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Atlas MFA Spindle pulley

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Yorkus

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#1
I am restoring a MFA Horizontal mill. It had a broken spindle pulley when purchased so I have acquired the technical drawing from Clausing. ( I uploaded a copy to downloads) I am going to attemp to make one but am wondering if rather than making it from aluminum maybe I should use some 1018 steel I have. I have recently learned that 6061 Aluminm which I was going to use is not as strong as the original ZMACK material.
 

pontiac428

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#2
Are you talking about the V-belt pulley? The Zamak pulleys did well enough for a long, long time. Make it out of 6061, unless you feel the need to replace the belt with a chain for "strength". What are your strength concerns, exactly?
 

Yorkus

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#3
Are you talking about the V-belt pulley? The Zamak pulleys did well enough for a long, long time. Make it out of 6061, unless you feel the need to replace the belt with a chain for "strength". What are your strength concerns, exactly?
Yes the V-belt pulley on the spindle. I just got through turning the matching counter shaft pulley out of 6061 and it seems very soft. I just want to make sure the part is strong so it will last. I am concerned that the direct drive pin in the Bull Gear will tear up the Aluminum pulley when engaged.
 

francist

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#4
What about putting in a small sleeve insert out of steel for the bull gear pin to engage? In other words, a steel liner for the hole in the back of pulley.

I know what you mean about the hole getting chowdered -- my MF spindle pulley has more wear in the holes than I would like, but it's still the original pulley. I never really thought about aluminum wearing faster than the Zamak, but you may be correct. Seems daunting to me though to make the new pulley out of steel.

-frank
 

pontiac428

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#5
The bull gear pin hole has a boss in the original casting to provide some meat. It would be easy to sleeve/bush like francist said above. By sleeving, you are essentially driving the pin with a larger diameter hole, which reduces the pressure per unit area that the pin exerts on the pulley.

I'm not a fan of Zamak, but I do care for a number of Zamak parts. It's a war-economy substitution metal, not a high performance alloy. I don't know where to find engineering specs for that material, but I don't think that 6061 could be much weaker, if at all... is your billet T6 heat treated? The list of products taking daily abuse made of 6061-T6 is really, really long. I have trusted my life to it in vehicles, sports equipment, motorcycles, and more. I can't say the same for Zamak, but my catalog year 1937 lathe is still going, so maybe there's something to that.
 

Yorkus

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I don’t have much understanding about the different metals but have seen on some web sites that current day Zamak is catigorized in 3 different grades. They all seem to be a little stronger than 6061 aluminum. I don’t know what grade Aluminum I have beyond the 6061 classification. It is a remnant puchased with just the 6061 label maker on it.
I like the idea of steel inserts with the drive pin hole in them.
 

Nogoingback

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#7
If you want to do it in aluminum, you could use 7075, which is stronger than 6061, and machines very nicely. How big is the pulley?
 

wa5cab

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#8
Actually, the characteristics of Zamak are closer to cast iron than to aluminum.

I don't remember now where I saw it, but I have had it fixed in my head for several years that the Zamak grade used by Atlas is & was Zamak 5.
 

Yorkus

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#9
If you want to do it in aluminum, you could use 7075, which is stronger than 6061, and machines very nicely. How big is the pulley?
I would love to make it out of 7075 but that is very rare at my remnant outlets. To buy it new is $700 per foot in the 3” diameter that is needed. Way out of my budget. At this point I have almost finished making it out of 6061 and will “just see what happens” when I try using it. I haven’t tried to price cast iron, anyone know where to get bar stock?
 

Yorkus

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Actually, the characteristics of Zamak are closer to cast iron than to aluminum.

I don't remember now where I saw it, but I have had it fixed in my head for several years that the Zamak grade used by Atlas is & was Zamak 5.
I read something just the other day that someone thought it was comparable to Zamak grade 5. They indicated that grade 5 has a strength of 45,000 but over time it weakens to 39,000. The said that 6061 has a strength of 43,000 so with how old our mills are getting maybe 6061 will work out fine. I can tell you a finished pulley in 6061 weights a lot less than an original Zamak one.
 

Nogoingback

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#11
I would love to make it out of 7075 but that is very rare at my remnant outlets. To buy it new is $700 per foot in the 3” diameter that is needed. Way out of my budget. At this point I have almost finished making it out of 6061 and will “just see what happens” when I try using it. I haven’t tried to price cast iron, anyone know where to get bar stock?

Here you go:

https://www.ebay.com/itm/1144-Steel-Bar-Rod-3-750-3-3-4-Dia-x-2-50-2-1-2-Length/283049600849?hash=item41e7122751:g:LGQAAOSwlv9aZQRu&_sacat=0&_nkw=1144+round+bar&_from=R40&rt=nc&_trksid=m570.l1313

1144 is stronger than 1018 and is nicer to machine.
 
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wa5cab

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#12
The problem with aluminum as compared to Zamak, cast iron and steel it that at least many alloys tend to cold flow under impact loading.. Which will happen with interrupted cuts. This characteristic will first manifest itself in the direct drive pin hole, as it elongates. The second point where this may happen will be at the pulley-small spindle back gear interface.

Edit - I should add, however, that I have no experience with 7075
 

Yorkus

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#13
I am not familiar with 1144. I am guessing it is Steel and not Cast Iron?
Thank you for the link, sorry to say that piece is just a about .25 to .375 too short.

Thanks again!
York


Sent from my iPhone using Tapatalk
 

Nogoingback

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#14
It's steel.

Look around, the same vendor offers offcuts in other lengths. Or, you might find
something else suitable.
 
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