CON RODS for TRIPLE -2
by John
The con rod shafts have a taper of approx 1.5 degrees. I turned the shafts between centres, using a tangential tool.(a Diamond tool holder from Eccentric Engineering). The HSS cutter has a round cross section which gives a good finish, and automatically fillets the joins.
Of course left and right hand tools are required to do the whole taper.
Another jig!
The con rod casting is difficult to hold accurately for milling, so I made a jig to assist.
10mm aluminium plate, with a cut out section to accept the con rod casting.
The jig had to be made as accurately as possible. So it was milled square and parallel, then centre pins were installed to hold the casting by the previously drilled centres. A further pin with a sharp point was installed to stop the casting from rotating during the drilling and reaming for the gudgeon pin. That gudgeon pin hole was continued through the jig, so a large pin could be inserted to really hold the casting securely. It also allowed an accurate 180 degree rotation of the casting.
A bit clearer with the swarf swept away!
You can see the gudgeon pin in place, while further surfaces are milled.
Close up of the jig and my metal workers’ dirty hand. Just as well there is no more gynaecology.
Progress!
Not a clear shot, but here I am using the flutes of a milling bit to smooth the flat section under the gudgeon pin. Not ideal but it worked OK. Tomorrow I plan to round off the external surfaces and mill the slot for the cross head. Not much to show for a full day in the workshop, but it was fun…
johnsmachines 
Have you finally retired from gynaecology etc??
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Yes retired from O&G, but not from etc. In fact the etc seems to take more time than the O&G did.
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Now with 20 years of experience as a surgeon by day and mechanical tinkerer for play, I have a robust hand care regimen.
I use barrier cream (ask swmbo if in doubt)- It is dimethicone cream which coats the skin with silicon. Supposedly it offers some small degree against exposure to toxins. It does make it easy to get greasy hands back to consulting standards pronto and without damaging the skin. I use it every time I step out of the door, rubbed carefully around the nails.
The “septone” grit-free cleaner from super-cheap on one of those blue “huck” towels gets the last bit of grot off if needed.
I teach this to any of my registrars who look like tinkerers (we do see them in ortho).
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SWMBO has lectured me on the need for barrier creams, so when still working for a living I used them sometimes. The machining grime was usually less apparent by the third scrub of the list.
I confined myself to wood working for the first 20 years of operating life and the ease of dusting off and cleaning up was a major incentive to confine myself to that trade. But, with the machinery maintenance and fabrication of the next 15 or so years, then into model engineering, the “mechanics hands” were harder to disguise. So it was with some relief that I retired a year ago.
Are you in Oz?
John
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Yes – Across the Bass Strait. I’m in Northwest Tas.
As you might have guessed – I was on call for the weekend and had a great time reading your blog instead of marching about like a caged lion during the obligatory waits.
I have appeared as “anonymous” in my posts – Due to error not intention.
Russell
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