# Had my first crash on the lathe



## gt40 (Mar 18, 2012)

I had my first real crash on my jet 13x40 lathe and now there are issues. I failed to take into account the dro which overhangs the cross slide a bit and it made I nice groaning noise and a snap before I could shut it off.

Here is a pic of the gear that I can see damaged:








If you watch it turn there are a couple of flattened teeth:
When you engage the advance in either direction it works for a bit and then stops + you have a moan from the lathe until you help it along. 

Here is a video of what it is doing:



I got it a year or so ago second hand and am not sure what to do next. I can understand the broken teeth stopping the feed but the moaning sounds when it gets to that point from the gear box are a bigger concern. 

Any suggestions or help would be appreciated.


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## gadget_lover (Mar 19, 2012)

And here is where you swear at the 'shear pins' for not breaking and saving that gear. It seems that way too often the gears go first and save the sheer pin.

The flattened teeth are jamming (binding, actually) in the leadscrew thread, not at all good for the rest of the gear train. 

The only thing I can think of is to remove the apron o access the gear. Then see if you can clean up the teeth well enough to keep them from binding while you wait for a new gear to replace it.

Do NOT run it while it's binding or you might find the other sacrificial gear hidden in the headstock. 

Daniel


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## precisionworks (Mar 19, 2012)

Awful feeling, easy fix 

Contact Mary McWilliams, Tech Service, Walter Meier Manufacturing (who is now the supplier of all Jet replacement parts). She will need both model # and serial #, and will then email a parts breakdown. After you select the parts needed, she will provide pricing & availability.

ph (615) 793-1332

fax(615) 287-1532


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## wquiles (Mar 19, 2012)

Been there myself, when I could not stop the carriage while threading and smashed into my fancy and expensive Bison 6-jaw chuck. I never replaced the damaged jaws not only due to the expense (they are a matted set!), but also as a visual reminder every time I use the lathe to be more careful. Live and learn.

Sorry to hear about the problem, but looking forward to the fix


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## Davo J (Mar 19, 2012)

That gear runs off a worm gear which is keyed to the feed shaft. You will have to dismantle it and see if you have also damaged the worm gear. I am sure you will be able to buy replacement parts.

Dave


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## fyrstormer (Mar 19, 2012)

If the shear pins don't break when they're supposed to, perhaps your first post-repair job should be machining some new shear pins from a weaker metal.


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## gt40 (Mar 19, 2012)

precisionworks said:


> Awful feeling, easy fix
> 
> Contact Mary McWilliams, Tech Service, Walter Meier Manufacturing (who is now the supplier of all Jet replacement parts). She will need both model # and serial #, and will then email a parts breakdown. After you select the parts needed, she will provide pricing & availability.
> 
> ...



I spoke to Mary and she was extremely helpful. She was able to help me ID the messed up part(gear that engages the lead screw), + she e-mailed me disassembly/assembly instructions to replace it. I was really concerned because I got the lathe second hand and someone had replaced the shear pin holding the lead screw with a stainless bolt. Mary said basically the gear in the apron is brass and it dies in that case. She said it is more common than you might think for lathes in school shops. She has never seen anyone do any thing more than break the gear if it isn't an impact with the chuck.

So basically it is looking like my crash will result in:

New 78 bucks gear and back ordered till April 30 
New brass shear pins
Time to disassemble/reassemble the apron

I am just happy it doesn't look like I have to get into the gears on the headstock...


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## PEU (Mar 19, 2012)

The flipside of this accident is that you will know your machine a lot better after the repair/replacement job. 


Pablo


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## precisionworks (Mar 19, 2012)

gt40 said:


> I spoke to Mary and she was extremely helpful.
> New 78 bucks gear and back ordered till April 30
> New brass shear pins
> Time to disassemble/reassemble the apron
> ...


 Mary is great to work with & the parts are usually not expensive. You will be back in business before you know it.


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## darkzero (Mar 21, 2012)

Are both the leadscrew & power feed shaft supposed to spin simutaneoulsy as seen in your video? I've only used about a handful of different lathes with power feed & none of them had them both spin simutaneoulsy. They all had a method of activating either or, or disable both altogether.

Just curious, never seen that before.

Also in the video, when you're power feeding, is your halfnuts lever engaged or just sagging & possibly partially engaging?

Crashes suck but they make you more aware. Luckily I haven't had a major crash causing considerable damage. But just this past weekend I broke my favorite Manchester parting tool. I thought the tool holder looked funny when I saw the insert & entire front portion was missing.


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## gt40 (Mar 21, 2012)

darkzero said:


> Are both the leadscrew & power feed shaft supposed to spin simutaneoulsy as seen in your video? I've only used about a handful of different lathes with power feed & none of them had them both spin simutaneoulsy. They all had a method of activating either or, or disable both altogether.
> 
> Just curious, never seen that before.
> 
> ...



Both shafts have turned independent of each other. There are dials to disengage the threading. You either activate the power feed lever or the threading lever. I only had the power feed lever engaged during the video.


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## gt40 (Mar 21, 2012)

I got home from work a bit early and was able to get it. Pulled the 3 shafts off, took off the dro and was able to remove the gear.

A few pics:






You can see the damage better on this pic:






The hidden side of the apron with the offending gear removed:






I had no idea it could get that scary in all those "dark" places on the machine that you don't look into normally. I have a month now to clean the machine while I wait for my parts.

Thanks for looking 

Mark


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## BVH (Mar 22, 2012)

Did you buy two gears or are you making something else the sacrificial goat?


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## gadget_lover (Mar 22, 2012)

I know it's not a great idea, but you could clean up the smooshed teeth and possibly even rebuild them with brazing rod. Even if they are not perfect they might allow it to be used for roughing passes and such where the slight imperfections will not be noticed as much.

A close inspection of the worm gear is also a good idea since the brass gear was forced in there pretty bad.

Dan


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## precisionworks (Mar 22, 2012)

gadget_lover said:


> ... A close inspection of the worm gear is also a good idea since the brass gear was forced in there pretty bad.
> 
> Dan



The designer of that machine could have used a steel pinion gear but choose brass as a fail safe. Even though someone already defeated one safety measure by replacing the soft shear pins the brass pinion acted as a back up. The worm gear is probably hardened & may not show even a ding. 

Some time ago I looked in my lathe owners manual at the gearing selection & saw that one additional gear was available. It would slow the fine feed to half of the current setting. No joy calling the importer - he said one could be custom cut for as little as $350-$400 USD


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## fyrstormer (Mar 22, 2012)

If that pinion gear is driven by a worm gear, isn't it equally likely the pinion gear was made of brass to better withstand the massive amount of scrubbing between the teeth on the pinion gear and the screw on the worm gear? If both were made of steel, less-than-perfect lubrication could result in a shower of sparks under heavy load. Automotive differentials are completely filled with lubricating oil, and the oil still has to be made resistant to burn damage caused by the hardened steel gear teeth sparking under hard acceleration.


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## precisionworks (Mar 22, 2012)

fyrstormer said:


> If that pinion gear is driven by a worm gear, isn't it equally likely the pinion gear was made of brass to better withstand the massive amount of scrubbing between the teeth on the pinion gear and the screw on the worm gear? If both were made of steel, less-than-perfect lubrication could result in a shower of sparks under heavy load. Automotive differentials are completely filled with lubricating oil, and the oil still has to be made resistant to burn damage caused by the hardened steel gear teeth sparking under hard acceleration.


A magnet would tell for certain but the worm appears to be the color of steel:


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## gt40 (Mar 22, 2012)

The worm is steel per magnet...


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## fyrstormer (Mar 23, 2012)

precisionworks said:


> A magnet would tell for certain but the worm appears to be the color of steel:


I wasn't disagreeing about the composition of the worm gear, I was just speculating on the reason why the pinion gear is made of brass. Brass-on-steel won't spark (though it may grind off anyway), whereas steel-on-steel will, which is why hammers made for use in potentially-explosive environments have brass heads.


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## precisionworks (Mar 23, 2012)

fyrstormer said:


> I wasn't disagreeing about the composition of the worm gear, I was just speculating on the reason why the pinion gear is made of brass. Brass-on-steel won't spark (though it may grind off anyway), whereas steel-on-steel will, which is why hammers made for use in potentially-explosive environments have brass heads.


Brass is sometimes seen in a gear train for a couple of reasons. Cycle time on the gear hobbing machine is super fast when compared to steel & the soft brass acts as a "weak link" that prevents damage to more costly components. 

OT but interesting: The Atlas Press Company made the small Atlas (Craftsman) lathe using ZAMAK for all the gearing in the machine. Stronger than most plastics but not nearly as strong as steel. Economy was the driving force as ZAMAK can be gravity cast or pressure cast. Lots of Craftsman/Atlas machines still in use today but check gear condition before buying one.

http://www.fieldingmfg.com/choosing-zinc-alloy-for-miniature-die-casting.asp


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## VegasF6 (Apr 10, 2012)

precisionworks said:


> OT but interesting: The Atlas Press Company made the small Atlas (Craftsman) lathe using ZAMAK for all the gearing in the machine. Stronger than most plastics but not nearly as strong as steel. Economy was the driving force as ZAMAK can be gravity cast or pressure cast. Lots of Craftsman/Atlas machines still in use today but check gear condition before buying one.



Learnt that in this video from Tubal Cain, starting at about 5 minutes and 10 seconds.
http://www.youtube.com/watch?v=1MqYOgtQGdA
Got a kick out of his take on it


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## gt40 (May 2, 2012)

Update, I just got my missing gear to repair the lathe. looking forward to having power feed again. I did a lot of work on my cnc mill conversion using the lathe without any feed and it has been missed...


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## will (May 3, 2012)

Generally I order a second part as a backup when I have to replace something. This does depend on the cost of the part. I do this for two reasons. The first - If it broke once, it will break again. Second - why pay for shipping a second time when you already have the replacement part already on hand. 
( there is a third reason, if you have a spare, it will never break. Like carrying an umbrella on a cloudy day, you know it won't rain, but leave the umbrella home and for sure it will rain ) 

My little ENCO lathe has plastic feed gears. The gear teeth never break but the keyway slot in the gear gets stripped. I ended up making a new center the first time I broke the gear and I did not want to wait for a replacement.


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