Author Topic: Seelok, Roll or Spring Pins ??  (Read 383 times)

Offline Bluechip

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Seelok, Roll or Spring Pins ??
« on: March 30, 2019, 11:03:05 AM »
These wretched things are driving me up the wall ...  :rant:

I want to pin a Hostaform gear to a 8mm S.S. shaft. Not what you might call particularly heroic, been done before I'm sure.
I have a kit of roll pins, all sorts of sizes but  NO INFO. re: dimensions.
So I have no idea whether they are supposed to be Metric, Inch or a mixture ..  :headscratch:
Just squandered about 2 hours of my remaining days on Earth measuring the damn things. Well, some of them.
The only conclusion I can draw is, unless some are 64 ths they are metric. But not dead to size.
BUT .... here's the clever bit .. IF I assume they are in increments of 0.5mm AND are 6% oversize they seem to make sense.

ie. 2mm = 2.12mm ; 2.5mm = 2.65mm etc. etc.

This does seem the hold true up to 6mm. ( Didn't bother any further. Even I can work out a 8mm hole through a 8mm shaft is not likely to work too well ).

So, the question is this:

Would it be correct to ream a 2mm hole through the gear boss and shaft and then stick the 2mm roll pin in?

Is that why the apparent 6% oversize is there ??  Dunno ...

I cannot seem to find ANY real info. on the net ... bugger ...  :headscratch:
I did find this:
But the dimensions given, even allowing for the tolerances, don't match up.


« Last Edit: March 30, 2019, 11:21:54 AM by Bluechip »

Offline Baner

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Re: Seelok, Roll or Spring Pins ??
« Reply #1 on: March 30, 2019, 12:05:41 PM »
I've no official documentation to prove it, but I've always assumed roll or spring pins were oversized and are compressed on insertion making for an interference sort of fit, so they don't fall out.

I'd say you're correct in assuming metric sizes.

In practice I drill/ream a hole to the nominal metric size and tap in the roll pin. Seems to have worked so far.

Also I drill through both parts at the same time. If there's any misalignment roll pins have a tendency to get stuck.


Offline derekwarner

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Re: Seelok, Roll or Spring Pins ??
« Reply #2 on: March 30, 2019, 12:36:18 PM »
Google has plenty of detail on Sel-Lok or C-Lok securing pins  :hammerbash: [and their generic cousins] which could be considered as Industries answer to lower the cost mechanical securing of components in production environments

However hand reamed Taper pins.....both Imperial and metric have been used for 100 years to the complete mechanical attainment of the required action

These same hand reamed procedures do not require the sudden impact action of components

One could consider using any such forcecful insertion of any type of retaining pin without proper support has the obvious potential to critically affect  :zap: mechanical alignment

You get no second chances with these newer securing devices........however with the correct setup, it is a pleasure hand reaming a size OO taper pin hole  & inserting the pin as the prize  :cheers:

Derek Warner - Honorary Secretary [Retired]
Illawarra Live Steamers Co-op - Australia

Offline cnr6400

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Re: Seelok, Roll or Spring Pins ??
« Reply #3 on: March 30, 2019, 01:14:09 PM »
Hi Dave, I would suggest you size the shaft hole 2 to 5% undersize of the pin diameter. I'd suggest selecting a pin that JUST fits the Hostaform acetal part. The pin should not be a press fit in the Hostaform part, or the stress may eventually split it.

Offline Bluechip

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Re: Seelok, Roll or Spring Pins ??
« Reply #4 on: March 30, 2019, 03:22:08 PM »
Thanks for the replies folks ..  :ThumbsUp:  I think I/we have a solution of sorts.

To put this into context, I'm making a Wimshurst / Bonetti  generator. These need the front and rear discs to contra-rotate.
In the att. pic. the two shorter shafts drive the discs and the longer goes to the leccy motor. There is a 2:1 reduction, ie; motor faster than discs.
The usual method is to cross one of the drive belts but this created no end of crap on the last one I made and any contamination on the discs is bad news.

The hubs / bosses on the larger gears are some 18mm IIRC, the smaller is less.

Now, acetal don't glue very well but I'm going to epoxy a steel sleeve over each of the hubs. It won't stick in any spectacular fashion but it will be enough I think.
I have ordered some 2mm roll pins, the ones I have are too short.
There's no great power going through the set-up. I would guess around 10 - 15 W tops, also there won't be any shock loading.

We will see .... thanks again ...  :cheers:


One last thought:  Am I alone in thinking Pozi. Pan Head screws are 'kin ugly ??