Boring large hole on lathe without a ton of waste?

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62Scout

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Making up some spacers out of 3.5" OD 6061 rod stock, 2.4" ID, 2.5" long. I was able to get solid stock considerably cheaper than tubing with a thick enough wall locally. I figured it would be a double bonus as I could simply cut a dowel of sorts out of the middle with a hole saw, and end up with smaller rod for future projects.

Yep... I'm sure there's laughter already, knowing I was about to find out the hard way that wasn't going to work well. Made it about 3/8" in, while pecking at it, before the teeth started loading up immediately, even with cutting oil. Took a few minutes for the "duh! Chips have no way to evacuate!" moment.

Obviously I could run a large drill through it then start eating away at it with the boring bar, but that would create a ton of waste. Is there another way to go at this, short of an expensive annular cutter?
 
62Scout said:
Making up some spacers out of 3.5" OD 6061 rod stock, 2.4" ID, 2.5" long. I was able to get solid stock considerably cheaper than tubing with a thick enough wall locally. I figured it would be a double bonus as I could simply cut a dowel of sorts out of the middle with a hole saw, and end up with smaller rod for future projects.

Yep... I'm sure there's laughter already, knowing I was about to find out the hard way that wasn't going to work well. Made it about 3/8" in, while pecking at it, before the teeth started loading up immediately, even with cutting oil. Took a few minutes for the "duh! Chips have no way to evacuate!" moment.

Obviously I could run a large drill through it then start eating away at it with the boring bar, but that would create a ton of waste. Is there another way to go at this, short of an expensive annular cutter?
Click to expand...
Mount an annular cutter in a boring bar holder and use it to take out the bulk of the material; depending on your lathe, the tail stock may not be the best choice.
 
Per above I routinely use an annular cutter to core solid stock and then finish with a boring bar for final ID dimension. Example is some lathe spiders I recently made with an overall length of 3.5", I use a 2" deep annular cutter in my tailstock cut one side and then flip and core from the other side. I then use the plug to make a bunch of jam nuts for the spider bolts. I use to sequentially drill out the material and then final bore, took much longer and a lot of swarf. In your case I would probably use a 2 1/4 or 2 3/8" diameter annular cutter at around 200-225 RPM with constant feed and some lubrication. It is easier to do on the lathe, but have also done it with a mill. Annular cutters needs continuous feed pressure no hunt and peck. I find HSS works well, Champion® RotoBrute, Hougen, Milwaukee are the main annular cutters that I have been using. I use a MT to 3/4" holder in the tailstock. You need a rigid machine and low speed RPM with at least 2 Hp in that size cutter.
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The alternative in this case is to spend a bit more for tubing IMO
Or just accept the waste- Just like industry does! LOL
 
Jim F said:
Trepanning ?
Click to expand...
Yes, trepanning. Basically a face groove 1.25” deep in from each side, that is pretty deep. Heck it is just aluminum - drill it a decent size and hop to with a good boring bar. It won’t take long (per others saving that plug is going to be an expensive effort - your time and other tooling options cost something too).
 
Sometimes it becomes more difficult trying to save the bits than they are worth but often good to think about.

Stu.
 
drill 4 holes lengthwise through the stock. Place them 90 degrees apart.
Make the outer edge of the drilled hole tangent to the center of the kerf made by the hole saw. This will give the chips a place to go.
Lots of lube and frequent chip clearing.
You loose a little of the diameter of the plug depending on how big the 4 holes are. A good starting point might be twice the diameter of the kerf.
I haven't tried this so it is just an idea in my head.
 
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