Hick & Son Crank Overhead Engine

I am currently building the above engine from Hemingway Kits, having completed a Stuart 10V, a Mount Cross Engine, A Vulcan Beam Engine and part completed a Sir William Pumping engine. This time I fear I may have bitten off more than I can chew.

I have now got to the stage of making the connecting rod and have no idea how to proceed. In particular the 3/64'' slots for the bearing strap cotter pins seem impossible.

Having followed the Stuart Victoria thread I wonder if I could crave some of the same advice.

Thanks

Peter

Hi Peter,

For Norden I had to make similar slots 1/16" wide. That extra 1/64" seems a lot!

The slots will be hidden so they don't need to be perfect, although the end the key bears against needs to be correctly placed.

After I finished my engine someone suggested drilling axially down from the curved surface for the bearing. This can remove a significant proportion of the metal the slot has to cross, and at the centre, the hardest part to reach.

Now chain drill the slot with a 3/64" drill as accurately as you can. It may be worth drilling from each side in turn rather than trying to do so in one go.

Now cross your fingers and using a 1mm end mill as fast as it will go and taking cuts of no more than 0.4mm or less gently remove the metal between the chain drilled holes.

If you are lucky the tip of a flat but pointed (does that make sense?) diamond file will enter the slot and let you tidy it up.

An alternative rout would be to make a chisel from gauge plate or silver steel with a short tip 3/64" thick and 3/32" broad. Bevel it so the cutting edge is at one, narrow end. A second with the cutting edge on a long side could be useful.

You can either use this by hand to chip away between the drill holes or, if made on the end of a silver steel rod, you may be able to use in the mill with a gentle up down planing action.

Final thought, as 1mm end mills snap very easily, an alternative would be to file a d-bit shape on the end of 3/64" silver steel, just for about 3mm. Make one at each end of the rod so you have a spare immediately to hand. This will be slower, but if carefully tempered will probably outlast and end mill (which will probably be far too long in the fluted section, and therefore too fragile).

Neil

P.S. I'm sure someone else will suggest spark erosion, and that's probably the best solution of all, but requires making a whole new machine.

Peter, take a look as Jo's thread on her S&P she has posted about wedge and cotter slots several times.

I tend to drill out as much as possible, mill and then file with ground down needle files, these are all 1/16" wide.

As for how to generally proceed with making the conrod I would take an overlength bit of 3/4x5/16 bar,  clamp it to the mill table and machine it to the profile, you would have to flip it over at the end to do the other side of the outer webs and then finally mill or file them to the tapered shape, something like I did here

Edited By JasonB on 15/01/2014 15:28:11

Edited By JasonB on 15/01/2014 18:31:27

Hi Neil,

Re spark erosion, you could certainly make an EDM machine to do these slots, and in fact I did make one for similar jobs, to the Ben Fleming design. However, for a one time job it probably is not worthwhile. Many commercial mouldmaking and tool and die shops will do EDM work by the job, and Peter would likely be able to find a shop and get a quote without much trouble via google and/or yellow pages. When enquiring Peter should be sure to tell the shops he is working on steam models.

Your method of drilling and milling to finish will certainly work, though, and is probably least expensive method to make the slots. One note- feed slowly when milling with small mills, with a .010" or .015" depth of cut. It would be wise to chain drill with new, good quality twist drills also, preferably drilling in the mill.

JD

Edited By Jeff Dayman on 15/01/2014 16:14:10

Peter, something did not look right about the section XX view. I sketched up the rod in Solidworks and a jpeg of the drawing is as shown. The cross section hatched area should reach to each side, unlike the section on the hand drawn view as section XX. I don't think the height proportion on section XX is correct either. Hope the correct section AA view helps. JD

Gentlemen

Thank you for all your advice. I had previously made similar slots of 1/16'' width by chain drilling and then carefully milling with a 1/16'' slot drill. With a lot of patience a reasonable result could be obtained without breaking too many mills. However as Neil notes in his first sentence, going down to 3/64'' seems a step too far.

In addition I had not been able to find any mills under 1/16'' at my usual sources.

I like the idea of making a d-bit out of silver steel and so I will get some at Ally Pally tomorrow, along with a stock of 3/64 drills!! Then I will practice on some scrap. Having put a lot of effort into shaping the con rod I don't want to start experimenting on it.

The other problem I foresaw which you have identified was that of filing the slots to shape after drilling / milling. The tip of my precious Swiss files would just fit into a 1/16th slot but certainly not 3/64''. I never thought of grinding them down. to fit! I think I will have to invest in anew set also tomorrow.

Looking at Jasons pictures it occurred to me that i might modify the ends of the con rod forks to receive circular bearing shells. I dread making split bearings in which one half is square and the other round and at this size the problems would be even greater. I know it is not strictly correct but I am not planning to enter any competitions. These are just memento for the grand children.

Finally thanks for correcting the drawing Jeff. I will have to explore Solidworks. looks a useful tool.

Peter

Peter if you need them MSC/J&L have 0.050", 3/64" and 1.2mm cutters

J

Jason

Gulp. I will need a new mortgage at those prices! Thanks anyway.

Peter

Maybe its me but I did not think £14 for a double ended cutter that small was too bad a price, not much difference to two FC-3 cutters at list price

At 1.2mm lets be honest you could drive a tank and full artillery regiment through such a huge hole! They are not in any way difficult.

When I cut the slots on the S&P that Jason pointed you at earlier I had a major problem.. I foolishly initially cut them 0.6mm wide and then wasted a lot of time cutting them wider. Wider is easy. You can always find methods to make it a simple job more difficult or choose to use tools that are not up to the job .

When I scale the S&P down to 1/12th scale I will be doing slots 0.4mm by 2.3mm long. I think I know how to do them but you will have to wait to see my solution.

Jo

Should be an easy job now that you have the Sixis Mill

No much easier by hand

Jo

Since MSC took J&L over their prices have become anywhere.

You can't go on catalogue or web prices any more.

You ring them up and say I want a blab - blab cutter in carbide.

yes sir that £82.78 each.

Bugger off, that way too expensive

OK sir we can do this today for £21.87

Why should you have to do this ?

Their interstate stub drills in 3.00 which are Chinese are dearer than a Dormer ?

Average of £7.00 for a FC3 throw away cutter [ hint to J&L you are supposed to throw the cutter away when blunt, not the cutter and chuck ]

I used to spend £200 to £300 a month with them, in the last two months I have spent £35 on a new bandsaw blade and that's only because they do Lennox blades.

£3.52 for a 1mm cutter from Cutwel

My problem is I can break 1mm cutters by looking at them.

Neil

Mine arrive pre broken so it cuts the middle man out

Why are you using a 1mm cutter? Wrong tool .

Jo

Peter, if you think cutters are pricey, sit down before looking at quotes for buying a Solidworks license!

I have a license of it for work, which pays it off gradually. It is great design software and very easy to use compared to other types of professional 3D modeling CAD software.

JD

John

The Cutwell prices are more realistic. Only problem is that they are straight shank and I have the quicklock? type of chuck which takes threaded cutters.

Jo

Stop being a tease! I like the approach you have used of chain drilling followed by sawing through and filing to shape. Seems infinitely less stressful than milling with a 1mm cutter. I am off to Ally Pally now and will be looking for some fine piercing saws and diamond files I can grind to size.

Peter

Peter, Don't just go on the picture but click on the link as they do threaded and plain in the same lists

http://www.cutweltools.co.uk/files/ww/HSS%20A33.pdf

A bit dearer in the threaded but you expect that. £4.91 for a 1mm

Edited By John Stevenson on 17/01/2014 10:00:37

John does the black square not signify that they don't do 1mm in screwed shank ??