Hi my next machine I'm looking to perches is a used mill. I would like sum
advice on what to look for in a used machine. How to tell if the machine is worth
buying and what are sum good brands to look at and sum to stay away from? Thanks
Used Mill purchasing and inspection?
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MarkLong
Give us more info
Well I think it would depend on these factors, maybe more:
1. How much cash do you have to spend on the machine (you will also have to set aside $ for tooling, which can be a pretty significant amount of $)?
2. How much room you have? Or more precisely what size are you interested in?
3. Who will move it? And place it?
I think you need to decide on what you wish to use it for and the size you need before anyone can really give you some advice that would pertain to your situation.
1. How much cash do you have to spend on the machine (you will also have to set aside $ for tooling, which can be a pretty significant amount of $)?
2. How much room you have? Or more precisely what size are you interested in?
3. Who will move it? And place it?
I think you need to decide on what you wish to use it for and the size you need before anyone can really give you some advice that would pertain to your situation.
Re: Give us more info
MarkLong it will be a full size Bridgeport or clone 9 X 49 table. A rigging
company will be moving it to is new home. I would like to spend about $2000 to
$2500 for it + moving expenses. What should I look for when I look at the ways
and the table where and if the head makes the usual noise when you run it at a hi
RPM how much could that cost in parts thanks Rod
company will be moving it to is new home. I would like to spend about $2000 to
$2500 for it + moving expenses. What should I look for when I look at the ways
and the table where and if the head makes the usual noise when you run it at a hi
RPM how much could that cost in parts thanks Rod
a couple of things to look for
On the ways of the "Y" axis, which move the table front to back, you can see the original flaking marks. These are on the horizontal flat surfaces. Around the corners nearest the operator, there should be a region that is virtualy unworn, so you can use that as a guide to how much wear is on the other regions of the ways. Mine has some visible wear, but the original flaking is still apparent.
There has been much discussion previously on the Chaski site on whether the flaking marks serve any purpose other than decoration (i.e., holding oil for lubrication as opposed to entrapping grit that makes wear worse, or preventing stick-slip effects, etc.)... One thing that they are helpful for is judging how worn a used machine is.
Another thing to check for is backlash in the longitudinal (x-axis) and cross (y-axis) feeds. Compare the backlash when the table is in the middle, as opposed to when the table is at the ends. If the backlash is constant throughout the range, then that is a good sign, as it indicates that any wear is in the acme nut. However, if the backlash is greater in the middle of the travel range than at the ends, that is an indication of a worn lead screw. If this has happened, there is probably a lot of wear elsewhere on the machine.
Some backlash, like about 0.050" in the nuts is nothing to be concerned about, especially with the cheapness and availability of DRO systems nowadays.
I think one of the most critical things is the condition of the spindle bearings. I don't know how to check these, but I have heard that you can tell if they are bad by looking at the finish of a piece of metal that is milled with the machine using a medium to big sized end mill..
There are some other bits of advice for buyers posted on a dealer's website, www.mermac.com
Good luck,
Jon Spear
San Francisco, CA
There has been much discussion previously on the Chaski site on whether the flaking marks serve any purpose other than decoration (i.e., holding oil for lubrication as opposed to entrapping grit that makes wear worse, or preventing stick-slip effects, etc.)... One thing that they are helpful for is judging how worn a used machine is.
Another thing to check for is backlash in the longitudinal (x-axis) and cross (y-axis) feeds. Compare the backlash when the table is in the middle, as opposed to when the table is at the ends. If the backlash is constant throughout the range, then that is a good sign, as it indicates that any wear is in the acme nut. However, if the backlash is greater in the middle of the travel range than at the ends, that is an indication of a worn lead screw. If this has happened, there is probably a lot of wear elsewhere on the machine.
Some backlash, like about 0.050" in the nuts is nothing to be concerned about, especially with the cheapness and availability of DRO systems nowadays.
I think one of the most critical things is the condition of the spindle bearings. I don't know how to check these, but I have heard that you can tell if they are bad by looking at the finish of a piece of metal that is milled with the machine using a medium to big sized end mill..
There are some other bits of advice for buyers posted on a dealer's website, www.mermac.com
Good luck,
Jon Spear
San Francisco, CA
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Anonymous
Re: Give us more info
If the mill has all the frosting pattern across the ways, that is a good sign. Otherwise you will have to run with the gibs loose and that's not good.
You can't see the frosting on the x axis ways but you can quickly tighten the gib with a screwdriver and try to run the table end to end. Sometimes you can put a large drill bit in the spindle, grab it and see if the spindle moves. Run it slow and fast and make sure it is quiet. Check the power feed. It's ok for the table top to have dings and a few holes with in reason.
If you can so some tests with an indicator, that would be best but if it passed the basic tests, you probably have found a nice one.
Good luck,
Dave
You can't see the frosting on the x axis ways but you can quickly tighten the gib with a screwdriver and try to run the table end to end. Sometimes you can put a large drill bit in the spindle, grab it and see if the spindle moves. Run it slow and fast and make sure it is quiet. Check the power feed. It's ok for the table top to have dings and a few holes with in reason.
If you can so some tests with an indicator, that would be best but if it passed the basic tests, you probably have found a nice one.
Good luck,
Dave