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Clausing 5914 Lathe Threading Problem

NonSheep

Plastic
Joined
Jul 10, 2023
Hello, I have an old beat-to-death Clausing model 5914 lathe. For years I have pondered why I can't thread on it, so today I want to ask for help or ideas how to adjust or repair it.
I am a novice machinist, but I am not dim witted. I know the fundamentals of threading, and I can adjust the knobs/levers, but the thread pitch this lathe cuts, is not the same thread selected (see photos). One thing I have observed is that on the A-B-C knob, it only adjusts A & B, but I only want "B" anyway, I just need to cut 40tpi & 32tpi. I have never taken the gear box open, but I can see signs of some FrankenHack work on the motor mounting so anything is possible internally. Does anyone have a starting point I can try to fix my issue here?
ClausingLathe_20230709_213252963.jpgClausingLathe-40threads_20230709_212837680.jpgClausingLathe-32threads_20230709_212709118.jpgClausingLathe_20230709_213233860.jpg
 
that flat bottom thread looks very odd. and the other doesn't fit the gauge.
*Are you engaged with the half nut and using the threading lever?
*Is the part soft enough to file? too hard and it will turn the tool post.
A lathe that turns an Od well should thread well
Possible your cutting edge is not sharp enough.
Possible that you are not at 30 and so trying to cut with the whole bit/insert at once.
Possibly the headstock is \pushing away from tool pressure.
Possibly something wrong in the saddle or compound.
I would give a hard push-pull on the chuck perhaps with a 2x2 under an indicator
Give a hard by-hand push-pull on the tool holder.
Inspect my tool bit to shave a fingernail.
*Be sure the tool post can tighten properly.
Try turning the compound to and feed at *30
 
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Maybe a previous operator installed a metric conversion kit. That could make the pitches come out different from the chart. You need to remove the cover from the left end of the lathe and take a picture of the visible gearing. There is probably no need to mess with the quick change selector gears.

Here is a manual: http://vintagemachinery.org/pubs/182/29606.pdf

Have you verified that the shear pin is intact? Probably not causing your problem, but worth checking on "an old beat-to-death" lathe.

The profile of your cut threads looks very strange. Is your tool a standard 60 degree angle?

Larry
 
You might put a 40 or 32 TPI screw in your chuck and with not tool-touching the part travel to see that the tool point stays with the thread.
Set the tool point near the thread by looking through your loupe.
then come back to the same half-nut number and pass again, if it chances at the second pass then it is likely the Metrick gear

My rough guess is that the part is too hard and the tool post or the compound is turning allowing the tool to push away from the part.
Or : The bit has no clearance so it can't cut and is pushing away.
Pushing away/radial swinging would make the pitch change....and change the depth of the cut.and change the angle toward the part..the 60 included would not be 30 -30 but 25-35 or the like

Here is some gear information about the 127 gear, I am not a late or a Logan guy so like ly another PM guy can give better help.
3
 
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I have a 5914, and it cuts threads just fine.

Do you have the manual for that lathe? They are available from Clausing Industrial. You'll need model number and serial number.

Do your experiments making a scratch pass on blued aluminum, to eliminate all issues with things being pushed this way or that.

I would not be surprised if the gears are mixed up, or a metric kit is installed, but this is easily checked with a manual.
 
1. If you don't have a manual, Clausing will supply one that pertains to your S/N (oops, just saw Joe's post)
2. If there is some issue with A-B-C gear selection as you note, this could be an indication of gears that have moved somehow.
3. And yes, if the machine is set up for metric threading, that'll give some strange results.
 
Thank you all for the good intentions, and most especially a BIG thank you to "L Vanice" for the info, ideas & manual!
Firstly I want to amend my comment about not being able to set it to "C", it does go A-B-C, it was just stuck. But I will only be using "B" setting anyway.

Here is another photo of a 32tpi cut on soft 3/4" plastic. Near as I can calculate when I am setting the lathe to cut 32tpi, it is actually cutting about 28.5tpi (+/- .2tpi) and when I set it to cut 40tpi, it is actually cutting about 38.5tpi (+/- .2tpi). I did try to match the threads with a metric gauge and nothing matched up at all. So I am back to square 1 again :(

Here are 3 photos of my gears, I hope this is what you guys were asking for? I'm sorry I don't know where the shear pin is located to check, I looked in the manual and I did not see it, maybe I missed it. Any more ideas?
 

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Your thread does not look like a crisp thread, what kind of insert or tool bit are you using? Even cutting a wrong thread pitch, your thread should look better.
are you absolutely sure your tool holder and compound are not moving/turning?
and your half nut is closed/engaged..and using the thread engaging lever?
 
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If you have the sliding gear in instead of out and are using the longitudinal feed instead of the half nuts, you will get a thread that is not terribly different from the 32 or 40 TPI that you want, but will be wrong, of course.

The shear pin is at the left end of the lead screw, just to the right of the threading gear box. See page 19 in the manual link I posted. It is an aluminum rivet with a round head on one end and a tiny steel push nut on the other end.

Larry
 
I just realized all my text evaporated when I inserted my photos.
Firstly I need to say again, unfortunately I am only a novice machinist and I am ignorant to many of your advanced terminologies, sorry.

When I try to thread, I am using the L/C handle/knob, and I am lifting it up to L to start the threading (moving the carriage into the chuck), I am ASSuming that this is the 1/2 nut you mentioned? If i use the handle/knob to the right of that as "lazz" suggested, it moved VERY fast, like maybe 5tpi?

I wanted to open the box that resides behind the A-B-C knob, but even after loosening the 2 bolts on that cover, + the 2 bolts on the 1-9 selector, it was still frozen to the lathe body. So I don't know how or if it is possible to remove this cover (see photo) for inspection.

My clutch rod/handle is loose, and the engagement slips out of gear apparently, so while working the rotation often slows to a crawl or stops unless I physically hold that handle upward. (just FYI)

On the 2 photos of the lead screw, there is about a 30° rotation of the lead screw without any gear movement, so i suspect that might have some effect on the threading?
I'm not sure if I'm looking at the right thing, but on the 2 photos of my lead screw you can see holes where I suspect the shear pin "should" have been?

Thank you all for your time to help.
 
Well, I am glad we got that issue resolved. You need to read that manual, especially page 9. The L/C lever is for longitudinal and cross feed, never threading. The feed per revolution figures are below the TPI figures on the quick change chart. The lever to the right of the L/C lever is the half nut engagement control, only used for threading. The knurled shaft on the left side of the end of the lathe is the sliding gear, which can be in (pushed to the right) or out (pulled to the left). You need to engage the back gears in order to get a slow spindle speed that lets you have time to operate the half nut control while threading. Engaging the back gear requires pulling out a small pin on the left end of the spindle and rotating the back gear knob on the front of the headstock. All that stuff is described in the manual.

I think your shear pin has been broken and replaced with something that may not shear at the required torque. That could lead to breaking expensive or irreplaceable parts if you make a mistake while running the lathe. The shear pin is explained on page 13 of the manual.

Note that Clausing changed the 5900 series lathes over time and the manuals are specific to certain ranges of serial numbers. It is best to use a manual for the serial number of your lathe.
Here is a later (1975) manual:

Larry
 
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When I try to thread, I am using the L/C handle/knob, and I am lifting it up to L to start the threading (moving the carriage into the chuck), I am ASSuming that this is the 1/2 nut you mentioned? If i use the handle/knob to the right of that as "lazz" suggested, it moved VERY fast, like maybe 5tpi?
In your post #8 in the third picture is your slide handle. It is the knurled shaft about 1" in diameter with the oil point in the end . In the in position it is a 5 TPI. in the out position it is 40 TPI.

My clutch rod/handle is loose, and the engagement slips out of gear apparently, so while working the rotation often slows to a crawl or stops unless I physically hold that handle upward. (just FYI)

This is a common problem . Should you google clausing 5914 loose clutch lever there are videos to watch.
In the base under the headstock there is a detent and spring that position the clutch lever. Also the clutch adjustment is there too.


On the 2 photos of the lead screw, there is about a 30° rotation of the lead screw without any gear movement, so i suspect that might have some effect on the threading?
This sounds like backlash.


I'm not sure if I'm looking at the right thing, but on the 2 photos of my lead screw you can see holes where I suspect the shear pin "should" have been?


Thank you all for your time to help.
That does appear to be a missing shear pin. I have used hunk of aluminum weld wire while waiting for the shear pin to show up.

Two things I noticed in your pictures...
1) Your lead screw could use a cleaning. in the last picture of your lead screw there are curls of metal on the lead screw. That could lead to problems.
2) Your thread dial is not in position to be usable to thread. You dont have to use a thread dial to cut threads... but it does make the process easier.

Here is a video that may help

Also [email protected] is a great place for parts and info.
At one point a user named Blue Chips had shear pins for sale.
 
I just realized all my text evaporated when I inserted my photos.
Firstly I need to say again, unfortunately I am only a novice machinist and I am ignorant to many of your advanced terminologies, sorry.

Be aware that a 5914 is perfectly capable of maiming or killing its operator. It only takes a moment's inattention, or a small-seeming ignorance.

You need to read some textbooks on how to run such a lathe, in safety.

Courses may be available locally, as will places where machinists gather.

You probably will need to repair the lathe as well; they usually do.
 
Wow, you guys are awesome. I can't believe that in this sad & self centered world you guys would take the time out of your lives to help a complete stranger like me, and someone so naive at that. I never would have believed that my threading problem was solely my ignorance, I am humiliated but VERY appreciative of all the help you guys have provided me. I have owned and operated this lathe for about 15 years, but as far as threading I was never able to make it work, I really appreciate you guys helping me out.

I triple checked I was doing everything as you all instructed, and again I got 4tpi, I then realized I overlooked the slide gear (again). I spent the last 45 minutes screwing with it, first trying to pull/force it out, then I removed the cover and lightly used a CROW BAR to try to pry it outward as I rotated it. While it feels loose, it has zero horizontal slide movement, so I am back to the beginning again :( I have no clue what I am doing here (obviously) but in my ignorance, I am looking at a nut holding the shear handle to the body and asking myself HOW is this supposed to slide if it is held by a nut? Or is the handle/shaft hollow and somehow supposed to move in/out like a telescoping radio antenna? I know I am ignorant about this lathe, but I am generally mechanically inclined, yet without actually taking the entire thing apart, I'm just not understanding why I can't move the shear handle/gear IN/OUT. I should also note that the back-gear-driver-pin on in the turret handle was frozen and I needed to remove the cover and use a pry bar to pull it out.

Last question is on the lead screw / shear pin. I have 3 sets of holes on mine. One had a broken tap in one side, I chipped the tap enough that I think it will not bind the shaft. My questions are, which set of holes should I use for a shear pin (1, 2, 3 on my photo) and can anyone tell me the diameter of aluminum I should use to make a shear pin?

THANK YOU GUYS SO MUCH!!!!!
 

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I triple checked I was doing everything as you all instructed, and again I got 4tpi, I then realized I overlooked the slide gear (again). I spent the last 45 minutes screwing with it, first trying to pull/force it out, then I removed the cover and lightly used a CROW BAR to try to pry it outward as I rotated it. While it feels loose, it has zero horizontal slide movement, so I am back to the beginning again :( I have no clue what I am doing here (obviously) but in my ignorance, I am looking at a nut holding the shear handle to the body and asking myself HOW is this supposed to slide if it is held by a nut? Or is the handle/shaft hollow and somehow supposed to move in/out like a telescoping radio antenna? I know I am ignorant about this lathe, but I am generally mechanically inclined, yet without actually taking the entire thing apart, I'm just not understanding why I can't move the shear handle/gear IN/OUT. I should also note that the back-gear-driver-pin on in the turret handle was frozen and I needed to remove the cover and use a pry bar to pull it out.
Don't pry it at all, but some cleaning may be useful.

It's often necessary to rotate the chuck slightly before the slider pins will seat properly, so just fiddle/jiggle things till the pin just drops into place.

Last question is on the lead screw / shear pin. I have 3 sets of holes on mine. One had a broken tap in one side, I chipped the tap enough that I think it will not bind the shaft. My questions are, which set of holes should I use for a shear pin (1, 2, 3 on my photo) and can anyone tell me the diameter of aluminum I should use to make a shear pin?

It has to line up with the through hole of the sleeve coming out of the headstock into which the leadscrew fits. If I recall, the rivet diameter is 0.100" or so.

But just use a bit of solid copper wire for now, the largest that will fit (it will be loose), and bend the tails over by hand.
 
Wow, you guys are awesome. I can't believe that in this sad & self centered world you guys would take the time out of your lives to help a complete stranger like me, and someone so naive at that. I never would have believed that my threading problem was solely my ignorance, I am humiliated but VERY appreciative of all the help you guys have provided me. I have owned and operated this lathe for about 15 years, but as far as threading I was never able to make it work, I really appreciate you guys helping me out.

I triple checked I was doing everything as you all instructed, and again I got 4tpi, I then realized I overlooked the slide gear (again). I spent the last 45 minutes screwing with it, first trying to pull/force it out, then I removed the cover and lightly used a CROW BAR to try to pry it outward as I rotated it. While it feels loose, it has zero horizontal slide movement, so I am back to the beginning again :( I have no clue what I am doing here (obviously) but in my ignorance, I am looking at a nut holding the shear handle to the body and asking myself HOW is this supposed to slide if it is held by a nut? Or is the handle/shaft hollow and somehow supposed to move in/out like a telescoping radio antenna? I know I am ignorant about this lathe, but I am generally mechanically inclined, yet without actually taking the entire thing apart, I'm just not understanding why I can't move the shear handle/gear IN/OUT. I should also note that the back-gear-driver-pin on in the turret handle was frozen and I needed to remove the cover and use a pry bar to pull it out.

Last question is on the lead screw / shear pin. I have 3 sets of holes on mine. One had a broken tap in one side, I chipped the tap enough that I think it will not bind the shaft. My questions are, which set of holes should I use for a shear pin (1, 2, 3 on my photo) and can anyone tell me the diameter of aluminum I should use to make a shear pin?

THANK YOU GUYS SO MUCH!!!!!
 
I jiggled it, I wiggled it, I tapped it, I smacked it, I beat it in, up, down, and sideways, I heated it, I pried it, I cussed at it, and nothing helped pull it out. I even tried vise grips and beating it outward (as much of an angle I could get on it). I can rotate the handle/gear very smoothly & easily, and the handle wobbles very loosely up/down + side to side, but those internal bearing must be fused to the internal handle body. I know this is a long shot, but would anyone have a guesstimate of the distance in my sketch here? I thought maybe I would drill the handle and add penetrating oil (no, I can not get any oil in from the bearing seal on the outer end of the handle). I also considered taking the nut loose from the back, but then I thought the shaft would spin freely and I would be screwed not being able to loose it all the way, or re-tighten it. Anyone have any better ideas them me?

ClausingSlidingGearHandle.jpg
 








 
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