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(04-30-2015, 05:37 AM)EdK Wrote: (04-29-2015, 10:54 PM)Dr Stan Wrote: Still does not sound right. The spring pins could have been installed by an error at the factory. IMHO I'd replace it with a very soft steel or even aluminum pin just to protect the more expensive parts of the lathe.
Not likely a factory error, more likely a design error.
How would one go about figuring out the correct diameter and material to use to replace the spring pins with shear pins? 
Ed
SWAG. Unless you have finite element analysis CAD software.
OK, there's probably some kind of chart in Machinery's Handbook, but I've never taken the time to look.
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I put a piece of aluminum rod that came off of a casting where the molten metal had pushed up thru a vent hole. it was the right diameter to replace the 5MM spring pin that I removed.
If you change it I would use aluminum, the shear strength is quite high for the diameter. Aluminum Shear Pins is was was used in the winches on the trucks I used to have to take care of in the Army,
dallen, proud to be a member of MetalworkingFun Forum since Apr 2012.
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I'm embarrassed to say that a nail is the current sheer pin on the coupler of the x-axis leadscrew to the power feed.
Hunting American dentists since 2015.
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(04-30-2015, 07:35 AM)Mayhem Wrote: I'm embarrassed to say that a nail is the current sheer pin on the coupler of the x-axis leadscrew to the power feed.
From an engineering shear point of view the nail is probably much better than a roll pin/spring pin.
DaveH
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The following 1 user Likes f350ca's post:
EdK (04-30-2015)
Calculating the shear strength of a pin is easy enough, the tricky thing would be determining the strength of the weakest part in the gear train behind it.
Free advice is worth exactly what you payed for it.
Greg
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(04-30-2015, 05:37 AM)EdK Wrote: (04-29-2015, 10:54 PM)Dr Stan Wrote: Still does not sound right. The spring pins could have been installed by an error at the factory. IMHO I'd replace it with a very soft steel or even aluminum pin just to protect the more expensive parts of the lathe.
Not likely a factory error, more likely a design error.
How would one go about figuring out the correct diameter and material to use to replace the spring pins with shear pins?
Ed
I'd just go with an aluminum 6061 pin turned from .25" stock. If you want to get "real fancy" make a taper pin and ream the hole with a taper pin reamer. McMaster (and probably others) has low strength aluminum dowel pins.
http://www.mcmaster.com/#standard-dowel-pins/=wz7hs5
