Thinking of buying a lathe

[NitroSteel]

I've been looking pretty hard into the possibility of buying a small lathe, possibly a combination machine that has a milling machine attachment built into it.  I do realize with a small lathe I will be limited to fairly small projects and the work will be much slower than with a larger lathe, also that with the small Chinese made lathes (that I'm looking at) precision is not always the best in the world right out of the box.

If I bought a 8x12 Harbor Frieght lathe (around $600.00) how big of a piece could I actually machine with it?  I believe it has jaws that will hold a 4.5" diameter piece of roundstock, but I'm not sure how long of a piece it can bore through or machine.  Would I be able to make round steel balls with it, say 2 or 3 inches in diameter?  Approximately how long of a piece would I be able to cut threads in?  If I could deal with a 6 or 8 inch long piece of steel, I'd be happy.

I've heard it would be best to try and find a old used machine that is much larger for about the same amount of money.  I've been having a hard time finding one reasonably close (shipping on a big machine is a killer).

Thank ya'll for your help.

Sincerely,

NitroSteel

[jeeper1]

I have heard multiple reports of the plastic gears in the mini lathes breaking, in fact there is a company that does nothing except sell replacement parts for them.
The combo mill/lathe does nothing well and you spend more time doing setups and changes than work.

I've heard it would be best to try and find a old used machine that is much larger for about the same amount of money.

Often you will also get extras thrown in that you won't get with a new machine.

[Rickk]

unless you have 3 phase coming into your house for some reason, pay attention to the motor's power requirements when shopping for a used machine. Bigger lathes want 3 phase power.

There are ways to derive 3 phase from single phase. It isn't a complicated process, but unless you stumble across the required transformers (crude way) or a motor generator set (preferred way) to generate the third phase, it won't be cheap.

Motor replacement would probably be the best option.

[Powder keg]

I started out with a Harbor freight 7X10. It is way to small for what you want. I have an old Southbend That I use a bit. It is a pretty good lathe. It will swing 9X30. I think a 4" o.d. cannon would take a looong time to build on it though. Try and get the biggest you can find/afford. If you need any help, I can help answer your questions.

Wes

[GGaskill]

This subject has been discussed hundreds of times at Practical Machinist.  Look in the Gunsmithing forum and the General forums and then look at Transformers, Phase Converters and VFD to see about the single phase to 3 phase issue.

[accuratemike]

I'm pretty poor too. I got a HF9x20 for around $600. I can turn parts about 18" long (barely), you could thread that far too. I have turned 4" od SS in it. It was SLOW going but workable. ( http://www.accuratepower.com/Mortar/  ) Remember you can only bore a fraction of the length of the bed. The boring bar will eat up the rest. I have heard the 8x12(14) is more rigid that the 9x20, I don't know. It would allow you to take heavier cuts. Motor HP helps here some too (9x20's are 3/4HP, I don't know what motor an 8x12 has). I'm going to try a 4"x18" tube in it next ( http://www.graybeardoutdoors.com/smf/index.php/topic,105118.0.html ) I'm going with DOM seamless/breech plug (4"ODx1.75"ID) to avoid the boring issue. If I thread the plug I'll have to go elsewhere (work) to do the ID threading at the end of the tube. If I weld it, I may be able to do the whole job at home. I may still have to use a larger machine to clean up the bore for a welded plug to fit well enough (the chunk I have looks pretty darn true, I'll dial bore guage it to be sure).
I would buy as big as you can afford for sure. I'm looking at the 1ton Birmingham 14x40 for my next machine. It is more substantial than the 12x36-13/14x40 bench top models and has a 3hp 3ph motor (~$4k to start). 12x36's start at around $2k. These are really the next step up from 8x12's & 9x20's.
If you had 40" you would still have to farm out some stuff to do full scale, but ~18" would be do-able. And keep in mind you will spend more on tooling, hop-ups and accessories than the lathe is worth. I know I have. Good hunting, MIKE
(I really want 16x108-120 but I have to be realistic, I do have friends so equipped if I get stuck )

[GGaskill]

I'm going with DOM seamless ...

So far as I can tell from the manufacturers' viewpoint, no one makes any seamless DOM tubing.  All DOM tubing is seamed.  Seamless is formed over a mandrel but apparently is not considered DOM.  Seamless is not perfectly round inside or out, so prepare to do some machining if you need a good fit.



Just for the record, I did all the external work on the 1/5 scale 24 pounder (24" long) I am building on a 1000 lb. Logan 12 x 24.  The tailstock was hanging off the end of the bed a little but it worked fine.  But I had to resort to my big lathe to drill the bore since it is turned from solid.

[accuratemike]

Ok, my invoice says 1pc 18" 4 OD x 1-1/8 Wall HR SMLS. I had assumed that all seamless had been formed over a mandrel. I guess that doesn't directly mean you could call it DOM. I suppose it would have been better to say that working from seamless tube, and using a breech plug, would enable someone to build a longer barrel on a shorter lathe. Sorry for any confusion. BTW, nice looking tube George. 

[gary michie]

HI:
You were advised to find a single phaze motor  well  if you wish you can have 3pz.
First add up all the 3pz hp. you wish to use at one time.
Add 33% of the number to it.
Find a good but used 3pz. motor ,that size or bigger.
Wire up a 3pz. knife switch to the motor .
Run jumpers from the motor terminals to a 3pz. breaker ( sized to the hp. you wish to use).
Now power the knife switch with single phaze,wireing to post 1 and 2 but not 3.
You should have power to post 1&2 on the supply side of the switch and the 3 wires and the jumpers on the switched side
Now all you have to do  is rap a pull cord around the shaft of the and give it a hard pullthen QUICKLY turning on the knife switch.
You got 3pz......If you can't get ithemotor up to speed(it starts to growll as if it changing driection ) when you through the switch get a 1/2 or1/3 horse 1pz. motor and couple to it.
start it with the small motor flip the switch then  turn off the small motor

Off of your 3pz. breaker set up your motor controls for your shop.
this works nice I live up in the sticks and am lucky to have 220v sometimes I think they just invented running water.

[NitroSteel]

How are the old Logan lathes (1940's and 50's models)?  What should I watch out for/ask about if I am buying one?

I think I have found one for what seems to be reasonable and close to home, but want to make sure it is not a piece of junk.  I haven't seen it yet, but was told nothing was wrong with it other than the carriage needed to be adjusted - it is a bit loose.  It is a 3/4 horsepower model, 11x24 with 1-3/8 spindle.

Thanks again,

Nitrosteel

[GGaskill]

Assuming you are not a machinist, you should try to find one to help you inspect the lathe.  For starters, read Some Helpful Tips on Evaluating a Lathe for some idea of what to do.  I can tell you from personal experience that there are thieves out there who sell used machinery to the uninitiated and unless you can afford to lose the money spent, you need to be careful.

My Logan is from the late '60's which was near the end of production by the original company.  I have no experience with the older ones.  There is a Yahoo! group called lathe-list that discusses Logan lathes of all vintages.