Looking great Dave. Can you explain how you went about drilling the deep holes? (I want to copy your successful procedure)
Hi Cogsy
I thought it would be very difficult to drill both the crank and cam tunnels especially the cam tunnel but it turned out OK albeit very slow it took me about 3-4 hours to complete both.
I started with the crank tunnel as I thought this would be much easier because of the voids in the crankcase, having no long drill bits I started with a 4 mm bit, after centre drilling I drilled with this until it was at its full depth, this reached through the centre main bearing cap, I then went straight up to a 6mm bit and drilled through again this bit was long enough to punch right through, I then went up in 1/2 mm drill bit sizes until I got to 10mm, it was now time for the boring head with a modified boring bar ( attacked with an angle grinder until it would give enough relief to get it to full depth) I took light cuts .2mm until I was nearly there then I went down to cuts of .01mm until the bearing was a nice snug fit, I wasn't as close as I thought I was and this took many passes and over an hour.
I started with the same 4 mm bit on the cam tunnel and pecked away with this until it was at its full depth again I went up to 6 mm and drilled to the same depth, this gave me a 6mm hole about half way through the block, I then went down to a 5 mm bit and pecked away again withdrawing the bit a lot and blowing the hole out with compressed air, the 5 mm bit was about 15 mm short of breaking through. I then went up again to a 7 mm bit and drilled approx half way through the top of the block again, back down to a 6mm bit this went through the last 15mm easy, so I now had the bottom 50% of the hole at 6mm the the top 50 % at 7 mm, but I had broken through, I thought this was going to make the going easier but I hadn't really thought about it, I now went back up to a 7 mm bit a started widening the bottom 50% of the hole, once I was nearly there I could hear my machine under strain because now the hole and drill were both the same size for the full depth of the block, (about 75mm)I broke through again with this size and went up 1/2 mm to 7.5mm it was ok at first but once I got over about 50-60 mm the friction was to much and I withdrew the drill, by chance there was a can of Harley Davidson 60 weight oil on the bench next to me, I put a few drops of this down the hole and on the bit and it cut through easily, again increasing in 1/2 mm drill sizes I drilled the hole to 10 mm and then back to the boring head and the same story until it was at 15 mm, hope this makes sense and is of some help to you. I'm using metric bearings what about you?
