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Old 12-30-2012, 06:51 PM   #31
FixerDave
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I can tell you what not to do

The mistakes I've made

Crib notes: big specs on cheap tools will generally buy you chatter... and you don't want chatter. That said, you can do a lot with cheap Chinese tools... might take a little longer, might have to deal with a few issues (like chatter), might really piss you off a few times , but, yes, you can get a lot done. Oh, and +1 on tooling costing more than the machine. Yes, you can do a lot by improvising rather than having the right tooling, but that's also a fast way to buy frustration and waste a whole lot of time.

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Old 12-30-2012, 09:12 PM   #32
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Originally Posted by Ricardito View Post
The idea of doing brake drums or rotors is something that I'd forgotten about, but sure does have its appeal
Personally I'd get the idea of cutting rotors out of your mind pretty quick on a small lathe.

The lathes that do this job are actually kind of specialized.

And not that you couldn't do the job, but there are a few things that make this job VERY hard to do on a small home lathe, or even a Large Commercial Lathe.

First - Rotors are friggin hard.

Second - Rotors have two parallel faces - the inner face and the outer face.

Three - They must be round.

Four - The feed is almost entirely cross feeding, no longitudinal action.

To address this a "brake lathe" does a few things.

For the Hardness - Carbide Insert Tooling.

For the Parrallel faces - They use tooling set to cut both faces at the same time.

For roundness - They have special clamping fixtures instead of a chuck and or collets.

For the feed - a good brake lathe has separate controls for cross feed completely independent of the speed of the lathe, this lets the machine control the RPM of the rotor, while feeding the carbide tip across the rotor smoothly. Something that sounds simple, but leaves grooves if you bung up.

Comparing this to your average lathe - small lathes HATE carbide - not that you cannot use it, but carbide is aggressive tooling, meant to take good passes, small lathes aren't super rigid, and this will make your life evil. Small lathes usually lack the ability to fine tune cross feed, and do not have fine RPM adjustments. Parrallel faces are tough, you'd have to cut both separate and lock everything down on your lathe to ensure no feed screws backed out and created a tapered cut!

Also brake rotors cost no money for small cars/trucks.
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Old 12-30-2012, 09:40 PM   #33
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Originally Posted by Ricardito View Post
what an education I'm getting for free! (I ought to know a good deal in this regard since I'm a prof at CU Boulder). Thus far, I'd jump at the chance of buying, among a few others, either the "Myford 7" given to Chobro by his dad or the blue "Smithy" suggested by pvangel in his post. Also please know that I am very very mindful of how dangerous these machines are. I plan to hang a large red lettered sign on the wall above the lathe so that I never forget to operate it with ample caution and never in a hurry.
Again, I'm grateful for all of the great advice offered here. And, also again, if anyone knows of one or has one for sale, please PM or email me landeira@colorado.edu
Keep an eye on Craigslist. I got a 1936 Atlas 8 inch that will do all that you've listed, along with a ton of tooling for $400. Just needed some belts. Use the Denver CL as well and look for items in Commerce City and that area. You could also try ebay and craigslook.com, but you'll need to arrange for transportation from those sellers. And even with all the tooling, i ended up dropping another few hundred on tooling (3 jaw chuck, live center for the tail stock, precision measurement tools, etc). With an older machine you're going to end up getting really familiar with it as you try to get it level and lined up. My tailstock and headstock were different heights, it took me about a week to discover that and then figure out how to fix it.

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Old 12-30-2012, 11:28 PM   #34
Donkey Hotey
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I'm going to place a vote for not being afraid to buy too much machine. I promise that you won't buy too big of a machine even with 2-3 times your budget. I REGULARLY run out of clamping range with an 8 inch chuck. The size of the chuck is the outside diameter, not the clamping size. The through hole size will also affect what you can put in the lathe. Bigger pieces of stock or long parts that need to go down the bore, can't. You mentioned making washer-like parts. That's a perfect example: you need either short pieces of stock that are only held in the chuck jaws or a big enough chuck for the material to fit inside. My 8" chucks BARELY take a 2" bar inside.

The typical lathe that can use an 8" chuck is a 16" swing...16x30, 16x40, etc. You ain't gonna' get into one of those for your budget.

So what I'm saying is: keep all of the stuff you've read here in mind when you look at some of the machines. We have a manual lathe at work that if it were for sale, your initial reaction would be to pass because it looks "too big" for a home shop. The reality is that it's a 13x40 and barely adequate for many jobs.
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Old 12-31-2012, 04:12 AM   #35
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If you have the space its sometimes possible to get a big old manual lathe for next to nothing, as many engineering people are going over to CNC, or going out of business. Only downside is that the machine will be 3 phase, and will in most cases take up quite a bit of space.
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Old 12-31-2012, 05:28 AM   #36
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i'm not a machinist, i don't have the patience for it. but i use my lathe every day.

it's pretty simple. GET THE BIGGEST LATHE YOU CAN FIT. bigger=more rigid. the more rigid, the more accurate and faster material removal. there's a reason lathes are big.

age of the lathe is irrelevant, older is generally better if you're on a budget.

there is absolutely no reason for a lathe to have plastic parts inside of it. if it does, you will break them. repeatedly.

don't worry about 3ph power unless the motor is bigger than 3hp. vfd's are cheap and work well. the torque curve drastically drops off at 25% (15hz). as long as you have some kind of variable speed on the lathe (usually a pulley system in your price range) you're good to go. back gears and a vfd combo can run a lathe slower than you'll ever use. a rarely change the speeds via anything but the vfd now. 90% of what i do is between is between 300 and 900 rpm..

i would assume most of the time you'll be doing small shit on a lathe - a big lathe does small and big stuff. a little lathe is an exercise in futility. a mini lathe might be ok as a second lathe.

the most important things to look for to me:

does it have power feeds (both!). for me this is important. i can get by without it, but i'm spoiled without them....

are the ways worn? some things cannot be fixed....

are the bearings good? they can be ungodly expensive, and you can easily get quite deep into the lathe to repair..

is it a major brand? some of the oddball brands have non-existent parts

everything i do is metric. i don't even have metric threading capabilities. would be nice, but not a deal breaker...a good die/tap set and die holder will do most jobs. when i get into the larger threads, i just buy the die/tap. they can be very expensive in larger sizes. if metric change wheels are available for the lathe for inexpensive, that's a huge plus. but you may never use them. i get by without.

is everything tight? i yank on the lathe pretty good like i'm checking swingarm bearings......nothing like making a cut and your tooling moves on it's own. is there a ton of backlash? lathes will inherently have some backlash, but if everything is worn, you can chase tightening up blacklash through many parts. using a dro pretty much eliminates all the backlash issues - you can see on the readout if the tooling is moving...

a good quality chuck makes a world of difference. bigger is better. through hole size of the spindle is pretty important if you want to do anything long...


tooling:
you can spend a lot more on the tooling than the lathe.

i'm big on the aloris/qctp. that lantern style shit is for the birds. a good tool holder makes set up a lot faster, and tooling changes are WAY faster with repeatability.

i do everything 99% of the time carbide. there is a ton of specs/variations in carbides. they can get very expensive. i'm lazy and like carbide.

a bigger lathe can take bigger (more common) tooling. them little shit lathes give you a lot less options - you're kinda stuck with chinese tooling....

steady rests/taper attachments/etc. can be very expensive. some attachments are pretty useful. some will sit for years before you ever use them.

i have a dro on my lathe, and a trav-a-dial. i don't even look at the trav-a-dial anymore. the dro makes many jobs very easy. 90% of the time i'm doing the same operation on hundreds of pieces. the dro speeded this up tremendously.

you can find a quality lathe built from 1940-1970 for under 1k with some decent tooling if you look and spend some time researching.


once you get your lathe expect to spend a bunch of time and potentially money refreshing parts, and tightening up tolerances, setting up gibs so everything moves smoothly and doesn't bind, etc...


OR you could buy a mini lathe, and buy a bigger lathe down the road.
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Old 12-31-2012, 06:01 AM   #37
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Echoing the above, yes, expect to spend more on tooling than the machine over time. Metalwork (to me) is a lifetime hobby in itself. If you nave no clues about safely working around machinery, read up and try to get some advice from an older machinist. The best advice I got was - go slow. Learning from other people's mistakes is smart.

A metal lathe is great at making 'stuff' from metal and making tools. As for metals, most mini-lathes work ok with aluminum but struggle with steel. A good machinist can work around the tooling and machine deficiencies, but it takes some skill and knowledge. Modern plastics (delrin and nylon) are good choices and the abs pipe from hardware stores makes adequate plastic swarf. Lubricant and cooling also become important for metals - dependent upon tooling.

Small lathes do not like carbide tooling because of the speeds and forces needed. High speed steel (HSS) tooling is easier to work with because it is sharper - hence cuts easier, thus requires less force than carbide and cuts at slower speeds. But, most tooling and inserts are carbide. Hence, grinding your own lathe tooling is needed for HSS, but some HSS insert holders are available (I have some). Realistically, carbide will work on a small lathe with light cuts. HSS gives a better finish with more control under manual operation. But, both will work.

The size and weight of the lathe determines what type of tooling works best. Even a good used 9x South Bend or Atlas lathe will work best with HSS tooling because these older lathes were designed for use with HSS tooling. A 3000 lb lathe will have enough rigidity to cut with (just about) any tooling. The 125lb mini lathes - not so much. Like most things in life, there are trade-offs.

My most prized tool is an inexpensive harbor freight 4x6 metal cutting bandsaw. All the ideas, lathe tools, milling attachments and measuring instruments don't work without having metal near the correct final size. Good luck!
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Old 12-31-2012, 07:52 AM   #38
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If you wait and look long enough something will come along. Don't be scared by an old machine. Often an older machine will be sold with all the tooling. Sure new tooling is much better but it's expensive and after all this is a hobby/home project lath and old school will be all you really need.

I got my Southbend from an old gunsmith many years ago. He just told me to come and get it. Stone age yes, but deadly accurate and true. The leather belt works suprisingly well.

The list of projects I have done with this machine is very, very long. I list as varied as chambering a rifle barrel to making bushings for my lawn mower wheels.



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Old 12-31-2012, 08:40 AM   #39
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Never thought it would be so complicated--or so much fun--learning and then searching for a suitable metal lathe for my garage. Slowly I am drawing the parameters that will suit my small, limited use of this machine. I am not in a hurry and would prefer to find something locally, or at least no more than a couple of hours drive from home. I am flexible (after reading and considering ALL of your comments and advice) as to age, price and size. Hopefully something will turn up in the next few weeks--months?
many thanks to all. and Happy New Year!
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Old 12-31-2012, 08:48 AM   #40
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Murphy's Law of lathes !

Your lathe will always have insufficient capacity for you next project.
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Old 12-31-2012, 09:21 AM   #41
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Just keep looking.

I was about ready to break down and get a mini-lathe when my Craftsman/Atlas showed up at an estate auction, semi-tooled, for less than a mini-lathe would have run.

I would suggest some books as well, old school metal shop texts are cheap. It kind of depends on what you are really interested in doing.

Do some reading here if it hasn't been suggested.
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Old 12-31-2012, 09:50 AM   #42
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Excellent thread. I'm also interested in machining, and haven't a clue, so this thread is great. My current work schedule prevents me from taking a machining class at the local community college.

A couple other gents here turned me onto Keith Fenner on youtube.

He is a machinist in Cape Cod who has 260 or so awesome videos on youtube of himself machining parts, welding, fabricating, etc, etc. I have already learned a lot from him by watching about 10 videos so far. I will watch them all in time. Some people can teach. Some people can do. He is one of those rare birds who can do both - and do both well - in an easily understandable manner.

I'm not currently in the market, but thanks to all for all the excellent feedback. It will help to make a good purchase sometime down the road...

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Old 01-01-2013, 07:52 AM   #43
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Originally Posted by LuciferMutt View Post
REgarding a VFD to power a three phase machine:

I did this in my shop to an old 12" Clausing and tore out the old hydraulic vari-speed cone pulley assembly and fabricated my own motor mount and just a 1:1 belt drive from the motor to the headstock pulley. New inverter duty motor.

It works fine except that the motor does not supply very much torque at lower RPM and I have stalled the machine attempting to drill large (1-2" diameter drill) holes through plastic stock at 600 RPM and down. Back gear has a maxium speed of something like 256 RPM as measured with a tach, so there is a range from about 300-6/700 RPM in open belt where the motor does not make much useful torque. Other than that, it performs very nicely and is VERY quiet! Could never say that about that stupid vari-speed.

So, in short, VFDs are a great way to get three phase in your garage if set up properly, but low MOTOR rpm does not produce much torque.
+1 Dont get focused on small 115V , my experience finds that a bigger machine sometimes sells cheaper then a small one. If it plugs into your wall in the garage and can be unloaded with the help of a couple buddies - every one wants it, if it takes 3ph + a forklift to unload you just cut the potential buyers by about 80% or more. The only small lathes I really love are Hardinge - from there I look at 15" or bigger. Soon as you get over 17" it seems the price will flatten out a little or the increments in value are smaller, comparatively speaking.
My buddy loves the South Bend small lathes, has rebuilt a few from Ebay parts, and has great luck with them. I know the old craftsman lathes were great garage models, I believe they were made by Atlas. Every one here has mentioned the tooling costs and that is also spot on, tooling can break the bank, if you have the skills you can get tool blanks cheap, (I actually had a great guy here send me some of his surplus at one time- I owe him still) , and grind your own tooling. I worked with a tool maker about a life time ago that could whip out a turning tool in less then a minute. I have made many of my own small boring tools and grooving tools and there is a science to it, but there are good books out there that can help get you going. And personally I pride myself on making some of my own custom tooling - its just cool (clearly I am amused easily).
VFD's and phase converters are your friend - dont sweat the power issues- find a good machine, there is always a way to make it work (with in reason). There are tons of guys running 3-5hp 3ph motors on converters. I did it for years and never once had a issue .
Not sure if any one mentioned this, but - look at the local machinery dealers in your area, they seem to know where to get anything you want most of the time, ya they make a few bucks but sometimes it pays off in other ways , like they know everyone , even the guy with the forklift down the road to help you unload, or a guy with a bunch of cheap tooling, you never know : "what you dont get in grapes; you get in bananas" , (my favorite saying when I let someone talk my price down on a job).
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Old 01-01-2013, 09:43 AM   #44
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Your lathe will always have insufficient capacity for you next project.
+1, but making due usually makes for a good story!
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Old 01-02-2013, 09:56 AM   #45
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Originally Posted by kirkster70 View Post
Excellent thread. I'm also interested in machining, and haven't a clue, so this thread is great. My current work schedule prevents me from taking a machining class at the local community college.

A couple other gents here turned me onto Keith Fenner on youtube.

He is a machinist in Cape Cod who has 260 or so awesome videos on youtube of himself machining parts, welding, fabricating, etc, etc. I have already learned a lot from him by watching about 10 videos so far. I will watch them all in time. Some people can teach. Some people can do. He is one of those rare birds who can do both - and do both well - in an easily understandable manner.

I'm not currently in the market, but thanks to all for all the excellent feedback. It will help to make a good purchase sometime down the road...

Tubalcain on youtube. All you ever want to know about basic machining.
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