Cheers Rob/Ralph
These post are coming in big lumps, My Dad is in hospital, his dementia has got worse over the last month, so I've been spending quite a bit of time visiting, and taking R and R in the shop, to keep my mind off things, so the posts have been a bit spread out.
Any way making the con rods, first I spent a bit of time getting a bit of old rusty garage door squared up and milled to size then a stuck the two rods together with two sided type, and doweled them through in a part that will be milled away later, and marked the rod out.
This is one of those jobs where you have to get the sequence correct cutting the wrong bit off at the wrong time and you will make things difficult for yourself, so I spent quite a bit of time machining the rods in my head first before doing it for real.
Making two together save a lot of setting time.
Rough drill the bearing holes and holes for what will eventually form the middle of the rods
Then drill through for the clamp holes for the big end bearings caps.
Then over to the RT and radius the ends
Big end
Little end
Then with a slitting saw cut off the big end bearing caps.
Drill for a 3mm dowel hole that will stop the bearing shells turning.
Tap the bearing caps M4 I'm going to bolt things together from the rod side this way the bolt heads won't fowl the cross head.
Chew away the meat from the middle.
As the cap bolts will be on the rod side the bolts won't sit flat due to the rad, I could square this off but that wouldn't look right, the solution is to back face to give the bolts a flat seating.
To make the back facing tool.
Using a length of 8mm silver steel (drill rod) mark it out for length for the back facer, turn a 4mm holding spigot, then gash out a single flute, and with a file back the cutting edge off, heat to cherry red hold it at this for a couple of minutes and quench in water, temper to a straw color, and sharpen the cutting edge on an oil stone.
To use pass the tool through the bolt hole grip the end in a chuck, tightened good and tight, and slowly wind it back so that it cuts a flat platform for the bolt.
Worked a treat the bolts sit nice and flat now.
This is my set up for using the coaxial on my mill and No 3 morse taper collet with a concentric split bush:- I didn't have a collet of the correct size but it runs dead true.
This gives me plenty of head room on my X3.
Clock the little end up to get thing on centre and zero the dials.
I then worked back from the big end, finding the edge and zeroing up the Y, set the vice stop, removed the rods from the vice, fastened the caps tight onto the rods, returned to the vice hard up gainst the stop, and them with a 15mm end mill finished off the big end bearing seat.
Move to little end position, and finished of that bearing seat with a 12mm end mill.
Now I have to decide how I'm going to fancy up the rod, when at John,s the other night he showed me a con rod that he had made, it was tapered toward the little end with a radiuses scallop that matched this taper looked real nice, so I was wanting to do something similar.
Tried a lose assembly of the parts to try and get a feel for how things would looked.
Decided that I would stay with the square parallel lines but to thin the rod off up to the little ends with nice radiused corners and a scallop down the middle.
Radius the corners both sides first with a ball nosed cutter then with an end mill thin it out by 1.5 mm a side.
Then mill the scallops with a ball nosed cutter I just went 0.5mm deep.
And last I reduced the width of the little end, If I'd done this earlier it would have made gripping thins difficult.
Thats them done a bit of a tickle with a file and a rub with some emery and I reckon they'll do.
Stew
