Copyright 1997 by Dave Ficken
It's 7am and you are casually sipping coffee and reading your favorite local paper. Suddenly, an ad catches your eye in the classified section. It reads: 10" Atlas Lathe w/ tooling $600. Hurry, won't last. Call 555-3353. Your adrenalin is pumping, you have to see this machine first, before someone else grabs it. What to do? Is it too early to call? Throwing politeness to the wind, you dial the number. Alas, it's busy. In your mind, you can see the other 200 eager callers all dialing at the same time while your fingers frantically pound the redial button. Finally, you get through. You determine that the lathe is still available, and get directions while grabbing your coat, wallet and car keys. You are out the door the second the phone is back in its reciever. The drive to the sellers home is a blurr of high speed driving and numerous traffic infringements. You barely noticed that you backed over your son's bicycle getting out of the driveway. The seller mentioned that someone else was coming over in an hour. The desire to get there ahead of this person overcomes you. The lathe looks great (probably because of the fresh coat of paint) you ask a few cursory questions, but are afraid to ask anything that might reveal that you really don't know what you are looking at. All the while, you are nervously aware that you must act quickly, before someone else grabs it. "Will you take $500 for it?" You ask nervously. "Nope!" Comes the reply. "I got someone else comin' over in half an hour who said he was definately takin' it." "O.K., I'll take it" You say, taking the bait. Meanwhile, across town, a savvy buyer is reading the same ad. He wonders about the "hurry, won't last" part of the ad. "I'll bet that means it will fall apart as soon as you try to use it" he muses. "Those 10" Atlas lathes can be real trouble if you don't check out the castings real carefully!" It's not long before you find out just what he means. You have just spent $600 ($700 if you include your son's bike!) for your fist course in "how not to buy a Lathe"! Back at the seller's home, the phone is still ringing. Disappointed callers hang up and mutter something under their breath like:"anything good always sells right away, I'll have to be first next time!"
In the above scenario, the buyer did not make any effort to educate himself about the do's and don'ts when buying a machine prior to making a decision to buy. The key to getting a good deal is to "be prepared". Another mistake made by our fictitious buyer was in letting his judgement be clouded with the thought that he must act quickly or lose the deal. Ofcourse, it is usually necassary to act quickly to come away with a bargain, but if you are well prepared beforehand, you will be better able to make a rational decision in the heat of the moment.
More often than not, I must evaluate machinery that I am buying without
ever getting to see or hear it run under power. Typically, there is little time
to make a detailed evaluation. It is possible to get a reasonable estimate of a machine's
condition without ever hearing it run.
Your general impression of the shop and it's inhabitants can give valuable insights when evaluating a machine. It is fairly easy to get an idea of what type of person you are dealing with.
Hint: The 20lb. Sledge hammer and 48" Stilson wrench next to the lathe you are considering may have been used to adjust its spindle bearings.A clean, well organized shop is generally a good sign that the machines were handled by someone who cared about their wellbeing.
It is absolutely possible to buy a lousy machine from a well kept shop and vice-versa. The most important thing that you are trying to piece together is whether or not the owner is on the level. It takes a good deal of experience and lots of detective work to determine the latter. If you reallize that things may not be "on the up and up," you are well ahead of most prospective buyers. You will also have taken the first step toward getting the best possible deal.
Question: Does it appear that the machine belongs in the spot it presently occupies?Trap: Often, at auctions and sales, machines are "dragged in". This means that someone is trying to unload a machine by having an auctioneer or seller include it in his sale. The number one reason for this is that something is wrong and the owner wants to sell it anonymously. Also, sometimes a seller will pretend that he is selling a machine that was part of his shop when in fact the machine was never used by him. Neither of these senarios should stop you from buying the machine, but they should definately send out a warning signal!
Tip: Telltale signs of a machine that might be "dragged in" are: 1)the machine is on a skid, pipes or blocks. 2) The machine is nowhere near a power supply 3)The machine is a completely different color than all other machines in the shop. Note: There could be innocent reasons for all of the above as well- it's a judgement call.
Trap: I know of several people who are (more or less) machinery dealers, but pretend to be a private individual selling private property.
If they represented themselves as dealers, they would have to offer some kind of warranty or guarantee (and pay income tax on the profit!)
It may be ok to deal with such a person, but remember that you are likely to pay dealer prices without recieving any of the benefits of dealing with a reputable dealer. These benefits include: Support after the sale, some kind of warranty or guarantee, and the ability to return an unsatisfactory item. A private individual typically sells items "as-is-where-is". A buyer has little legal recourse after the sale has been completed. It takes a bit of homework to uncover someone that is a dealer pretending to be a private individual. Follow the classifieds for several weeks or months and see who places multiple ads.
Once you have gathered some general impressions, It's time to begin evaluating the machine.
Don't be afraid to trust your instincts. If something feels wrong, don't be afraid to walk away. I once walked away in the middle of a transaction because I reallized that the seller wouldn't look me in the eye any time he made a statement.
Now that you've taken 30 seconds or so to evaluate the seller and the machine's surroundings, it's time to move on to actually inspecting the machine.
This section includes general advice on lathe inspection. Brand specific advice will be discussed in a later section.
Tip: You should spend some time familiarizing yourself with Lathe nomenclature and basic operations. The book "How To Run A Lathe" by Southbend is an excellent source of information.
The bed ways:
The heart and soul of any lathe is its bed ways. The condition of the bed ways will determine the accuracy that the lathe is capable of. In my opinion, the condition of the bed has the greatest effect on the overall value of the lathe.This axiom holds true for other types of machines as well. Ideally, the ways should be perfectly parallel and even so the carriage travels parallel to the axis of the spindle, and the tailstock center is perfectly on center with the headstock spindle.
A large percentage of lathe work takes place close to the headstock. This leads to uneven wear of the bed ways. Uneven bed wear, in turn, causes the carriage (and therefore the cutting tool) to travel in a plane that is no longer parallel to the work piece (and no longer at the same height as the starting point.) The result will be a workpiece that tapers in proportion to the bed wear. All used machines have some degree of bed wear, your goal should be to determine the severity of the wear.
Tips for inspecting the condition of the Lathe bed:
Under ideal circumstances, cutting a test bar between centers would be the best way to test the accuracy of a lathe. Unfortunately, circumstances seldom permit such a test.
You should first determine the method employed by the manufacturer for finishing the bed ways. Grinding or hand scraping are the two general means. Hand scraping is generally followed up with decorative flaking which produces characteristic marks (usually crescent shaped marks in a uniform pattern), whereas grinding produces a uniform, brightly finished surface. Since the carriage is unable to travel in the area directly under the headstock (and cause wear), check this area to determine what the bed looked like originally. If you determine that the bed was originally hand scraped, the presence or lack of hand scrape marks over the length of the bed will give some indication of the degree of bed wear.
View the original handscraping on a Southbend Lathe bed under the headstock
Tip: Since the bearing surfaces of the carriage do not ride on the full width of the bed ways, a ridge will generally form at the top or bottom (depending on the machine) of the ways (the same holds true for the tailstock.) The absence or presence of such a ridge can give an indication of the severity of bed wear.
Trap: Many unscrupulous sellers will file away any ridges on the bed and touch up the surface with a honing stone. To the casual observer, the bed will appear to be in excellent condition even though it is actually quite worn.
Countermeasure: With the carriage as close to the headstock as it will go, tighten the carriage binding screw until the carriage can no longer be moved. Loosen the binding screw slightly until the carriage just begins to move smoothly again. Now crank the carriage all the way toward the tailstock. If the bed is in real good shape, the carriage will make it all the way to the other end without binding.
You can also try to lift the carriage off the bed. You should not be able to see much movement if the machine is in good shape.
Note: You should now have some idea of the condition of the bed ways. If there is excessive wear, you may want to avoid the machine entirely, or you may choose to live with it. I generally consider that a worn bed is one of the few things I can't fix myself. Figure that it will cost between $1200 and $2000 to have an average lathe reconditioned (ie bed reground and components hand scraped to fit.)
Advanced Reading: The book "Machine Tool Reconditioning" by Edward F. Connelly (Machine Tool Publications St. Paul, Minn.) Is an excellent source of information on the art of hand scraping in particular and machine reconditioning in general.
The condition of the spindle bearings and the spindle itself is the next most important thing to check. If either is damaged beyond repair, you will be looking at a costly replacement. I happen to have spare headstocks for certain lathes in stock, so I don't sweat this part of the inspection as much as you should.Ideally, running the spindle would be a big help in determining bearing condition. Unfortunately, this is not always possible. If you are able to run the machine, run the spindle at one of the higher speed settings for a while. Listen for unusual noises. After the spindle has been running for a while, feel the bearings. They should not be too hot to touch.
Assuming that it is not possible to run the spindle, you will have to rely on your sense of how the bearings feel, how much slop or play is in the spindle etc. It is a good idea to take a look at the oil cups (if fitted.) You will want to see that they are full of clean looking oil. On lathes with wick lubrication such as southbend, you should be able to fill the oil cups to a certain level and have that level remain fairly constant. If the oil cups lose there level quickly and often, it is an indication that something is wrong with the wicks. The resultant lack of proper lubrication of the bearings will in turn lead to costly damage.
The condition of the spindle nose is also important as it will determine how true the chuck or centers will spin. The first time lathe buyer will generally encounter one of three spindle types. These include L-type, D-type, or threaded.
The L-type spindle (or long tapered spindle) features an external spindle taper with a key way. A threaded ring draws the chuck tightly against the spindle taper. The taper centers the chuck on the spindle. The threaded ring can be backed off to push the chuck forward and unseat it from the taper.
The D-type spindle also has an external taper, but it is much shorter than the L-taper. The D-type spindle uses cam pins to pull the chuck onto and off of the spindle taper. A common misconception about D-type spindles is that the associated number designation has something to do with how many cam pins are present on the chuck. Following this rule, you might wrongly think that a chuck with three cam pins is a d1-3, a chuck with 6 cam pins is a d1-6 and so on. This is not always the case. For simplicity sake, just remember that a D1-4 has a larger taper (in terms of the opening) than a D1-3. The larger the number, the larger in turn will be the opening.
On either of these tapered type spindles, it is important to check the condition of the tapered section of the spindle as well as devices for pulling the chuck onto the taper (ie the threaded ring or camlock as applicable)
On a threaded spindle, as the name implies, the chuck is threaded onto the spindle. There is a shoulder at the rear of the threads that serves to center the chuck on the spindle. It is important to check the condition of the threads as well as the shoulder.
On all of the above spindle types, the spindle should also feature an internal taper. This taper will be used for driving the headstock center and collet adapter sleeve. The condition of this taper is also important.
The back gears are essentially a set of reduction gears which serve to provide low RPM and high torque to the spindle. On some lathes (Southbend, Logan, Sheldon, Atlas and others) the back gears are easy to inspect. On other machines (particularly geared head machines) it is not possible to view the back gears without minor disassembly of the headstock. If the gears are readilly visible, they should be inspected for chipped, broken, or worn teeth. If they can't be visually inspected, the next best thing to do is listen to them run.
Geared head Lathes generally feature a belt drive (timing belt or double V-belt) from the motor to the headstock. In some cases, the motor may be a multi-speed unit. Speed changes are accomplished by shifting gears in the headstock. It is generally not possible to visually inspect these gears prior to buying a machine. Damaged gears can be costly to replace. In general, the best you can do is to run the machine at various speed settings and listen for unusual noises. Keep in mind that geared head lathes tend to be louder than most to begin with. If you are unable to run the machine, the purchase becomes a bit of a gamble, so set your price accordingly.
Tip:You can work backwards by manually turning the spindle (difficult in some speed settings- especially if there isn't a chuck on the spindle) This can help detect *major* problems, but is generally not that useful in determining minor ones. Some geared head machines feature a magnetic plug somewhere in the oil sump to catch metal shavings . If you can locate and remove this plug it may furnish some clues. You certainly wouldn't want to see huge chunks of steel attached to it. Small shavings, however, will occur through normal wear. Ofcourse, the seller may have cleaned the plug prior to showing the machine, so be careful how you interpret the data.
Since we're in the neighborhood, having just checked the headstock, checking the geartrain, gearbox and leadscrew would be a natural next step.
By geartrain, I am refering to the set of gears that connects the headstock spindle to the leadscrew and causes the leadscrew to rotate in direct proportion to the spindle rotation. A mechanism for reversing leadscrew rotation should be part of this train as well. As before, I am going to generalize a bit. Keep in mind that we are concerned with lathes that a first time buyer is likely to encounter. Here again, it would be great to hear the machine run to check for unusual noises. If there is a removeable cover, check the gears for broken or worn teeth; check for cracked handles or mountings (ie. the quadrant); check for worn bushings; and check for evidence of proper lubrication.
Note on lubrication:
The following is an opinion based on my experience to date:
The geartrain and quick change gearbox are two places where you tend to find someone using grease rather than oil for lubrication. In my opinion, this is a dangerous practice, even though some manufacturers recommend it.
Imagine if you will that you are able to magically *magnetize* the gears to hold chips of steel, aluminum, brass, etc., etc. Would you do it? Guess what, grease will hold all of these chips and other foreign objects firmly to your meshing gears, causing premature wear and risking chipped or broken teeth. This is why I do not like to see grease used anywhere except packed or sealed bearings. Even though the gearbox and geartrain seem to be covered and therefore free of chips, if you've done any machining at all, you will know that chips get everywhere and anywhere. I've worked on enough machinery to know this fact.
While the owner may be using grease because it was actually recommended (which I think is wrong) by the manufacturer, there could me a dubious reason. It's possible that the grease is being used to quiet gear noises that might scare off a prospective customer.
You are welcome to disagree with my opinion that grease should not be used, but at least consider that it's presence could be a warning sign that there is *hidden* gear trouble.
The lathe you are inspecting may or may not be fitted with a quick change gearbox. If no gearbox is fitted, and the lathe is capable of screw cutting, you should make sure that the seller is supplying a set of loose change gears with the lathe. This will enable you to cut the various thread pitches and change the feed rates. In some cases, these gears are readilly available on the used market at reasonable prices ($10-$15 per gear or $125-$150 per set.) Used gears are readilly available for Logan, Atlas, and Southbend Lathes. Other brands may not be so readilly available. In such cases, the absence or presence of the change gear set may be a determining factor in wether or not to buy the machine. In all cases, lack of proper change gears is certainly a bargaining chip when negotiating the price.
When checking the gearbox, we want to verify the following: A) the gears are all in tact, B) the bearings or bushings are in decent shape, C) there are no cracked castings or broken handles, D) Everything seems to run smoothly and quietly.
The gearbox (and especially its handles) is situated in a position were it will generally be one of the first things to impact the ground when the lathe is tipped over, a cracked or repaired handle or gearbox housing could be an indication that the lathe was dropped at one time. This applies for other extremities on the machine as well. You should look at the machine and ask yourself: "if this thing fell over, what would get damaged first?" Be sure to check these areas carefully
The gearbox is yet another item that is best inspected under power. If this is possible, Run it in all possible settings and directions of rotations and listen for unusual noises. In many cases, the ends of the shafts that hold the handles and gear clusters are accessible at the sides of the gearbox housing. You can try to move them in their bushings to check for wear. In the case of the shaft and bushings that the handles ride on, you can lift the handle and watch for play in the bushings. In most cases, you can look at the gearclusters within the gearbox from underneath.
This part of the inspection should illustrate the importance of carrying a flashlight whenever you are inspecting machinery. I reccommend something small enough to tuck away in your pocket.
The leadscrew rotates in direct proportion to the spindle rotation to facilitate thread cutting. On most lathes that the average hohobbyist will encounter, the leadscrew also serves the secondary function of driving the power feeds (if fitted.) On more sophisticted units, there is actually a seperate drive shaft for the powerfeeds that runs parallel to the leadscrew. Certain types of lathes (Atlas for example) which use the half nuts for longitudinal powerfeed as well as threading, can exhibit excessive leadscrew wear (this will be discussed later in the brand specific advice collumn.) A worn leadscrew can be a sign that a machine has been heavily used. Leadscrew wear tends to occurr in the same area that bed wear occurrs (for the same reasons we discussed under bed wear.) If the leadscrew has a keyway running down its length (for driving the powerfeeds), check that the keyway width is uniform over the entire length. Here again, the keyway will wear close to the headstock. Excess wear on the keyway may indicate that the lathe has been heavily used and excess bed wear is likely.
The apron generally contains the half nuts (for threading), the handwheel for longitudinal feeds, and (if fitted) the feed selector, and clutch and worm assembly. The half nuts are often close enough to the rear of the apron that they can be examined for wear. If they are not visible, you can engage them (without the machine running) and gently attempt to move the carriage back and forth with the handwheel for longitudinal feeds. you should not be able to move the carriage very far in either direction. The same technique, without the half nuts engaged, will give an indication of the amount of backlash present in the rack and pinion that moves the carriage. The power feeds can be tested even if you can't run the lathe. You can engage them and spin the headstock spindle manually to check for proper operation. A check I like to make on my machines is to run the machine with one of the powerfeeds engaged. I then gently grab the appropriate handwheel for manual feed and cause a slight resistance. The sound made by the gearbox, and drive train will change. When things are *really* worn, the noise is unmistakeable. Again, this is something that the owner of the lathe might not appreciate you doing. Let me say again that I apply *light* resistance to simulate a cutting force.
The carriage (or saddle) is actually the part that rides back and forth over the bedways. I mentioned a few checks earlier on when we were discussing the lathe bed. Additionally, the saddle contains the ways that the crosslide moves back and forth on. These ways can be examined by moving the crosslide all yhe way in.
The compound mounts atop the crosslide. It can typically be swiveled to different angles to cut tapers, or feed the toolbit in lesser increments than the crossfeed screw will allow. The compound could get damaged by someone running it into the chuck (while the chuck is spinning) or by someone overtightening the tooplost (which in turn can damage the T-slot.) I discussed backlash in the feedscrew earlier.
The tailstock is generally used for drilling and reaming holes and holding work between centers. Toward this end, the height of the tailstock relative to the headstock is important in performing accurate work. Of equal importance is the fit between the tailstock ram (spindle) and the body of the tailstock. If this fit is too loose, the toolbit, or center will be able to shift or chatter. The fit can be determined by trying to move the ram up, down, or side-to-side with the binding lever both locked and released. The height of the tailstock relative to the headstock can be determined by mounting centers in the tailstock and headstock and sliding the tailstock toward the headstock until they meet. A visual inspection of how the two centers mate up will give you a good idea. Bear in mind that this height differential is affected by bed wear. The reading could be different at various points on the bed due to uneven wear. The tailstock, if light enough, can be removed from the lathe and its bottom surface can be visually inspected for wear. The ram (spindle) typically has an internal morse taper for holding tooling. The condition of the taper is also important for accuracy. There shouldn't be any nicks, dings, or scoring.
Many people have emailed me (and likely not recieved an answer) about why I don't tell people to take along a test indicator. Here's
Reason No. 1
I've given advice on field testing machines anytime, anywhere the need arises. You never know when and where you might have the opportunity to evaluate a deal before someone else grabs it. What if your precious indicator isn't with you when you stumble upon a creampuff of a Lathe at a garage sale you just happened to drive past? This advice is mainly for first time buyers. Most first time buyers are likely to introduce more error into an indicator reading than they are able to read with any certainty. Also, even if the would-be first time buyer could get an accurate reading, he must then know how to interpret that data and how it speaks for the overall condition of the machine. I have bought and sold many nice machines in my day using the methods I've outlined here. Never once did I use an indicator to test them.
Reason No. 2 (personal)
As a buyer, my goal is to get the best equipment possible for the best price. It is tough to negotiate from a point of weakness. Having the seller think you are an annoying tire kicker is definately negotiating from a point of weakness. I feel that bringing and using an indicator is going to hurt your relationship with the average seller. The seller is not likely to be inclined towards generosity if you annoy him. I make it a point to be on time for appointments to look at machines. I never need more than 5 minutes of the sellers time to decide to buy or not to buy a particular machine and I never nit-pick a machine to death. As a seller, I give my best deals to buyers who behave the same way. I'm not saying here that I mind someone taking the time to make an informed decision, that has never been the case. I am saying that the way you are percieved as a buyer can definately affect the final price you pay and how many goodies get thrown in as a deal sweetener.
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