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?

Chinas QC not up to snuff?

RJT said:

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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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

RJT said:

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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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".

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

RJT said:

Is that normal for metric roll pins to be that much larger?

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No. You either ordered or received the wrong pin for your application.

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/CataloguePDF/TensionPins/Combined_PDF_TensionPins.pdf

Mike1974 said:

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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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