# 12x36 hp issues..... need advice or recommendations



## chevydyl (Oct 22, 2014)

So today I was turning a piece of 4140 turned ground and polished 2 in stock at about 400rpm taking .030 DOC and when I got closer to the headstock it would stall out the motor. Using carbide. So I lightened up to .020 and it still stalled. Using power feed with the shortest cut per rev. So I upped the rpm a little and it no longer stalled. However I realized that to get to my final od is gonna take FOREVER. Has anyone increased their hp and by how much? What are the risks of the extra power? I would assume the little cheapie gears would be at risk. I have access to a 1.5hp 3 phase motor that I am seriously considering installing. Using a VFD to control the motor. BTW my lathe currently has a 1/2hp motor wired 220v. The motor I could use is a little longer than the current motor but I have no problems with cutting a hole in the cabinet to make room for the new motor. My lathe is an underneath drive. looking at picture my lathe was made the year before they added the lever to the power cross feed. Mine has the pull knob. Other distinctive features like the compound add to the time period.


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## Rbeckett (Oct 22, 2014)

At lower RPM's you will find the smaller motors would  stall and overheat.  to eliminate the problem you are on the right track with the 1.5 HP Motor.  I think you will find that will cure most if not all of your stalling issues at low rpm.  Good luck and let us know that you solved the problem and how.


Bob


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## chevydyl (Oct 22, 2014)

Thanks for the reply. My concern is overpowering the rest of the components in the machine. I ripped the teeth off a gear cause my leadscrew was too tight  at the far end. Took 2mo of searching ebay to find that stupid gear lol. But I guess I'm not really gonna be taking huge cuts because of the rigidity issues of these lathes. Tired of having my big drills stall out also. it sure will be nice to drop or raise the rpm with a button though. Within reason of course. Not sure how the motor would react to overspeed. I wonder if it's more of a bearing issue to on the motor when you increase the speed.


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## Ozwelder (Oct 22, 2014)

I also run 12 x36 lathe.It has a 2 hp 240 volt motor. I have owned it for 8 years and never had problems relating to over stressing the components due to motor size.
If you have any specific questions about operation of my lathe,I am more than happy to answer them for you.


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## chevydyl (Oct 22, 2014)

Thanks Oz welder that's what I wanted to hear. You have a picture of the install?  And have you ever actually used all that power? Or has it been enough power that you've never really had to push it's limits?


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## Mondo (Oct 22, 2014)

I am concerned that the machine stalled as you got closer to the headstock.  What would the position relative to the headstock have to do with the forces involved? The forces for a given DOC at constant feed and constant speed should be constant from start to finish. I think there is something wrong with the setup or the cutter is dulling rapidly as it cuts due to incorrect positioning of the cutter.  

Make certain the leadscrew is clean and free of chips and swarf and properly lubricated.  Make cerain the carriage gib screws are properly adjusted and it isn't binding up due to uneven bed wear. Be certain the bed is properly lubricated, too.  SAE 20 non-detergent is recommended for that lathe, you can use Way Oil on the ways if you wish.

Check your cutter setup against the textbook recommendations for the material.  Check relief angle, rake angle, etc.   You did not say what make of carbide cutter you were using, or if you were using it as-is out-of-the-box or if you sharpened it yourself before use.  There are a lot of inexpensive carbide cutters out there and I doubt any of them are ready for use out-of-the-box.  Make certain the cutter is properly sharpened before starting the cut.  Inspect with a stong magnifier, use a diamond hone on the carbide cutter if necessary. 

That lathe is rated for 3/4HP motor maximum.  You should need nothing more powerful than that.  Certainly not for a .030 DOC!


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## Round in circles (Oct 22, 2014)

Nice post SC.. it took me a while to discover why the carriage on my old ( circa 1943) lathe was tighter at the head stock than four inches from it.
 On carefully looking with a magnifying glass I noticed a slight change in the colour of the ways there was a glazed & slightly sticky patina of ancient old dried up oil causing it to stick .

I ended up using a stainless steel knitted pans scrubber and WD40 to loosen it up then a used clean green Scotch Bright kitchen pan scrubber to follow on with some clean detergent engine oil to deep clean the ways on the top , sides and underneath . It's now as smooth as silk from end to end for both carriage & tail stock .

I've also taken to following the old engineers habit of wiping and then oiling the ways whether Ii use the lathe or not and keep it covered in some canvas sheeting to keep any dust / moisture off it when I'm doing other things close by .


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## Ulma Doctor (Oct 22, 2014)

i don't think 2 hp is unreasonable to put on a 1236.
 i'm gonna put 3hp on mine:nutsi have one laying around) 

i'll relate it like this...
top fuel dragsters scatter drive trains routinely,
just plan on working on your lathe if something goes wrong.


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## chevydyl (Oct 22, 2014)

Sorry I was using a brand new Kennametal insert ccmt 21.52 for roughing. The carriage feeds nicely. With no binding. My tails to k is off a thou but it's larger od at the headstock. And I must say that the finish of the cut is absolutely gorgeous. I can spin the leadscrew by hand. She's always well oiled with sae20.  The only thing I can think of is maybe the.l carriage Gibs are too free maybe causing it to bind. Start of cut you can hear the motor start to work then the rpm gradually drops until it would stop.


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## mws (Oct 22, 2014)

I thought the same thing, that carriage position should have no affect on loading. But if what your saying is that the crudded ways were enough to stall the machine I'd say a motor upgrade is in your future. I have an 11x36 and it has a 1hp on it.  If I think I might get into some trouble I just don't lock the belts down on the cone pulleys underneath.  I only snapped a taper pin on my leadscrew once, but 1 horse has been enough for me so far.


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## JimDawson (Oct 22, 2014)

I am having trouble understanding why it would require more power as you approach the headstock.  Something must be binding.  The cutting load really can't be changing or you would see some major discrepancy in the part.  So that means that the additional load is coming from the carriage drive.  Does it do anything like this when running but not actually cutting, just running the carriage?

Many years ago when I had my 12x36, I had a 1HP on it, and never stalled it.  I did a lot of work with Inconel, really tough nasty stuff to work with.


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## Ulma Doctor (Oct 23, 2014)

how solid is the lathe? is it worn or does the carriage have excessive slop?
1/2 hp is way too light in my opinion and may be a source of your problems


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## chevydyl (Oct 23, 2014)

The bed ways do have some wear. Idk maybe the motor I have is overrated. It's some hashimoto no name that the guy I bought the lathe from put on it. Says .4 kw on it. I'll check some things tonight and report back then I'm back to work for a week and will be away from the machine.


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## Ozwelder (Oct 23, 2014)

chevydyl said:


> Thanks Oz welder that's what I wanted to hear. You have a picture of the install?  And have you ever actually used all that power? Or has it been enough power that you've never really had to push it's limits?



Instal ? It came with the motor. I have it struggle once  taking some stupidly deep cuts but backed off as I was chicken.I have damaged it in the past where I bound the travel up on the spiral swarf shield and bent the travel shaft/pinion. I think the cross slide and tool post assemblies on these lathes could be stronger and that is where their limitations are as far as over powering the machine.

Accordingly I insure that tool over hangs and are minimized. I quite regularly part off stainless solid and tube to 50mm(2") with a HSS tool, with out any bother.The head stock gear train has always seemed noisy to me  but, I can't be positive that as I have not seen any other  gear head lathes of that size to compare to. The lathe will be shifted to its new home in the shed I have just built. So I"ll take some snaps when i can access the back of it.
Hope this helps


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## wa5cab (Oct 23, 2014)

I have a 3/4 hp single phase motor, US made and connected for 240 VAC, on my 3996.  In 30 years, I've never even slowed it down.  Putting anything larger on the machine is a waste of money, plus if you ever have a crash, you will just break more parts.  If the motor slows down in one area and not the other, something else is wrong.  Try running coolant (oil) on the cutter.

Try flipping the part end for end.  If you get the same results, the material isn't the problem.  Put an AC voltmeter and an AC ammeter on the motor and check what the voltage and current are doing.  Also calculate the HP input from those numbers.  One thing that could be wrong is a bad splice.  

If you do put a variable speed system on it, you should probably use a 1 HP motor as the motors tend to overheat when operated below their rated RPM and should be derated.


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## chevydyl (Oct 23, 2014)

Ok so I just fired up the lathe it's 45 deg in my shop no warmup time and dialed in a .030 cut. No problems. Didn't even sound worked. And a great finish on the cut. I watched the pulleys and didn't see any issues. I also with the lathe off placed the carriage close to where it was stalling and engaged the half nuts and turned the belt by hand to see if I could feel any abnormal resistance. Just pulled a .040 cut without a hiccup.Then .050 and wow. That's definitely where the insert wants to cut at. Very nice pile of small chips. At .040 the chips were about an inch long. Now they are small chips like they should be. And still that perfect finish. No tears just that nice rainbowesque look. Hmmm....it seems to be cutting fine now. I made no changes.


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## chevydyl (Oct 23, 2014)

Well dammit. Went out in the shop this morning and tried to take an .080 cut and cha-cha chaAaaatteeeerrrr!!!!!!! I may have spoiled the workpiece last nite on those deeper cuts. I was using oil not coolant. I'm not setup for that. The chips from the .050 cut were blue right off the nose of the insert so I am suspecting that I may have added a little hardness to the workpiece. Not sure how deep it went but is there any way to fix it or should I just scrap the part now. Honestly it was scrap to start with I was just cutting to see if I could make a shaft good enough for bearings... but I would like to keep going as 8 only need to remove about .400 to get to size.


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## Mondo (Oct 23, 2014)

Sumpin' changed.   A change in performance ALWAYS indicates a change in something else. 

I trust you are using a QCTP.  No change in position, up or down?  Cutter is on the center line or a thou below for external cuts? 

Sorry I didn't discuss this yesterday....  Early on I found if my cutter was a tad above the axis of the spindle it would start to bind and stop the spindle as it approached the headstock.  Why?  The workpiece was bending upwards and away from the cutter - a normal response to the cutting operation - but as the cutter approached the chuck the workpiece could not flex upwards as much so the cutter began to hog in taking a deeper cut and this would stall the spindle.  (BTW I keep my belt drive a little slack so the belt will slip under such conditions preventing serious damage to the machine.)

The cure was learning to get the cutter dead on the axis of the  workpiece, or when in doubt a thou or two below the axis for OD cuts,  and a thou or two above the axis for internal cuts.  No more hogging in  causing stalls! As I gained more experience and became more skilled at setting up the cutter I didn't need to offset below (for OD) or above (for ID) as much and rarely do this now unless taking deep rough cuts where precision is less important than time.  

When cutting an OD the workpiece will tend to flex up and back just a wee bit while the cutter will tend to bend downwards.  If the cutter is just a tad higher than the axis of the spindle (OD cuts) then as it gets closer to the chuck the workpiece can't bend up and back so the cutter starts hogging in and can jam.  The same will happen on an ID cut if the cutter is a tad below the axis.  Too far below for OD or too far above for ID cuts and it will chatter horribly if it cuts at all.  There is a fine line between enough and too much.

In the absence of any reasonable explanation for the change in performance you might want to maintain a log book and record every measurement, setting, shop temp, and all other observations so you can go back and refer to previous notes if you see a similar problem again. Sometimes we are not able to nail down the cause of the change right away, but is sure is nice to have a record to review and sometimes find the root cause there later on.


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## chevydyl (Oct 23, 2014)

Yes I am using a BXA qctp with a 1/2 inch shank sclcr tool. Ccmt insert. I faced the end of the work to dial in the height of the cutter. No nub. I changed nothing from last night. I made those cuts I spoke of. I made the .050 cut and shut the lathe off and went to bed. Came out the next morning dialed in an .080 cut and it left a terrible finish chattery finish. I decreased the depth and the same all the way out to .020 I think the material may have gained a little tempering from the last couple cuts from the night before. The chips were blue....


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## Mondo (Oct 24, 2014)

Yes, heat generated during turning, especially when taking deep or fast cuts, can slightly "work harden" the surface.
Keep up the good work!


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## iron man (Oct 24, 2014)

I think you may want to slow it down a bit I agree the material is probably getting tough on you with the build up of heat. On the other side of things I have had a 21/2 horse DC motor on my lathe for some time now with no problems at all no over heating and the only gears that have gone out are the ones with many years of wear. Since the DC motor has a higher top RPM I just leave my belt setup geared to the slowest spindle speed the PWM speed control gives me any speed I need for turning or polishing something. Ray


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## chevydyl (Oct 24, 2014)

Yeah I didn't have any problems with the cutting until I let it sit over night and cool after taking several .050 cuts. The motor I would use is a Baldor Industrial use for class I div I hazardous atmospheres. It was a take out motor that ran nonstop but was upgraded to 2hp. It's in good shape. 3ph. I would continue to use the belts on the machine to control speed for the most part. That way I'm keeping the motor in its rated rpm. What's the most spindle rpm you guys would feel comfortable with? I'm not at my lathe now but what's the stock configuration worth? Almost 2000 rpm right?


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## iron man (Oct 24, 2014)

The maximum chuck speed  on a 6" chuck is 3000.


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## oldschoolcj5 (Oct 26, 2014)

I run a 1/2HP 90 volt dc motor on my bench 12x24 lathe. I don't normally take very deep cuts but i can take a .030 cut in steel. the belt will start slipping before the motor stalls out. that i think is the benefit of having a dc motor. you can hear the controller just giving more amperage to the motor to keep the rpm constant. 

stephan


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## wa5cab (Oct 28, 2014)

Chevy,

The published Atlas spindle speed chart hasn't changed any since 1937.  It gives a speed range of 28 to 2072 RPM.  But it never has specified a motor RPM.  1725 RPM has been the most common spec on single phase 60 cps motors for the past 50 years.  Which would presumably be the full load RPM.  At no load it would be running very close to 1800 RPM (synchronous speed).  But in the 1930's and 1940's, stated ratings of 1750 and 1740 were common.  I also don't know whether the original chart was calculated or measured.  I've never put a tachometer on my spindle.  

In any case, around 2000 is the maximum with the original setups.

Robert D.


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## chevydyl (Oct 30, 2014)

It currently has the 1725 motor on it. The 3ph motor is a 1740


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## chuckorlando (Oct 30, 2014)

You got something going on cause my little 9x20 can just pull off .05 with some cheap inserts and even then it aint slowing the motor but you can hear the on set of chatter. I just pushed it this weekend to see using 4140

If you did work harden it, I would think the first .05 would have took a case harden off let alone the passes after that. Unless you hardened the whole thing.

Maybe you got some bad bearings and that cold weather helped them stay cool? Or made something flex or bend that allowed a decent cut.


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## chevydyl (Oct 31, 2014)

Yeah it seems to be cutting ok now. Around 600 rpm .05 been taking two or 3 passes the. Letting it cool before cutting again. I already have the motor so I'm gonna prolly just swap it out. I need 2 pulleys. One for the new motor it has a bigger shaft than stock. Also one of the 4 step pulleys on the side is sprung so I can't go above the 600rpm setting.i had to remove the 4 jaw and put on my 3 jaw for another project....when I put the 4 jaw back on I was happy to see that it indicated at zero with no adjustments.


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## GarageGuy (Nov 1, 2014)

Ulma Doctor said:


> how solid is the lathe? is it worn or does the carriage have excessive slop?
> 1/2 hp is way too light in my opinion and may be a source of your problems



I was thinking the same thing.  My 10" lathe came with a 3/4 HP motor, and a 12" lathe would require more power than that (I would think).  I put a new (single phase) 1 HP Baldor on mine, and it seems to work great.  The previous owner that put the 1/2 HP motor on it probably just used whatever he had laying around.  A 1 1/2 HP sounds reasonable for a 12" machine, and maybe even 2 HP.

GG


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## chevydyl (Nov 1, 2014)

I would have loved to have a 2hp but all we had laying around the salvage pile at work was some 1 hp and a couple of these 1.5hp. On another note I mentioned above about a sprung pulley...I turned an alum pulley for the 800rpm. Started with 4 in round that was about 4 in long. When I turned the hub it would have been nice to have the extra power. That turned into a 2 day project haha one for the hub diameter and the other for the v groove and shaft hole. Reaming and broaching.


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## wa5cab (Nov 1, 2014)

I've said this before, but I have an honest good quality US made 3/4 HP TEFC motor on my 3996 (12x36).  In 35+ years, I have never bogged it down.  Unless you convert to VFD (especially if you scrap the countershaft) or are using a Chinese made motor, you don't need anything larger.


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## chevydyl (Nov 2, 2014)

The current half horse motor is some takigawi Chinese motor. I'm gonna use a 2 horse vfd for the new Baldor motor. Plus I will need the vfd for the harig 612 I bought last night...... one inverter will run both machines. Not simultaneously of course haha. Got the grinder for 600 bucks. Smokin deal!

Edit
There's a sticker on the Baldor that says it's wound with inverter duty insulated wire so that's a plus. The motor is also a TEFC design. I think I'm gonna keep the counter shaft pulleys. That way I can keep track of speed better until I get a machine tach


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## chevydyl (Nov 3, 2014)

Something I took note of is my little 4x6 saw has a half horse GE motor on it and it's about half the size of my lathes Chinese motor...


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## tkitta (Nov 3, 2014)

I have a new 12 x 24 and it came with 1hp 120v motor... I cannot even get the motor to get warm not to mention get hot or stall... But I just started few weeks ago, so maybe I am not aggressive enough.


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## wa5cab (Nov 4, 2014)

If you get a single speed 1 HP motor hot or stall it on anything smaller than a 16", and if it isn't an overrated Chicom motor, you are doing something wrong.

Robert D.


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## chevydyl (Nov 4, 2014)

I lied my 4x6 bandsaw has a 1 hp GE motor. Thing is tiny though. I cut a stainless 1.5in bar yesterday.....Bout 20 min worth of cut


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