Kiwi build 2

KIWI Mk2 I/C ENGINE BUILD

Part 2 By Vince Cutajar

I marked the lengths of the rockers and hacksawed the excess. Filed the parts a little closer to the line and then milled off the sides. Ended with two pieces of BMS for the rockers ready for further machining.

I drilled the oil hole for the shaft by using a 1.6mm centre drill. That means I drilled the holes and coutersunk them in one operation. Next I drilled the 3mm holes for the pushrods using a 3mm ball nosed mill. As these holes are off the centre line it will help me keep track of which is the front and back of the rocker arm.

At first I was thinking of drilling the 6mm hole for the shaft that goes through the rockers but then I thought that when clamping the rockers for further work I might bend or squash the hole. So no holes for now and decidedm to start reducing the side faces as per plans. The plans also show the cuts to end with a radius but no radius dimensions a given. Using a radius gauge I estimated that 1.5mm radius should be close enough. I could have opted to do with without a radius but decided that as this part was visible, a radius cut would be nicer.

At first I thought I would use the faceplate and use a profile tool that I have but when I checked the tool it had a diameter of 6mm. Too large. Faceplate method went out of the window. My other option was the rotary table and use a 3mm ball nose mill. Out came the rotary table and it was located on the table. New problem. How am I going to clamp that small piece of steel to the rotary table. After a bit of head scratching I remembered I have a small 25mm pin vice. Would this work? There only one way of knowing and that is by trying it out.

Marked the centre of where the hole should be and clamped it in the pin vice. Put the vice on the table, located the crosshair (a bit fiddly) and clamped the vice on the rotary table. Reset the DRO x and y to zero so that I do not need to locate the rotary table again and with a scriber in the collet marked the sides of the cuts by displacing the y axis the required amount.

Started the outer cut and brought it down to required depth using light cuts (0.1mm). The plan was that then I would do the inner cut and then clean up the middle with an end mill. But as usual this plan changed. When I finished the outer cut I started going inwards slowly in 0.1mm increments using the same 3mm ball nose cutter. Don't ask because I can't remember how many times I turned that hand wheel. Eventually I finished.

I worked on the front part of the rocker arms, that part which pushes the valves down. Does it have a technical name? Well, it calls for a radius. So I marked the edge of the radius, put both rocker arms in the vice and milled off the excess material keeping just shy off the mark. Removed the vice, installed the rotary table and using my trusty 25mm vice located the origin of the radius under the spindle. Then using a 3mm end mill I cut the radius to the desired dimension (4.76mm). Easier that I thought it would be.

The angled cuts were just eyeballed.

Drilled a 3mm hole with a slot drill. I then milled the excess material, and cleaned it up by milling.

I then decided to mill off the angle on the top part of the rockers. Marked it off and put them in the vice then realised that if I take the cut it would be difficult to do the next operation. So instead I reduced the front and back thickness to the required dimension.

Re-marked the angle at the top of the rockers and milled it.

Filed the back and bottom contour and sanded the arms. Removed most machining marks. Some still evident in the main body recess. Just could not remove them. Polished with a dremel to a shiny finish. At one time, rocker arm literally flew from my hand whilst polishing. I am not going to repeat what was said at that time. Took me 30 minutes to find it.