Gordon Nichols posted:Do you stagger-drill partially through from both sides or just go partially through from one side?
Also, how difficult is it to drill through hardened gears?
sethsaccocio posted:Do you drill these on a computer controlled milling machine or a manual mill?
The 1st and 2nd idler gears have synchro teeth on the backside so you can only drill so far, Gordon. You could drill through the matching gears, but they are on the mainshaft and not big enough to be able to do anything with, so they got left alone. 3rd and 5th aren't drilled all the way through because iIrc there are thrust surfaces on the other side. In the odd instance where you can drill all the way through, with set up time being what it is it's easier to drill them all the way through from the 1 side. You just have to be very careful.
The first .035 or .040" on each side is hardened and neither HSS, titanium or cobalt will leave a mark so you have to use carbide bits, which are expensive up here- close to $25 for a 1/8" bit (I broke 2) , 58 or $60 for a 1/4" bit (broke 1 of those too- bet you can guess how hard I yelled!) and the 7/16" bit was over $120! Going through the hard surface and then into the softer middle isn't too bad (remember to keep using fluid to keep things reasonably cool); it's when you start into the hardened surface on the other side where you have to be really careful- a little too much pressure, the drill tip really digs in and snap (this is where I would yell a bad word or 2) goes the bit. I would start with a center-finder drill go to 1/8", step up to 1/4" and repeat until at the desired hole size. Setting up (occasionally having to clean up the remnants of someone else's project) , doing the work, putting the 8" rotary table and away (it weighs 115 or 120 lbs and you have to be so careful you don't mark the table surface!) and then cleaning up after myself (I was in a friend's shop) would take 2 1/2 or 3 hours and I'd only drilled 10 or 12 holes. Mind you I'd drilled each hole 2, 3 or (in the case of the 7/16" holes in the first idler) even 4 times. I broke 4 or 5 carbide center finder bits along the way as well.
I did them on a rotary table bolted to a manual mill, Seth. The rotary table makes drilling holes in circular things very easy...
And you're a funny guy Mitch!