Stuart V10 Drilling initial 3/32 hole in valve chest

[Frank SmallParticipant @franksmall87776]

[Frank SmallParticipant @franksmall87776]

Hi

I am building a Stuart V10 steam engine with little difficulty till now. The problem is to drill the initial 3/32 hole in the valve chest for the valve shaft. This has to be perfectly aligned in all planes or the efficiency of the valve is greatly reduced. There is no problem in drilling the initial part of the hole in the bottom  of the chest however this drill has then got to continue a further 25mm aprox  unsupported before drilling the upper hole in the chest to support the shaft, any error is therefore amplified. It is impossible to  punch a guide hole  at this point so you are relying on the drill not to wander. The guide suggests the  point of entry be filed flat to minimise that danger but even then it is a bit of a hit or miss affair.

I tried drilling from both ends as an experiment with a view to plugging the entry hole at the top of the chest. This was only slightly more successful.

I am sure there are plenty of people who have successfully built this or similar engines and I would be grateful if you could offer any suggestions

Thank you for your interest

Regards

FS

[Sub MandrelParticipant @submandrel]

Hi Frank,

 

I had the little book by Andrew Smith, but i can’t find it. If memory serves  me right I held the valve chest in my four-jaw chuck, then using the tailstock chuck I centred the hole, then drilled undersized and reamed it to full diameter. I then had a pretty accurate first hole which guided the drill accurately into the second.

 

Don’t tell anyone, but assuming the valve is allowed the vertical and sideways play it needs on the rod, then if the rod is slightly out of true it doesn’t really matter. The biggest source of problems is making the hole in the gland cover too small – it should be big enough not to bind on the valve rod in the slightest.

 

Finally, I think the ‘flatten the entry point’ bit refers to drilling the steam passages not the valve rod holes. I did these by supporting the cylinder in a wooden cradel shaped like a ‘crooked L’ to get the correct angle.

 

Neil

[John ShepherdParticipant @johnshepherd38883]

Frank

I have just had a look at Andrew Smiths book and it says:

‘Face and turn the gland boss to size, centre drill, then drill through with 3/32 inch dill and continue to the back of the valve chest for about 10mm. Re-drill and ream the gland boss to 1/8 inch then open with a 7/32 or 5.5 mm drill and tap 1/4 inch by 32 tpi)’

 

From memory I followed this method without a problem but I can appreciate the concern you have.

[steve 1Participant @steve1]

Frank

  To support the drill you can fill the rectangular void with car body filler and then drill the hole through it.Then just finish the gland end complete.The car filler can be drilled out when done.

 

  steve

[JasonBModerator @jasonb]

If the gland boss is going to be opened out to 1/8″ , drill and ream the boss hole then use a long series No 1 center drill to start the 3/32nd hole at the other end. You can get them upto 6″ long but I used a 3″ one on my traction engine valve rod and thats a bigger job than a stuart.

 

Jason

[Frank SmallParticipant @franksmall87776]

Hi Everyone,

Many thanks for ur hints and guidance. I now feel confident that I can now succeed wehen I next tackle the job

Many Thanks

FS

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