Metric roll pins vs English roll pins
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  1. #1
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    Default Metric roll pins vs English roll pins

    Usually an English roll pin is a few thousandths larger than nominal , but compresses fairly easily to get a press fit into a nominal size hole. I bought 3 mm roll pins from 2 different vendors and they measure 3.5 mm diameter and are next to impossible to get in a 3 mm hole. Is that normal for metric roll pins to be that much larger?

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    Chinas QC not up to snuff?

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    Quote Originally Posted by RJT View Post
    Usually an English roll pin is a few thousandths larger than nominal , but compresses fairly easily to get a press fit into a nominal size hole. I bought 3 mm roll pins from 2 different vendors and they measure 3.5 mm diameter and are next to impossible to get in a 3 mm hole. Is that normal for metric roll pins to be that much larger?
    Not sure, but found this. It appears they are slightly bigger than std? 3mm being 3.14-3.25 (.123-.128 so up to .01" over nominal, seems like alot)

    Metric Size Slotted Spring Pins from FASTAR Fasteners | Quality Fasteners

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    Quote Originally Posted by RJT View Post
    Usually an English roll pin is a few thousandths larger than nominal , but compresses fairly easily to get a press fit into a nominal size hole. I bought 3 mm roll pins from 2 different vendors and they measure 3.5 mm diameter and are next to impossible to get in a 3 mm hole. Is that normal for metric roll pins to be that much larger?
    Why 2 different vendors and who were the vendors?

    It'd also be good to know what you specified when you ordered. 2 different vendors getting it wrong?

    3mm is 0.118". 3.5mm is 0.138".

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    even a little big for 1/8 roll pins it would seem

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    Quote Originally Posted by RJT View Post
    Is that normal for metric roll pins to be that much larger?
    No. You either ordered or received the wrong pin for your application.

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    Circlips Australia

    3mm roll pin min diameter 3.3mm and max diameter 3.5mm

    Also says following:
    "ASME is the preferred standard for a number of reasons
    Lower Insertion Force: Smaller diameter to nominal hole ration due to increased wall thickness,
    Higher minimum hardness and minimal slot gap after insertion.
    No Interlocking: Slot gap width is less than the wall thickness which makes them ideal for plating.
    Higher Shear Strength: Due to increased wall thickness, higher hardness and narrow slot."



    In my experience metric roll pins in GM/Saab transmissions are sometimes tight as hell even to remove.

    Coiled spring pins (DIN8750) are more close to size in my experience and dimension tables here say the same:
    http://www.headland-eng.co.uk/Catalo...ensionPins.pdf

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    Quote Originally Posted by Mike1974 View Post
    Not sure, but found this. It appears they are slightly bigger than std? 3mm being 3.14-3.25 (.123-.128 so up to .01" over nominal, seems like alot)

    Metric Size Slotted Spring Pins from FASTAR Fasteners | Quality Fasteners
    Your table is for the ASME standard mentioned in my previous reply and those indeed seem to be smaller than roll pins to DIN/ISO standard.

    Sooooo... next time OP ask for ASME B18.8.4M


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