# Making larger holes?



## DianneB (Dec 16, 2013)

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!


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## rgray (Dec 16, 2013)

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.


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## RandyM (Dec 16, 2013)

+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.


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## GK1918 (Dec 16, 2013)

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.


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## Tony Wells (Dec 16, 2013)

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.


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## Ray C (Dec 16, 2013)

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

Ray


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## DianneB (Dec 16, 2013)

Ray C said:


> 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.


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## RandyM (Dec 16, 2013)

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.


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## Ray C (Dec 16, 2013)

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



DianneB said:


> 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.


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## DianneB (Dec 16, 2013)

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.


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## swatson144 (Dec 16, 2013)

V blocks would work. Or as mentioned off set in a 4 jaw chuck should do unless the chuck/lathe is 2 small. I've done 1/2 " plate for 6" sheaves that way.

Steve


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## astjp2 (Dec 16, 2013)

Chain drill and a file, no cost, just time and you can get a very accurate fit that way.  Tim  

Chain drilling requires you to drill a series of holes along the inside of the major hole you are trying to drill and then filing out the extra material until you have a smooth hole that is the right size.


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## refinery Mike (Dec 18, 2013)

Just a word, to silver solder those large pieces of copper will take a lot of heat. I doubt you will be able to do that with a standard brazing tip in a torch. The copper steals the heat away so fast that you have to heat the whole piece at once. maybe try to braze it while the piece sets over a charcoal grill. or heating the whole piece with a rosebud then brazing with a tip. Also copper is a strange material. It cuts funny and not well at all, it can be grabby as well as much harder to drill than it's hardness would suggest. Also what kind of copper are you using, if it is electrical grade copper you will find that it becomes quite brittle when heated. The metal tends to absorb oxygen into the metal and oxidizes the grain of the metal. Plummers copper has alloys to prevent this so you can safely braze their copper pipe.


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## DianneB (Dec 18, 2013)

It is plumbing copper and I plan to set the whole thing up over a 10,000 BTU propane burner and go at it with the oxy-acetylene torch. I will shroud as much as I can with firebricks, etc.

I am aware of copper's machining peculiarities - just makes machining fun LOL!


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## george wilson (Dec 18, 2013)

I got used a set of boring tools and can't recall the name right off. Not something I use very often. It consists of a 3/4" drill,and a steel shaft you can put progressively larger flat cutters into,with pilots for the last size hole. With it,you can gradually drill large holes with a Bridgeport. I can't recall offhand how large they get. 2 1/2"? The set costs about $400.00. I wouldn't pay that,but got this used set off of Ebay a few years ago for much less. The type thing you never use unless you need to bore a BIG hole! I had bought one for the shop at work and used it. Except,I took a light grind along the 3/4" drill to reduce the diameter,to make it fit the 3/4" bar better,for a more accurate hole diameter with the inserted flat cutting tool.

For thinner stock,maybe up to 1/2" max.,a drag cutting trepanning tool is available. It costs money too. How thick is the material you are drilling? I hate turning copper.


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## DianneB (Dec 19, 2013)

I guess I will set up the flat plates on a faceplate and bore the holes. For the smaller hole in the curved surface I think I will wait until my rotary table arrives 
(next week?), set it up on V-blocks, and use the mill to make the hole. Seems like the safest way to get an accurate hole without screwing anything up.

Thanks for the ideas gang!


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## george wilson (Dec 20, 2013)

Be careful to have the work securely clamped. Copper is grabby as anything,and I hate to machine it. Silver is a close second,and nickel (German silver) is another bad metal to machine. I've done them all,but they aren't my favorite!!


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## DianneB (Dec 20, 2013)

I decided to bore the 1-5/8" holes in the flat plates and it worked out fine. Quite a bit of time in getting the plate centred on the hole but it did a nice job.



For the 1-1/8" hole in the boiler barrel I thought I would try a crude, huge, and OLD plumber's reamer that I had in the bottom cupboard.



That worked as well! So now I have all the large holes completed and all the pieces made for my boiler.



Thanks gang!


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## xalky (Dec 20, 2013)

We want to see pics of the soldered assembly.  )


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## stevecmo (Dec 20, 2013)

This looks like a very cool project.  You'll definitely have to post more pics as it comes together.

Thanks for sharing.


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