Boring a large diameter hole in a lathe

prasad

prasad

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My equipment: Grizzly G4000 9x20 lathe with 6 inch 4-jaw independent chuck

My work: Most my (recent) work involves boring a large diameter hole - typically to a 5 inch ID in solid metal (aluminum and some brass). I initially did it the hard way. Start off drilling a hole as big as my largest drill bit, and then switch to a boring bar to enlarge the diameter gradually. That took a long time and was very tiring.

I have tried using round nosed turning tool too. It was faster than my first method but I want to know if there is any better way to cut a hole.

Thanks
Prasad
Wynnewood PA
 
If this were something that I was going to do often, and the material is not too thick, I would get a hole saw just a bit smaller than the desired ID. Use it first, then finish the hole to size with a boring bar. If you only need one or two of them, the methods you have used thus far might be your best bet, even though they make the process a bit tedious.
 
You can use a "parting style" tool on larger holes like that. It is plunged in to the face of the work. You need to grind a lot of relief on the outer side of the tool to allow for the arc of the cut. But for brass and ally I would go with a holesaw. You can also drill a small hole, (just 1) on the perimeter of the holesaw. Makes it easier going and helps clear the chips

Cheers Phil
 
I use hole saws quite often to cut steel. I've cut 1" holes in 1" steel and larger holes in thinner steel. The key is to slow things down, use cutting oil and clear the chips often. You could use the hole saw in a drill press first, then set the piece up in the lathe to bore to finished size.
 
You may not have the equipment, but I'd do a 5" hole in the mill with a rotary table. Or even CNC. Use an endmill to just cut a slot.
 
If it's not too thick/long you could use a trepan tool. If it is too long for a trepan tool or hole saw, you could drill a number of holes (with a drill press or by hand) in a circle pattern close to the dia you need bored out, then use a coping saw to saw out the slug.

The coping saw would work fine for alum or brass, remove the blade from the saw, stick the blade through one of drilled holes, put the blade back on the saw & saw away.
 
12bolts said:
You can use a "parting style" tool on larger holes like that. It is plunged in to the face of the work. You need to grind a lot of relief on the outer side of the tool to allow for the arc of the cut. But for brass and ally I would go with a holesaw. You can also drill a small hole, (just 1) on the perimeter of the holesaw. Makes it easier going and helps clear the chips

Cheers Phil
Click to expand...


The tool Phil described is called a trepanning tool. A good "how to run a lathe" book will probably have a diagram of it. I "Googled" You Tube Videos & found trepanning by Frank Stearns. It shows an example of what you are trying to do.
 
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