Sunday, August 5, 2012

Looking at used lathes Part 2

I can tell you a few general things to look for when shopping for a used lathe. The first impression is important. If you walk in and it looks clean and new that's a pretty good indicator. If you get closer and it looks like it been recently painted you will need to look a little closer. Look for over spray and bad paint masking. Hopefully the owner has power to it so you can run the spindle. Question them about where it came from how they got it, how they moved it in, and what they use it for. You will get a sense if the owner is a machinist or a backyard hacker. Most importantly ask why they are selling it.
Not a good first impression for a lathe in this picture of a Mori Seiki above. Electrical cover is off and a can of WD-40 is sitting on top like somebody has an electrical problem and was trying to free something up. Looks like the owner was trying to get it running before his potential customer arrived.Hummmm.
Probably not a good metalworking lathe any more. These guys in the picture above are machining stone on their lathe. If you see abrasive piled up like this when your shopping for a lathe, run away.

Try everything you can on the prospective lathe. If you don't know how have the person show you. If he or she doesn't know how to make it go, do your best to try most of the spindle speeds, the longitudinal feed and cross feed. Do this with several feed rate changes at the gearbox. This exposes shifting or gearbox problems. Try it in reverse also. Most lathes will make more gearbox noise in spindle reverse but this is normal.

 Lathes that have seen heavy use will have the paint worn off up in the headstock and chuck area with the paint wear leading down into the chip pan. Check the backlash of the cross feed (X axis)screw. This is when you turn the handle a turn or two turns in one direction then stop, then turn it in the opposite direction and note how many thousandths on the dial it takes before the apron moves in the second direction. A nice tight machine will be .010 but anything up to .025 is not bad. Run the apron the full length of the machine note any clunks of notches. Up near the chuck is where the apron gets used most. Note if it gets tighter when you run it all the way to the tailstock end of the machine. This can indicate wear or just lack of lubrication to the ways. It can also mean there is accumulated dirt so if you feel some tightening look for a logical reason.

Check the corners of the compound rest. Many lathes that have had a hard life show it at the corners of the compound. This gets clobbered by the chuck from unwary users. Machines that were in student shops sometimes have the corners completely blasted off. A couple of smallish dinks are okay like in the picture above. If the corner is obliterated then proceed with caution and take your time with the rest of the inspection.
 In the picture above we see a couple of things. First is the ways up near the chuck are in excellent shape. This machine is a Japanese machine (Mori Seiki) and has hard heat treated ways. They should look good. Quite a few American machines have soft ways and show their age in this area. Another thing we observe is a little chunk taken out of the cross slide. This is pretty small but it indicates it got hit at some point. This nick would not put me off this machine unless is was combined with a number of other negative points and the cumulative negatives outweighed the positives, or the asking price.
Everything should work smoothly on a good industrial grade machine. All levers and knobs should engage and disengage smoothly without trying very hard. The exception is the half nut engagement lever. This lever requires the leadscrew to be turning to allow the nut to engage. In this picture you can see a couple of things. One is the half nut lever and thread chasing dial. The second is the empty bracket on the right. This held a Trav-a-dial gage at some point. A very good question for the owner is whether they still have the dial unit and does it go with the machine. Major plus if they have the gage.

Look for signs of physical damage or weird repairs and jury rigs. Things like missing screws, bailing wire, sealant etc broken and welded knobs and levers. The modification in the picture above is screaming of a bad owner. The apron stop screw on this Whacheon itself is a good idea, but welding it to the machine is a total Bozo move. Oil leaks are common with lathes and not a real problem unless the machine is surrounded by a moat of kitty litter.
In the picture above you can see the modification to the tailstock adjustment screw was done badly. A set screw was welded to something else to replace the factory adjuster. This was a Whacheon lathe I looked at on the San Francisco peninsula. You can see that somebody did a spray can rebuild on it with a crummy coat of grey paint without cleaning the gunk off. This lathe particular had some additional serious problems and was a no-go. The modifications and repairs are a window into the mind set of the person who did them. If you see something really bad then keep looking because you will probably find more.

 This picture of the electrical cabinet of this Mori Seiki is actually good news. Its very clean for how old the machine is and all the factory laced wiring is intact and UNMODIFIED. Seeing this cover off would not put me off this machine at all. It just becomes a negotiation point. If you see wet oil and chip contamination in the electrical area this is a negative point. The machine designers intended to keep these areas clean for the life of the machine so if they are compromised then its not a good sign.

Also ask about tooling that is going with the lathe. Tool holders, tool posts, extra chucks and collets, drill chucks, centers, steady rests, follow rest. If its close to the lathe and looks like a lathe thingy ask about it.

If your still not sure take your camera with you and take A LOT of pictures including closeups and general shots or even video of it running. With modern digital camera there is no excuse for not taking more pictures than you need. My rule is when you think you have enough, take ten more. Give the owner a big enough deposit (check if they will take it) to get it off the market, or at least slow it down so it doesn't sell to somebody else while you check it out with somebody who knows machinery that you trust.

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