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Crossdrilling small diameter rod

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EdH06/02/2013 23:02:43
47 forum posts
27 photos

I have tried to reply to the Small Drill thread which is currently active but have had no luck so will add it as a new thread.

To drill a #71 hole across a 5/32” rod you could try this method, it needs to be done in a drill press or drill/mill with a vice that is fixed to the table. I’ll use some sizes to help illustrate the method so just change them to suit the size of material you are working on. Do use a new or known sharp drill so stop burrs occurring.

Take a 3/8” square piece of bar ¾” long and square off one end then put a mark on one of the long sides to identify it. Close it in the vice that is fixed to the drill or mill table with the marked side against the fixed jaw and standing on the squared end so that the drill lines up approximately in the middle, no need to measure just do it by eye then lock the table in both X&Y directions if on a mill. Drill a hole that is a close fit for the 5/32” shaft right through. Now loosen the vice and put your shaft into the hole just drilled, turn the piece on it’s side with the marked face still against the fixed jaw and close the vice. Now with the #71 drill in the chuck drill down through both the pieces and the shaft. The hole should be central to the shaft as both drilling operations took place the same distance from the fixed jaw.

Remember to stand the piece of bar on a parallel packing piece and remove the packing before drilling either of the holes so you don’t drill into your vice.

I’ve used this method successfully to drill 1mm holes in a 3.2mm shaft for the smokebox locking handles on a Gauge 1 engine.

mick H07/02/2013 09:36:37
795 forum posts
34 photos

Ed ....I have also asked this question on the Small Drill Thread, but perhaps you can help. I have used the method that you describe above to good effect but I have had several breakages in small drills. What is the secret?

Mick

JasonB07/02/2013 13:22:57
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25215 forum posts
3105 photos
1 articles

High speed, lubricant and peck drill eg cut a little clear the drill, cut a little more etc.

Ian S C08/02/2013 11:23:32
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7468 forum posts
230 photos

The smallest I'v made are .5 mm hole in a1/8" pin. I centered a V block on the vertical milling machine, used the maximum speed, 1250 rpm, and drilled the hole, just lightly tapped the point of the drill on the pin, then start drilling, when it started cutting, I lifted the drill, then do it again, 3 or 4 times like that and its through, if the pin had been thinner a little block of wood under it to stop it flexing would help. Most machining methods in this workshop are devised right here, and are not nessesarily correct. Ian S C

Michael Gilligan08/02/2013 11:42:29
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23121 forum posts
1360 photos

I must just mention this !!

MichaelG.

Old School08/02/2013 12:25:44
426 forum posts
40 photos

All the above plus a good quality sharp drill then no problems.

Regards

dave greenham24/05/2013 23:32:20
100 forum posts

Hi Ed

I use the micro feed on the mill for small drills. saves a lot of drill as not to much pressure is put on a very fine drills

Dave.

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