How to drill opposite holes on round stock?

RVJimD

RVJimD

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This is one of those questions that I suspect most are too embarrassed to ask but not me.

How do you locate and drill two holes opposite from each other (180 degrees) on round stock. I am attempting to build a solid rear axel for a Tonka truck conversion with a set of bevel gears in the center as a locked differential.

Here is a picture of the stock I'm starting with.

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The first iteration of this I milled a flat on the first side and flipped it over and milled the opposite side flat giving me the 180 degree opposite flat. Then I drilled the holes, but for this one I was going to leave it round.

This is likely one of those things that tomorrow morning it will seem simple, but right now, not so much. I hope this generates an educational discussion. Thanks for the support!

Jim
 
If you can't drill through, put a pin into the first hole and use that to index. You can put the pin directly in the vise, or fashion a flat block of appropriate dimensions with the hole in the center and use that to index the part in the vise.

Sent from my SM-G930V using Tapatalk
 
Tough problem that many of us face, Jim, so not an embarrassing question.

I cannot tell how large the aluminum collar is but there are a number of ways to come at this. I'll give you my thoughts and the others can jump in:
  • Easiest way is to cut a single flat, indicate it flat and then drill before flipping it ... but you don't want to.
  • If it will fit in a collet then collet blocks is the next easiest.
  • You can make a mandrel that locks into the work piece and lock the mandrel in a collet block.
  • You can put the work piece into a 3 jaw chuck mounted on a vertical rotary table.
  • You can try marking a line (with a height gauge) across the end with the work in a v-block, then transfer the lines to the sides and then locate your drilling points. Depends on your tolerances.
Okay, ran out of gas ... anyone?
 
If you have a toolmakers or drill press vise with the flat sides it could be clamped lengthwise in that and the vise flipped for the second hole. I've also been known to drill a snug fitting hole in a block of scrap wood so that the round part slides in but doesn't rotate around in there. Then same procedure as the vise -- drill one side, flip to opposite face, drill second side. And if the hole isn't snug enough, well, masking tape, hot melt glue, all manner of crudeness abides in my shop to hold things from rotating.

-frank
 
a spindexer with a 5c collet would suffice for a mill
a dividing head would provide the very same function
i fab'd a crossdrilling fixture out of my lathes AXA clone 5/8 boring toolholder - a turned shaft, a couple bearings and a small drill chuck- that works well and could also produce the same function
a crotch center in a lathe tailstock could be used
if the shaft was small enough, mount it directly in a lathe toolholder and put a drill in the chuck, drill accordingly
lathe milling attachments
V-blocks and a protractor
that's what i got from the hip.....
 
How many holes? If you have a mill and its tramed in , your vise should hold it in line, if it was my job id go thru and not go half way. If you spot the top of the shaft it should go straight. As long as you center the shaft it will stay straight. Another idea, You could mount a bushing the size the shaft fits thru use it to drill thru the shaft by mounting it in a vee block that would keep it from moving while drilling with two vee blocks it would keep the bushing locked but the shaft moving lots of ways to do it but why drill twice if its set up sauare and centered .
 
Ok. Try this. Make a sleeve with the holes placed as you need the sleeve can have flats milled on it. Slip your part into the sleeve and dill your first hole,. Remove the drill and insert a pin to hold the reffeance , rotate the sleeve and part with the reference pin and drill the other side. Seems that this may be a lot of fuss for one part but if your making multiplrss it works well. Tom
 
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