Pinning

This topic has 7 replies, 6 voices, and was last updated 26 August 2011 at 10:36 by AndyP.

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25 August 2011 at 21:14 #73954
Peter Wood 5
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@peterwood5
I still consider myself a beginner though I have built a couple of stationary engines.

I am currently building a Vulcan stationary steam engine. Various parts have to be pinned to shafts when assembled eg the rocker arms of the valve mechanism and the retaining collars on the bridle links . Having spent many hours machining these parts I don’t want to spoil them at this stage. Hand drilling 1/16” diam holes on a ball end or circular collar sounds like a recipe for disaster.

Can anyone give me advice on how to accurately drill the pin holes and what to use for the pins. Most of the collars and ball ends on the bridle links are 1/4” in diameter, the shafts are 1/8” and everything is BMS.

Edited By Peter Wood 5 on 25/08/2011 21:28:58
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25 August 2011 at 21:14 #5632
Peter Wood 5
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@peterwood5
How do I accurately pin collars, links, rocking levers etc to shafts.
25 August 2011 at 22:16 #73961
Ramon Wilson
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@ramonwilson3
Hi Peter,

Any work on a previously machined part can be a bit daunting but pinning is not particularly difficult either to do or disguise though the latter is not quite so easy on the ball ends.

When you say ‘hand drill’ I’m assuming you mean on a drill press. As long as you can hold the work piece rigid under the drill on the drill table you should have no problem.

Ideally pins should be mild steel – I have used silver steel in the past and as this is more likely to be available in smaller diameters it’s okay to use but anything hard like piano wire is not.

Centreing can be a problem as if the pin is small then the centre needs to just be deep enough to allow the drill proper to be able pick up. A turned 120 degree point hardened out can be sufficient if gently pushed into the workpiece. Keep the drill well up in the chuck to gain maximum rigidity and drill through just deep enough into the shaft for the pin to work.

Don’t debur the hole – can’t stress that enough – cut the pin to length such that it will protrude about half its diameter, put a touch of Loctite on the ‘pin’ then tap it gently in the hole. Hold the part on to a soft support – eg ali and lightly tap the pin to swell its top area then clean any residue of loctite off – Meths is ideal for this. Once set the pin can be gently filed down to the surface using a fine needle file and emery. If you have deburred the hole you will have a ring to bear witness it’s been pinned but if you don’t in all probability you will find it hard to see I think there are some pics in my album showing this op but you will have to go back quite a few pages to find them

Of course depending on it’s usage it may be that Loctite alone will be sufficient as it has remarkble strength if used correctly ie the right fit and the correct type – ‘601’ would be ideal.

Hope this helps – look forward to seeing the finished engine

Regards – Ramon
25 August 2011 at 23:07 #73965
Alan Worland 1
Participant
@alanworland1
Peter, I think Ramon has hit the nail on the head so to speak!

I recently finished a stationary engine (photo to be uploaded shortly) and when it came to the reversing gear involving a 3/16 shaft with a 1/16 pin through it didn’t quite go to plan as I found the pins allowed the parts to move

I increased the pin size – actually a nail, to .105 and drilled tight fitting holes for these – wacked them in with loctite and the bloody things still moved!

I then opened out the parts to take 1/4 silver steel with the pins made from my newly discovered nail stock, once again assembled with loctite and it all seems tickety boo!

This somehow was achieved without damaging the parts concerned

A simple process is pinning, but to be treated with the respect it deserves!

Alan
25 August 2011 at 23:44 #73968
Steve Garnett
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@stevegarnett62550
All good advice, of course. That said, for some jobs I quite like using tapered pins. Especially useful if you think you may have to remove and refit them. Okay, you need either a special pin drill or (I think preferably) a tapered reamer to fit them, but you can get suitable pin sizes from clockmaker’s part suppliers relatively cheaply. Without much looking I found somebody selling 100 for £7-99, and that would probably last you for ever! Chronos also sell them in smaller quantities, but they aren’t quite as cheap.

The fitting of them is pretty much in line with what Ramon said. But, if you ream through the whole assembly after drilling, you can pretty much guarantee to get a remarkably good fit, with a little bit of care.
26 August 2011 at 02:05 #73973
Pat
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@pat
Peter – I agree with Steve Garnet – best to use taper pins and the associated taper reamer and drilled hole. That way the pin is a good fit and can easily be removed and refitted for maintenance or assembly purposes. Both pins and reamers are available from suppliers specialising in clock makers tools and materials. In the bigger sizes roll pins are good if you must use a plain drilled hole. Normal engineering practice for the holes for parallel pins is to use reamed holes to ensure a good fit. The taper on a hand reamer can in an emergency be used to good effect with care.

Regards – Pat
26 August 2011 at 09:40 #73983
Peter Wood 5
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@peterwood5
Thanks to everyone for all the excellent advice. The original build article implied that the rocker arms etc were pinned after assembly but I think that prior assembly drilling the pin holes in the vice on my mill is probably the safest way.

I have done a quick search of clockmakers suppliers and found a wide choice of tapered pins but so far no tapered reamers. Any links would be welcome

I have attached a photo of the assembly showing the points which have to be pinned. I am still a bit worried about the collars on each end of the valve crosshead but may resort to just Loctite as they are merely retainers.

Ramon – terrific photo of your Ed racers. I am just off to the BMFA Nats so we obviously have other mutual interests.
26 August 2011 at 10:36 #73987
AndyP
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@andyp13730
I will speak up for tapered pins as well, just don’t mix up metric and imperial – the tapers are subtly different. My tapered reamers came from Tracy Tools.

Andy
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