Atlas MF Backgear locks spindle

[vtcnc]

OK, I'm confused.

I've never used the backgear on my Atlas MF mill. I engaged the backgear spindle with the main spindle. Spindle locks and will not turn while backgear is engaged.

I looked at the manual and notice that there is a two pulley on the main spindle, indicating that the pulley slides in and out of the spindle gear in order to engage the slower speeds of the backgearing. Nowhere do I see how this sliding action can happen.

To confuse matters, I look on the speed chart on the cover - it shows a three pulley setup on my main spindle so - original gear. If the pulley should disengage from the bull gear I can't see how that would work.

Directions in the manual are:

N. BACK GEAR LEVER -engages back gears with spindle gears. After back gears are engaged be sure to pullout sliding pin which locks the large spindle gear to the spindle pulley. Use the spec:al wrench furnished. When back gears are disengaged be sure sliding pin is replaced in the large spindle gear.

Ok, fair enough. I don't have the wrench but I'll figure that out. Problem is, I cant see any flats anywhere on any spindle that would indicate wrench use. Plus, no other directions about what to do with the wrench?

Any help here?

 

[JPMacG]

There is a pin on the right side face of the bull gear. When pushed in, the pin locks the bull gear to the pulley. Take a flashlight and look at the gap between the bull gear and the inner right side of the head casting while you rotate the spindle. It is not easy to see. The pin has two positions - engaged or not. There are spring stops to hold it in either position. The "wrench" is actually a bent fork. It is used to pull out or push in the pin. The pin has a notch in its diameter that the fork fits in.

If you are familiar with the Atlas lathe, it uses the same mechanism. But on the lathe the pin is easy to see and operate. On the MFC the pin is hidden and a PITA to operate.

 

[JPMacG]

Some early models of the Atlas mill had three pulleys on the spindle. You must have a "Frankenstein" - put together from mixed parts.

 

[vtcnc]

There is a pin on the right side face of the bull gear. When pushed in, the pin locks the bull gear to the pulley. Take a flashlight and look at the gap between the bull gear and the inner right side of the head casting while you rotate the spindle. It is not easy to see. The pin has two positions - engaged or not. There are spring stops to hold it in either position. The "wrench" is actually a bent fork. It is used to pull out or push in the pin. The pin has a notch in its diameter that the fork fits in.

If you are familiar with the Atlas lathe, it uses the same mechanism. But on the lathe the pin is easy to see and operate. On the MFC the pin is hidden and a PITA to operate.

Ok I’ll take a look and see what I can see! Thanks!


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[vtcnc]

Ok I’ll take a look and see what I can see! Thanks!


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Found it. Thanks @JPMacG. I need to laser cut a wrench tomorrow so I can get at.

 

[vtcnc]

Found it. Thanks @JPMacG. I need to laser cut a wrench tomorrow so I can get at.

edit: incidentally, you are spot on about this being a PITA. Not a very convenient design, but I suppose compact machines tend to suffer these design compromises.

 

[wa5cab]

The Atlas M1, MF and MH mills originally came with 4-Step spindle and counter shaft cone pulleys. The M1A, MFA and MHA had 3-Step pulleys. The M1B, MFB, MHB, M1C, MFC and MHC had 2-Step pulleys. The 4-Step and 3-Step pulleys went NLA decades ago. The only way to acquire a replacement 3-Step or 4-Step pulley would be through salvage.

 

[vtcnc]

The Atlas M1, MF and MH mills originally came with 4-Step spindle and counter shaft cone pulleys. The M1A, MFA and MHA had 3-Step pulleys. The M1B, MFB, MHB, M1C, MFC and MHC had 2-Step pulleys. The 4-Step and 3-Step pulleys went NLA decades ago. The only way to acquire a replacement 3-Step or 4-Step pulley would be through salvage.

I have a machine marked as MF so mine must have been upgraded by the owner when the A series was released? Does that sound plausible?

 

[wa5cab]

No, I'm sure that it shipped with 4-Step pulleys. Years later some owner either wanted to or had to replace one or both pulleys and 2-step was the only thing available by then. But the 2-Step pulleys were not available for anyone to special order when the MF was the current model. The MF was current in 1941 and early 1942. The 2-Step Spindle Pulley drawing is dated 6-2-44. And the 2-Step pulleys were standard on the MFB and MFC, not the MFA. The latter had 3-step pulleys. I happen to have one.

 

[ThinWoodsman]

I need to laser cut a wrench tomorrow so I can get at.

No need to even go that far. I drilled and filed a notch into the end of a small steel flat (1/16 x 3/4 x 6" maybe?) and bent the end in a vise.

I saw somewhere online a guy had made a wrench out of an old PC card slot cover.

But hey, you wanna overkill, go for it