Making larger holes?

[DianneB]

I need to cut a couple of larger holds, beyond the range of my drill bits - one 1-1/8" diameter and another 1-5/8, both in copper. The 1-1/8 hole is in a curved surface and both holes need to be accurate enough to fit tubes with a silver soldered joint. Being inherently frugal, I am trying to determine the most economical method.

Hole saws are the most economical but are notorious for producing inaccurate holes.

I could buy a drill bit for each size but they run between $50 and $90 each and I only have a total of 3 holes to do.

Hollow mills (plug cutter?) are also fairly pricey.

I could bore the two larger holes in the lathe but that doesn't solve the problem for the smaller hole in a curved surface.

I have a smallish fly cutter that I might be able to set accurately enough to cut the holes on the mill but that's a bit risky.

I don't have any steel stock of a large enough diameter to make a circular cutter.

Are there any economical options I am over-looking? How would YOU go about it?

Thanks!

 

[rgray]

Probably a boring heard for the mill. Not to expensive and usefull for many other things. The large drill bit might never find much use.
cdcotools has them on sale right now the 2" is $64.00 and the boring bit 9 piece set is $19.00.

 

[RandyM]

+1 on the boring head. You'll be amazed at how many more uses you'll have for it beyond this application. Money well spent.

 

[GK1918]

I think this would require an "annular" cutter but thats a lot of money. So why not make one. Turn a round pipe the exact diameter and grind
away. I dont think there would be a need to harden it for its only copper. The difference is, this is way more ridged than a wiggley
wobbley hole saw. I would reason that a boring head may be tragic for a thin cut. Then there are abrasive hole saws, that work well, but
the problem is, there are only so many diameters. I prefer to make my own annular cutter isnt hard.

 

[Tony Wells]

My choices would be:

1) Boring Head

2) Flycutter

3) Rotary table (provided the part could be fitted)

4) Annular cutter (bought or made)


But, I base that on what I have on hand. I did leave off the normal drills, but I do have them as well. I don't really like using a largish drill on soft, thin metal. But then you didn't say how thick the metal is. The flycutter isn't all that risky. You can gage how much you move the bit out with an indicator, and if you want, do a sample of the finish cut in some scrap to see the actual size.

 

[Ray C]

What are the sizes of the pieces and how deep are the holes?

Ray

 

[DianneB]

What are the sizes of the pieces and how deep are the holes?

The 1-5/8 holes are on 1/4" copper plate about 4.5 x 5.5" and somewhat off centre.

The 1-1/8 hole is in the side of a 4" diameter pipe, about 6" long, and 0.130" wall.

 

[RandyM]

Well Diane,

Just my two cents, but by what you describe here is how I'd go about it. I'd probably use some undersize hole saws and then finish with the boring head. This (in my opinion) will be the quickest, cheapest, and most accurate. Not sure of the accuracy you require though. Good luck.

 

[Ray C]

Do you have a lathe with a 4 jaw chuck and a boring bar? If so, you might consider doing this in a lathe if you have a chuck large enough to hold the pieces at offset positions.


Ray

The 1-5/8 holes are on 1/4" copper plate about 4.5 x 5.5" and somewhat off centre.

The 1-1/8 hole is in the side of a 4" diameter pipe, about 6" long, and 0.130" wall.

 

[DianneB]

Although I could use a faceplate and bore the flat plates, there is no way to hold the 4" dia. 6" long piece of pipe solidly on a faceplate.