Midas 1220 LTD Broken Power Feed Shear Pin/Gear

[MikeIsMachining]

I broke this little gear that fits inside the D gear on the power feed gear train. My carriage got bound up and locked into position when I engaged the power feed. This was likely from burrs on a new part I installed in the carriage. This essentially crashed my gear train and instead of shearing the shear pin, this tiny gear broke. I plan to remake the gear but it doesn't appear to be made of mild steel like the larger gears are.

This is the second one I broke, the first was from legitimately crashing the carriage while I was starting to learn how to operate a lathe. I tried tig welding the first one I broke, but it doesn't weld right at all which makes me think it's not steel. Plus it's granular at where the part broke, almost like cast iron looks like when it fractures.

Does anyone know what this little gear is made of? I was thinking of making it in either A36 mild steel or 360 brass. Has anyone made one of these? Looks like I have a new side project to work on.

 

[markba633csi]

It looks similar to zamak which is a zinc alloy- Atlas used it
Might be easier just to buy it new from Smithy?

 

[MikeIsMachining]

It looks similar to zamak which is a zinc alloy- Atlas used it
Might be easier just to buy it new from Smithy?

Zinc alloy would be an interesting choice. I think this part is supposed to be sacraficial in the case of a crash. Smithy sells it but they charge $34 for the part, and it only lasted this one event. I would rather use a shear pin and replace pins and not the more expensive gear.

I would also like to make my own parts and learn something in the process, but I may end up buying this part to keep me moving for now.

 

[matthewsx]

If one is available for $34 I'd buy two.

Making one is a good idea but having a non-broken part to model will be helpful. Also, if you can make a CAD model you could 3D print it and have an effectively unlimited supply.

John

 

[markba633csi]

Could be made on the mill with a dividing head
Atlas has the same kind of part only with 2 "ears"

 

[MikeIsMachining]

If one is available for $34 I'd buy two.

Making one is a good idea but having a non-broken part to model will be helpful. Also, if you can make a CAD model you could 3D print it and have an effectively unlimited supply.

John

I think this is the path I will go down and I’ll buy the smithy parts for now. Eventually I think I will make this part in brass and find thin wall roll pins to use as shear pins. I would rather a little pin get broken and not a $34 part.

 

[MikeIsMachining]

Could be made on the mill with a dividing head
Atlas has the same kind of part only with 2 "ears"

Funny you say that, I started a new side project. I bought a rotary table with dividing plates, I also got a small chuck. The plan is to make an adapter plate to mount the chuck to the table so I can have both a dividing head and a rotary table.

 

[Weldingrod1]

I'd use brass or aluminum shear pins. Tubular steel is likely to do bad things.

Soft Aluminum might be a good match for brass. You need the shearing parts to be significantly harder than the shear pin. You might also use a steel insert as the shearing surface.

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