Hi John, You could maybe mill a small flat on the bar and spot and drill it after marking out in the old fashioned way or indexing across the dia. with wobbler. Or better, you could produce a drill bush from rectangular bar and use that?

Jim.

I would drill a square section piece lengthways the dia. of the rod,drill a ,cross hole dia vertically through the lengthways hole, couple of threaded holes to clamp, face off one end of the block to give positive location.

Material and hardening to choice and need. Vertically drill hole cut of surplus, piercing saw or Dremel, step and repeat as required

I am a simple soul, there could be very complicated alternatives

John R,

You have been given multiple options but nobody has asked what equipment you have & how many pieces do you want to drill?

Please advise as it's going to have some relevance to a practical answer

Tony

I have, with a very fine hole done it this way:

• Saw off a section of the bar, about the same length as your drill bit, put it in the drill chuck.
• Clamp the drill vice to the bar and then clamp the vice down to the drill press table while the quill is extended by the amount of bar in the chuck.
• Put the drill in the chuck.
• Put the bar in the vice and use a tiny file to make a very small flat.
• Now drill, it'll be pretty well in the centre, the offset being only as much as you deflected the press while tightening things up.

This has worked for me with tubes as small as 1.5mm with a 0.7mm cross hole in a drill press bought from Argos.

Regards,

Richard.

Edited By richardandtracy on 19/06/2017 16:14:11

A method I have used involves a custom V block.

Clamp a bit if MDF to the mill table and use the tip of a centre drill (or something else that produces an approximate V groove) to cut a V groove across the MDF. Lock the table so the groove is directly under the mill axis. Now clamp the round bar into the groove and drill in the normal way. I have done this with 1mm rod and a 0.5 mm drill successfully.

I drill mine last

have already made the valves…..methinks this may make the job harder?

Practise on a piece of scrap 2.38mm bar first?

Take a short length of brass round and chick in the lathe.

centre drill 1mm about 6 mm deep.

part off , do not disturb in chuck

centre drill through hole 3/32 – ream if you are fussy

set up in vice with 3/32 hole horizontal and 1mm hole resting on the bar – like a laid-down 'L'

1mm hole provides a guide that will be centred. best if you drill right through the brass first then insert the piece you want to put the hole through.

Just out of interest I thought I would see how the two centering methods I suggested in my first reply compare. Used a 3/32" stub drill held horizontal in the mill vice with 1/4" sticking out

Mill, DRO and electronic edge finder put it to 0.000 as far as the DRO accuracy will go. so set the Absolute to that

Mill, and rule was used to find ctr on the incremental setting then switched between the two to compare the difference in the two readings.

0.00019" or 0.005mm difference, this is actually the smallest increment my 5micron DRO will give. So as I said for me the ruler method is good enough 99% of the time.

And while drinking my tea I has a count up of the small cross holes ( >.250" rods) in the current hit and miss engine I'm making. I would need 9 jigs to suit the rod/hole combinations on that one model alone and for what when I can get 5micron accuracy without them better if I use the edge finder.

Maybe back in the day when all that was available was a lathe and possibly a drill press the jig was the way to go but for me at least things have moved on. A mill with DRO makes a very accurate drilling machine.

J

PEC, Got it from MSC but not sure if they do them now. It's the 1/2" shank 0.200" tip one as I mostly work in imperial, the cylindrical end is better than the ball type for use on round items like this as it is not critical on ctr height hich saves having to wind the table about to position it either side of the bar.