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My version of Bogstandard's Paddleducks engine build log

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spuddevans:
I just thought I would post up a copy of the build log of Bog's famous Paddleducks marine engine. The plans are available at a couple of places including Here

I hope that this is in the right section, if not please accept my apologies. I also apologise for the sheer size of this log, it turned out a real epic tome.


Part 1.

I have finally got round to making a start on my next project, and while tempted to do a Rocking engine, I had to stick with with my initial plan of building

Bog's Paddleducks engine.

So I had previously got some materials gathered for this build, and not having any cast iron at all, but having a brass block that was itching to be reduced

to a nice cylinder-shaped block, I decided to use brass for the cylinder.

Here is the raw brass block, the other dimensions are 25mm thick and 50mm high.



I then used my very expensive marking dye system and used my vernier caliper to mark out a rough shape to then transfer to my very expensive bandsaw

(my right arm)



So I next ground up a tiny toolsteel for my tiny flycutter as per the Bogstandard curved profile that I read about. This is my second attempt at grinding the

curved shaped flycutter, I have a larger flycutter that doesnt cut as well as this latest attempt, practice I guess  ::)


So with this newly ground up tool I am totally impressed with it. The finish on brass is soo silky smooth!!! Compare it to using a end-mill and there is just no

contest. I also learnt that my X2's Z axis is made out of a very tough but flexible form of spagetti. I am intending on re-inforcing the upright column, but in

the meantime I have to be mindful of taking lighter cuts.



I have an even smaller flycutter, they're so dinky.

So after squaring and sizing the 4 sides I then squared off the 2 ends with a 4-flute mill.



It's amazing how the little brass chippings/shavings get everywhere (especially down the neck of my teeshirt, and they are pretty hot too) My workbench

was (and still is) covered with a golden snowstorm.



I then had to smooth the 2 ends with some 360grit wet+dry placed on a granite plate to try and get them to match the smooth flycutter-ed surfaces.

And here it is, the first part made to size (well within 0.02mm on 2 dimensions and dead on the 3rd )


 If you want to see larger versions of the pictures of this build click here

I got some time in the workshop today, and started out by Tramming my mill. A frustrating exercise as when you think it is in tram and then tighten the big

nut holding the column in place, the act of tightening will throw the mill out of tram again. 

After tramming the mill I started marking up the main block for the cylinder holes, then clamped the block in the vice on top of some 1/2" parallels. I then

used the edge finder to locate the hole centres as accurately as possible, and then centre drilled them. Working out the graduations on the mills

handwheels it worked out at 18 full turns to traverse from the center of one hole to the center of the other.



I then drilled and then opened out the holes starting with a 4mm drill, then 6mm, 7mm, 8mm, 8.5mm 8.7mm, 8.8mm, 8.9mm and then finally reamed the

bores to 9mm. ( I would have drilled/reamed them 10mm but I dont have a 10mm reamer, but I do have a 9mm reamer so I figured that making the bores

slightly smaller would not make a big difference. I'll just make the pistons to match )



And this is the end result.



I then turned (groan) to making the Top-Caps. I chucked up a length of some unknown steel ( to contrast with the brass ) in my 4jaw ( my 3jaw

self-centering has too small a bore to allow the length to go into the headstock in order to use it without cutting it down ) Turned a section down to 18mm

diameter, put a 9mm spigot on to fit the bore, then parted it off, and then repeated for the other.



Then I mounted my ER32 chuck, the 18mm collet and mounted the topcap in it to turn the "Top" side. The 2nd one turned out better, practice makes

perfect better.


Here's what they look like mounted on the block.





Then I started on the packing nuts, I chucked up some 8mm hex brass bar, turned a 6mm section and then threaded it.



Then we parted it off and did the same again.



The only thing that bothers me a bit about these is that, because of the width of my parting tool there isnt much thread left, about 2.5-3 turns on each nut.


Then we cut off some 22mm round brass bar for the packing gland, chucked it up and turned down to 18mm.  Then we turned down an 8mm section and

put a center drill in the chuck and almost drilled it.



I then started off by grinding up a new undercutting tool, about 0.8mm wide, here shown with one of the previously made gland adjustment screws for

comparison



Then I chucked up the brass hex bar in the 3jaw and turned down a little section for threading using a 6mm round profiling tool.



Then I used the new undercutting tool to, umm, ........ undercut a groove



and then single point threaded a M6 thread



And within a short time I had a little family made up.



After changing over to the ER32 collet chuck that still had the packing gland mounted in it. I centre drilled, drilled and then tapped M6 to 5mm depth as per

the plans. ( I had to grind down the tips of the taps as they were quite long and tapered to a point, too long to use in this application)

Then I mounted one of the gland screws and screwed it well in, then tidied up the backside of the screw, and then drilled the two pieces at once to keep

concentricity, I drilled them 2.2mm then 2.9mm and finally 3mm.



Then I removed the adjusting screw, then reversed the packing gland and turned down the reverse side to fit the bore. This is the result.



Here is what it looks like in its place.





So I got a little more done today. I started by making the 2nd packing gland. I didnt take any pics of this, but here's one of the 2 packing glands in place.



I then made a start on the piston assembly, starting by roughing the pistons to within 1mm of final size, drilled and then tapped M2.5 and then bored

2.5mm 1mm deep to allow the rod to seat properly.



then parted off approx 6mm and repeated to make the other piston.



I then started on the rods, and following on from the single point threading thread I was determined to single point it. However, the chart of gears for my

lathe did not list 0.45mm pitch as an option. After some not inconsiderable head scratching and vain calculations I gave up and came indoors to download

Mklotz's "Change" program, entered my leadscrew pitch and the change gears that I have and it gave me a solution.

Back out to the workshop and a few mins later I was ready to cut. 1st off I centre drilled the end of the rod and brought up the tailstock with my new

ball-raced center. Then it was just a case of making a few passes to get to near depth.



Then I removed the tailstock and finished the thread form off with a Die.

Then did it again for the other piston. Then I assembled the bits with some loctite and set them aside to set.

spuddevans:
Part 2.


Well having the day off today I was able to steal a few hours in the playroom workshop.

I started off with the pistons, I chucked one up in the ER32 collet.



I then turned it to 6mm length, turned the diameter to just be able to fit into the bore, then installed an oil groove. Then I used some 600grit and then

1000grit wet+dry to polish the piston to be a nice snug fit in the bore. ( I also eased the sharp edges off with the same 600grit )


I did the same to the other piston, this one was ever-so-slightly smaller ( to match the ever-so-slightly smaller bore ), and so I marked both the pistons and

the bores so that I can match them up again, I used a couple of pop-marks on each part.



I then turned my attention to the crossheads, and after hacksawing some brass to make some smaller brass, I started to clean up and square up the pieces,

and then to finally size them.



Here they are marked up and ready for drilling.



I didnt want to just rely on the markings, so I used my edge finder and then used the dials to get to the right position. I then drilled one hole before using

the dials to get to the next position. This might seem overkill, but one of the blocks of brass was just slightly smaller than the plans called for, so I marked

a datum face on both crossheads and indicated off this datum to get to the hole positions. This would make sure that the holes will be in exactly the right

places relative to each other ( if not relative to the sides of the block )



I then drilled the hole in the side of the blocks



Here are the 2 crossheads drilled and ready to mill. Can anyone spot the (almost catastrophic) Boo-Boo?



On the second block ( cunningly labeled "2" in the pic ) I drilled the 2.5mm hole correctly, I then moved over, using the dials, to the correct place on the

X-axis, and misread, or miscalculated, my dial position on the Y-axis and drilled the 4mm hole 0.5mm too close to the edge ( the centre was 3.5mm in from

the edge instead of the 4mm called for in the plans. )

Instantly thoughts of how I was going to rectify this sprang into mind, the 1st one being to silver solder a 4mm brass rod into the hole and then to re-bore in

the right place. But after I thought for a while it occurred to me that if I make the other 4mm hole out by the same error I can just position the crosshead

rods to match. Hence the numbering of the crossheads.



I started on shaping the crossheads. I used a plunge-cutting-rounding-over mini-router bit from my dremel-clone to shape it.



Then after centering it I cut it down both sides and the middle.



Then the other one, and then I marked them both up for milling.



Mounted in the vice on some parallels and cut down both sides of the fork.





Then I milled out the centre of the fork, opened out one hole from 3mm to 4mm, and then rounded off some edges and then spent a fair bit of time in

smoothing out with 360, 600, and then 1000 grit wet-n-dry, and then re-reamed the deep 4mm holes for the crosshead rods and tapped the M3 hole.





And here it is next to the unmilled crosshead block.





As you can see on the unmilled crosshead, I've drilled 2 6mm holes in order to get a nice curve profile between the upright guide portion and the fork part.

I had been toying with the idea of milling a couple of, say 2mm slots to expose part of the crosshead-rods, but I didnt have a 2mm or smaller cutter and I

wasnt sure if it would negatively effect the crossheads themselves.

That's all that I was able to get done today, the shaping took a little longer than I thought, but I didnt want to rush at it as it would be a real bummer to

mess up on one of these crossheads. I'll work on the 2nd crosshead over the weekend.

----------

This afternoon I got started on the 2nd crosshead. It is amazing how much quicker you can make a part when you know what you are doing ( well I sort of

know what I'm doing  :lol: ) This one went quickly and I managed to get a bit better finish of the tool on this one.

Here's the 2 finished crossheads.



Now, the observant of you may have noticed that when I made both the top-caps and the packing glands, I didnt drill them for mounting holes. Well after I

finished the crossheads, and feeling a little left out of the whole "I-made-a-jig-to-drill-these-parts" party, I made a jig to help drill these parts.  :D



The idea is to drill one hole through the relevent top plate or packing gland, insert brass pin into newly drilled hole and release vice and rotate 90degrees,

retighten the vice, drill again, and then from then on just take out the pin, rotate the topcap 90 degrees insert pin again and drill.





The jig made it very quick to drill the holes in alignment. The jig didnt take long to make, the centering of the square block of ali' in the 4jaw took the

longest.


So here is a pic of all the parts I've made so far.


As you can see, the topcaps are a little rough looking, so I may remake them at some later stage.

spuddevans:
Part 3.

Well I got just a little more done.

I marked up the main block for the steam ports, and realising that they are centrally aligned and are set in the same distance from the end I decided to use

my very high-tech vice stop to make drilling a lot easier. ( hey, I'm really getting into this whole "using jigs and stops to make machining easier" thing! ) 1st

up was center drilling the 4 ports, then drilling through to the cylinder bores.



Then, not yet having in my grubby little hands the 2mm brass sheet needed for the mounting plates, I skipped on a couple of steps in the plans to make

some of the little things. I made the 4 crosshead rods, well, when I say I made them I just cut some 4mm stainless rod to length and then drilled and

tapped one end.

Then I marked up the piston+rod assembly for cutting to length, chucked up a piston with the rod facing out of the ER32 collet and parted off to size, then

did the same to the other piston assembly. Then I single pointed a M3 thread on each piston rod and finished off the thread with a M3 die.

So here is a mockup of the crosshead rods in the crossheads, along with the threaded piston assemblies also mounted in the crossheads.



Well I made a little progress today (the emphasis being on "little")  I got some 2mm brass sheet and hacked off a section and then milled the 2 freshly cut

edges smooth and to size. I then blued ( well, blacked actually ) one surface with layout dye ( a big black marker from tescos ) and then spent a fair bit of

time marking out all the holes, remembering that I had to make an adjustment for one set of crosshead-rod-mounting-holes as I had drilled one crosshead

slightly incorrectly.




Just after taking that Pic I removed the piece from the vice and just made little centre punch marks ( more like "pop" marks actually ), then remounted it in

the vice and drilled all the small holes. For the 2 packing gland holes I drilled out as big as I had drills ( 13mm ) and then switched to my Boring bar setup.

While not ideal for this, it seemed to work ok, although a little slow. ( My boring bar is marked in imperial and I was working in metric, so progress was a

little slow as I approached final diameter as I didnt want to over-shoot if I could help it )

Here's the top-plate bored out, sitting on the main cylinder block and the packing glands sitting in place.



Next I have to drill and tap for the packing gland / top-cap mounting holes, and drill and tap for the mounting plate holes.

I started by milling out a recess on the mounting plate for the steam chests.

Then I drilled and tapped the cylinder block using a newly aquired tapping stand, I totally reccomend everyone either make or buy one, makes tapping so

much easier 

I only drilled and tapped the bottom of the block as I've decided to remake the top-caps as I messed up the holes on them.

I then did a little assembly. After a little polishing on one piston, ( on the rod not the actual piston, as the rod was slightly oversize ( about 0.04mm ) and

would not go through the packing gland ) I was able to assemble the pistons and packing glands into the cylinder, and then attach the mounting plate.

Then I assembled the crossheads and rods, and after a little fiddling and messing around, widening one set of crosshead-rod-holes a little, and ...... It

slides in and out !!! (ok a little stiff, but it still works)








Today I got started on remaking the topcaps, this time out of brass.

I started with a chunk of 22mm brass rod in the 3jaw to which I trued up the end and turned as much as could be reached down to 18mm.



I then mounted my ER32 chuck and reversed the brass rod into it and turned the rest of it down to 18mm. Then I turned down the top of the 1st topcap to

8mm appox.



I then extended the rod out a bit from the collet, and parted off leaving enough stock to be able to turn a spigot to fit the cylinder bore. Then I did the

exact same again for the 2nd topcap. Then I remounted the topcaps in a 8mm collet ( gripping the freshly turned 8mm top of the topcaps ) to turn the

spigot that would fit into the bore. I took off a fraction at a time, checking it against the cylinder bore, until it just fitted inside.

Then I got out my little jig mentioned earlier to drill the 4 holes in each of the topcaps. Then it was over to the cylinder block itself. Using the newly

(re)made topcaps I marked out the positions for the mounting holes, drilled them and then tapped them M2 using my tapping stand.



Then it was just a case of building all the parts back up again. Funnily enough, the crosshead/rod-assembly that took all the fiddling the 1st time I built it

up, took almost no fiddling this time to get moving. And wouldnt you know it, the one that went together easily last time, it took ages of fiddling and

enlarging of the rod mounting holes ( I hadnt enlarged this set of holes the 1st time ) 

But here is what the top looks like with the newly made topcaps.



Next it will be the bearing blocks. I am toying with the idea of using ball races in the bearing blocks, its only 4 ball races so the cost wouldnt be too bad.


I got started on making the bearing blocks. I took some square brass bar and chopped 4 pieces off it. I put the 4 bits in the vice on some parallels.



Now, I know that all 4 pieces came from the one bar, but I wanted to make sure that they each would be clamped tight so I put 4 little thin pieces of ali,

one inbetween the moving jaw and each block. Then I tightened up the vice as tight as I could, and gently flycut the surfaces.

After a while I ended up with this,



Then I set up my very delicate and expensive vice stop, and after marking up the bearing blocks I set about center drilling and then drilling 4.8mm and

then 5mm, all 4 blocks.



Resulting in this,



Now, getting impatient I carefully deburred the holes and whipped out a length of 5mm stainless rod and, aligning the blocks, I quickly shoved it through

and immediately tried to turn it. Imagine my joy to find the rod spun freely....... But hang on, it spins a bit too freely  :scratch:

And it kinda wobbles a bit too 

I immediately double checked the drill to make sure, yep it was 5mm. Then I checked the stainless rod with 1st calipers and then my digi micrometer,

spuddevans:
Part 4.

I started today working on the bearing blocks. I have decided to go with ball races, here they are nest to the blocks,



With the mill still set up from drilling the bearing blocks I 1st of all drilled through each block with a 5.5mm drill to give clearance, being careful to clean

the vice, parallels and vice stop between each operation to make sure the blocks went in the vice in exactly the same position.

Then I mounted a 7.5mm drill, set up a depth stop and drilled both sides of 2 bearing blocks and one side of each of the other 2 bearing blocks. ( when

drilling the double sided ones I was careful to deburr each side before re-clamping to drill the other side, drilling seemed to raise a burr that I fear

could've thrown off the accuracy )
I then followed up with a 8mm endmill to finish off both the diameter and the depth.



Here they are in the bearing blocks,



Anyway, I then marked, drilled and tapped the mounting holes on the bearing blocks. Then I turned down the bosses on the bearing blocks. I turned

bosses on both sides of the inner bearing blocks, and just the one face ( the one facing inwards ) of each of the outer bearing blocks.



I got a little more done today, started off by hacksawing a piece of 2mm brass for the baseplate, then sized it up on the mill. Then I slathered it with layout

dye and marked it up.



Then it was over to the mill and I drilled all the 3mm holes and then all the 2.5mm holes, then I mounted the bearing blocks and marked up for the cutouts.

Over to the mill again to mill out the cutouts.



The obligatory posed shot



I got a little more done today, somewhere inside both of these lumps of brass there are 4 crankwebs and a flywheel, my mission, should I choose to accept

it, is to find them.



So I hacked off a length of the long bar and chucked it in the lathe, faced it and turned it down to 28mm. Then I centre drilled and then drilled through

progressively to 4.9mm drills, then finished it off with a 5mm reamer. (I guess this was a little overkill but I thought is would result in a good fit for the

crankshaft)

I then chucked a 4.5mm drill in the tailstock the wrong way around and just positioned it so that it just stuck into the hole in the brass bar. Then I parted off

a 5mm section, and rather than it dropping into the swarf it just got caught on the backwards drill. Then repeat for the other crankwebs.



Then, after de-burring the parted off crank-webs, it was time to make another jig for drilling the holes for the big end pin and the little

compression-hinging-hole-thingy. I made the jig as per the instructions in the plans. I drilled all the 2.5mm holes first, then using the pin to lock the disc I

repositioned the x-axis and drilled all the 4mm holes.



And so I ended up with this,



You may notice that one of the crankwebs is not as good as the others. When parting off the carriage moved slightly, but it's not too bad ( a blind man on a

galloping horse would never notice) I think I might be able to salvage it.


Got a little bit more done today, spent a bit of time hunting around for a 0.5mm shim for setting up for milling the balanced areas of the crankwebs. Spent

about 15mins, but came up with nothing. Then I remembered the set of feeler gauges that I got years ago when I was building some guitars, ok they were

imperial, but with the help of a digi-mic I was able to sort out 2 pairs of feeler gauges that equaled 0.5mm.



After milling both sides I cut the slot on each crankweb. Then I drilled, counterbored and tapped M2.5 for the clamping screw.

Then I turned down some brass to make the flywheel.



Next is finishing off the flywheel, I'm a little undecided as to doing a lot to the visual design of it as, looking at pictures of the finished engine, the flywheel

is not as obvious as some other engines.





--- Quote from: NickG ---Presume the crank journals set 90 degrees apart on this engine? Do you have a method of achieving this or just by eye?

Nick

--- End quote ---

Hi Nick, yes, as I understand it ( and that is quite a statement  ) the cranks are set at 90degrees. I think that it is set by trial and error ( in my case, probably

more error than trial ) I could be in error in saying that, I have read through the plans a few times but I have the memory of a fish.

I got a bit more done today, worked on the flywheel recess.

I started off by re mounting the flywheel in the 3jaw, I wasnt too worried about it being precisely concentric. I ground up a new Hss blank to do the job and

then had at it.


I then changed tools to a 6mm round profile and put a little radius to take the sharp edges off.


Then I had to tackle putting the 3 holes in the flywheel. This meant breaking out the rotary table. I now have yet another item on my "To Make" list, as I

need a means to attach my 3jaw self-centering chuck to the rotary table. But until then I have to make do with a slightly more convoluted means of

attaching items to it.

So then, how does one secure a round item, ie my flywheel, to the Ro-Tab and get it centred up?

Well this is how I did it, there's probably many other ways, and maybe easier ones too 


I eyeballed the flywheel into the center and attached with 2 clamps, but only tightened them thumb tight. Then mount a Dti on a mag base mounted on the

table, with the finger set against the inside of the 5mm mounting hole. Then just rotate the table and "bump" the flywheel ( or whatever you are centering )

until the Dti reads the same all the way round the flywheel, or within reason ( I haven't finished the outer edge of the flywheel yet, so it still has some

marks which bounced the Dti needle a bit, but I just got the reading at an average all the way round it )

Then drilled the three 4mm holes at 120degrees spacing.

Then I drilled and tapped m3 for the securing screw.


And this is the resulting flywheel,



Got a bit more done, started work on the crankshaft rods, I only had 5mm stainless ( got some 4mm stainless rod on the way ) so I just cut the 3 lengths of

the 5mm, sized them on the lathe and then polished them while still on the lathe with some wet-n-dry.

Then I set up the spin indexer on the mill and milled the 2 flats on the longer 5mm rod, and then the flat on the other one.



Then I moved on to the eccentrics, I grabbed some steel and chucked it on the lathe. Turned it down to 18mm and installed the 4mm groove's on each

eccentric.



Got a bit more done today, got some 4mm stainless rod so I cut off 2 pieces for the big end pins.

Then I turned to the eccentrics, and the slight problem as how to hold them in order to drill the offset hole in both of them. It occured to me to try clamping

my little 3 jaw self-centering chuck directly onto the mill table, and what do you know, it worked!!


Then after drilling both, it was back over to the lathe to re-mount them using a 5mm rod that was tapped M3 and a M3 screw.



After a little turning



One lesson I have learned is to keep your mouth in the closed condition when turning steel (or other metals too), if you think the little chips are a bit hot on

your bare arms, wait til you get one shoot into your mouth 

Anyway, after that I drilled and tapped the fixing holes, then I discovered that I dont have any M3 grub screws left, so at the moment the eccentrics are

fixed by faith. Being the excitable type I quickly assembled the bottom plate, bearing blocks with ball races, crank assembly (in my hurry I mounted one of

the crank webs the opposite way round to the others, it doesnt make a real differance I think, but it looks a bit odd) and flywheel and eccentrics.


Whoo hoo!! It's starting to look more like an engine and less like a collection of parts 



--- Quote from: Bogstandard ---Tim,

For the low block, just shim it up with layers of bacofoil, it might only need one or two. But get it before you have done the Sunday roast in it, less crinkles.

If you start to try bringing the others down to match the low one, you just might make it even worse.

John

--- End quote ---

That's a good point, I'll try the tinfoil shims 


I got a little more done today, I got some temporary ( unless I can't come up with a fancy blingy design ) columns. Nothing fancy here, just some plain

stainless rod cut to length and then tapped m3 at each end.
Then I cut up a couple of pieces of 4mm stainless for the Little end pins and single pointed one end of each piece m3, then cut a small slot for a

screwdriver in the other end.



Then I got excited again and assembled the top and bottom





It's looking more like an engine now 

spuddevans:
Part 5.


Got a couple of hours in the workshop today, started on the con-rods. I decided to try a little something different and used some brass Hex rod. I then

marked up for drilling the 2 holes. I set up and drilled the 1st hole in both con-rods before repositioning the y-axis using the dial to make sure the spacing

would be exact.

While I was worrying about getting the holes precisely at the right distance I neglected to make sure the hole's were exactly on centre on the flat of the

Hex  :bang: But it should be ok, I cant notice it with my eyes closed 

Here's a pic of the setup for drilling, I dont have a hex collet so this was the best way of holding the hex bar to drill perpendicular to the flat of the hex. I

squared up the hex rod with a small square and then tightened the vice up.



I then made up a little filing button ( my first forray into the world of filing buttons  ) and then used it to round over one end of each con-rod.



After that I only had a few mins left before I was called to do "more important things", so I cut down some 19mm square brass bar for the 2 steam chests

and milled them to length. Next time I'll be breaking out the little flycutter to bring them down to the final dimensions, and then the fun starts when I start

boring it out.


EDIT

Since getting this engine to run I have found a number of places that can cause friction, one of which is my design of Con-rod would tend to catch on the

crank-webs. But the fix was very simple. I just put a m4 threaded rod in the chuck and placed the crankshaft end of the conrod over it and tightened a nut

to hold it on. Then I just shaved about 0.5mm off the side of the conrod to leave a little boss. Then flip the conrod over and do the same.

This really helped ease the friction and catching issues with the conrods.


I started off today by flycutting the steam-chests down to size, then I marked up the Datum end and drilled the hole for the spool valve using progressively

larger drills until I got to 5.9mm.



Then after marking up one side for the steam inlet flanges I set up a stop on the vice and drilled the 1st hole on each block, using a vice stop ment that it

was easy to find the 1st hole, drill it and then swop over the steam-chests to drill the same hole in both without having to measure and re-check. Then it

was just a case of winding on the x-axis the right amount for each hole.



Both chests



Well I started off today by drilling the thru-holes for attaching the steamchests and for the steam porting, and then tapping the inlet flange fixing holes.

Then it was time to use a 6mm machine reamer to clean up and finish off the piston valve bore's. Prior to this I have only used hand reamers that kinda

centre themselves just using a tap wrench to turn them. However, machine reamers are a different kettle of fish ( or so I am led to believe ) they need to be

accurately aligned to the bore.

This was still a new experience for me, mounting a previously drilled item back into the vice and then centering it accurately to the spindle. So this is how

I did it.


I mounted a Dti in the chuck but offset it slightly on its mounting so that the spindle can be turned 360 degrees and the finger will still stay in contact with

the wall of said hole. Then by sweeping it round and nudging the x and y axis until the needle stays still through a whole revolution. Then lock up the axis

and  :doh: watch the needle deflect, unlock axis and estimate deflection and then compensate and then re-lock. I managed to get it to within 0.005mm

which I thought was ok.


This may be a little offtopic but I thought I'd just share a little thing I do when removing or changing tools on my little mill. I dont know if I'm the only one,

but when changing tools it seems like you need about 4-5 hands, one to hold the tool in position, one to hold the spindle lock and one to tighten up the

chuck, and if that is not hard enough, when it comes to remove the tool, say an end mill, you have one hand holding the spindle lock, the other is pulling

on the spanner to loosen the chuck, then as soon as you loosen the chuck by what seems like a gnat's whisker, said end mill drops at the speed of light

and drops on the vice chipping at least 2 of the cutting edges/teeth, whereupon the endmill will bounce onto the concrete floor. Do this a couple of times

and it can get kinda expensive. So this is what I do.


Just lower the mill's head and rest the tool on a sacrificial piece of ali so that the tool cannot fall completely out of the chuck.

I'm sure that all you experienced machinests out there do this or an even better method, but this is new for me.


Anyway, back on topic.


Then I broke the whole engine assembly down to bits as soon I would need to work on the main block to drill and tap for the steam chests. That done I

milled away some decorational clearances at the top of the steam chests. I still have a little shaping to do to these as can be seen from the hatched

markings. This is just a rough marking, I reckon I can't go quite up to the line as it may break into the main bore of the piston valve, but this gives a rough

idea of what I'd like to achieve.



Then my friend Stefan popped round and gave me a helping hand.

Together we rough cut some 2mm brass sheet for the steam chest blanking plates, then we milled them into shape, and then we milled a 3rd one to

replace the rather diamond shaped one we cut earlier without properly squaring it.

Then, lacking some superglue to temporarily hold the blanking plates to the chests, we used an engineers clamp ( at least thats what I think its called ) to

clamp the plate to the chest and then spotted thru to mark the holes, then we drilled both plates.

Then it was on to drilling the main block for the steam chests. With the lack of superglue spontainiously appearing in the workshop, and with the whole

block and steam chest arrangement being too long to use my engineering clamps on, we mounted the assembly into the vice, carefully lining everything

up while tightening up the vice. ( having an extra pair of hands was very helpful here )

But this meant that we could only spot thru on the upper mounting holes, this we did on both ends of the block. Then we drilled and tapped the 2 upper

holes of both ends. Then we were able to mount the steam-chests using the top mounting holes with some M2.5 screws and then when all aligned up right

we spotted thru the bottom mounting holes, and then drilled and tapped those holes.

Finally after all that we ended up with this.




I got a little more done today and got the 2 piston valves made.

Started where me and Stefan left off, having just faced and drilled the 24mm deep hole. So I turned around the piece and faced off the opposite end to the

required length, 46mm as I recall :scratch:. I then drilled it with a 2.1mm bit and then tapped it M2.5 ( I know the plan said to drill 2mm, but not having the

same confidence with tapping stainless, I just went with a slightly bigger drill to ease the strain on the tap. According to the tapping chart I have, 2.1mm is

still a strong fit )
Then with a bit more of the 6mm rod sticking out of the chuck, I turned it down to 4.05ish mm for a length of 26mm, then polished it down to 4mm with

some emery. It actually has a very slight taper, I say slight as when measured with a mic it tapers from 4.013mm to 4.006mm, I figure that it wont make too

much of a problem ( he says hopefully  )

Then I re-chucked it, gripping it by the 4mm end and faced the free end to leave me with 19mm of the 6mm diameter left. ( my measurements according to

the plans were 18.97, but the plans said it's better to be slightly long so I went for 19mm) Then after marking 3.5mm from each end of the 6mm diameter bit

I roughed out the centre bit, and then slowly brought the 2 ends to 3mm. Here's a shot of the 1st end brought to size.



Then I did it all again to make the 2nd one.

Then it was time to drill the little cross holes and so I used the spin indexer to hold the valves as I centre drilled and then drilled thru with a 1.5mm bit.




That's all I got done, next will be the eccentric straps, and that will plunge me into the world of silver soldering. ( that reminds me, I must pick up a couple

of firebricks to make a hearth. )


EDIT 13/03/2010 (for those reading this thread and wanting the build this engine.)

I have been trying to get the engine to run and had nothing but escaping air to show for my efforts. I have traced the problem to these piston valves. I

originally used 6mm stainless rods to make the piston valves out of, having just now measured the piece of 6mm rod used to make them I find that the rod

is actually 5.9mm and that 0.1mm allows a lot of air around it.

So beware when using raw material to make sure that it is the size you need. I ended up turning down some 8mm steel to make the replacements.


EDIT 6/8/2010

Something I have found when trying to get this to run is a problem with the piston valves sticking, and I eventually chased down the problem. It seems that

when you drill the cross-drilled holes there is an edge raised up around the edge of the hole. The solution was to just give the piston valves a Light wipe

with a fine cutting file and then a wipe of some w&d while they rotate at a slowish speed in the lathe.

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