ANSI RC, LC etc. seems to deal with shifts

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SUMMARY

The discussion centers on the clearances and tolerances for sliding parts in a sliding bolt firearm, specifically referencing ANSI RC 8 or 9, which corresponds to clearances of approximately 0.005 to 0.012 inches. The user, Alan, is uncertain about the impact of right angles on these clearances and questions whether a total clearance of 0.006 inches is adequate compared to a higher clearance of 0.013 inches found in a schematic from scribd.com. The conversation highlights the importance of experience in firearm design and the influence of factors such as dirt, lubrication, and bore straightness on tolerancing.

PREREQUISITES
  • Understanding of ANSI clearance and tolerance standards, specifically ANSI RC 8 and 9.
  • Basic knowledge of mechanical drafting and firearm design principles.
  • Familiarity with the effects of contaminants and lubrication in mechanical systems.
  • Experience with geometric tolerancing, particularly in non-round components.
NEXT STEPS
  • Research ANSI clearance and tolerance standards in detail, focusing on RC classifications.
  • Study the effects of contaminants on mechanical tolerances in firearms.
  • Learn about lubrication requirements for sliding mechanisms in firearms.
  • Explore geometric tolerancing techniques for non-circular components in mechanical design.
USEFUL FOR

This discussion is beneficial for mechanical engineers, firearm designers, and anyone involved in the manufacturing and tolerancing of sliding mechanisms in firearms.

palindrome
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I have a clearance question. I’m in need of understanding the clearances and tolerances associated with the sliding parts in a sliding bolt fire arm. The moles are really going to hate this. After some time goggling, reading, and with a year of mechanical drafting, I estimated that ANSI RC 8 or 9 meets my application, around .005 to .012 of an inch, clearance for a sliding bolt. I downloaded a schematic from scribd.com, that has .013 diameter clearance between a sliding bolt and its receiving part. Here is where I need help, ANSI RC, LC etc. seems to deal with shifts and holes, I’m not sure how much my part having right angles affect these clearances, i.e. my sliding part isn’t round. My doodling has .006 total clearance there, is that too small, and is the higher end of .013 a better fit?



Thanks for any help,

Alan
 
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This is really a question for someone very involved with firearm design. I can pull a clearance that I would think would work based on my experience, but that would be lacking the specific knowledge of application.

When it comes to tolerancing, experience in the particular application field is incredibly valuable. What effects does dirt and contaminants from firing have? What kind of lubrication is required? What tolerances are there on the straightness of the bore? It's a bit of a tough question to get right. However, we can take a stab at this if you can give some more of a description. A picture would help immensely.
 

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