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Thread: Mill accuracy. New chinese, new taiwan, old bridgport etc

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    Registered Apples's Avatar
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    Default Mill accuracy. New chinese, new taiwan, old bridgport etc

    How accurate are milling machines?

    If you took a bit of mild steel and milled the top and bottom to say 100mm (4") with a new chinese mill aka grizzly or Hafco what would you end up with? Exactly 100mm, or say 99.5mm?

    Then the same again with a Taiwanese unit.
    Then the same again with a good conditioned bridge port mill.

    Lets say a knee mill that has between a 2-5hp motor.

    Peter

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    This comparison is incomplete, and does not reveal sufficient information upon which you should base a purchase decision.

    You're not taking into consideration spindle quality, backlash, long term wear characteristics, parts availability, service life....and in some cases, the financial impact of your purchase dollars heading out of your country.

    What about surface finish? Repeatability? Thermal expansion and a change in dimensions as the machine heats up....for subsequent parts? Stick slip of the ways, operator fatigue from cranking a cheap table,, ...and all the other subtleties of running a manual mill that only years of experience give you...

    I was stuck with a Roundtower chinese knock-off for several years. It was a genuine POS. Could I get precision parts from it? Yes, I did. About 4 years ago I bought a brand new Bridgeport (now from Hardinge)...and don't regret a dime of the extra money spend over what a Chevalier or BridgeTower or Die Yung would have cost.

    How accurate? It's not the machine, it's the machinist. You need to look at the oranges.



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    Yeah okay then I can see all the other factors.

    So then how does/did that ching chong mill of compare to your new bridgeport unit. How much better did you find the accuracy?

    And another question, how much accuracy does one need? If I wanted to make a cylinder block for and air compressor or even and IC engine. Will a Chinese knee mill be up to the job?

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    Again..... the new Bridgeport replaces a 40 year old Bridgeport that was just plain wore out....which, IMHO was light years better than that POS Roundtower..

    And the choice between a slightly used chingchongtower and the decrepit Bridgeport? Given that the time and effort to achieve the same relative "accuracy" on either machine could be the same? I'll take the Bridgeport.

    You keep talking about "accuracy". That's a relative term when it comes to a manual machine.

    Sounds like you're trying to decide on which machine to buy. Buy the cheap one. Spend the savings on good tooling, which you can use on the new good quality mill you end up buying when you realize how much you hate that POS you saved so much money on.

    ....Some of the formerly cheap imports are getting better...because they've been forced to by the emergence of newer, even cheaper machines... but at the same time, corners get cut which may not affect "accuracy" in the short term, but compromise life cycle.



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    Quote Originally Posted by fizzissist View Post
    ....Some of the formerly cheap imports are getting better...because they've been forced to by the emergence of newer, even cheaper machines...
    It isn't that simple in my experience. It seems to me that there are actually two Chinas: old and new.

    The 'old China' is represented by the older State-run companies. Never mind the quality, just employ lots and lots of workers. Yeah, not such good quality. You can sometimes recognise them because they want you to pay by T/T or LoC, and will only sell in hundreds or tons.

    The 'new China' is new money, often with a competent European manager in charge. Their products are, in my experience, well-made and done to international standards. Some of the tooling from these new companies is good. And they will actually SELL to you.

    Can you get whole machines from the new companies? I haven't searched for that yet. It will happen, but when is another Q. Hey, if they can put satellites in orbit, they aren't that feeble.

    Oh, and do distinguish between China and Taiwan. Taiwanese machine tools are pretty good. maybe not quite up to Germany or Eastern Europe, but definitely getting there. I have a Chinese lathe and a Taiwanese mill, and the difference between them is huge.

    Cheers



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    RCafffin , yeah well the only places that I am aware of to get a new mill from is hare and forbes and asset plant and machinery. I know that the HAFCO ones come in chinese and taiwanese units. There is a machinist in town who has had a hafco for at least 2 years now. I should call in to see him one day to see how it is going.

    It is very hard for me to compare this with that because if you have never used the good old iron how do you know what the new ones are like. The only lathe and mill I used was at TAFE and the mill was some old russian battle tank of a thing. Cut like a champ.

    There are the older units getting around.

    What do you do to check them? And how do you check them? Is there a guid or check list that anyone knows about that I can print out and take with me.

    The obvious thing is to check the ways for big marks and scores, check for abused table top etc. What else? Do I stick my indicator onto the spindle area and then move the table left and right to check for play?
    Well that would not work as if the table is not dead level the indicator will read from low to high etc.

    How do you check the spindle? Put indicator base on table, lock it off then put indicator onto spindle shaft and try to push the spindle to check for play?

    The Tormach unit apparently lists it's tolerances etc. Do the Hafco one too?
    ie how my run out or play over a 3" distance etc.

    Peter

    My little site on MIG welding http://www.learn-how-to-weld.com/mig-welding/


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    Other vendors like Redfox, Standaco, and Applied Machinery to name just a couple also sell the Optimum / Vertex / Metex / Machtech branded gear, which companies now seem to have outsourced to Chinese/Taiwanese manufacturers, but are designed to their specs and requirements.

    I have a BF16 Vario mill and it's really quite nicely made, albeit small, and compared to my Chinese CNC machine there's a world of difference in the casting quality, and especially the finish.

    Standaco have probably the most superb Taiwanese lathes I've ever seen!

    The Hafco stuff is good, and cheap, but after having bought a few of their items, I've come to the conclusion that while adequate, they are made to a price point definately. Just my opinion. I'm looking at a Machtech V1000 over a H&F HM50-52 myself. The quality of the floor stock was very nice. Another thing you'll find in the cheaper Chinese stuff, is the fairly liberal use of bondo! Looks good until stress is put on the area and it cracks, or comes apart. On a lot of the machines you can actually see floorstock where this has happened, imagine under frequent use how it would look.

    I'd spend more time searching and googling if I were you, the small differences that add up to the end finish, accuracy, and user satisfaction are not quite so apparent as most would think.

    cheers,
    Ian

    Last edited by aarggh; 11-19-2011 at 06:56 PM. Reason: forgot bondo!
    It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!


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    Default Chinese and Taiwanese

    Quote Originally Posted by Apples View Post
    yeah well the only places that I am aware of to get a new mill from is hare and forbes and asset plant and machinery.
    Oh dear. Been that route and was massively NOT impressed. After buying a Chinese lathe and a Chinese bandsaw from the rabbit family, I sent a letter listing about 10 problems with the machinery to the management. I got ZERO replies. I was unhappy.
    I bought a Taiwanese mill from Herless before they were bought out by H&F. It's good, but you can't get what I bought from H&F any more. Herless got mine in from Taiwan to order. (Replace single phase motor with 3-phase, replace Morse taper with R8. Morse taper in a Mill??? Death and destruction.)

    It is very hard for me to compare this with that because if you have never used the good old iron how do you know what the new ones are like. The only lathe and mill I used was at TAFE and the mill was some old russian battle tank of a thing. Cut like a champ.
    Great big heavy lumps of cast iron. Yep, GOOD stuff. And often can be cleaned up well. A bit of hand scraping and maybe a new gib... (A chain hoist can be a godsend. ) But I would seriously consider replacing all screw/nut combos with GOOD ball screw systems and new ball races at the ends.

    And how do you check them? Is there a guide or check list that anyone knows about that I can print out and take with me.
    Like buying a car. You find an elderly (possibly retired) machinist or toolmaker and take him with you. I am actually quite serious!

    Yeah, dial indicators and lots of clean rags to wipe down the ways for checking are both good ideas. But experience is unbeatable.

    Sorry!
    (What State are you in?)

    Cheers
    Roger



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    Hi Roger, I'm up in QLD, Toowoomba.

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    Default Qld

    ooh - foreign lands ... sorry.
    (NSW)

    Find a model steam train club and visit them. Many old retired engineers... They would be delighted to help.

    Cheers



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    Default Why buy forein?

    I just bought a totally rebuilt Bridgeport 1hp J head, deliverd on my floor for under 3K. AND IT IS TIGHTER than the one we have at work. the shop in eastern Iowa competly pulls the old ones down and rebuilds them.
    X is under 0.004", Y is under 0.005, came with a one shot oiler and looks new!
    they are over by Waterloo Iowa, but I can not find the paperwork to give you their name.

    SBI


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    Quote Originally Posted by sbi1406 View Post
    I just bought a totally rebuilt Bridgeport 1hp J head, deliverd on my floor for under 3K. AND IT IS TIGHTER than the one we have at work. the shop in eastern Iowa competly pulls the old ones down and rebuilds them.
    X is under 0.004", Y is under 0.005, came with a one shot oiler and looks new!
    they are over by Waterloo Iowa, but I can not find the paperwork to give you their name.
    The only problem is that while it seems to us that there is a very large range and quantity of machines available in the States, to the point that they are almost a commodity item, here in OZ we have no such range, or pricing. We are limited to vendors who either bulk import Chinese, (and some Taiwanese) gear at what is approaching reasonable prices, or obtain the better gear at exhorbitant prices as they are almost one-offs.

    People who have good machines tend to not sell them, so there's not even a second hand market locally. Obviously there's always exceptions, but generally we get screwed in every way here in OZ for hardware and tooling, in fact, if it wasn't for the Chinese imports, we'd have hardly any range available here at prices that hobbiests could afford.

    Even just raw materials can cost an arm and a leg at times here.

    cheers,
    Ian

    It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!


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