Spring pins vs taper pins

[Alex]

This is directed to the model builders; I've used spring pins on some of my locomotives, but others say to use taper pins.

I've never used a taper pin smaller than 6mm (1/4") but I notice that they are available in 1/16" or about 1.5mm.

So, 3-1/2" gauge Model Locomotive - spring pins or taper pins for holding valve gear together? Why? (The model is Martin Evans' "Ivatt" locomotive that I'm finishing up)

Thanks for any thoughts  - JohnS.

[crueby]

I've  used taper pins for making steam engine  crankshafts, in conjunction with  loctite. Works great. Filed off at the ends, they are nearly invisible. They do require a taper drill, or step drilling and a taper reamer.  I've  used both, prefer the taper drill, after drilling a pilot the size of the narrow end.


Only used roll pins a couple times, one advantage of  them is they could be removed. The hole could be drilled with a normal drill. After installation  they are very visible. I've  only used them on tools.


Hope that helps!

[Jasonb]

Taper pins for me, usual to leave some of the small end protruding so they can be driven out and should hold without loctite

[Jo]

I don't use spring pins on models or tools. I use lots of taper pins, which I have acquired from the clock making hobby. 

You can install the pins and file them flush on both sides so they almost vanish  . To withdraw them you just knock them out from the thin end using a "Pin Punch".

Jo

[Bluechip]

Taper pins for me, usual to leave some of the small end protruding so they can be driven out and should hold without loctite

Absolutely wrong!
Having fitted a few thousand of the things on adding machines, accounting machines, tabulators ,80-column punch card machines and the like, the small end should be slightly recessed. When they are removed the pin punch will then self-locate and the pin will not be damaged.
Large end slightly protruding.

D.

Beware the taper angle changed decades ago. 

Got rid of all my imperial stuff to the late Mr. Stevenson M.B.E.  ages ago.

https://www.modelenginemaker.com/index.php/topic,2172.msg34687.html#msg34687

[Charles Lamont]

So, 3-1/2" gauge Model Locomotive - spring pins or taper pins for holding valve gear together? Why? (The model is Martin Evans' "Ivatt" locomotive that I'm finishing up)

Thanks for any thoughts  - JohnS.

IMHO taper pins. For authenticity. 'Cos that is what was used in full size. Tiny ones are probably easier than spring pins to remove without damaging the surroundings.
On bits of loco valve gear they can be awkward to get at even in full size (been there, done that, on an Ivatt engine, but not a 'Mickey Mouse'). The thin end is therefore left protruding so that you have some chance of hitting it to extract the pin which can be replaced cheaply.

[Jasonb]

Maybe we need another thread asking if you leave the end in, out or file it flush.

Not sure about those small machines but in model terms I try to replicate full size where I see the head and small end left proud of the surface, same as Charles. More chance of getting at the protruding end with a soft drift than a small parallel punch.

Also worth noting is that clock makers taper pins are not the same as engineering ones. Can be a steeper 1 in 30.5 taper for the "universal" ones or a touch steeper for Gauged pins and the hole is cut with a broach not a reamer

[Michael S.]

Opinions can be divided.
When I dismantled my large locomotive (portable engine) after about 90 years, there were some of these conical pins. In the end they all stood out a little. So the full length as they are delivered.
If you try to remove these pins with a hammer after all these years, the following happens:
These pins were hammered in really hard and have also rusted.
The thin end of the pen is compressed. So it gets thicker and no longer fits through the hole and everything just gets worse.
I later learned that it is better to remove the thin end flush. To drive it out with the mandrel during dismantling.

Michael

[Jo]

I like the idea of leaving the small end slightly in because you can use the correct sized pin punch 

Also worth noting is that clock makers taper pins are not the same as engineering ones. Can be a steeper 1 in 30.5 taper for the "universal" ones or a touch steeper for Gauged pins and the hole is cut with a broach not a reamer

Yes you need to drill/ream a hole with the same taper as your pin or it won't work 

Jo

[Alex]

Interesting replies - thanks all.

My current thought is to go with 1/16" taper pins from EKP Supplies.

Roll pins are available "over here" in the local stores and in my workshop, but, I'm always looking at trying something new. The roll pins that I've used on models I fit flush, but agree that they can take away from the look of the finished product.

One concern - after the Kozo Shay (version 1), where it went together beautifully, the Evans' Ivatt is "put it together, take it apart, re-make the part so it actually fits ..." so lots of on and off again and on again seems to be the way.

Bluechip - the late Mr. Stevenson was a really nice man. My wife and I had the pleasure of having dinner with him in Banbury UK a while ago now; we were just talking about him this week.

Thanks all - JohnS.