# Looking for (constructive) recommendations



## rficalora (Friday at 3:16 PM)

Go easy on me; I am a newbie.  I am not a machinist, but am working to learn.

Right now, I am trying to clean up and functionally restore a lathe I recently bought and I have an issue with one of the shafts in the gearbox.

This is the main input shaft to the gearbox.  I assume it should spin freely and smoothly when fully seated but it gets tight.  In the video below, I insert it to about 3/32" from fully in.  If I go further, I can't turn it by hand without putting the drive gear on to get more leverage.






I'm considering chucking/spinning it in the lathe and using some emery paper to clean up the shaft.

*Am I right that it should rotate freely/smoothly?*

Assuming so, *what are your thoughts about whether using emery paper would address the issue?  Or, would you recommend a different solution?*


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## aliva (Friday at 3:28 PM)

I agree it should turn freely. I would check for burrs in the bosses  and shaft, check the shaft for a slight bend.


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## DeadGuyAle (Friday at 3:33 PM)

I'm also a complete newbie so don't laugh if this is all wrong   
Maybe dykem or felt pen the shaft to see where the high point is as a start?


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## Provincial (Friday at 3:44 PM)

First, clean the bearing surfaces of the housing and shaft.  Apply oil to both surfaces and see if that helps.

Do you have a dial indicator?  If yes, put the shaft in as far as it will go and still turn by hand.  Then use the dial indicator to see if the input end of the shaft is running true.  If the reading is changing more than a couple of thousandths, the shaft is bent.  

If the shaft isn't bent, polish the input shaft where it runs in the housing, but very little.  You want to smooth it, but not reduce the diameter of the shaft.  

Then report back.


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## tq60 (Friday at 3:49 PM)

It looks like it is not straight.

If the outside bearing has shifted it causes the shaft to not properly align with other end.

It could have moved when torn down.

Look closely as it goes into second bearing.

You may gently tap the shaft with a chunk of 2x4 to see if it lines up better.

Sent from my SM-G781V using Tapatalk


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## rficalora (Friday at 6:59 PM)

Ok, I have it running smoother, but I believe, based on this, the shaft is bent.  This is with the end of the shaft just before going into the 2nd hole.






But, by running some 320 emory paper over it for a few seconds it is running smoother.






It does not spin freely but does not have a lot of resistance either.

Next steps?

I assume I will need to make a new shaft. Correct?  Or can it be straightened?  

If it needs to be re-made, can I use this shaft as it is to reassemble the lathe to do that (I have a mill to cut the key slots).


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## Provincial (Friday at 7:25 PM)

Glad that you are making progress.

Now insert it fully and check the input end of the shaft for runout with your indicator.


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## markba633csi (Friday at 8:07 PM)

Looks like only about 6-7 thousanths bent.  Borderline usable.  Take all the measurements of it and plan on making a replacement.  You probably could make a replacement now without the gearbox in fact if the rest of the lathe is up and running
You could try straightening it also


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## rficalora (Friday at 8:22 PM)

Thanks both.  Here's what it looks like fully installed:

Outboard side: 




Inboard end:


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## talvare (Friday at 8:46 PM)

That's pretty dang close. It's not like you're measuring run out on the spindle bearings. I would run it as is.

Ted


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## rficalora (Friday at 8:57 PM)

Thanks Ted.  I hope you are right.  At the same time, I'm a little concerned that the light drag that remains is enough friction to heat up the shaft causing it to expand and then bind.  

I'm hoping a few folks will chime in on whether I need to dress it slightly more to get it spinning more freely.


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## talvare (Friday at 9:12 PM)

Is there any form of lubrication at those journals ?


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## tq60 (Friday at 9:23 PM)

When you were turning the shaft it did move the dial, but the dwell time too short.

If bent it should have moved as an arc but instead it acted as it hits a bump in the shaft.

Are there any dents or nicks in the shaft?



Sent from my SM-G781V using Tapatalk


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## Provincial (Friday at 9:27 PM)

The next step is to put the input gear on that shaft and check for runout at the base of the gear teeth.  The bend in the shaft will translate into wobble of the gear, so put the indicator where it measures that wobble.  If it doesn't wobble, go back to the shaft and look for issues where it is supported in the gearbox casting.  

I did notice in the first video that you had trouble getting the unworn part of the shaft through the outboard bearing support.  Is there a bushing in that spot?  Is it in good shape?


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## rficalora (Friday at 9:33 PM)

talvare said:


> Is there any form of lubrication at those journals ?


Yes, there are oiling holes in the casting that lead to each of the journals.


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## rficalora (Friday at 9:35 PM)

Provincial said:


> I did notice in the first video that you had trouble getting the unworn part of the shaft through the outboard bearing support.  Is there a bushing in that spot?  Is it in good shape?


There is no bushing at either end.  Just smooth holes through the casting


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## vtcnc (Friday at 9:36 PM)

I'd say you are good. Bent shaft wouldn't blip like that. I would make sure no galling or burrs anywhere, make sure lubrication can get to where it needs to be and then run it. Make a new shaft if you want it perfect.


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## rficalora (Friday at 10:07 PM)

tq60 said:


> Are there any dents or nicks in the shaft?


Yes, especially on the part that's outside of the case where the drive gear goes on.  When I disassembled it, I found that gear it was missing the key and was just being held on by a set screw.  It had slipped as evidenced by the markings on the shaft.


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## OTmachine (Yesterday at 9:18 AM)

Sounds Chinese, and if so, I would kind of expect this condition from new.  Need to clean up and adjust.


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## rficalora (Yesterday at 3:06 PM)

@OT Machine.  It is a Taiwan import.  I know there are a LOT better machines out there, but i looked for quite a while before finding one in this size range at a price I could afford.  Since I'm learning, I figured cleaning it up and then using it would help me learn.  Then, if down the road I learn enough to need something better, I can upgrade then.


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## Richard King 2 (Yesterday at 3:26 PM)

Does the housing bolt to something?  If it does bolt it to where it goes.  It might have a twist in it just setting on a table.  when did you remove the shaft?  I am sure you checked for burrs and stoned them, right?


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## rficalora (Yesterday at 5:37 PM)

It does bolt to the bed casting; I didn't feel any change when I bolted it back in place.  But, that was before I used the emory paper to get it fitting better.  

I removed it about a week ago.  It was snug then too, but I believe made a bit worse when I removed it (see above where there was a key I didn't know about).  In any event, I have to assume I damaged it and am now working to correct as much as possible until I can re-make it.

And, yes, burs have been removed (there were a few of them).


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## OTmachine (Yesterday at 6:19 PM)

rficalora said:


> @OT Machine.  It is a Taiwan import.  I know there are a LOT better machines out there, but i looked for quite a while before finding one in this size range at a price I could afford.  Since I'm learning, I figured cleaning it up and then using it would help me learn.  Then, if down the road I learn enough to need something better, I can upgrade then.


My intention was not to insult, rather just to say that in today’s world, with a vast majority of parts coming from China, substandard is the new norm, usually requiring some sort of rework to put into service.  Yours, being from Taiwan, is definitely a step up from China, and will more likely serve you well.


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## rficalora (Yesterday at 7:14 PM)

No offense taken.  I'm with you on the import quality.  A buddy just bought a brand new Precision Matthews 940V.  They're supposed to be one of the better import companies but his mill had flashing on the bottom of the table that impeded it from making full travel.  Easy fix, but, unfortunately, he only found it when the table hit the base while auto feeding in the X direction.  When the table hit, it stripped the *plastic* table feed gear.  In his case, it was probably good that that gear was plastic so more damage wasn't done.

The lathe I got is a Samson TD-5AA (10" x 36" with a 1-3/8" hole thru the spindle).  For my home/hobby shop, I think it will be plenty (I don't have room for a bigger lathe anyway).


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## Richard King 2 (Today at 10:54 AM)

Over the years as a Pro Machine repairman I have seen things like this happen.  You take something apart and it gets dinged up somehow and it won't fit when you assemble it.  I like to do dry runs when I assemble spindles or shafts.  Years ago I was replacing the spindle bearings in a K&T Horizontal mill inside a customers shop.  We spent a day assembling a spindle without the new Timken bearings so we knew the gears would slide on with ease.  We laid everything on a table so the the next day we could assemble the spindle with the new and expensive bearings and not have any issues.  

The next day we started to assemble the spindle, sliding the new bearing on the shaft and when we got to the gear which was heavy and hard to align as we slid in the spindle and it would not slide on like it had the day before.  We tried and tried and finally had to take out the spindle, it was a miracle we didn't ruin the new bearing.  Once out we discovered a burr on the spindle that wasn't there the day before.   It was getting close to quitting time and as we were getting ready to go home a nightshift machinist came over and said "sorry about knocking your parts on the floor last night"...  He had ran into the table with a fork truck and the parts fell on the floor.   That day we learned to double check everything as you assemble it plus we made signs and said DO NOT Touch.


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