# Bull gear index pin and holes, what are they used for?



## calstar (Nov 3, 2013)

I have the atlas lathe manual and the index only mentions the pin and holes to be found on on pg. 14, but they are'nt there. What are they used for and how do you use them? Any info on use or a link to use will be appreciated. I did a google search and a HM search but no luck.

thanks, Brian


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## Terrywerm (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*

Many of the older lathes like the Logan, South Bend, and Atlas machines have a bull gear in the headstock. 

When running in normal or high speed mode, the pin is pushed in so that the gear is joined directly to the headstock pulley. The spindle then runs at the same speed at the headstock pulley.

When running in back gear, the back gears are engaged and the pin is pulled out, releasing the bull gear from the headstock pulley. The spindle then runs at a speed much slower than the headstock pulley, and has far greater torque as well.

If you engage the back gears while the pin is also engaged with the headstock pulley, the spindle will be locked up and will not turn at all.

I have included photos of the bull gear and pin on my Logan, but your Atlas should be very similar. The first photo shows the pin pushed in, engaged with the headstock pulley. The second photo shows the pin pulled out.  If you are unable to see the pin on yours, try turning the spindle around until the pin comes up to the top.


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## itsme_Bernie (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*



calstar said:


> I have the atlas lathe manual and the index only mentions the pin and holes to be found on on pg. 14, but they are'nt there. What are they used for and how do you use them? Any info on use or a link to use will be appreciated. I did a google search and a HM search but no luck.
> 
> thanks, Brian



Do you mean the pin and holes that are around the bull gear like an index table? 
I always wondered that too.  Especially on the six inch I had- I wasn't going to be compound toolpost milling on that??


Bernie


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## mattygee (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*

I used the index holes to mark out my chuck backing plate hole locations.


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## calstar (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*



itsme_Bernie said:


> Do you mean *the pin and holes that are around the bull gear like an index table? *
> I always wondered that too.  Especially on the six inch I had- I wasn't going to be compound toolpost milling on that??
> 
> 
> Bernie



Sorry if my question was a little vague but yes, this is what I am asking about. These are not mentioned in the Atlas operation manual(at least that I could find), so I'm hoping to learn what purpose they serve.

Pictures always help so here you go. Index holes on bull gear and index pin that can engage them:




thanks for the replies, Brian


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## pipehack (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*

You're asking one of the same questions I did when I got my 6" lathe. Check out this thread. Not sure if it will help though.
http://www.hobby-machinist.com/showthread.php/17842-Indexing-pin-on-Cman-Atlas-6-quot-lathe


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## CluelessNewB (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*

I suspect this feature was aimed more at the woodworking crowd.  Even the early Delta woodworking lathes had the "Indexing Mechanism".  I believe this was mostly used to make fluted or reeded columns using a router jig.  I sold an old Delta steel bed wood lathe a couple of years ago to a guy that only uses it for that.  He doesn't even have a motor driving the lathe spindle! 

Here is a link showing it done on a larger Oliver lathe with a homemade indexing plate:

http://youtu.be/5iO05_UzSfY


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## Bill C. (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*



calstar said:


> Sorry if my question was a little vague but yes, this is what I am asking about. These are not mentioned in the Atlas operation manual(at least that I could find), so I'm hoping to learn what purpose they serve.
> 
> Pictures always help so here you go. Index holes on bull gear and index pin that can engage them:
> 
> ...



From your photo I don't see a pin on the gear face.  Its possible your lathe doen't have a low gear.  Do you use that dowel pin to lock the spindle to remove the chuck?


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## Dranreb (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*

I found it can be useful to use the indexing holes to scribe divisions using a tool in the tool post, across the face or on the edge of a work piece held in the chuck,

Useful when setting out set out a PCD on the face.

Also useful if you have rigged up a drilling fixture using the cross slide.

Bernard


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## pdentrem (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*

There are 60 holes on the bull gear. This gives you the capability to layout markings on dials, mark and drill holes around a circle, such as 5 holes for a wheel hub - one hole every 12 pin holes etc etc. it is like a built in spin indexer or rotary table. Can also be use to lock the spindle and cut a key way on a shaft. Lots of ways to use these holes.

 BTW The new 10F bull gears do not come with the holes anymore. I had to add them when I got the replacement from Clausings.
Pierre


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## Terrywerm (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*

Boy, I guess I missed the mark on that one!!  I had forgotten all about the index holes on the Atlas bull gears. I don't know the 'official' intended purpose on those, but I believe some of the other guys are hitting pretty close on that.


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## calstar (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*

Thanks guys, I now see how they can be used. 

Regarding the guy fluting with the Oliver: 1) he really needs to get the lead screw working(if it has one),   2) he's probably near deaf with that screaming router and no hearing protection.

http://youtu.be/5iO05_UzSfY

Brian


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## itsme_Bernie (Nov 4, 2013)

*Re: Bull grear index pin and holes, what are they used for?*



pdentrem said:


> There are 60 holes on the bull gear. This gives you the capability to layout markings on dials, mark and drill holes around a circle, such as 5 holes for a wheel hub - one hole every 12 pin holes etc etc. it is like a built in spin indexer or rotary table. Can also be use to lock the spindle and cut a key way on a shaft. Lots of ways to use these holes.
> 
> BTW The new 10F bull gears do not come with the holes anymore. I had to add them when I got the replacement from Clausings.
> Pierre



Funny, that's what I WOULD have used them for!  I guess I was thinking too much...  But you can always learn something new to find out!  


Bernie


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## wa5cab (Nov 5, 2013)

Bill C. said:


> Do you use that dowel pin to lock the spindle to remove the chuck?



This is a bit late but you should never try to use the indexing pin to lock the spindle for chuck removal.  If the chuck is fairly well stuck, you can shear the pin off and ruin one of the indexing holes..

Robert D.


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