Start your holes using a 3-flute milling cutter, to a depth of [say] 3/16” or more.

MichaelG.

This is not a Stuart pump but a similar design could be used.  All holes were drilled square to the faces and a slot milled at the end to transfer steam to the bore.

Is there enough room to fit  liner to recover the cylinder? It need only be say 1mm thick, and can be loctited in. Then restart the holes with a slot drill.

Just had an identical problem myself and as Duncan and Noel have suggested, got a length of K&S tubing as a + 0.032″ liner and stuck it in with Loctite 603. I like K&S because it is pretty much dead to size and so no need to do a rebore.

Mick

I “inherited”a pair of part machined cylinders which have proved to be a bit of a nightmare in that the top of the cyinder bore is only 5/32″ from the valve face. This caused problems in drilling the 1/16″ steam passages. Sod’s law being the default in my workshop, I managed to drill 3 of the passages in each cylinder perfectly OK but the fourth passage in each cylinder breached the cylinder bore. It would probably been quicker to fashion two more cylinders from the solid but ever the optimist thought I would have a go at a rescue.

So at this stage I was probably in the same situation as David. The cylinder bores are 1/2″ so I reamed them out to 17/32″ (handy, that reamer) to take 17/32″ K&S tubing.Once reamed the steam passages were visible when squinting down the bore so carefully needle filed them to just over 1/16″. Then thinking ahead to the fitting of the K&S liner I drilled through the exhaust hole in the valve face (1/8″) straight through the cylinder and out through the bottom. In my thinking this was to allow for the addition of extra Loctite to seal the liner in whilst preserving the steam passages.  Then the liner was coated with Loctite 603 which is a bit less viscous than 638 and the liner pushed in by hand. At intervals I stuck a piece of nylon bristle up the steam passages to keep them clear of Loctite. Subsequent fiddling with a 1/16″ reamer cleared any remaining adhesive. Extra 603 was inserted into the 1/8″ holes and a surprising amount was absorbed.

At this stage I was reasonably satisfied that the liner and steam passages were sealed. After letting it set for a couple of days I tested the steam passages with soapy water and compressed air at 60 psi. I had to obviously ensure that there was no leakage between the steam passages feeding each end of the cylinder. There was not, although I have to admit the test was a bit rudimentary.

There is still a problem. Whilst I cannot discern a leakage between the fore an aft steam passages and the exhaust drilling at workshop temperatures, live steam at a nominal 60psi might be a different matter. At 60psi the steam temperature is of the order of c.150 deg.C. Loctite 603/638 has a working temperature of the same order although I am heartened by the advice that to dissociate components held together by these adhesives requires heating to a whopping 250 degC. Is this overkill?

Troubled by the thought that I might put everything together and then find a leakage, I pondered on. My main concern was whether the adhesive between the liner and steam passages would eventually fail. I wondered whether a liner in the steam passages would solve the problem. I found (and ordered) a length of 2mm od stainless steel capillary tubing with a wall thickness of 0.2mm which would give me an orifice of 1/16”. I have not yet received the tubing but I have successfully reamed out the steam passages to 2mm in anticipation.

As mentioned earlier I could have made two new cylinders from the solid in half the time I have spent messing about with these two but I do like experimenting and trying out unorthodox methods Purists will no doubt throw their hands up in horror and demand that I resign from the Forum and I would find it difficult to argue against that. Wish me luck. (New Year resolution : don’t take on any more part machined projects).

Mick

I am a great fan of Loctite products which for me, have always performed well up to spec. However I am always wary of Sod’s Law as mentioned above. I have a question though, which would probably justify a thread of its own. Are all methacrylate type adhesives much the same, in the way that gas, water and electricity in our houses is the same whoever bills you for it?

Mick