Stuart V10 Cylinder Casting

Hi Everyone,

Just had a disaster. Drilled the cylinder for the steam chest screws.

I was tapping the 7BA holes and snapped it.

Is there any way I can recover the cylinder, the tap is broken off flush with the casting.

I guess, probably not, which gets me on to the second question which is, has anyone a casting surplus to requirements?

Thank you for your interest and hopefully a reply

Hi Frank,
If the cylinder is cast iron then I think spark erosion (EDM) is the only solution. If it is bronze then chemical means may work. (I think i remember someone suggesting a solution of alum. ) Try searching on this forum for things like removing broken taps or drills etc. It has been covered quite often.

I have just tried my suggestion and found this thread.

Les.

Edited By Les Jones 1 on 30/05/2015 17:39:49

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Mmmmmmmm. Not good. I can only imagine your hollow feeling. I would imagine it's not just the feeling of the fiscal cost of a new casting it's the loss of the work you put into the casting thus far.

How about (as you have nothing to lose)

1) Carefully grinding around the tap with a Dremil type tool as deep as you can. Blow out the grinding swarf to minimising any possible jam. Then try to get the broken tap out.

2) Drill out the hole left to leave a tidy hole. e.g. 1/4" Then turn a piece of CI to be a nice snug fit into the hole. This can then be fixed with loctite.

3) Machine face to be all nice and flush.

4) Buy a nice new good quality 7BA tap and try again.

Possibly.

Nick

One method I have used with success is a hollow drill.

Take a piece of silver steel of suitable size drill it out to the thread clearance size and file / machine a couple of cutting edges. (Like a hollow end mill really) Harden and temper the end. Then carefully and slowly drill out around the broken tap. Then plug hole as above.

Cant remember if I read about the method here or some other forum

If your working on a 10V then its a fair assumption that you might be new to model engineering, and removing the tap may prove extremely difficult if possible at all. I would look at a way to work around the issue. You can secure the chest to the cylinder by drilling another hole close to the one broken, countersink screw with its face flush with the top face of the cheat/under the lid. This you can use to secure the chest and it wont matter that its off set as no one will ever see it. Then plug the hole in the chest you originally drilled (broken tap lines up with) and tap this 7ba, make a very short bolt to go through the chest lid and into this. That's the easy way I think, and you wont need to buy any new castings.

I got one out of a base casting on my first engine, also a Stuart 10V, with a very home made lashed up spark erosion setup. Unless you are familiar with electrical work it is probably better to find someone who has the right gear than to try and do it yourself, but it can be done.

John

Frank, this topic has been discussed in the "What did you do today (2015)" over the last three days - well worth a look, especially for advice on how best to avoid the problem in future. Steve

If nothing else I think Stuart will sell you a new casting.

JA

There is a design for a simple spark eroder that would probably do the job on Mike Cox's website As you do not give any idea of you location in your profile members with the required equipment cannot offer to help.

Les.

> One method I have used with success is a hollow drill.

If the 10V castings of today as are easy machining as those of 15-odd years ago, then a hollow bit is the way to go. Make it of silver steel with a hole the size of the tap (which will guide it accurately) and a convenient outer size. Use a small file to make a series of crude teeth (they can be quite crude as long as they have reasonable sharp cutting edges).

Dip in washing up liquid, harden by heating to red heat and quenching, then clean and either gently heat the shank until the end (outside the flame) starts to turn straw/pale brown or put in the oven at mark 6 for 20 minutes.

This will work, but you will need to lift it clear to get rid of the swarf often.

I suggest plugging the hole with a stub or brass loctited in, much easier than a threaded plug and as long as you don't plan to use superheated steam (and who would on a 10V?) it will be fine. The easiest way to finish it flush is with a curved flat cross-section riffler file, but I'm sure you can improvise.

Spot through from the steam chest and re-tap.

Neil

Frank,

Good advise given on recovering.

One thing, DON'T become despondent, or loose faith!

It's happened to ALL of us, and more than once.

It will happen to you again.

It's part of the hobby and character building as me old Man would tell me, grinning from ear to ear.

As long as you learn from such happenings, then you have achieved something.

My first moment was less traumatic in stripping the head off of a 12BA bolt, all too easy, and covered the fact by gluing it back on so nobody would know.

Geoff - Well it has snowed in June before!

Hi Guys

Many thanks for all that good advice and encouragement.

I like the idea of the hollow silver steel bit but will experiment first.

Possibly end up with using 3 holes, nice to know there are alternatives!!

Regards

Drip some alum into it for a few days? Or even weeks

Could save a lot of hassle

Edited By Ady1 on 18/06/2015 00:53:43

I have used the hollow silver steel drill solution before, and it really works.

The more important issue may be to ensure you don't snap the tap in the first place. Most breakages occur because the tap is wrenched slightly sideways, and the solution to this is to use a tapping guide of some sort.

I use my GHT Tapping and Staking machine for all small tapping jobs, and it really is brilliant at what it does.

Hi Guys,

Just a quick update.

After a lot of consideration I decided to drill a further hole in the Steam chest housing and use the counter

sunk screw solution as suggestion in one of the posts. Excellent result. I adopted this solution as it was a

technique I could identify most with. Oh, by the way, what is alum and where could I get it.

Thanks again

Alum, you can get a refined grade at the chemist, or the stuff you want (it's cheap) at the garden shop. Its described as Hydrated Potasium Aluminium Sulfate. It's non toxic, used in food products such as baking powder.

Ian S C

Hi Guys,

Thanks for the info Ian.

I sadly have another question. I am proceeding well with the Stuart engine and am taking my information from "Building a Vertical Steam Engine" by Andrew Smith Revised by Pengwren. However when I assemble the crank shaft, con rod, piston, column etc I find that on the top of travel the piston protrudes by nearly 6mm. The valve assembly seems fine and will be adjustable to carry out its function which indicates that the column is ok. Piston travel is 20mm which indicates that the throw is ok. I have measured all relevant components and even if I say so myself the dims are not bad. I am beginning to think that there may be an error in book and I have even checked the conversion from imperial to metric and can't find an error. My question:

is there an error in my work or in my information?

I look forward to your replies

Thank you

I made mine to the book, and didn't get any errors, although I used the imperial measurements.

Do you have the lower cylinder cover in place between the cylinder and standard?

Neil

Frank, I have my 10V at the same stage minus valve gear, i can measure later, what units would you prefer?