Maximum rpms on old lathe

Hi,

Anyone have any idea on what the max rmps old babbit bearing lathes will handle. I've got a 16" swing L&S. The original drive has been replaced with an electric motor with a v belt driving a jack shaft with flat belt to spindle. Max spindle speed is 300 rpms and I'd like to increase it to 500.

Thanks in advance.

Steve

hi steve

max speed as set up on my 1895 reed 14 in is 744....no problems ...xcept under a good load ,i need to increase the drip oiler feed rate ,or it drags down & trips a breaker ...spindle is 2 inches in d. ....with large enuff boxes ,reckon could go to 1000 or so .,but thats a guess ..dissipation of heat is the problem

will get out my daddys old engineer ing handbook & see what it says ...may have to just give u the formula if it gets much beyond ist yr algebra...sad to say .....too soon oldt und too late schmart

best wishes
docn8as

Doc,

Thanks for your reply. I'm finally getting around to this project. I've managed to scrounge up some carbide tooling and I'm hoping increased rpms will give me a better finish.

Steve

Do yourself a favor and stay away fron carbide cutting tools on Old Lathes.

They were never designed to turn the work against the blunt edge of Tungsten Carbide. Even if you gan get the spindle speed up, the belt drive might still not transmit enough power.

They don't have the power available in the Feedworks to maintain the rate of advance usually associated with cutting with carbides.

If finish is your problem, then properly grinding a good high speed steel cutter bit is the solution.

Stay with between 3 and 5 degrees clearance but on older, slower machines you gan go with maybe as much as 15 degrees Side Rake and up to 10 degrees Back Rake.

The slower rotative speeds of the older lathes won't develop surface speeds fast enough to burn very keen cutting tools.

The high degree of rake causes the edge to cleave the metal easier thereby requiring lass power and developing lower reaction forces in the tool holder and the machine.

All high speed tool bits should be finished after grinding by carefully honing the cutting edges on an oil stone. This is the key to getting a good finish on the work and also the key to long edge life in the cut.

A radius at the tip of the tool is essential for finishing cutters. Roughing tools need only enough tip radius to keep the end of the tool from breaking off.

If you can, get an older copy of South Bend's "How To Run a Lathe".
The illustrations and the advice are just the thing for tools that will give satisfactory performance on Older Belt drive lathes.

I like the convienience of quick change carbide tooling.. saves alot of time fiddling with center height etc. I changed drive pulley on my lathe tonight, increased rpms from 350 to around 600. The finish has improved and I didn't notice any loss of power, can hog .200 if I care to. Time will tell if bearings heat up.. they didn't in the one half hour I ran the machine.

JimK. I have "How to Run a Lathe".. fine book. Thanks for your input.

steve ...i agree w/ jim & think you will get better finishes w/ high speed ( acyually theese lates were designed for carbon steel!!) secret of using hi speed tooling w/ quick change is DEEP chipbreaker,across bit, just behind cutting edge & extending to it ...this gives needed back rake for ease & sharpness & by DEEPENING the groove in direction away from cut ,u get the needed side rake .chip breaker put on w/ edge of stone....hard to describe w/out seeing ...master machinist doug king(canada) visited for 10 days last summer & ground some bits for me ....i keep them in chest so i can compare & dont stray too far in grinding new bits .he made a #9 B&S 1 1/4 X 10 mill arbor on my 100+yr old reed 14 in. that indicated dead nuts at the end ...still in disbeleif ..some luck there , but i find the better one is the luckier they seem to be !
grind ur bits this way & u will get way better finish than w/ carbide on these machines..would send some drawings if u wanted......fortunately my old tymer has an elevating x/slide & a quick crank puts the tool on center abt as fast as a q.c. ....carbide really comes in handy for LARGE pieces cast iron allowing decent rpms rather than ist /2nd speed back gear ..love it for that ..but i cant shave a 1/2 thou like i CAN w/ hi speed chipbreaker

best wishes
docn8as


best wishes
docn8as

clarification ...chipbreaker put in with edge of GRINDING stone(wheel)

..imagine a carbide ar bit....... grind a deep groove in back of cutting edge .make the edge of this groove touch the cutting edge & have this groove go deeper (& wider) the further u go across the bit from rt to left ( bit in cutting position)....now do this to ur hi speed bit ...it IS worth the practice

best wishes'
docn8as

Doc,

I'll bow to JimK and your experience. The only reason I want to use carbide is that I can take advantage of qc tooling and also the fact sometime you can buy carbide inserts cheap on eBay.

I'm thinking of trying HSS T-15 inserts, they are a bit spendy but might be worth it. If you have the time a diagram of how you grind the chipbreaker would be appreciated.

Thanks again for taking the time to reply.

Steve

steve ....just reread my post .....error! ...groove gets deeper & wider from left to right ...sorry


docn8as

ps will draw a couple & see if i can emailthem ....just got a demo /talkthru today from computer guru

dhammer:

Go for it! I have "modernized" four old lathes now, 2 16" South Bends, 1 20" Walcott, and recently an 18 in. Hendey, circa 1921. I install large motors, real transmissions, and poly or banded V belts to the largest flat pulley. You will have plenty of poopy for carbide or any other tooling you wish to use.

The Hendey I recently finished has large tapered babbit bearings in oil bath. With the top speed set to 650 rpm and 250 lb load (12" four jaw + peice), I ran the machine solid for 4 hours with a pyrometer attached to front spindle bearing. After 30 minutes the temp rose 15 degrees above ambient, so I changed the oil from 20w hydraulic to Mobile light spindle oil. The temp never rose again. Sold me on spindle oil forever. With the addition of a VFD, I have since increased the top speed to about 800 rpm.
In the Walcott I installed Bronze headstock bearings and a top speed of 900 rpm, and the bearings would seize if you didn't loosen the caps and let the oil flow. It seemed to run ok at 500 with a drip rate of say, 1 per minute.
Now, All this being said, The machine cannot take the huge bites that you will with modern lathes, but I can get pretty rough with a piece of 4140, and drill 2 inch holes, the old girl takes it just fine.
Also, you WANT to buy insert tooling on ebay, there's so much to choose from, and great deals are there if you are patient.
The Hendey is the first rebuild that I photographed and you can see it on my new website at www.lesebergs.com

Good luck, and make some blue chips!
Ed

Eddie,

Wow! Your website had some great pictures, impressive. Thanks for your encouragement.