on you Josh, but unless you've driven a 12Z you don't know what you're talking about. This thing has a bunch more mass/rigidity than any of the other rf45s I've seen/used. Matt's new 9x40 is probably the closest I've seen but I'm reserving judgement until I see one.

 

[wrmiller]

Bill, Thanks for the response!

I sure do NOT consider myself an "experienced machinist"; please help set my expectations, have you got any references?
The Bridgeport website and brochures seem tight lipped on any claims of accuracy, precision, repeatability.
This is why setting expectations is so difficult.

...and no, I would not expect that from used/worn machines, what I said (or tried to say) was that I expect a price/precision trade-off, the more I pay the more precise. For used machine I expect to pay less, and expect to get less precision due to wear, but at least my expectations may be met.

-brino

Hey Brino,

No references written down, sorry. My comment was based on my actually measuring on various machines and talking to guys with WAY more experience than I doing the same thing. Example: In setting up my PM1340GT I managed to get under a half thou taper across about 10" or so IIRC. To hold that over the entire 40" of the center-to-center working range? Impossible. Nor, is it ever needed. As others here would tell you, if you need to hold that kind of tolerance you should be doing cylindrical grinding or whatever it's called.

OP: Sorry for the hijack, I will not post any more unless it's on topic.

 

[wlburton]

This thread is extremely informative to a fledgling hobby machinist thinking about buying a milling machine (like me). Thanks for all the voices of experience who have weighed in! You've put into great perspective the role of expectations and the ability to identify and rectify issues with this type of machine (or any machine, apparently). One concern I have is that if I bought a machine, say from Grizzly or Precision Matthews, I wouldn't be in a good position to judge what was okay or at least normal and what was something that would need to be dealt with as a warranty issue (other than things which were extremely obvious). I think I will make it my business to educate myself a little more about critical and non-critical defects before I jump into ordering a machine--and this thread has gotten me off to a good start.

Bill