Hi Dave
The WD 40 idea seems reasonable, but it depends a bit on the condition and contour of the cutting edges. Ideally a sharp reamer with the edge just dulled a bit to deter digging in.
I do not want to play the know all, after all, there is some truth in the saying, that “Nobody loves a smart arse”
So I thought a while before deciding to throw in my two pence worth.
I am not so bothered by how you produce the hole, but am concerned about its truth.
Have a look at the section “Results of little end misalignment” on my website page
https://www.mossengineering.co.uk/index.php?area=5&content=94
The majority of excessive wear in engines I receive have their origin in lack of alignment accuracy in little ends. The examples shown had errors of six thou, measured on a gudgeon pin either side of the rod little end. This was measured from a good clean parallel big end side face.
If you have access to a reasonable machine tool, clamp the rod down on the big end and carefully support and clamp the little end without moving it. Check this with clocks on it while you clamp it up. You can see the general idea from the fixture I use seen on page —
https://www.mossengineering.co.uk/index.php?area=5&content=84
I copy my operation sheet for your general interest
Small End
Phosphor Bronze from EMAM is 27 OD x 12 bore as A4358
rough to 21mm od x 67 lg x 19/32 drill bore but watch that rough bore is true.
This blank makes two bushes. Hold in 21mm collet to produce first bush, hold on first bush to make second bush, then part off, face and chamfer.
check internal bore as this is always marginal on boring
Nom bore in rod 0.8125″
Hone out to give 85% clean up
Turn bronze bush blank +0.0015 / 0.0020″ OD
Bronze bush rough bore 0.593″ = 19/32″ drill
Length = Rod width + 1.4mm
Chamfer ends + bores
Turn lead Rod bore – 0.0005″ x 1.5mm
Push in rod
Mill cutout + ( side oil reliefs for racing)
Drill + Tap 2BA for security screw (Racing)
Loctite in 2BA brass cheese head screw flush to inside of bush blank (Racing)
Bore to 0.6245″ dia on jig to correct centre distance
Internal oil grooves on racing engines by hand.(Racing)
Hone to loose SF on gudgeon pin 0.6262 / 0.6265″ dia
Cut off brass screw (Racing)
I do realise that my methods are perhaps more “particular” than normal, but I have made many machines for car factories and note the tolerances specified. The reliability of Japanese products is, to a large extent, a result of accuracy of manufacture.
I am not looking for work and if you do not have the facilities, perhaps a local engineering shop or good model engineer can help.
Whatever you do, I do urge you to be sure that you have accuracy within two thou in parallel and twist. I aim for one thou.
I would strongly recommend that you do not resort to the trick of putting in the hole and then bending and twisting the rod till it seems to have alignment. The rod usually “Unwinds” in service and reverts to its unstressed attitude. A rod that has been running will have settled into its natural attitude and will not move again in normal use. It therefore follows that the hole should be put in correctly first time.
An engine with rods in good alignment will give a good service life.
Alfred Scott knew exactly what he was talking about when he chose the logo “Made to limit gauge” Of all the components in this deceptively simple engine, the rod little end to big end alignment is by far the most crucial.
Kindest Regards and Happy Christmas
Roger Moss
