What tool do I need?

[DrPhill]

I am contemplating a small task, but it is an odd one, and I need an odd tool.

I wish to drill a hole in a piece of brass tubing. I do not know the exact size of hole until I try it. I have a reasonably confident guess for the minimum and maximum size I might need (5-10mm). So I will drill a 5mm hole and try it. Then enlarge the hole.

What tool would I use to enlarge the hole, neatly, in very fine increments? I imagine a sort of tapered reamer or grindstone (this is a once-off task, so I do not mind wearing out a grinder).

Any suggestions?

 

[katellwood]

http://www.google.co.uk/products/catalo ... gBEPMCMAI#

 

[Ringo83]

Or a step drill. Same as a taper drill but with specific, stepped increments.

 

[DrPhill]

Aaaah, thank you - that is the term I need. Though I might need to consider the tube diameter - I do not want A hole through to the other side.

Tapered Reamer - that is the (a?) suitable tool.

The two flute looks a bit brutal - I may search for something that has more flutes. Or is my reasoning wrong? Cutting brass is not my forte.

[Edit: Crossed with Ringo83. I will look at those as well. It depends upon the steps and the overall length].

 

[blurk99]

or use a hand deburrer to open the hole out??

http://www.newmantools.com/noga.htm

jim

 

[gus3049]

When I'm dong that sort of thing, I usually use a countersink bit as there is no depth problem. Does depend if the top has to be flat of course because otherwise you get a 45 degree rim.

 

[MickCheese]

When I'm dong that sort of thing, I usually use a countersink bit as there is no depth problem. Does depend if the top has to be flat of course because otherwise you get a 45 degree rim.

That seems like a good choice of tool and if it needs to have parallel side just finish off with a drill bit of the correct size.

In fact why not start with a 5mm drill bit then just keep using a ½mm larger drill bit until it is the right size.

Mick

 

[DrPhill]

When I'm dong that sort of thing, I usually use a countersink bit as there is no depth problem. Does depend if the top has to be flat of course because otherwise you get a 45 degree rim.

That seems like a good choice of tool and if it needs to have parallel side just finish off with a drill bit of the correct size.

In fact why not start with a 5mm drill bit then just keep using a ½mm larger drill bit until it is the right size.

Mick

Both good ideas, I have a good countersink that may work, and it should be a 'self centering' solution, neh?.

I thought about drills of increasing size, but I am not sure of my ability to centre the second and subsequent drill bits though I could rely on the play in the drill bearing/stand/etc to follow the path of least resistance.

 

[Oryxdesign]

Normal twist drills wil self centre but this is a less aggressive option

http://www.axminster.co.uk/axminster-ax ... prod23107/

 

[marcros]

is there any way that you can determine the hole size off the workpiece, eg on scrap, and then drill once?

 

[Jonzjob]

Any chance of telling us just what you are trying to do? It would make it so much easier to help?? :mrgreen:

 

[DrPhill]

Any chance of telling us just what you are trying to do? It would make it so much easier to help?? :mrgreen:

Hmmmm, yes, I can tell, but the details may be distracting.

I have a whistle (brass tube ~ 25mm diameter, less than a mil wall thickness) in which I wish to drill an extra hole. I know where I want the hole, but not the exact size. These things cannot be calculated with exactitude, and the normal strategy is to drill a hole undersize, and slowly increase it until the right effect is achieved.

I can (and will) practice hole drilling, and a friend has promised me a pillar drill and clamp. I will get one shot at this, and one shot only. I am still unsure as to whether I will go for it - just looking at options.

If I can reliably drill holes - no tearing, or distorting of the metal, then I may well go for it. Otherwise I will leave well alone.

There, I am not sure that helped any with the explanation.

Must to bed - up at 04:30 tomorrow.

 

[Jonzjob]

What would be the chance to have a 'practice' on a short length of 1" copper tube? The pipe ere has a 1mm wall and at the same length may even be able to get the note you want?

At least that way you may be able to get the feel of the job?

 

[DIY Stew]

If you push some dowel inside before you drill it will stop any distortion of the metal.

Stew

 

[Jacob]

Somebody said twist drills are self centering. Not in metal even less so on a curved surface. You need to start with a pointed punch mark to locate the drill tip.
Why not drill your 5mm hole and just enlarge with a reamer? That's the "normal" way to do it if you haven't the right drill to start with. If the reamer is too long then cut a bit off.

 

[DrPhill]

What would be the chance to have a 'practice' on a short length of 1" copper tube? The pipe ere has a 1mm wall and at the same length may even be able to get the note you want?

At least that way you may be able to get the feel of the job?

Thanks, a good suggestion, and one I plan on doing.

 

[DrPhill]

If you push some dowel inside before you drill it will stop any distortion of the metal.

Stew

Another excellent suggestion. This may be a bit harder to do as the tube is tapered. I am sure that I can get close though.

 

[Oryxdesign]

The other problem off course with twist drills is they don't drill round holes which is especially noticeable in thin sheet.

 

[DrPhill]

Somebody said twist drills are self centering. Not in metal even less so on a curved surface. You need to start with a pointed punch mark to locate the drill tip.

Thanks you for that caveat. I have some pretty small drill bits (3/64?) that I might use as a pilot. I am not too keen on any kind of impact technology, though maybe that will change with practice.

Why not drill your 5mm hole and just enlarge with a reamer? That's the "normal" way to do it if you haven't the right drill to start with. If the reamer is too long then cut a bit off.

Will a reamer allow me to enlarge a hole neatly by that amount? I do not mind using hand tools (especially if it slows the process down, so that I can be more accurate**). The reamers I have seen on the web look too long and thin. I could cut the reamer, but then I will need to buy whatever it is cuts the metal reamers are made of (unless a hacksaw blade would work). You can tell I am new at this, can't you....

**Though I have the impression that a pillar drill will be more accurate than a hand drill - at least with me in charge.....

[quoteOrydesign]The other problem off course with twist drills is they don't drill round holes which is especially noticeable in thin sheet.[/quote]
Thank you, that is certainly a point worth taking into consideration. Not having much experience with metal work this would have surprised and disappointed me. If I drill undersize, and then use a reamer (hand or electric) will that return the hole to circularity?

@all: thanks, this is good stuff - it is making me think carefully about each stage in order to get the best chance of success.
(1) Marking out - masking tape and careful line drawing
(2) practice on cheap stuff
(3) dowel insert
(4) pilot hole or punch mark?
(5) reamer?countersink?

 

[Oryxdesign]

Mark out carefully
centre punch
pilot hole

Once you have done this the following holes will centre on the pilot hole

Enlarge hole with a drill to near the required size
ream out to the correct size

If you knew the exact size you could use a plain reamer but as you want to slowly enlarge and check as you go you might be better with a tapered reamer like I linked to earlier. I would buy 2 because as you get bigger the reamer may bottom out on the other side of the tube, you can chop the end of the reamer off with a grinder and carry on. I would advise using the reamer by hand but if you get inpatient you can put it in a drill.
The reason I suggest buying 2 is that if you cock it up you have one as a backup and they are useful to have around anyway.