Tech Talk Article
I just found Livesteaming and read the articles about finding a newlathe or mill---and I wish to make a few comments.I have run lathes since I was thirteen years old and I apprenticed atthe National Bureau of Standards to the trade of Scientific InstrumentMaker. Of all the machine tools I have run, the Lathe and its cousin,the horizontal boring mill are by far my favorite. I will comment onlyon the smaller size lathes for this article.In the previous articles there was only slight mention of the South BendLathe and one of the authors passed them off as probably being old andtherefore sloppy. This is not necessarily the case. I have two SouthBend lathes, one is a 1955 model "A" Nine Inch bench lathe and the otheris an Eleven Inch South Bend made in 1936. Both machines turn outrevenue work in my shop and neither has any trouble holding size orrunning dependably.Of course the South Bend lathes won't compete with our high speed Lodgeand Shipley lathes, but the South Bend machines are assigned to workmore like that done by hobbyists and we take good care of all of ourmachines.If someone wants a very good lathe for model making or general machineshop work, I would heartily recommend three of South Bend's most popularlathes,the Nine Inch model "A", the Ten Inch (1 1/16" collet) or theThirteen Inch lathe.The Nine Inch - Never underestimate the South Bend 9" Lathe. Yes, itwas their economy model and it is small, but its record of accurate anddependable performance on small work speaks for itself. I have visitedinstrument shops where they had many little 9" South Bend lathes makingsmall brass parts and doing it for years. The machine is easy to run,quiet and invariably turns a very good finish. It can pull a surprisingcut in back gears and is an excellent screw cutter. Since a majority ofwork on small steam engines is very small, don't pass one up if it is ingood shape even if you already have a larger lathe.Don't be concerned that the 9" South Bend is a light machine. When theyare in good condition they are definitely not prone to chatter. Manymachinists complain when the tool and the machine vibrate during a cut,usually the fault is in the cutting tool but it is easier to blame amachine, especially a small one. In my experience I have heard many 20and 25 inch heavy duty American built lathes get up a miserable howl andin every case the cause has been either the cutting tool or the set up.No, the 1/2" collet capacity of the 9" lathe won't gomp down on a hogleg, but I have found that the little 3C collets make small work morefun. If most of your collet work is less than 1/2" in diameter thenthis is your lathe. By the way, Hardinge stocks the 3C collet in manysizes, round and hex.The Ten Inch - This is South Bend's tool and instrument maker's lathe.It is and has always been one of the best lathes in the business. Thenewer models (1960's and later) have an extended thread cutting rangeand of course, the fine feeds associated with the extended range.Despite the machine's small size it is a true industrial machine tool.It is the workhorse of the research and development shops inuniversities and industry. The back gears give this lathe more turningeffort than it really ought to have, while the flat belt drivegives it all the speed it actually needs.In all aspects the 10" South Bend lathe compares exceptionally well withthe Hardinge HLV-H lathe. This may sound outlandish, but I haveconsiderably more than a thousand hours logged on each of these lathesand I find the South Bend machine to be a bit more versatile in a widerange of small lathe work. More on this later.The 10" South Bend uses the 5C collet and swings a pretty big chuck forits size. The machine has a nice large faceplate and the back gearedslow speeds make for safe faceplate work. All South Bend lathes,especially the Tool Room models have very good lead screws so they canbe depended upon for chasing precision threads. The overall design isclean and open and the half nut lever is easy to work, making threadcutting easy. It seems to be my fate in the machine industry to have tocut a good many screw threads on the lathe, so I have come to judge theworth of a lathe by how conveniently it can be manipulated during threadcutting - The South Bend lathe is right near the top of my short list.The South Bend lathe is characterized by its flat belt drive and plainbearing spindle. The machine won't rotate very fast, but the trade offis that there is no finer machine for cutting thin wall cup shaped work,especially in brass. There is a smoothness to the drive and the spindlebearings that defies chatter. In general there are few lathes in anyprice range that can turn as fine a finish as these lathes. I havefound that high speed lathes tend to tempt the operator to run way toofast, resulting in tools that dull quickly and a considerable amount ofspoiled work.The trick with the South Bend lathe seems to be to give the cutting toolconsiderable top and back rake. This allows the cutting tool to shearthe material easily and demand less power. The resulting finish is justgreat and the reasonable cutting speeds allow the rather sharp tool tocut for a long time without dulling. Remember, both the hobbyist andthe instrument maker are interested in accurate size and fine finish.Let the production departments deal with high rotative speeds and hot,heavy cuts.The 13 Inch - This machine is just a 10 Inch machine made large. Ithas a robust bed and a large headstock leg with the motor mounted in it.The left hand legs are solidly cast and the machine levels right up withease. The South Bend 13 Inch lathe is heavier in the bed and carriageand tailstock than most modern lathes of comparable swing.Be careful in your comparisons, many lathes are quite heavy because ofthe gear transmission in their headstocks. weight there does not make arigid machine, the size and weight have to be in the bed and carriageand tailstock.The 13 Inch strikes the best balance between the tool and instrumentlathe and the regular engine lathe. It is sensitive and very easy tomanipulate and every bit as accurate as any lathe made. It also isstout and strong and it will not fade in front of large diameter work.This lathe will chase a 1/4-28 thread or a 1 1/2 - 8 with equal ease.Along with its 10 Inch brother it handles large diameter very finethreads so well that they are a joy to cut.For the live steam hobby, this is the lathe for locomotive drivers andlarge flywheels.These large diameter castings are too delicate for the speed and powerof the big gear head lathes and they require a fine finish forappearance. Again this is where the flat belt drive and the plainbearing spindle come into their own.A note about headstocks. When engine lathes were used in production,speed and power were essential. Manufacturers of lathes designed geartransmissions for lathes to get high turning effort at high speeds inorder to allow the lathe to remove a great deal of metal in the shortesttime. From the late 1940's on, engine lathes had even heavierheadstocks with larger power transmission capacity so the machines couldtake advantage of the tungsten carbide tooling that was being applied toproduction work.For general lathe work and especially for the hobbyist, none of thisspeed and power is necessary. I can't understand why lathes of 13 Inchswing and smaller have to have the complication and potential mechanicaltrouble associated with a geared headstock. It seems that, especiallyamongst the newer imported lathes, the geared headstock was what wasexpected or what was scaled down when the machine was designed.On top of all that, to save cost, the headstock was somewhatminitaurized - the spindle is quite short and the gearing is rathersmall. I have known several owners of the newer imported lathes whowere disappointed with their machines because of problems with theheadstock drive.Generally speaking - if you are not doing a time and motion study ofpart production you don't need a gear drive headstock on your lathe.The South Bend back gears do their job when heavy cuts are needed,otherwise they do not turn with the spindle causing wear and heat buildup. Modern flat belts do not slip, I have seen a thirteen inch lathealmost stall a three horsepower motor without the belt slipping.A note on speed - Most modern lathes are capable of turning way toofast. When I was a young, hot apprentice I wanted to have my lathe turnfast. Yes, I cut a lot of metal in a hurry, but I was frequently at thegrinder sharpening my burned out tools.When they say to run a chucking reamer at half the speed for drillingthey mean half the proper speed for drilling. I could get away withdrilling too fast, but I never got away with reaming too fast. Mybosses didn't care if I learned the hard way with turning tools but theysure showed displeasure at my turning the ends of expensive reamers darkblue.Point here, Spindle speeds over 900 rpm are for Star Trek. I am oldenough to admit that I am no Captain Kirk. I turn slowly and I turncarefully.The cult lathes - Many hobbyists and even shop owners pay large sums ofmoney for the Hardinge HLV-H and the Monarch 10 Inch model EE lathes.These are what I call trophy machines. These machines came out in theearly 1050's when there was a lot of experimentation with electromechanical devices. Government and private industry research anddevelopment accounts financed them and most of the work done on them wasa cross between watch making and fine istrument work. Their highspindle speeds served well on aluminum and magnesium and they were andare very good at cutting fine threads. I have logged many hours onthese machines since they were very common at the Bureau of Standardsshop and at other shops I have worked in.Frankly I think they are impractical. The Monarch Model EE should havehad a 13 inch swing and a foot longer between centers. The lathe sure ispowerful enough to be a 13 inch and it is way too short. The tailstockhas only a No.2 Morse taper in its spindle, consequently the machine's 5horsepower isn't available for drilling and the lathe doesn't likeknurling close to the tailstick any better than a 10 Inch South Benddoes.The HLV-H. We apprentices soom came to the conclusion that if the workcan fit in a 5C collet then it is all right to put it on the Hardinge,otherwise go find a Pratt & Whitney.The Hardinge lathe is one of the most beautiful lathes ever made. Eventhe Swiss and Germans buy them. Sadly to say they are one of the mostclumsy things ever called a lathe. The full width carriage doesn'tallow the tailstock to come close enough to the spindle for short, smalldiameter work. If you have to support a short, skinny piece with acenter, you have to extend the tailstock spindle way too far just to getsome carriage travel for the turning cut. Wait a minute - aren't youusing the Hardinge for small, short work? Oh, well, if you need atailstock center, go find a Monarch EE or an old Pratt & Whitney. Bythe way, when I started my apprentceship, the NBS shop had just got allnew Hardinge lathes because they replaced all their 10 Inch South Bends.Even the journeymen were just learning the Hardinge lathes.The Hardinge is almost useless with a four jaw chuck. To get the spindleto run slow enough to cut steel, you have to run the motor in slowspeed, there are no back gears. Anything like a heavy cut causes themotor to stall. So much for turning steam engine flywheels andcylinders.Both the Monarch and the Hardinge run normally with their end gears andlead screws disconnected, their feed mechanisms are drivenindependently. This allows the lathes to turn at fantastic speeds -which are impressive but useless. The chips coming off brass make apainfully hot shower, aluminum wads up its chips almost immediately andforces you to stop the machine to clear them and you just can't cutsteel that fast even with carbide.The lathes don't like it either I have seen HLV-H headstock bearingsfail and they failed on a lathe that wasn't often used by apprentices.Am I ever glad, we got the blame for enough mischief in that shopanyway.If you plan to do a lot of thread cutting on fine work, the Monarch andthe Hardinge are worth the investment. Both of them are the best threadcutting lathes I have ever used. They have setable stops and quickreversing features so that threads can be cut right up to shoulders andinto blind holes without a problem. For collet work these lathes can'tbe beat and, of course they are more accurately aligned than any latheneeds to be. For work in a collet or a pot chuck, no lathe is moreconvenient than the Hardinge.Both of these machines were popular in industry because they are able tomake super accurate complicated parts within their range of operation insmall to medium lot production runs. This is not what hobbyists do.My advice to the hobbyist is to talk to a reputable used machine tooldealer. Don't get the idea that he is your adversary, just tell himright out that you want a good used lathe and work with him. He wantsyou to be satisfied and what you pay for a good machine tool will bereturned many times in satisfying operation. I have run my 11 InchSouth Bend since 1966 and the machine was new in 1936. any cost of themachine by now has paled to insignificance. That machine has become alifelong friend.Don't get scard by stories of worn out old machines, there are many usedmachines that are in first class shape and the price of manual machinesis way down due to the new CNC machines. Frankly I won't buy a new lathefrom anybody because of all the really nice machines out there rightnow. They are really a good value and they come with most of the chucksand tooling that you have to order extra with a new machine.Most used machine tool dealers belong to the Machinery Dealers NationalAsociatioon (MDNA) they have a thirty day return policy, if the machineisn't right they will take it back. See if the new import dealers offerthat kind of back up - most don't.Next time around, I'll jump on the subject of the machine shop's mostugly necessary evil, the milling machine.