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This weekend I read a thread on the Practical Machinist forum asking what size hole to drill for a given diameter of spring pin (which we often call a roll pin). I never gave it much thought, but it turns out to be a pretty simple answer: drill the hole of the nominal size of the spring pin (and in many cases up to a few thousandths over), so for a 1/8″ spring pin, a 1/8″ diameter hole. I decided to poke around and of course Machinery’s Handbook has all the data for both slotted and spiral spring pins.

Never being one to overlook a chance to waste time on the internet I did some surfing and found the technical data from both Driv-Lok and Spirol (slotted pins, coiled pins) for their spring pins. Spirol also has application case studies, such as this interesting look at the way to replace machined, clip retained, pins with spring pins in an air rifle trigger. No data is available for the cheap import pins found in those assortments from Harbor Freight, etc. so we wouldn’t use the technical data for quality pins when designing with the imports.

Spring Pin Applications [DRIV-LOK]
Application Case Studies [Spirol]

 

3 Responses to Spring Pins

  1. johnnyp says:

    I have used a great many of these type of pins. Their primary application is blind holes (roll pins don’t work well, a bleeder hole is required) and I believe the hole is smaller than the pin dia. Some of the applications that are illustrated are also questionable, in particular the T-handle. Here is a link that gives a pretty concise description of the various pins that are available http://www.mcmaster.com/#pins/=48rrqr

  2. fred says:

    One other interesting side use for “roll pins” is to file a angled cutting edge at the tip of pin along the centerline separation. The pin can then be chucked in a drill and be used as a cheap small holesaw – useful for drilling around broken off screws and similar embedded objects

  3. Tommy C says:

    Vise Grips use them on the handles.

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