Milling drill bit?

On 04/01/2017 10:35, T i m wrote:

It is the nut that is hitting.
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Ahh! It's a lathe you need to produce a counter bore in the piston. If ther e is enough thread on the piston shaft that will allow the nut to screw dow n further but looking at the photo the shaft is level with the top of the n ut so that will start to hit the top of the cylinder so it will need shorte ning. Alternatively if the other end of the shaft length protruding out of the cylinder is not critical than a few washers on the underside of the pis ton will pull the shaft down enough on the piston to avoid shortening and a s Tim suggested a locknut which is about half the height of a standard nut might avoid the need to counter bore.
Richard
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On 04/01/2017 11:12, ss wrote:

Some thoughts: - You could use a thick gasket to solve the problem but would lose the centring action of the step on the top plate ... probably not too important. Whether a non-metallic gasket is viable depends on whether the engine is single or double acting and the pressures. - I presume the piston tightens onto a shoulder so you could file that back 3mm - Could you reduce the stroke by moving the fulcrum or changing the beam length? - You could enlarge part of the hole with a jobber drill and accept that the nut tightens onto a sloping surface, or you could make a suitable washer - Could you bore a recess in the cylinder end?
Finally, if all you have is a hacksaw, and no mates with a pillar drill, drill stand or lathe, then I suppose you could saw a few mm off the piston as a last resort.
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Ah. ;-)
As others have said there are several solutions, especially if you have access to a lathe or mill.
One that you could do yourself is as has been mentioned is to create a counterbore with a std drill (ideally in a press) and then shape a nut accordingly to match the taper of the drill. If you knew the thread and nuts were available (it's probably an imperial size) I could do the nut bit on my lathe and stick it in the post to you?
Is the piston shaft screwed into the piston and the nut just acts as a locknut or is there a shoulder on the piston rod (the rod looks like it could be slightly bigger diameter than the thread).
Is the threaded portion of the rod deep enough to allow the nut to be recessed?
Has the thing previously worked OOI (has something else been changed that has impacted this issue)?
Cheers, T i m
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On 04/01/2017 19:32, T i m wrote:
"> Has the thing previously worked OOI (has something else been changed > that has impacted this issue)?"
Thanks for the offer Tim (the nut), I have resolved the problem by filing making the nut slightly thinner, that has cured the problem.
The piston shaft is screwed in to the piston and then the nut to lock it. No shoulder on the piston rod. Has it previously worked I do not know, I have had for 40 years stored in the attic. I have taken apart now and cleaned up the bearings etc and it turns very smoothly, it was just this last part of the piston bottoming out I had to resolve. I believe it was an apprentices model of a Stuart vertical steam engine.(it came from an engineering works) I never paid much attention to it years ago, I have a very vaque memory of slackening the pivot bolt on the connecting rod so the flywheel would turn when my kids played with it years back so maybe back then it was bottoming out.
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You are welcome. I could also have counterbored the piston (Myford ML10) if stage 1 (or any alternatives) hadn't worked. ;-)

Yeah, sometimes the difference of just a few thou is all it needs.

Ok.

Ok and thanks. So (I don't know much about steam engines as such) but I wonder if the distance from any crankshaft to the cylinder could have changed or is it all pretty well defined when bolted up?
e.g. Is the piston running around the centre of travel, eg, not too near the bottom and further away from the top (at the extremes of the stroke). If it is and if the assembly allows, you might be able to pack the 'crankshaft' (or whatever determines that dimension) away from the cylinder a touch?
If it were mine (and especially if you were going to get it running, even if only with compressed air) I might like to know all was symmetrical, or there was a reasonable space under the piston (nut) at full stroke etc.
Cheers, T i m
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On 04/01/2017 21:32, T i m wrote:

“So (I don't know much about steam engines as such) but I wonder if the distance from any crankshaft to the cylinder could have changed or is it all pretty well defined when bolted up?”
Everything is fixed and not adjustable apart from the bolts that fix the pivot on the piston rod but tried minor adjustments and it then either bottoms out or tops out. So the issue was inside the cylinder which I have now resolved.
“If it were mine (and especially if you were going to get it running,”
It does not have the inlet/outlet valves but someone with an interest should be able to convert it.
This is part of a bigger plan, the model is worth at least £100+ as it stands and I have other items ...clocks/plate cameras/carbide lamps/paraffin irons/old scales and other stuff that has been in the attic for 40+ years and a load of other stuff that my children are not interested in so as I have recently retired I will sell it off and I intend to get a high quality working steam model of a beam engine with the proceeds.
This is almost identical to the model I have:
https://www.youtube.com/watch?v=B_unVRB4UKw

This is what I want or something similar:
https://www.youtube.com/watch?v=3Wb_AAKMXGQ

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Understood. I was thinking more likes shims that 'adjustment' as such but the latter part of your reply makes that irrelevant in any case. ;-)

Understood.

Ah.

Ok.

I have recently been given a Drummond lathe and other workshop tools on the same basis. ;-(

Ah, even better idea of what we were talking about. ;-)

I can see the appeal as I love all things mechanical bit it looks a bit big for the mantelpiece (well, mine anyway). ;-)
Cheers, T i m
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On Tuesday, 3 January 2017 22:41:13 UTC, ss wrote:

Grind to, or buy, a flat-bottomed twist bit.
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On 03/01/2017 22:41, ss wrote:

Drill hole with a 10mm HSS bit Then use a 10mm forstner bit to flatten the bottom, use it slowly and with good cutting lube and it should be fine.
Alternatively buy a 10mm end mill and finish hole with that
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On Thursday, 5 January 2017 18:13:51 UTC, rick wrote:

that would get you about a 3mm wide hole.

NT
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