# Atlas Horizontal Mill Bushing Help



## jster1963 (Mar 15, 2020)

I really hate asking for help, but I've looked for an answer and just can't find it.  I have researched and tried to figure this out and don't want to ruin this part on my mill.

I'm restoring my Atlas mill and it has a broken bushing.  Someone brazed it to the gear/pulley in the headstock.  I was able to get a new bushing (M1-255) from Clausing but it is slightly different. The ID fits correctly, but the OD is slightly too big to fit right in.   I have the parts diagram, but don't know how tightly these parts are supposed to fit together.  

The gear has 4 square protrusions that mesh with 4 protrusions on the pulley.  To me it doesn't seem that they will ever come out of mesh while on the machine. I don't think there is room to pull apart while it's in the headstock.   

Also, there are 3 holes in the smaller pulley.  I think there is only supposed to be one for oil, but I'm not sure.  I think they put the other holes into the pulley and bushing to lock the 2 together.  However, there were no screws in the holes when I pulled it apart, except the one in the large pulley for oil.

So....
1. How tight is the bushing supposed to fit into the gear (M1-242A)?  Sliding or pressed?
2. How tight is the gear and bushing supposed to fit into the pulley (M1-79C)?  Sliding or pressed?
3. Are there supposed to be 3 holes in the small pulley and bushing?
4. Are there supposed to be slots in the bushings?  The Clausing bushing did not have either holes or slots.

Here are a few pictures.  Any help would be greatly appreciated.  Ps.  I'm doing the restoration on YouTube if you want to see it.


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## 4ssss (Mar 15, 2020)

I would say a slight press. It looks like it's pinned anyway.


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## jster1963 (Mar 16, 2020)

4ssss said:


> I would say a slight press. It looks like it's pinned anyway.


Thank you.....


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## wa5cab (Mar 16, 2020)

It is not pinned and the holes visible in the photos above are not original.  The only holes that should be in the pulley are the one through the center where the spindle fits and one tapped oil hole that is NOT tapped all of the way through.  The set screw that fits it is being used as an oil plug and should not touch the spindle.  This is a common problem found in the 10" and 12" lathes.  It doesn't get noticed until the operator puts the machine into back gear.  Then it becomes "Houston, we have a problem".


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## jster1963 (Mar 16, 2020)

wa5cab said:


> It is not pinned and the holes visible in the photos above are not original.  The only holes that should be in the pulley are the one through the center where the spindle fits and one tapped oil hole that is NOT tapped all of the way through.  The set screw that fits it is being used as an oil plug and should not touch the spindle.  This is a common problem found in the 10" and 12" lathes.  It doesn't get noticed until the operator puts the machine into back gear.  Then it becomes "Houston, we have a problem".


AWESOME info!!!  Thank you very much.  I think I will machine the brazed bushing out and press in the new one.  The bushing says Oil Lite so my guess is that oil is impregnated.

My oil screw screws all the way through, so I will have to fix that somehow.  I think I will leave the holes that are there and put oil in every now and then.  And I see where the oil screw has rubbed into the spindle.  So fix it time because I do hate "Houston, we have a problem"  LOL!

Thank you so much for the info.....


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## wa5cab (Mar 17, 2020)

Yes, "real" Oilite bushings, presumably including those supplied by Clausing, come from the factory already oil impregnated.  However, one should always keep the oil cups (where fitted) topped up and one should pretty much follow the lubrication instructions in the manual.  The one place that you could safely vary them would be on the pulley unless you routinely use back gear.  The modification for for the pulley could read something like "remove set screw and inject a few squirts of SAE 20 either weekly or daily before every usage of Back Gear.  

I would strongly recommend that you replace the spindle cone pulley and gear rather than trying to bore out the brazed bushing.  The two step pulleys are not that hard to find, unlike the three-step or four-step.  The two-step were in production for around 16 years versus the two or three years of the other two.  In the event that the new bushings are not a press fit, you can safely knurl them but you will have to have an expanding arbor to do so.  

If the oil plug has been forced through to the ID, the best solution is to buy a box of nylon patch set screws.  Ideally you should use a new one every time that you oil the bushings but you may find that you can get away with using a screw 2 or 3 times.

Fortunately, the spot on the spindle that gets damaged is between the two bushings.  So although it will probably damage one of the bushings when you disassemble the spindle, so long as you file it down and don't repeat the damage, there will be no problem with using the original or a replacement spindle.


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## jster1963 (Mar 18, 2020)

wa5cab said:


> Yes, "real" Oilite bushings, presumably including those supplied by Clausing, come from the factory already oil impregnated.  However, one should always keep the oil cups (where fitted) topped up and one should pretty much follow the lubrication instructions in the manual.  The one place that you could safely vary them would be on the pulley unless you routinely use back gear.  The modification for for the pulley could read something like "remove set screw and inject a few squirts of SAE 20 either weekly or daily before every usage of Back Gear.
> 
> I would strongly recommend that you replace the spindle cone pulley and gear rather than trying to bore out the brazed bushing.  The two step pulleys are not that hard to find, unlike the three-step or four-step.  The two-step were in production for around 16 years versus the two or three years of the other two.  In the event that the new bushings are not a press fit, you can safely knurl them but you will have to have an expanding arbor to do so.
> 
> ...


  I tried to replace the pulley/gear with Clausing and it is no longer available.  Hey, I'll try Sears.  Sometimes they still have replacement parts.  If not, I'll have to try to machine the bushing.  I'm taking heed to your warning though!  I'm trying my best not to do the "Ready, Fire, Aim" way I usually do with my projects.  Also, I'll try to find those nylon patch set screws.  If not, I will try to use a nylon piece in the set screw hole or try to fix it so the set screw doesn't touch the spindle.

Thank you very much for the information and I will Keep everyone informed on my progress......


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## wa5cab (Mar 18, 2020)

Most of the mill parts, unfortunately, are only available on the used market.  That includes all three of the spindle pulley types. 

You might also try a nylon set screw.  They are usually made slightly oversize so that they are self locking.  Would be ideal for this application.  Try McMaster for either type.

Also, if you do try to bore out the existing pulley, I would recommend holding it with an expanding mandrel.  There is a relatively inexpensive 4 or 5-piece Chinese made set available that is cheap enough to machine the next larger one to fit either the bushing bore or the pulley bore.  I am pretty sure that one of them is large enough for the 618 and Mill spindle pulleys.


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## jster1963 (Mar 18, 2020)

wa5cab said:


> Most of the mill parts, unfortunately, are only available on the used market.  That includes all three of the spindle pulley types.
> 
> You might also try a nylon set screw.  They are usually made slightly oversize so that they are self locking.  Would be ideal for this application.  Try McMaster for either type.
> 
> Also, if you do try to bore out the existing pulley, I would recommend holding it with an expanding mandrel.  There is a relatively inexpensive 4 or 5-piece Chinese made set available that is cheap enough to machine the next larger one to fit either the bushing bore or the pulley bore.  I am pretty sure that one of them is large enough for the 618 and Mill spindle pulleys.


I don't plan to bore out the pulley or the gear.  I plan to machine the bushing.  I will need a mandrel for that and only need to take off about .003" from the OD so  I think that is more do-able.  I will check McMaster as well.  Thank you again for the reply......


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## jster1963 (Mar 19, 2020)

Update...2 steps forward, 1 step back.  I machined off the brazing and pulled the broken bushing from the gear.  After measuring again, it see that the OD was just .002" over the ID of the gear and the pulley.  So I froze the bushing and heated the gear and pressed them together.  Once that was together, I froze the gear/bushing and then heated the pulley.  Then it was all pressed together.  

Here's the problem.  Before I pressed in the new bushing, it would slide right onto the spindle.  Now that it is pressed into the gear/pulley, it is WAY too tight on the spindle.  I think I will try to machine it slide on the spindle.  My guess is 1 or 2 thousands.  Now I have to figure out how to hold this in the lathe and not damage it.  YOWZA!


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## wa5cab (Mar 20, 2020)

I can think of several ways to hold the pulley with the bushings installed but if the "holder" is going to be a 6" lathe, the only one that you have room for is going to be an expanding mandrel.  And I suspect that it will take two mandrels as if you cut the mandrel to fit the bushings as they are now and bore out one bushing, the mandrel might be too small to hold without wobbling in the now larger ID bushing when you turn the pulley around to do the second bushing.

In any case, be sure that you use a carriage stop to prevent you from running the boring bar into the mandrel.

As far as how much to remove, first you need to accurately measure the spindle outside diameter in the region of the pulley and the inside diameters of the two bushings.  Then you need to pick the class of fit, and look up what the clearance range should be.  Reference pages 1540, top of 1541 and the table on page 1544 of the 21st edition of Machinery's Handbook.  1540 and 1541 define classes of fits.  In my opinion, the spindle pulley bushings and spindle need a class RC6 or RC7 fit, where "R" means Running and "C" means clearance.  For a nominal shaft OD and bushing ID of 0.71" to 1.19", the clearance between the shaft and the bushing should be between 2.5 and 5.7 Thousandths.  That's for a Class RC7 fit.  RC6 is a little tighter.  And for both classes, the clearance requirement increases and decreases with diameter.  In any case, you are probably looking at more like removing 3 to 5 thousandths than 1 or 2 (but note that that is on the diameter, not per side).  Which increases the probability that you will need two of the mandrels to do the job.  Unfortunately, "I cut it off twice and it is still too short" is only funny in the comics.  Fortunately, clearance here has no effect on machine accuracy and the Chinese mandrel sets are relatively cheap.  Unfortunately, I have not seen the individual mandrels for sale.


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## jster1963 (Mar 20, 2020)

wa5cab said:


> I can think of several ways to hold the pulley with the bushings installed but if the "holder" is going to be a 6" lathe, the only one that you have room for is going to be an expanding mandrel.  And I suspect that it will take two mandrels as if you cut the mandrel to fit the bushings as they are now and bore out one bushing, the mandrel might be too small to hold without wobbling in the now larger ID bushing when you turn the pulley around to do the second bushing.
> 
> In any case, be sure that you use a carriage stop to prevent you from running the boring bar into the mandrel.
> 
> As far as how much to remove, first you need to accurately measure the spindle outside diameter in the region of the pulley and the inside diameters of the two bushings.  Then you need to pick the class of fit, and look up what the clearance range should be.  Reference pages 1540, top of 1541 and the table on page 1544 of the 21st edition of Machinery's Handbook.  1540 and 1541 define classes of fits.  In my opinion, the spindle pulley bushings and spindle need a class RC6 or RC7 fit, where "R" means Running and "C" means clearance.  For a nominal shaft OD and bushing ID of 0.71" to 1.19", the clearance between the shaft and the bushing should be between 2.5 and 5.7 Thousandths.  That's for a Class RC7 fit.  RC6 is a little tighter.  And for both classes, the clearance requirement increases and decreases with diameter.  In any case, you are probably looking at more like removing 3 to 5 thousandths than 1 or 2 (but note that that is on the diameter, not per side).  Which increases the probability that you will need two of the mandrels to do the job.  Unfortunately, "I cut it off twice and it is still too short" is only funny in the comics.  Fortunately, clearance here has no effect on machine accuracy and the Chinese mandrel sets are relatively cheap.  Unfortunately, I have not seen the individual mandrels for sale.





wa5cab said:


> I can think of several ways to hold the pulley with the bushings installed but if the "holder" is going to be a 6" lathe, the only one that you have room for is going to be an expanding mandrel.  And I suspect that it will take two mandrels as if you cut the mandrel to fit the bushings as they are now and bore out one bushing, the mandrel might be too small to hold without wobbling in the now larger ID bushing when you turn the pulley around to do the second bushing.
> 
> In any case, be sure that you use a carriage stop to prevent you from running the boring bar into the mandrel.
> 
> As far as how much to remove, first you need to accurately measure the spindle outside diameter in the region of the pulley and the inside diameters of the two bushings.  Then you need to pick the class of fit, and look up what the clearance range should be.  Reference pages 1540, top of 1541 and the table on page 1544 of the 21st edition of Machinery's Handbook.  1540 and 1541 define classes of fits.  In my opinion, the spindle pulley bushings and spindle need a class RC6 or RC7 fit, where "R" means Running and "C" means clearance.  For a nominal shaft OD and bushing ID of 0.71" to 1.19", the clearance between the shaft and the bushing should be between 2.5 and 5.7 Thousandths.  That's for a Class RC7 fit.  RC6 is a little tighter.  And for both classes, the clearance requirement increases and decreases with diameter.  In any case, you are probably looking at more like removing 3 to 5 thousandths than 1 or 2 (but note that that is on the diameter, not per side).  Which increases the probability that you will need two of the mandrels to do the job.  Unfortunately, "I cut it off twice and it is still too short" is only funny in the comics.  Fortunately, clearance here has no effect on machine accuracy and the Chinese mandrel sets are relatively cheap.  Unfortunately, I have not seen the individual mandrels for sale.


Excellent advice!  I will probably be using my South Bend !0K for this one but my Atlas 6" is still not out of the question.  Thank you very much and I'll keep everyone informed......


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## Moderatemixed (Mar 20, 2020)

Hey jster. I’m about to start the same restoration as you, and ironically I’m right seat on the ‘37 up here in Canada. Looks like I’m going to have some time to do the project over the next couple of months. You might try putting it into a vice and if you have a cylinder hone, Chuck it into your drill and hone a couple thou off. I would think that putting it into the four jaw of the lathe will work fine but if it is just to “fit” the hone or and expanding reamer might just do the trick..... Cheers. Derek


Sent from my iPad using Tapatalk


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## wa5cab (Mar 20, 2020)

I don't think that I would do that (use a hone).  Were it not for one thing, I would have already suggested clamping the pulley assembly down to a drill press or vertical mill table with a half inch spacer with a hole in the middle so that a brake wheel cylinder hone could just barely start coming out the bottom but not run into the table.  That one thing is that although the oil hole in the pulley supposedly bypasses the bushings, they are Oilite.  And using a hone rather than a sharp reamer could smear the ID surface, plug up the pores and make the bushings effectively the same as solid brass.


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## Moderatemixed (Mar 20, 2020)

And that is a remarkably good point. I just watched Kieth Rucker, (Vintage Machinery on YouTube) I assume that you are likely familiar, he used the hone to enlarge a couple of “guide ways” and thought I’d bring it forward. That said your point is very valid. Cheers 


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## wa5cab (Mar 20, 2020)

Thanks.  If your mill or drill press has enough headroom, you could clamp the pulley the same way only use an adjustable reamer instead of the hone.


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## jster1963 (Mar 20, 2020)

Moderatemixed said:


> Hey jster. I’m about to start the same restoration as you, and ironically I’m right seat on the ‘37 up here in Canada. Looks like I’m going to have some time to do the project over the next couple of months. You might try putting it into a vice and if you have a cylinder hone, Chuck it into your drill and hone a couple thou off. I would think that putting it into the four jaw of the lathe will work fine but if it is just to “fit” the hone or and expanding reamer might just do the trick..... Cheers. Derek
> 
> 
> Sent from my iPad using Tapatalk


The mighty '37?  Awesome!  I have a few years in the 737-200.  That's the old round dial bird.  And yes, I do believe we will have lots of time in the shop in the near future!  Crazy.

I did it!  I just used my 4 jaw chuck in my South Bend 10K.  I was worried about marring the pulley surface.  But all is good!  I will post pix in a separate post.

Stay warm up there and fly safe......


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## jster1963 (Mar 20, 2020)

wa5cab said:


> Thanks.  If your mill or drill press has enough headroom, you could clamp the pulley the same way only use an adjustable reamer instead of the hone.


I got it!  I'll post below.  Thank you for all of your help....


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## jster1963 (Mar 20, 2020)

Well ladies and germs I did it!  I was able to use my 4 jaw chuck in my South Bend 10K and dial it in.  I was worried about marring the pulley, but I didn't chuck it with "Chuck Norris" torque and it worked great.

I bored out about .005" after measuring it and the spindle.  .005" of the ID is really small so I took my time.  I hope to put the head stock back together tonight or tomorrow.

Thank you all for you help.  I have a spare bushing just in case.....


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## jster1963 (Mar 20, 2020)

Moderatemixed said:


> And that is a remarkably good point. I just watched Kieth Rucker, (Vintage Machinery on YouTube) I assume that you are likely familiar, he used the hone to enlarge a couple of “guide ways” and thought I’d bring it forward. That said your point is very valid. Cheers
> 
> 
> Sent from my iPad using Tapatalk


Of course I watch Keith Rucker!  I just watched him today.  There are a couple of guys you have to watch on Youtube that have great videos on restoring this machine.  I'm posting as well.  Mine will not be as in depth as some but more than others.  I hope to have mine up and running soon.  I have lots of parts to make too.

Thanks for the reply and good luck with yours........


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