Roll Pin Hole Sizes

[ron]

Hi Everybody
What size of hole do you drill for roll pins, I tend to use a rough size of a couple of thou under for small ones an 5 thou under for bigger ones, anyone got a more scientific method?
Ron

[waggy]

Hi Ron,
I use a fair amount of these pins and usually use the nominal diameter (the size on the box) as the drill size. I would imagine fitting the pin into a smaller hole would make them very difficult to remove should the need arise?
My machinists handbook gives guidelines for the hole size from 1/16" to 3/4" pins. The recommendation is not to go smaller, the hole sizes vary with the size of pin from 0.003" up to 0.014" as the diameter increases. They are also referred to as "American National Standard Spring Pins".
I must ask for some of those when I next stock up!

Regards,

Waggy.

[SteveW]

Ron,

In my experience these things ain't round so when you measure them you've got to pick the actual size carefully. What you don't want is for them to fall out.

I bought a bag of roll pins various a while back so don't have the luxury of knowing the size on the packet.

[mmaidnz]

So,Waggy,if I understand you correctly,the pins are actually slightly over the nominal size to start with?I was pondering this question only last week,but could not get a consistent answer from several people in my club

[jackrae]

"...but could not get a consistent answer from several people in my club "

So what's new ! If I asked at my club what 2+2 made I'd get a dozen different answers

Jack

[Shawki Shlemon]

My experience is the same as Waggy , I alway used high quality pins in aircraft industry , the holes are standard size and the pins are actually slightly larger . I have not used any in the hobby .

[ron]

My problem is the same as Steve, I've got a large mixed collection of them without the luxury of knowing the sizes, basically I mic them across the largest dimension and drill as I said before, it looks from the answers to be as good a method as any. Although I've used them for other purposes I've only tried them a couple of times for model engineering, very small ones to pin the lifting arms etc to the weighshaft, I was also going to pin the return crank with them, is this not a good way to do it?
Ron

[pondok]

Hi Ron,

I had to recently replace all the roll pins on the weighshaft of a loco - since putting in PTFE rings deliberately tight in the valve sleeve, the resistance was enough to create a fair bit of flex in the roll pins on the weighshaft, more than enough to put the valve timing out severely.

I can only imagine they 'spring' in on themselves because of the linear split, maybe even curl in as the lever tries to turn on the shaft.

Once I had the weighshaft off, the flex was obvious even twisting by hand. Now it is all taper pinned and solid as a rock.

cheers
Andy

[freddo1]

Hi Ron

You really don't want to be using roll pins for model locos except perhaps as a locating device for preventing rotation - as in wheels on axles - hole bored half in the wheel and half in the axle.

As Andy says - don't use them where there is any forces being applied laterally - taper pins are the business.