Drilling a tube

[rickharris]

I need to drill 2 x 4 mm holes accurately in a 6mm dia thin walled brass tube. I am having some difficulty as despite centre punching the marks the drill tends to wonder.

Is this because of the thin wall of the tube - unfortunately the holes need to be dead on to fit the already assembled parts.

Any suggestions before I ruin another?

 

[itowbig]

maybe use a spoting drill bit or a really short broken bit resharpened so it wont flex.
just a thought. hope it helps some

 

[RobWilson]

Hi ,You could try turning up some similar material to fit in the tube to give it some support
Rob

 

[bearcar1]

Rick, you are working in the realms of madness ;D :big: It would be best if you could turn up a piece of something that would give the tubing a bit more support internally. Several things are going to effect your success. A means of securely holding the tubing to prevent its rotation as well as using a small center or stub drill will do wonders towards the jobs success. Without the internal support the piece will compress as the drill is advanced into the work and as the drill breaks through it will spring back into its normal state and very possibly snatch the bit and crawl up onto same. :toilet: Also without a secure hold down the piece will want to 'turn over' or rotate away from the pressures of the drill. Again, causing all kinds of nasty things to happen. My suggestion would be to afix some sort of temporary internal support and secure the tubing on a "vee" block that has been carefully centered under the drill/quill spindle and use the associated clamps that slide onto the blocks and have a screw to firmly hold the workpiece as it is being machined. These steps and the usage of a short drill will go a long way to prevent a disaster. Good luck in your quest to make a penny whistle. Rof}

 

[GailInNM]

If you have a center cutting end mill/slot drill the right size and can support the tube internally with close fitting rod so it does not crush in the mill vice that works well. I have made a lot of manifolds that way.

If you are doing it with drill on a drilling machine, a simple fixture made by drilling a hole for the tube in one direction and cross drilling for the required hole works well. If you are only doing a few holes, light alloy is OK or if you are doing a dozen or so mild steel will work.

Gail in NM,USA

 

[steamer]

I agree.....endmill and rod inside.

If no endmill...or slotdrill on that side of the pond......take the rake off the drill with a small stone to keep the drill from grabbing and tearing up the work.

If you do that DEFINITELY center drill or spot drill, as the drill force will go up and a drill makes a terrible column....it will wander.

Dave

 

[tmuir]

Go to your local hardware or hobby shop and buy some wooden dowel that will fit inside the tube. It needs to be a good fit.
Thats what I did when I needed to drill holes in thin brass tube to make wick holders.
It works well about 70 to 80% of the time. I also held them in a V block

 

[SignalFailure]

Probably too late but...

You could make an accurate 6mm hole in a block of (square section) scrap and put the tube in it (with internal support as above if needed). That'd make it easier to hold and a lot easier to get the holes in the right place.

 

[rickharris]

Thanks for the advice and ideas guys - I eventually sat and thought at the problem for a long time and several cups of coffee and ended up by:

1. Turning a dowel to fit the tube - I used some beech that was available. had to turn it on the metal lathe to get a parallel dowel.

2. Drilled a hole in another bit of beech to take the tube. Clamped the tube in the hole and drilled through the whole lot. Worked!.

So a mix of your suggestions came through in the end thanks.

I am making a valve for an engine that for various reasons has to be external to the cylinder and I decided to make it out of some brass tube we happen to have laying around. 5mmod - 4mm id and 3mm od 1.5 mm id.

Progress again.

Thanks

 

[bearcar1]

Well done Rick, I m always glad to hear of a successful outcome to a particular challenge as they present themselves. ;D

BC1