Power Cross Feed Repair/ Miter Gear Replacement

[chippermat]

Zamak metal has issues over time. The Zinc pest it is known as.
Pierre

Does this inevitably and unavoidably happen to all Zamak? I mean is my Atlas lathe going to crumble to bits eventually?

 

[Buffalo21]

The atlas gears I’m looking for are the two bevel gears for the table feed on my Altas MFC,

 

[francist]

Does this inevitably and unavoidably happen to all Zamak?

I have only ever seen this particular delamination or fracturing happen to gears. I have three Atlas machines of varying vintage and there is no apparent rhyme nor reason to the deterioration other than the parts themselves, but in some cases it can be quite dramatic.



I’ve also seen what has been described as zinc pest exhibit quite different appearance so I always wonder if it’s the same thing or whether there are separate things going on with each. Just my observations though, I’m no expert on the topic.

-frank

 

[bhusted]

I have only ever seen this particular delamination or fracturing happen to gears. I have three Atlas machines of varying vintage and there is no apparent rhyme nor reason to the deterioration other than the parts themselves, but in some cases it can be quite dramatic.
-frank

This has been my observation as well. Some of the parts on this machine have been perfectly fine, but others just crumble. One of the back gears flew apart into 4 pieces. Besides some gears, the pull knob for the power cross feed and the knob for changing feed directions have both fallen apart.

 

[francist]

Oh that’s interesting. Like I said, I’ve only ever seen it on gears but your experience with seeing it on knobs is quite illuminating.

-frank

 

[pdentrem]

Totally random, but very likely, depending on the impurities that are in the alloy. The older or cheaper, the more likely this will occur.

 

[chippermat]

Thanks for those responses.

Good job with the gear, bhusted, looks tricky to me.

 

[bhusted]

The replacement gear from Boston Gear arrived today and I can breathe a sigh of relief that it is a match with the original gears. For anyone looking to do this, the Boston PN is L102Y. L127Y would also work, but has a 1/2" bore instead of 5/8". If you're just looking for the specifications to buy from Browning, Leif, Martin or others, you need 12 diametral pitch, 18 teeth, and a 20 degree pressure angle. Any of these will require some machining to make fit, but isn't that the purpose of having a machine like this? I'll document the rest of the project here as I get to it.

 

[bhusted]

I'm still waiting on some material to be delivered for the keyed shaft portion of the miter gear. The pull knob to engage the cross feed was broken when I got it, so I took the opportunity to make a new knob for it and for the feed direction selector.

 

[bhusted]

Does anyone know how far the key is meant to extend into the slot on the leadscrew? I know it's a 1/8" key, but I dropped a square key in the slot just to check and the whole thing fits in the slot with nothing to engage the miter gear. Obviously I don't want it dragging on the bottom of the keyway, but deep enough to fully engage the screw. I plan to cut a keyway partway into the replacement gear and secure the key with silver solder.