Dr.K wrote:I was pretty sure the price was out of sight, but she had absolutely no clue and was likely throwing a wild $$$$ out there. I told her I would investigate, and get back with her in a week or so.
The ways had some rust and we're dirty, but everything moved. I'm certain there is not another machine closer than this one for at least 60 miles in any direction, so proximity is a huge selling point for me.
As far as the machine, is there something I should look for specifically that tends to be an issue? I'm just not up to speed on mills like I am lathes.
The reality is that other than ease of personal inspection, the distance isn't really that important. It's the same amount of work to get a mill on and off a trailer whether you're going 5 miles or 500 miles. I've picked up machines more than 900 miles away when I found a good deal.
A Bridgeport in good condition typically sells for $1,500-$2,000 depending on details like hard chromed ways, power feeds and DROs. A new Chinese DRO will run you $750, power feeds $250. The idea is not to pay more than a given feature is worth if you had to add it yourself. Hard chromed ways aren't something you can add, but they are a definite plus and increase the value of the machine.
I'm sure the Yuasa branded Taiwan clone of a Bridgeport is a decent machine when new, but the key things to look for in any mill are:
- Condition of spindle brearings. Turn the spindle by hand and listen for roughness. Run the spindle under power and listen for any odd noises. If you don't find a container of suitable spindle oil there and an oil can filled with it, there is a good chance it hasn't been lubed regularly.
- Condition of the ways. Move the axes from end to end and examine the ways closely with a flashlight if needed to check wear. If you see a regular scrape pattern from when the ways were scraped perfectly flat when new across the full length of each way then there is little wear. If the ways don't show such a pattern there is a decent chance the mill has a lot of wear. If you have a precision straight edge you can hold it along the ways with a flashlight behind it to get an idea of any grossly low spots. There are different types / grades of ways, some are hard chromed, some are ground rather than hand scraped, etc. so there are subtleties to assessing the ways.
- Backlash. You can coarsely check backlash by running the table some distance in a given direction, zeroing or noteing the reading on the dial, then reversing and noting the distance the dial turns before you feel the load of the table moving as well. There is always some backlash, but it should be small, and equally important it should be consistent across the length of the axis travel. Often a mill gets used mostly within a smaller area in the center of the travel and ends up with significant wear in that area while further out from that area there is a lot less wear. This type of uneven wear is the most difficult to correct, as you can tighten the leadscrew nuts to reduce backlash if the wear is even, but if it's uneven you can't tighten it enough to correct for the worn area without making the unworn areas too tight.
- Gibs. There are tapered gibs that are used to take play out of the dovetail slides on the axes, they are adjustable to correct for wear. You can get an idea of their adjustment state from how easily the axes move, but it takes some experience to judge. There are also lock levers for each axis, and when engaged they should hold the table in position when you try to move it. If the lock don't work that is a good inidcation of a lot of wear and gibs out of adjustment.
For these checks, you can tell a lot without tools if you have experience using a mill in good condition, but to properly check you need to use a dial / test indicator to get actual measurements.
I do see the mill has a central lube pump for the ways, which is a plus both operationally and also by increasing the probability the ways have been kept properly lubed. Again check for the presence of a container of proper way lube nearby and that the central lube pump has been kept full.
