The Bolton No 5 Vertical Open Column Steam Engine

[MJM460]

Hi Delta tango, I must admit that at the end of the work day, I had no energy for workshop activities, though occasionally had a little go at model boat building.  But nothing spectacular.

Good to know your procedure for drilling and tapping, I have tried it both ways and will stick with that now.  Though I think in this case the problem was I had not secured the chest in the right place well enough, and something moved. 

Hi Bear, glad my thread prompted an idea for you.  I am sure that ideas will go both ways before we are finished.  I did omit mentioning that part of the problem with holding the cover to machine that flat side was that the sides of the casting sloped.  I believe it is necessary to assist removing the cast part from the mould, but I had to square those sides before I could securely hold such a thin component.  Also, I did not try to thin it down to the drawing dimension of 2.5 mm, a bit of extra metal won’t get in the way of anything.

Hi Gary, sort of got away with it in that the evidence will be covered by the bolt heads/nuts, But something to try and avoid next time.

Today I set up the cylinder with the steam chest and cover firmly bolted in place, and faced the sides flush with each other and the cylinder edges.  This required a bit of thought to pack everything square and bridge the bolt heads, but it came out nicely.  I really like that little facing cutter with its integral MT3 arbour, nice and rigid with minimum overhang.

That went quite quickly so I centered the rotary table under the mill spindle, and turned up a dummy piston to locate the cylinder for drilling the cylinder head bolts.  The top head was finished except for the bolt holes when I received it, so that part was easy.  I sorted a clamping method to hold the head in place and squared the port face to the table side with the table set on zero degrees.  I wanted the bolts on the 45 degree positions to avoid meeting the steam passages in the cylinder which are on centre line.

I had to stop there.  I had suspected for a while that the head bolts would interfere with the steam chest studs, and needed to do some calculations to decide how to solve the problem, and of course I had not yet done those calculations.  It was not really obvious from the plans.  Despite 5 views of the cylinder, the two sets of bolts were not shown together on any one of those views.  But you can see it in the photo.  It could be the cumulative result of the metric conversion, who knows?   Bottom head will have the same problem.

So this evening I have explored the possible solutions on paper, changing the bolt circle, changing the number of bolts in the circle, or moving the bolt positions to give a satisfactory clearance.  I decided to shift the two offending head bolts apart to lie on 54 degrees instead of 45.  When I draw it out, it does not look as bad as I feared, and looks by far the best of the options I have  considered.  The head is thick enough that the slightly wider spacing is unlikely to be a problem.  It will also work on the bottom head.  So that is the plan for tomorrow.

Thanks to all for looking in.

MJM460

[Don1966]

Following along MJ and just catching up. Nice work all around!....


 
Don

[MJM460]

Hi Don, thanks for looking in, I really appreciate your comments.

With the decision on head bolt locations settled, and my trusty ARO set up to offset the rotary table by the bolt circle radius, the top head was soon drilled and the cylinder drilled and tapped, and all the holes were in the right place.

The bottom head is integral with the table that supports the cylinder on top of those columns.  It had already been mostly machined, and I decided that I wanted to retain that remaining cast surface to remind me of where it all came from.  I mainly just had to set it up on edge and pack the corners carefully so I could machine that straight side to use as an orientation reference.   It was a bit proud near the centre, but once it was sitting straight, a light skim gave a nice straight  edge.  The bolt holes landed on the raw casting surface so I spot faced the four locations to let the the bolt heads sit square, and again all the holes were soon drilled and tapped.  Two shots of the cylinder show both heads bolted in place.  Nice to achieve that point, because there are only a few grammes of swarf to show for a days work.

That looks like another milestone and an opportunity for a family shot.  The three remaining castings snuck in, but the valve casting missed the photo op.  Feeling like real progress, though there are some tricky details in the remaining components.  However, the completed items so far are starting to show what the engine will look like.  The piston and columns are from barstock.

A number of tiny but vital items to complete the cylinder group will occupy me for the next few days.  Some quite fiddly detailed work in those vital parts.  They will make or break the project, as I do expect it to run.

Thanks for looking in,

MJM460

[gary.a.ayres]

Great progress, MJM.
I like the way you have deliberately left a few of the casting surfaces 'raw'.
That's a neat little facemill.
BTW, what kind of milling machine do you have?

[MJM460]

Thanks Gary.  My thinking on the casting surfaces is that if I have to machine all over, it would have been easier to start with barstock and have regular surfaces for reference and to hold, especially on the smaller components.  So I am mainly machining where it is necessary for function, and perhaps paint with maybe just a little fettling with files or wire brushing for the remainder.  I am sure I will be asking for suggestions in due course.

The mill is home branded from the big blue warehouse that operates here and in NZ.  It looks a bit like the Grizzly, without some of the refinements.  Six geared speeds, dovetail column, MT3 quill, and no belts.  Not fancy but nice and solid.   I am quite pleased with it.  I have put a digital readout on the quill which is a great first step, but would like the full DRO system similar to what Propforward has just installed, with or without the extra column function.  I seem to have enough quill travel for my needs, so perhaps it has a bit more vertical room than the Grizzly.  The table is quite long so I leave the vice and rotary table on most of the time.  I am removing the rotary table more often these days as I learn to clamp down on the table and gain experience, but it’s easier to set up than re-setting the vice square.

MJM460

[gary.a.ayres]

Yes, and I think the 'natural' cast surface is a really good look too.

I think I know the kind of mill you mean. In my experience these Far Eastern import machines have improved greatly over the past few years. As you suggest, they lack the elegant curves of old Western machines, but they do the job.

Once you have a DRO on 3 axes you'll never look back. I was lucky in that my mill in my home (i.e. not France) workshop has a small built-in DRO on the quill, so I only needed to convert X and Y. I have never regretted it. I have mainly used it for finding the centre with the half function, which in conjunction with an electronic edge finder works a treat, and for accurately positioning holes. I haven't tried it for pitch circles etc. yet - that pleasure is still to come.

[MJM460]

Hi Gary, yes, not the elegance of the older machines, but with the dovetail slide on the column and plenty of mass, it is a nice solid and capable machine even if it is a bit basic.  And it makes a marvellous drill press.

Another day for small parts.  First the fork for the end of the valve rod. 

I machined this from the end of a 10 mm brass rod.  First I turned the round part, then drilled and tapped the end for the rod.  Then I transferred the collet to the collet block to mill the square end and the 2.5 mm wide slot. 

For the slot I followed my normal procedure of plunging the end mill at 0.25 mm intervals then fed the mill sideways to clean up the edges.  The block made turning 90 degrees easy to orient the hole for the pin.

Hmmm.  Sorry about the focus.  I have more to learn about the limits of the macro setting on my camera.  Note for next time.

I made up two filing buttons and held the tiny component in a 5 mm collet for filing.  Takes longer to describe than to complete.  So I was able to make the valve rod as well. 

The valve rod took a little more thought.  The ISO standard M3 thread pitch is 0.5 mm (or about 50 tpi).  To adjust the valve position on the rod, the minimum adjustment is half a turn of the valve nut, or 0.25 mm which feels a bit much on such a small engine.  In the absence of left handed taps and die, I machined the end of the rod to 2.5 mm, for which the thread is 0.45 mm.  This enables much finer adjustment by turning the rod.  I increased the length of thread on the fork end to accomodate a lock nut.

While I was threading rods I made up the piston rod, and threaded the end of a rod for the crosshead guide. 

Going well, so I turned the piston on the end of some 3/4” bronze bar.  The cylinder was already 5/8” or a touch over 15.8 mm.  So I left the piston 16 mm so I could skim it to final size after mounting on the piston rod.   I parted it off, then held it in the 16 mm collet, and after checking the fit of the thread, held the piston rod in the tail stock chuck, and screwed the rod in firmly with a drop of loctite, following the guide book, and left it overnight to cure.

Not much to show for a days work, but important parts, so good progress.

Thanks to all for looking in.

MJM460

[steam guy willy]

Hi, good progress, and you have some nice tooling there...

Willy

[gary.a.ayres]

Nice work.

[MJM460]

Thanks Willy, collets are perhaps not the most exciting tools to purchase, but they are really useful, and I am glad that I lashed out some years ago.  The gold standard for getting things concentric is still to turn all the relevant diameters at one setting, but these collets certainly seem to give adequate concentricity for many purposes.  And the blocks make the system so versatile. 

Thanks again Gary. 

Today I worked on the crosshead.  A tiny component in this design.  I found that the vertical sides cleaned up nicely enough with a file.  The sides were parallel, and after a few strokes with the file, could be held in the vice.  But nearly the whole casting was deep between the jaws.  I moved it around with tweezers.  I machined the lower edge on the guide bar side, then clamped the casting down on a tooling plate to machine the tab, then drill and reamed the little end pin hole.

The only critical feature is that the tapped hole for the piston rod, and the reamed hole for the slide bar should be parallel.  To achieve this, I set the casting in the vice with the top surface as close to parallel as I could, and took a light skim over the top surface to make it square and flat.  First I lined up to drill and tap the hole for the piston rod.  Then I moved the mill table across 8 mm (per the drawing) to drill and ream the guide bar hole.

For the next step, I needed that piston and rod in the cylinder.  I released them from where they had been sitting while the loctite set, held the piston rod in the appropriate collet and skimmed the final piston diameter.  As I approached the right diameter, I kept stopping the lathe and trying the fit in the cylinder, and when it just seemed to be entering, but would not quite, I quit and used a wrap of 400 grit wet and dry to just polish off the last bit until the piston would just slide in.  It’s too easy to take one cut too many.

The piston fit is a little tighter than my previous attempts.  I like to think it is a better fit.  I think it will quite quickly wear in.  I just hope it is not too tight, but both components are bronze, so even though probably slightly different composition, I am hoping not to much difference in thermal expansion.

Now with the piston fitting the cylinder, I could screw the crosshead on the end of the rod, and with the piston clamped down on the plate on the rotary table, I was able to spot through the guide bar hole to properly locate the guide bar in the bottom head. 

The crosshead slides up and down nicely on the guide bar, so I am calling it a success at this stage.  I have left the guide bar over length, as I would really like to add a lower support, mounted on the columns.  But I don’t yet know if there will be sufficient clearance from the conrod at its closest point.  I can cut it shorter later if necessary.

That leaves the valve and valve nut to do for the cylinder group.  Something for me to look forward to for tomorrow.

Thanks to all for looking in,

MJM460

[scc]

Nice progress 

[Bear]

I am learning plenty from this build thread. Thank's, MJM

[MJM460]

Thanks SCC and Bear.  Bear, I am fortunate to have a very experienced mentor who has taught me some ways of doing these things.  I am sure he will also be pleased that you are also learning something from what he has taught me.

Today the valve, which is another casting.  In my advance study of the plans I decided to check the valve dimensions and travel very carefully, as there are some critical relationships between valve travel and valve dimensions.  And all those metric conversions.  Plus me using larger cutters for the ports.  The drawing dimensions gave a valve that was long enough to just cover the ports, but the travel provided by the eccentric would only just uncover about 1.5 mm of the valve ports, and that with almost no lap.  I played around with the figures and found the valve throw really needed to be 6 mm.  Unfortunately I have already made the eccentric with the drawing throw of 2 mm.  A pity.  I could have made it 3 mm had I explored this issue earlier.  A closer look revealed that the dimension for the eccentric throw was 7/64, which is 2.78 mm, but the drawing showed  2 mm.   No reason this could not have been 2.8, but this is the only conversion I have discovered so far which is so far out. 

Fortunately, though a casting was provided for the eccentric it can easily be made out of round bronze bar, and I have some of the appropriate diameter.  So plan B is to make a new one.  After some more playing around with the figures, I decided on 2.5 mm throw for 5 mm valve travel.  The steam chest was a bit tight for 6 mm travel.  With about 1.1 mm lap this will open the valve port to about 1.4 mm and governor approximately 80% cutoff.  To some extent I think lap and valve opening can be exchanged during valve setting, and there are many ideas on what the ideal values would be, but I think this will work.  Then it was relatively straightforward to come up with the required valve dimensions.  And the casting seemed to have adequate metal.  With that done some days ago, I had what I needed to start machining  today.

It’s another tiny part.  The sides were sloping so that would not be good for holding.  Like the steam chest cover it was all quite thin, so hard to support in the vice. 

A few strokes with the file gave a surface on the valve face that sat flat without rocking, and the casting seemed fairly square.  So I put the valve face against the fixed jaw and sat the part on edge.  This allowed me to machine the edge square.  I turned the part over to put that machined flat on a parallel.  I machined the new top edge then shifted the table over so I could machine the side of top of the valve square to make a little step.  Then without moving the table turned the valve over and machined the matching step in the second side.  Awkward to describe, I hope the photos show it.  Then I sat the valve, face up with those steps on the vice jaws and clamped a stop to prevent any movement parallel to the jaws.

I faced the top surface and then used the largest cutter that would fit in the required cavity to rough out the cavity.  Then I fitted the 2 mm cutter and squared out the cavity.  The 1 mm remaining corner radius is close to the port end shape anyway.  My trusty ARO set up and the longitudinal stops helped with getting the dimensions required.

When the exhaust cavity was machined out, I turned the valve over and machined the slots for the valve rod and nut. 

That’s enough watch carving for a day.  The nut is even smaller to tackle for tomorrow.

Thanks to all for looking in,

MJM460

[MJM460]

Not much time in the shop today.  Phone calls, grocery orders, exercise, Pilates by zoom (would you believe “zoomilates”?)  Amazing how long it all takes in lockdown.  But I got the valve nut made.  Not very big, but very important.

The slot in the valve is 3 mm, and the nut 6 mm x 10 mm long.  And I only have 1/8” brass to make it from.  Am I the only one on the forum who does not have a 1/8” milling cutter?

I cut a piece 10 mm long from my bar.  This will allow me to machine a nut on each end with enough material in the centre to hold in the vice.   The length of the bar is too long to be manageable if I leave cutting until after machining.

With the cut off piece gripped vertically in the vice I could machine a strip across the end to 3 mm for the nut.  Then I turned it end for end and machined the other end, also to 3 mm so I can make two nuts.  Finally I drilled and tapped each end for the valve rod.

I used a piece of clear Perspex and the feeler gauges to check the valve lift.  First try the valve stood proud, which made it tricky to measure.  I ended up using two feeler gauges, one each side of the valve.  I then machined a touch of the edge of the nut.  I did the second one while I was at it.  I still find trimming the side of such a small component tricky.  There is very little room to make a cut then measure for a second cut.  Despite using cigarette paper to detect the tool touching the surface, I still too often get a few hundredths out.  I will see how it goes.  I can make another nut if necessary, or possibly fill a gap with a little strip of shim if the lift is too high.  Time will tell.

I will get back to making another eccentric tomorrow.

Thanks to all for looking in,

MJM460

[derekwarner]

You know the inverse...."if you ever lost your Day Job.........you could well get a start as a model machinist"  : 

Watching on, on a daily basis as usual MJM........more than suitably impressed 

Derek