Cylinder Boring Techniques for Steam Engines

Steam fittings usually have 40tpi threads, or about 0.6mm pitch.

Neil

Hi Clive and Hansrudolf,

Thank you for correcting me. My guess at ASB was only a guess. I've had a look for EDS but I'm maybe using the http://www.brw.ch catalogue wrongly. I can find ECS and EDK but not EDS. Any help greatfully appreciated!

Thanks for the explaination on coarse and fine threads. So for a steam model am I right in thinking that there's general agreement that if metric threads are used then fine metric threads should be used for all threads on the model?

(Maybe I'm failing to understand the difference between fastners and fittings?)

Will

Nuts, bolts, screws, studs etc can be metric coarse and these would be termed fixings

Pipe unions, packing glands, water gauges etc are all termed fittings and are best with a fine thread.

J

Will, on that link page that you quoted, click on the title 'Drehwerkzuege IFANGER. This takes you to a page where you will see the different types of tool.

Click on the ECS tool and scroll down to the No 2 size.

The number you want is 311110.0700 @33.70Sf

The tool holder KG1 is 311560.0300 @28.40Sf

Clive

Hi Clive,

Thank you very much. I looked up those numbers and I think I can see why this tool would probably give a better finish. Looking at BRW's P&P costs I realised that the postage and packaging is fairly high compared to the cost of the tools so I might as well get everything I'll need for a while in one order...

... which brings me to the subject of my piston valves - I'd planned to drill successively larger holes using drills from CTC or Arc Eurotrade then finish with a machine reamer from CTC or Arc Eurotrade.

One person commented in John's forum on his piston valve (spool valve) engine "It is essential that the drill be sharpened correctly, i.e., it's cutting edges must be accurate... Do not think for one minute that a brand new drill will be accurate... They should be, of course, but I have yet to come across many that are... in most cases they would need some correction.".

This makes me a bit uncertain. Should I use new drills from Arc Eurotrade or CTC? Should I order some drills from BRW? Are new drills from BRW any more or less likely to be accurate than new drills from CTC or Arc Eurotrade?

I don't have a drill sharpening jig and my guess is that the manufacturers could sharpen the drills to a much better precision than I could achieve by eye.

For the machine reamer for those critical piston valves, is there any benefit to buying one from BRW or will the machine reamers from CTC or Arc Eurotrade be good enough for my needs?

Will

Hello Will,

basically making the steam valves does not need critical accuracy, drills make a hole and reamers clean up holes so you then make the spool to fit the hole. No big deal really as if you make a mistake just re-make another piece untii you get it how you want.

I would buy from Brutsch Reugger, they supply excellent quality tools and drills and cutters. Many things we dont get in the UK. I used to sit and study the catalogue for hours, a page at a time just to get to know what was available.

Just do it how you feel and thats it, by becoming very critical you take the fun out of it.

Today I took delivery of a Seig X3 from Arceurotrades special deal. Its uncrated and sat on the garage floor and I have to shift it to the end and lift it up onto the bench, all 170Kilos of it.

Extras came with it, including a large machine vice and three 'Tin' cutters and a set of collets and a clamping kit. Well worth the money I think. Cant wait to get it running as I have jobs lined up already.

Initially it looks good and I can see things I can improve later. I will fit a measuring system in time.

busy making a small pipe bender, having to adapt bits and change the design a bit. Its from an American source and the drwg. is a bit Naff !

Bees are working very hard now with this Indian Summer and as the Ivy has now flowered its their last chance to fill their combs for winter, and for me ! The Ivy is covered in insects of all types, bees, butterflies and hoverflies and of course wasps. There is a lot of Ivy about here where I live as the orchards are now derelict and Ivy takes over.

Clive

Hi Clive,

Thanks for the advice. I'll just use new drills for starting both cylinder and valves. From what you say, I'm guessing that maybe the person who posted re. the accuracy of drills was referring to generally available drills rather than the drills from specialist engineering suppliers that we're talking about.

I'll maybe get a reamer from BRW and one from one of the Chinese suppliers and see how they compare.

For 20mm cylinder bore I'm guessing a 5mm spool valve - or should I go a bit larger?

It feels like a really long journey - but I reckon you're right - I think I've got the understanding of tools and materials needed to bore the main cylinder and valve cylinder now.

Hope the X3 goes well. I'm spoiled by access to a milling machine beyond my wildest dreams at the moment - don't want to think about what I'll do if I have to move away from it!

Good that the ivy is supplying nectar. Shame about the derelict orchards - English and Scottish apples are better than imported ones.

An infestation of caterpillars on my kohlrabi and romanesco here but welcome good weather

Hi Michael,

The first project is a re-build of the wreckage of an S50 from ebay. The second (more difficult) is a piston valve (spool valve) engine built from stock. The only diagrams are sketched on paper and generously poked by oily fingers. If you know of any good open source CAD software I could use that to re-draw them.

Will

Will you could save a bit of money and make the holder yourself, I think the majority of us have managed perfecly well with a piece of square bar drilled length ways to suit the tool and a saw cut down one side which is basically all that holder is

Have a look at Draftsight for free CAD

J

Will, if its a freelance engine then give yorself a bit of leeway on the piston valve/spool valve. 5mm may not be enough so allow a bit of metal so you could enlarge it if its no good. As its in the design stage it should be no problem.

Re. the mill, it does not go! I got it up on the bench all 160Kg with the help of 2 Sons and plugged in an 'Zilch' just a warning light. Have checked the fuse and its OK so will investigate further tomorrow.

If you make your own tool holder like Jason has shown, the shank size is 8mm for the boring tool.

Clive

Edited By Clive Hartland on 08/09/2012 20:50:59

Hi Jason,

Thanks for the suggestion. I was going to ask about making the holder myself as a small project but I didn't like to complicate things. I wasn't sure why the diagram of the holder had two slits at right angles instead of just one. I don't have much experience using slitting saws so I'll look for an appropriate one for steel and run it past you first - or would I get away with just a hacksaw?

Found Draftsight and will download it.

Hi Clive,

What's the minimum width of gasket I can get away with at either end of the cylinder? One design I have in mind involves reducing the width at one side of the cylinder to mount the spool valve assembly to the side of the cylinder but I'm a little dubious about this and wonder if it may lead to a weak point in the cylinder head gasket and a higher risk of leakage.

I'll allow some extra metal in case the spool valve needs to be enlarged due to - er... - unforeseen circumstances...

Sorry to hear about the mill

Will

The tool holder that I have has 8mm at one end and 10mm at the other, I think that you could carefully hacksaw a slot Will.

Re the Mill, odd one as the safety guard closed the light comes on and open it goes off ! I have emailed Arceurotrade and hopefully get an answer in the morning. There is definately something amiss with it.

The cylinder, why not drop the cylinder head a mm or so into the bore and have a seperate one for the valve ? No crossover then. I think 1.5mm would be OK for seperation.

I have really come to a dead stop with my workshop as to get the Mill in I had to shift stuff about and now I cant find stuff as its not where I left it. Also lost the ring spanner for the lathe tool post, its gone missing, Awol.

Clive

Edited By Clive Hartland on 09/09/2012 21:22:35

A hack saw will be fine, you are only making a slot so that the holder can be compressed by the clamping screws in the tool post.

Actually if your tool post has a V based holder or one for round tools you won't even need the holder.

You could use a liquid gasket which really has no thickness.

Clive you need to switch off the bottom dial at the side,, rotate and press the safety switch so it's a green light not yellow, switch on bottom side dial then select forwards next dial up and then adjust speed, top dial. Once it's running just usevthevfwd/rev dial as on and off adjusting speed as needed either while running or stationary. You will have to start it up this way whenever the yellow light comes on, usually due to stalling or jamming the tool or hitting the emergency stop button on the front.

J

Edited By JasonB on 09/09/2012 22:16:47

Jason, Thank you for the detail, its a very peculiar system indeed. Apart from that all is good and I am pleased with the build and the motion screws. They have a bit of backlash but I will not adjust yet until they have had some use.

One problem is that I already have some tooling with a 10mm thread in the end of the taper but they dont list a drawbar with 10mm thread ! I think I will have to make one !

The vice supplied has to lugs that you screw into the base to fit in the slots on the table, the slots on table are 12mm but the lugs are 14mm. Wondering what to do ? Maybe some stepped lugs somewhere perhaps.

Clive

That will be the length of M10 studding with a nut on it you will be needing then I only got one bit of tooling thats M10 and I don't use it much. I keep meaning to make a decent one but the studding does the job. and has done for 5 years.

If you look at the end of the prep guide on ARCs site it gives the switch on proceedure, may have given it slightly wrong sitting in the lounge last night.

I don't use any lugs on my vice (K4) only takes a sec to clock it in.

J

Hi Jason,

When you say "liquid gasket" do you mean a gasket formed using just gasket glue and no gasket paper? There seems to be liquid gasket material that's cured before the parts are jointed and material that cures after the parts are jointed. I remember when I was young my father taught me that many mechanical problems could be solved by intelligent application of gasket glue and the tube of blue gasket glue was much-loved. How careful do I have to be to avoid the liquid gasket being too strong and making the model difficult to disassemble? Is there a liquid gasket material you'd recommend for models?

Working away with DraftSight.

Hi Clive,

It sounds like you've habit of a fraught few days with the mill. Reassuring to the rest of us that even with your expertise things occasionally don't go according to plan.

The crux of the problem I'm trying to solve at the moment is that I need to fit the cylinder and cylinder heads (round) to the piston valve assembly (flat). One way was to mill a flat on the outside of the cylinder then I've got two flat surfaces to join - but the flat on the side of the cylinder along the length of the cylinder means a reduced gasket width at the flat part where the cylinder head and cylinder meet. Another option would be to machine a curved surface on the valve block with the same radius as the outside of the cylinder and then join these two surfaces - I'm guessing that might be difficult to do accurately enough though. Thought of brazing them together but the heat might distort the carefully-bored cylinder.

They must have put the switch-on procedure at the back of the book to discourage anyone from switching it on without striping, cleaning and reassembling it first

Will

Hello Will, First off, I would silver solder the two parts together and then lap the bores afterwards.

This what I did with the two cylinder engine that I am working on now. Turning a radius is easy and would make a nice fit and look good ! Look in my Photo's to see.

The Mill is now running and it was my inability to see the sequence. Did the first job this afternoon doing a pipe bender.

Thinking, why not use an 'O' ring to seal the head ?

Clive

Loctite make several suitable liquid gasket products, they are basically a silicon sealant, just a smear on the face then bolt it up. This is one I use.

Like clive says silver soldering the parts together will be the best method, I would leave a bit of metal on all surfaces and then you can treat the finished fabrication much like a casting and finish machine all surfaces. This one has a curved surface machined onto the valve block to suit the curve of the cylinder.

J

Hi Clive,

Thanks for the photos of your beautiful engine.

Thank you for your advice re. silver solder. I saw some paste silver solder and thought that it would be ideal for soldering the valve gear to the cylinder. When I saw the price (100 francs) I had to reconsider. Can anyone recommend a good place to buy this in smaller quantities at a more affordable price? (My memory from electronics was that paste solder always had a 'best-before' date so it was best to buy little and often rather than keeping a large stock for a long time.) For aesthetic reasons I'm trying to avoid bobby solder marks around where the cylinder and valve gear join which I think I might get if I use silver solder wire and flux.

An o-ring would be good for the head - better than gasket paper - I'll look into that in more detail.

Hi Jason,

Thanks for the link to the liquid gasket you use. I'll order some. It's not perfectly authentic but life's too short to fiddle around with gasket paper and I did enough of that when I was a child anyway.

Thank you for your photo - it give me confidence that this can be done. How did you machine the curved surface on the valve block? (I wasn't sure how to get the final radius exactly correct - maybe a boring tool or an accurate endmill?)

Hi Michael,

I agree - the monobloc design is certainly easier - though it is aesthetically pleasing to have a round cylinder. John's design on paddle ducks uses a square cylinder block and a square valve block and it looks good.

I think if I were building an engine like this full scale I'd start by planning some castings! I don't have the skills or equipment needed to cast metal though. Another option would be to buy castings but I'd like to make something which could be made again in 30 years without having to worry about whether the firm making the castings had gone out of business or changed their designs - hence the decision to use stock even though that would be a very bad way to build a full sized engine.

I think a bit about a mill engine I remember from when I was young (gone now).

I should try to explain some of the method in the madness of my design:

I'm trying to keep the steam path from the valve to the the cylinder as short as possible because both hot incoming and cold exhaust steam will be passing through this path and I'd like to try to minimise transfer of heat between the two. (I don't have the skills to make full Corliss valve gear unfortunately.) I'm also trying to keep the cross sectional area of the steam ways roughly constant until the steam expands into the cylinder where it can expand and do some work.

Will

The curve was cut with a boring head in the mill, the valve block just proud of one side of the vice. Don't have a picture of the exact process but this will give you an idea. The boring head is set so it swings the right radius and then the work advanced into the tool until the curve is of the right depth.

Personally I would us estick solder not the paste.

J

Edited By JasonB on 12/09/2012 07:29:05

Will, with enough heat you should be able to silver solder the combination without leaving blobs, if you get blobs you are applying the stick too early and melting the stick in the flame.

The job should be hot enough to melt the stick ,and if you have applied the flux properly the silver solder will immediately fill the join.

I am with Jason on the solder, use a stick and forget the paste. Paste is used for induction brazing where items are heated in an induction oven and the paste then is gap filling. Not for flame soldering.

If you plan your maching so that you get a 'Procedure' of work done instead of a hap hazard system then you will find that the work will proceed steadily and accurately. Plan it all ahead and see how it works out.

My next project is a jig to hold the Planer blades so that I can sharpen them on the Worden tool and cutter grinder. I can achieve the 30deg angle in the jig so i only need to clamp it to the table.

Clive