Oversize Cylinder

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Oversize Cylinder

This topic has 9 replies, 5 voices, and was last updated 12 April 2010 at 19:46 by chris stephens.

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11 April 2010 at 17:20 #50632
Richard Stacey
Participant
@richardstacey70920
A newcomer to model engineering, I am in the process of building the Stuart S50 Steam Engine and due to a bad error in measurement I have bored the cylinder

31 thou oversize. Will it be OK to machine the piston to fit or do I have to buy a new cylinder casting and start again?

Many thanks

Richard
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11 April 2010 at 17:20 #5031
Richard Stacey
Participant
@richardstacey70920
11 April 2010 at 18:04 #50633
JasonB
Moderator
@jasonb
Can’t see why you should not be able to use an oversize piston.

Just make sure the larger bore has not affected the cast in steam ways and remember to machine the spigot on the cylinder covers to fit the bore as well. You may want to drill the cylinder cover bolts and a slightly larger PCD if they come close to the bore.

Jason
11 April 2010 at 18:18 #50635
Richard Stacey
Participant
@richardstacey70920
Many thanks for that Jason, as far as I can see there is no problem with the steam ways. Having managed to make the cutter bit for the boring bar and machine the bore parallel, I would have been disappointed if I had to start again. Thanks also for the tips about the cylinder covers and PCD for the bolts – I hadn’t thought of that!!

Richard
11 April 2010 at 20:33 #50636
chris stephens
Participant
@chrisstephens63393
Hi Richard,

Don’t look on your “mistake” as a negative, just think of it as a larger, more powerful version of the engine.

chriStephens
12 April 2010 at 12:14 #50644
Circlip
Participant
@circlip
You have highlighted one of the traps that most who “Mod” a design fall into Richard. Yours was one of neccessity due to an error of machining, but the same thing applies to two other forum golden oldies, Merticating designs from imperial and the “Why are the drawings not corrected” whingers.

Pity they don’t engage brain before trying to melt the keyboard.

You may be able to re-centralise the PCD between the edge of the bore and the flange O/D.

Regards Ian.
12 April 2010 at 15:34 #50648
Richard Stacey
Participant
@richardstacey70920
Thanks Chris,

I’m all in favour of positive thinking – all encouraging comments gratefully received.

Richard
12 April 2010 at 15:37 #50649
Richard Stacey
Participant
@richardstacey70920
Hi Ian,

I have checked the cylinder flange and there is no problem in centralising the retaining bolts with just a small increase in the PCD.

Regards

Richard
12 April 2010 at 18:28 #50656
mgj
Participant
@mgj
How did you make the error in the first place – just as a matter of interest.

As I recall the first hole I ever bored was a trifle ! oversize too
12 April 2010 at 19:46 #50657
chris stephens
Participant
@chrisstephens63393
If you think about it, a hole can either be right or oversize, if it were “under-size” it would simply be ‘work in progress’ or if you like, unfinished. There’s one for you lot to ponder on.

chriStephens
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