Ok, I’m not 100% sure if anyone will be interested in this, however as far as I have seen, this site leans more towards software and electronics, than mechanical. That’s not a criticism, more of an observation. So I thought I could expand the site's scope, with my offering. I'll add photo's, etc at a later date, if this article proves popular.
If, however you feel this guide is inappropriately placed on this site, then please inform me, via my ridicule page, which can be found by clicking here.
When I was building my robot, I found my lathe indispensable. Although I realize not all of you need, want, or even care about lathes, others on here may be considering such a purchase. I was a center lathe turner by trade, a number of years back, so thought I could offer my assistance here, with a buyer’s guide and basics of using a lathe.
After this guide got too long, I decided to limit it, to just a buyers guide. If anyone shows any interest, then I’ll write a basic lathe operation guide, at some time in the future.
A lathe
A lathe is a machine designed for creating cylindrical objects, out of materials such as metal, nylon and wood. Since the majority of you, won't be turning wood and wood working lathes are a different species all together, we'll ignore them here.
Lathes come in all shapes and sizes. Large industrial CNC machines can cost into the millions, where as small hobbiest machines can be picked up in used condition for a couple of hundred. My own machine, is small and designed purely for the diy enthusiast. This doesn’t mean the machine is incapable, but it's only as good as the person operating it. Since you're more likely to be buying a machine such as this, I’ll concentrate my efforts towards this type of machine.
Safety
Always wear eye protection. Suitable eye wear is cheap and reliable. New eyes are not!
Never operate a lathe wearing clothing, or jewelry likely to dangle close to the machine! If a neck tie, for example becomes caught in the chuck, your head is going straight for the spinning chuck and you will not have time to stop the machine, before it rips your face off.
Swarf, (the waste material created by metal working machinery) is razor sharp and can be hot. Make every attempt to avoid handling. If handling is necessary, then always wear suitable gloves and try to use a rake, to remove from the machine bed.
The major parts of a lathe are,
Headstock
The headstock is the area, which houses the motor, gears and bearings. It would usually be situated on your left. The chuck connects to the headstock.
Tailstock
This is found on the opposite end to the headstock and can be slid along the length of the machine. A brake is usually fitted, to hold the tailstock in the desired place. There will also be a handwheel, which when turned will move a spindle, either in, or out, depending on which direction it's turned. The tailstock can hold numerous tools, such as a drill chuck, a live center, dies, or taps and many other useful attachments.
Chuck
The chuck holds the work piece. Unlike most machinery, a lathe keeps tools such as drills stationary, while the work piece revolves. Various chucks are available such as 3 jaw self centering chucks and 4 jaw independent chucks. Various jaws are also available for the chucks too. The chuck attaches to the lathe via a face plate. As a beginner, you will be using the 3 jaw chuck, more than the 4 jaw.
Saddle
The saddle is the large slide, which moves left and right along the machine bed. There will be a threaded bar (named the lead screw), striking through the saddle. The saddle has numerous handwheels, levers, etc and is where most of the operator’s input will be done.
Machine Bed
The machine bed, is the long axis, to which the saddle and tailstock sit.
Cross Slide
The cross slide sits on top of the saddle and as the name suggests, slides back and fourth across the front to rear axis of the machine.
Compound slide
This sits aloft the cross slide, however unlike the other slides, the angle to which it can be used is adjustable.
Tool post
Although this sounds like the name of a rubbish newspaper about tooling, it's actually the part of your lathe, which holds the cutting tool. It sits on top of the compound slide and comes in many different forms.
Buying
Deciding on what sized lathe you require can be difficult. You should think about what your wanting to produce. Do you really need a machine that can turn 8 inch diameter stainless steel bar? Probably not. Large industrial machines sometimes come up at auction, but this might not be the ideal machine for you. These things don't just run off a power socket on your wall, does your home have the appropriate kind of power requirements? They can weigh several tonnes, do you have a way of transporting it? Will your workshop floor support it? If all your producing is something half an inch in diameter, then it would appear to be over kill. I've worked on lathes large enough to fit a 16 inch alloy wheel in the chuck. The same lathe would be next to useless, when I was making parts for my robot.
A better option, would be something smaller. You may find one locally, in the classifieds, eBay, or similar. A smaller lathe is more likely to produce the precision work, you require. It will fit in your car for transport and plugs directly into a wall socket. A small lathe can turn larger work pieces than you would think. It’s not always the size of the lathe, that determines the maximum turning diameter, but the wisdom of the operator. My small lathe has a maximum chuck diameter of 45mm, however I can turn much larger diameters, by turning between centers. The distance between the centre of the chuck and the closest part of the machine bed, is called the “throw”, however, I’m led to believe the American way of measuring this, would be the throw measurement doubled. This would describe the maximum diameter the lathe can accommodate.
If you find a lathe and you're thinking of buying, here are a few pointers.
Research any lathe you’re interested in. some lathes can be very old, making spares impossible to find and even if you do find them, they’re expensive. I’ve come across unbranded lathes in the past. I’d suggest staying clear of these. If you need assistance, with parts, or maintenance, a brand name is the first question you’ll be asked.
When you view the lathe.
Grab the chuck, with both hands and rock it. Can you feel the bearings knocking? If you can, then they’re probably worn out. This could be an expensive repair.
The machine bed can wear out over years of usage. To test for this, apply the brake on the tailstock at it's maximum position on the bed. You should loosen the brake, until you can just push the tailstock by hand, but you can also feel the resistance of the brake. This might begin to move freely, however if the brake can't hold the tailstock further down the bed and it’s locked solid, without the brake at the far end, then the bed could be worn.
Hand wheels should run freely. Jumpy, sticky, or noisy movement suggest problems. They will show some play in their usage, which is permissible, however excessive lateral movement is a bad sign. There should be indexing marks around the handles, you'll need these, so make sure you can read them and they're firmly attached.
Obvious signs of a bad machine include thick rust, or chunks of metal missing on the bed and slides. Noisy operation.
You should run the machine. Lathes don't have the quietest of gearboxes, but loud knocks from the headstock should be viewed with caution.
Inquire what’s included with the machine. Spare parts can be hard to come by. Some lathes require screw cutting gears, to use that facility, so they should be included. Live centers and tailstock attachments can be expensive, if you can get these included, then all the better.
If there are cutting tools included, that's great. However these are probably something you can pick up cheap enough.
Digital read out (DRO). These are fantastic and make the process of turning so much simpler. They're not essential though and as a hobbiest, it's possibly an expense you don't need.
Coolant system. Some small lathes don't have this facility, but can be retro fitted. Any used lathe is likely to have gunge in the coolant pipework. A clean out is probably going to be needed, but check the pump works. Bacteria can build up in a coolant system, causing a health hazard. This is more likely to happen on a machine that’s infrequently used. If a coolant system is not something your machine has, then that’s not a problem. You’ll have to turn slower, make shallower cuts and apply a cutting fluid by hand.
Lathes have been made in both metric and imperial measurements. I was trained to use both, but if you only know the one system, then make sure your lathe employs that system. However a lathe fitted with a DRO, should have a switch, to move between the two.
Before you do anything else
When you've bought your lathe and got it into your workshop, there's a few things you should know. All lathes come with mounting holes. It’s always advisable to screw your lathe down. However, if your lathe sits on a stand, make sure it's securely bolted down to the stand. My lathe is a desk top lathe and I’ve never screwed it down. I've also known people use large one piece lathes, weighing a couple of tonnes and they have never secured them to the floor. If you're turning something that's off center and heavy enough to throw the lathe about, then chances are you using a setting that's way too fast. The only thing that is essential, if your machine is mounted on a stand, then secure it to the stand.
You will need to familiarize yourself with your new machine. As all lathes have slightly different configurations, I can't really guide you through this, but just try turning the various hand wheels and watching what happens. You can leave the machine off, you don't need it running for this to work. Remember lathes can be dangerous. They don't have sensors and if your finger gets caught in moving parts, then it will show you no mercy.
Make sure your cutting tool is held tightly in place. Never leave the chuck key in the chuck and always use the machine guards.
I’d welcome any feed back on this guide. Does anyone want a basic turning guide?
