Hole through side of a tube?

[RogerP]

Take a short length (say 100mm) of 40mm diameter round tube with a wall thickness or 5mm.

What method would you use to bore a 15mm hole going through both walls perfectly centrally in all regards?

 

[niagra]

If you have a lathe, stick it in a 4 jaw chuck so that two jaws hold the flat ends of the tube and the other two hold the sides. Line up where you want to drill the hole with the chuck centre and drill away. That's how I do it, as I don't have a drill press and it works just fine, and it is a great method for repeatability.

 

[CHJ]

Simplest method I know is to make up a Vee guide block which will hold the drill on cylinder centre.
Does of coarse assume you have the facility to make said block accurately.

Cross section:-

 

[Ed Bray]

It would depend on the material that the cylinder was made of. If a soft material (wood, plastic etc) I would use a wooden V block to sit the cylinder on with 2 further V blocks one at each side (on the top of the cylinder leaving enough room for the bit to pass) which would then be clamped to my drill press table to hold the cylinder in position. I would then drill straight down.

If made from a harder material I would give it to my next door neighbour who is a toolmaker to do on his lathe.

 

[RogerP]

Thanks very much for the suggestions.

I have a four jaw chuck but a self-cetering type so only two jaws could grip ... maybe with some spacing I could bodge it?

The V guide idea from Chas looks promising and is probably what I'll end up doing.

I have a fair number to do so I want to turn them out with the least fuss.

Thanks again.

Edit: They are mild steel Ed.

 

[paul-c]

best use a v block
can be purchased quite cheaply nowadays or make a wooden one as others have said

http://en.wikipedia.org/wiki/V-block

cheers paul-c

 

[Causebrookcleaning]

The last time I had to drill a tube I used 2 10 inch stilton's that held quite good.

 

[bugbear]

The last time I had to drill a tube I used 2 10 inch stilton's that held quite good.

BugBear

 

[DTR]

It doesn't have to be a "V" block. A suitably sized groove ploughed / routed along the centre of a block of wood will do. The tube will sit on the corners of the groove instead of the walls of a vee. Vee blocks are the ideal, but if this is a one-off and it doesn't have to be ridiculously accurate....

 

[RogerP]

Thanks very much for all the suggestions.
In the end I made up something like this, except I added a cross clamp and drill guide bush.

 

[flying haggis]

The last time I had to drill a tube I used 2 10 inch stilton's that held quite good.

BugBear

that made me laugh

 

[terrymck]

I would support it in vee blocks and use a series of drills in the drill press. Start off with small diameter gradually working up to full size. Be cautious when the drill emerges through the other side (of both walls) as it will snatch. If possible clamp the workpiece down to drill press table. Use some coolant to prevent the drills from overheating and keep them sharp.