How to drill opposite holes on round stock?

[RVJimD]

Here is my solution, I think this was suggested above....

I bored out a tube to hold my part, then milled flats on opposite sides. Then drilled a hole in the center of each flat.

Smaller part installed in the holder while I center drilled the holder.

Gear and axel installed. I think my original hole caused the first one to be off just a bit since the gear is almost exactly the size of the ID , I had to mill a tiny bit of clearance.

Jim

 

[fitterman1]

So how does the mating gear fit?

 

[RVJimD]

The tube ID is only a few thousands larger than the gear, so I milled out a slot for the front gear but that is as far as I got. Since the gear inside the tube is centered, the front gear will need to sit off center. I need to figure out how to make them adjustable and I want to drill out the holes for bearings. Jim

 

[Mutt]

Mikey had it right.
Place stock in vee block. Use height gauge to find center and mark two sides and end. Remove from vee block, stand on end and mark distance from end.
Sit stock in mill table top tslot and use square on end scribe mark to sit vertical. Clamp in this position and drill or drill and tap. Unclamp and rotate 180 degrees, reset vertical line on end, clamp and drill or drill and tap again. Job done.
Using tslots in this manner is timesaving.
Should take you 20 minutes, 30 if you crack a beer.

This is the coolest gadget I have found in a while. I used to hate drilling a hole thru a piece of round tubing or bar stock as it would always be somewhat off center. This makes it super easy !

http://www.ebay.com/itm/New-Made-in...hash=item20ce0158f0:m:m9Fyr5qKnGTn6IWq4s17j2w

 

[BoliverShagnasti]

I broke down and bought and indexing rotary table with 90 deg angles so it holds work flat or at 90 deg. I have to cut holes like this often. My holes are 7/16 and 12.5 mm for a prototype and consecutive versions.

I love this rotary table. I custom cut a 5 inch lathe chuck back plate and fit the chuck to it within .001. Took a long time with a lot of tiny adjustments to cut the back plate, but it is a tool, after all. First I put it in the lathe cut the shape for mounting, then set it on the rotary table.
Then use an end mill on the milling machine to cut it parallel to the milling table. Mounted the chuck and all is good.
When I mic the test shafts cut through through the "pipe" with 180 deg rotation, it is perfectly in center +- .004. This is without machining the stock "pipe" to round.

I was surprised at the accuracy of this table.
http://www.grizzly.com/products/6-Rotary-Table-w-Div-Plates/H7527

I use the Harbor Freight Milling machine and the Grizzly G9972Z Lathe. Both machines I recommend. The Harbor Freight mill has .008 take up in the wheels, but knowing that you can cut easily to .0005.

Before I purchased the rotary table set up. I made a V block jig with a pin at the center. You dril one hole then rotate it and pin it at 180, (pin in a steel angle iron at the vertex). It was OK but could not get it perfect enough.

 

[acmef150]

Funny this topic came up , I was just in the middle of this project and just thought I would show how I tackled it . This a 2.25 inch lathe spider from a piece of 2.5 inch 1018 I had .

 

[acmef150]

Sorry about the duplicate picture .

 

[Highsider]

If you do this very often and can drill the material with an electric drill motor, it's worthwhile to make a drilling jig that takes standard drill bushings and is on the centerline of your lathe when bolted to the compound. Then simply dial the workpiece into your 4 jaw chuck, index the chuck by resting a jaw on a metal spacer set on a flat part of the way and drill the Cross hole. If the piece is tubular, you can turn the chuck 180 degrees and index the opposite jaw on the same spacer and drill again.

 

[fitterman1]

I've marked out in a similar fashion by indexing the 4jaw with a spacer and scribing with a lathe tool. Quick and easy

 

[428Bird]

I wanted to make a 1" boring bar for my CXA holder. I don't have a decent drill press or a mill, so I held the bar in the holder. After setting the center height and locking the tool post, I gently pecked away with a center drill to get a good starter hole for the 3/8 stubby drill bit I have. It worked flawlessly.

Britt Bettell

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