Where should I have posted these comments? I’ll put them here, and maybe also in a forum.

We made the jig exactly as you described, and the plate is really tough “hot rolled” thick steel.

We do face the webs before parting, so there is one nice square face, and one groovy dishy one, and we initially used the jig in the way you describe – “upside down” – peg down between the jaws of the post drill vice. Then manually guided the drill into the holes in the thick steel plate of the jig, and down into the web.

Which way up should the web go? I guessed good side down – where it will sit on the drill vice squarely. We didn’t face the bad side as we couldn’t see a way to hold it. Your pot chuck idea is new to us, and perhaps we could make one, and use it to make new webs, but I don’t understand what the benefit would be beyond cosmetic. (that’s just a literal statement of my ignorance – not a contradiction of your advice!). In addition, since parting is such a noisy and stressful process, the prospect of putting my head near the lather through four more of them is very daunting.

Later on when our post drill-and-jig-upside-down method proved inadequate, we dumped the jig, and used the milling machine’’ table to drill accurately.

We are slitting with a hacksaw, and after the web is shaped, and I have to say it’s a carve-up. Not straight, not central, and not consistent between webs. I don’t know how we would do better. But we thought this wasn’t important – what seems to be important is that we make a gap to allow the straight, parallel sides of the holes to pinch on the shafts, thereby holding them in correct registration.

You say: “Hopefully, by using the jig, all holes should now be square.”

The central issue is that, simply, they ain’t.
And we don’t know why nor how to fix it.

We are using steel as recommended. We could use brass, but since it’s softer, I would have thought it’s more prone to allow deviations from true. The parting off could be more fun though…

Your offer of a visit is very kind indeed John, thank you. However, we live 150 miles away which is a six hour round trip, not including any “shed time”.

Perhaps the answer lies in tramming – I’d never heard of that phrase before. We did check that the quill was true – or seemed to be – but thinking about it, it was very crude – putting a rod in the chuck, and assessing its squareness visually, against a set square placed on the bed.

Another engineer suggested making the crank with the shaft all in one piece, glueing iti n place, then removing the unwanted parts of the shaft. I can see how this would true up the shaft segments, but the idea of relying on glue to hold a shaft in alignment in a hole which isn’t true seems very dodgy, and also, removing the unwanted shaft segments would seem far from trivial. In any case, it would not help us with trueing up the big end segments of the crankshaft.

We’ve also considered using square rods in place of the webs, and doing away with some of the bearing blocks to give us more room for a more chunky design.

Also, as I mentioned, criss stitch is looking very attractive.

If you have anything to add, John, we’d love to hear it, but if you’re out of ideas, then elt me thank you once again for all the time you have given us.

Best Wishes,
Chris

But anyway, I will attempt to get you back on the straight and narrow.

To answer your query about the crank webs.

I state that these are about the most critical bits, and my fault really, I should have gone into more detail about how I get them all perfectly parallel sided and with the holes exactly in the middle.

Before parting any of the disks off, you should have faced the end of the bar. That at least gives you one side exactly square to the OD. It doesn’t matter at all about the shape of the other side, as long as you have enough material left to bring it to the correct thickness.
I am lucky in that I use soft jaws in my chucks, but you can get the same results by using a ‘pot chuck’. Similar to the bottom one shown in the top picture on this link. It needs that outside step to ensure it presses against the chuck jaws squarely.

http://www.gadgetbuilder.com/MiniMods.html#PotChuck

You would insert your faced of side into the chuck and clamp it up, then face the rough side until it is the correct thickness. Before removing it from the pot chuck, drill (and ream if you have one)the centre hole to 5mm (or whatever size you are using for the main shaft), deburr centre hole both sides. You should be able to do hundreds of these discs, all the same thickness and all having parallel faces, plus the holes should be spot on centre.
Pic 49 on page 24 shows how the holes should turn out.

Now to the drilling jig shown on page 25 as pic 50.

Get yourself a bit of say 1/4″ thick steel (just to stop the drill cutting the holes larger) by say 1″ wide and 3″ long.

Put it into your milling vice and about half way across the 1″ side and half way down it’s length, drill a hole that will allow you to loctite or stick a piece of the rod you are using for your main shaft. Then step along your jig from the centre of the mainshaft hole, 10mm, and drill a 4mm hole (ream if possible). Go back to your mainshaft hole and step the other way 8mm and drill the 2.5mm hole, not really critical on that size, somewhere near enough is fine, as long as you have a piece of good fitting rod to go into the drilled hole.

How to use. Follow the numbers on the jig picture.

1) Obtain yourself a piece of very close fitting rod to go into the small hole.

2) Fit one of your now accurately turned and drilled discs onto the centre pin.

3) Turn the assembly over so that the drilling guide holes are at the top, and then the disc is sat onto two parallels, one either side of the centre pin in the vice, then tweak it up, but not enough to put flats on the side of the discs, just enough to hold it.Then drill thru the small hole with the correct sized drill(2.5mm). You really do need to make sure your mill is trammed correctly, to make sure that the drills go thru square

4) Then push your thin pin into the hole you have just made, thru both the jig and disc

5) Because you now have in effect two pins going thru the disc and locking things in position, you can now drill the 4mm hole.

6) Remove disc and repeat with another one. You should end up with discs like in picture 49, where you can get all three rods going thru all discs.

Now onto the slitting problem, where they will not clamp up tight and square.

Hopefully, by using the jig, all holes should now be square.

Material used will also play a part here. If you are using a hard material such as steel, it may not be able to deform the disc enough if your two main holes are slightly oversized or not square. I would definitely recommend brass for these parts if possible, if not, then aluminium, but that might distort and loosen over time.

I don’t know if you are using a slitting saw or hacksaw for doing the slot, but the slot really does need to be across the centre of all holes, or very close to it.

BTW, the slot is done after the disc is shaped with the counterbalance and before the clamp screw hole is done. Do the shaping as in pictures 52 to 54 on pages 26 and 27.

I do hope that this bit of text has put you back on track, if not, then let me know and I will see what I can do for you.

If you lived within striking distance of Crewe, Cheshire, you could come over to my shop and see how it is done.

John

Firstly, our parting skills are miserable. We make dishes rather than disks. Yes, evrything’s locked down, and the gib strips are tight, and the tool is as far in as it will go, and perpendicular, and the work is as close to the chjuck as we dare, and the tools are new and sharp and centred, but still it whails as though on the point of self destruction, and the cut surfaces are not flat and not smooth. It’s not the matal bar stock either, we tried it on another bar. The first part went perfectly, with no noise and no drama – the second one, about half an inch further down – and we’re back to the wailing banshee.

“But wait, there’s more!”

The jig you propose John, is puzzling us. You seem to contradict yourself in describing it’s construction and use. Should we have it upside down using the holes in it to guide the drill? We’ve tried it like that and also the other way up, using the milling machine’s table to measure the distances (which seems to render the jog pointless) – but we have no success.

Our first problem was he dishing on parting as described. We can get it good enough, we think. Stressful, and not pretty, but functional.

The next problem was that the webs would not tighten on both shafts at the same time. The central shaft would tighten up but not the outer one – or vice versa. We solved that by drilling out to half a mil less than final diameter and reaming the last part.

The next problem is that – no matter what we do – we can’t get the webs to pinch up on the shafts perpendicularly. They’re always a little out, and of course, the errors add up across the shaft and the thing won’t turn. We’ve made four sets of webs so far. Since the holes are (now) made in a milling maching, everything is rock solid and (we thought) guaranteed to be upright – so we’re at a loss. The bar is straight, the holes are clean and snug. They’re just not upright. The milling machine’s quill seems to be upright when tested with a square on the bed aganst a straight bar coming from the chuck.

Any insights from anyone would be greatly appreciated. At this point, we’re thinking of taking up cross stitch :o)

Any engine that a beginning machinist, such as yourself, could realistically build is probably going to look crude. I think the knowledge and skills that you will acquire by building this engine are much more important considerations than its looks.

The Paddleduck engine may not be a good first project for a new machinist, but it is probably an excellent second or third project. I don’t consider myself a newbie any more, but I’m also not that experienced either. So I may build it because I think I’ll learn a lot from “Bogs,” who is very well liked and respected for his willingness and ability to teach new home machinists.

One more thing. It’s not a very good picture of the engine and I was not impressed when I first saw it. It also doesn’t give a good indication of its size. Since then I’ve seen other pictures and now I think it is a nice looking engine. Although it is a steam engine and not everyone likes them.

Kerv