Thread: Drilling 30mm hole through 10mm plate

Originally Posted by Big Shed

Question, is it possible to cut the OD of a circle by turning the cutting point of the boring bar inwards?

Yes. It works remarkably well. You have to turn the cutting point inwards as you mentioned, but also run the spindle in reverse. Today I cut down a 50mm piece of solid medium carbon steel to 38mm using that technique. I do not have a lathe, so this is my go-to option for turning down the OD of stock. I have a rotary table, but there is something rather soothing about using the boring head and the rotary table is darn heavy! Just have to keep an eye to make sure the boring head does not come undone, as running in reverse can unwind the thread (which incidentally it has done more than once!). I turned the boss (to a perfect 20.00mm) on the following part which is 1045 BMS using the reverse boring method.

IMG_5603.JPG

I double checked this afternoon in preparation for a new and improved 'superdrill' type boring bar: the small cutting tool is in fact 3/16" (4.8mm) square, not 1/4"; the set screw for it comes in from the bottom down the centreline, not from the side and the main body is 1" (25,4mm) as already noted by BobL.

Superdrill.jpg

The idea of a Morse taper shank instead of a round or hex drive end is excellent. To that end I cut the very worn drive of mine today and drilled and bored the large body to suit a No2 Morse taper I had doing nothing and pressed it in with a little Loktite. I'll cross drill it tomorrow and press in a hardened pin to make sure and try that.

I think I'll make the new one with Morse taper and just a 24mm body in one piece (like others here, I have a 24mm drill and my drill presses will drive that).

Originally Posted by SurfinNev

Not sure if these will do 10mm but you could always flip it over and do from both sides.

http://www.ebay.com.au/itm/Tungsten-...-/261406077225

He has other sizes besides the 20mm in this listing.

Nev.

That's interesting - the videos seem quite compelling, like cutting through butter. Key selling points are no need for cutting fluid and only 10kg down-force needed.

From the perspective of my cheapo bench drill, I'm thinking that the low down-force will be quite useful. Also, I'm assuming my drill's too-high RPM might decrease a fair wack under load.

My only concern is that the website says 5mm is max thickness, but the videos are cutting ~10mm.

I'm tempted to give it a go as they have a 30mm for $20.

Originally Posted by variant22

Yes. It works remarkably well. You have to turn the cutting point inwards as you mentioned, but also run the spindle in reverse. Today I cut down a 50mm piece of solid medium carbon steel to 38mm using that technique. I do not have a lathe, so this is my go-to option for turning down the OD of stock. I have a rotary table, but there is something rather soothing about using the boring head and the rotary table is darn heavy! Just have to keep an eye to make sure the boring head does not come undone, as running in reverse can unwind the thread (which incidentally it has done more than once!). I turned the boss (to a perfect 20.00mm) on the following part which is 1045 BMS using the reverse boring method.

IMG_5603.JPG

Or use a left hand tool. My whizzo boring and facing head's arbor will unscrew itself if run in reverse. Photo 2 shows a left hand set up, the only thing left about it is the orientation of the square cutter. Looks simple enough.

KaiserPiccolop2_zpsbd15144f.jpg

Originally Posted by Stephen H

That's interesting - the videos seem quite compelling, like cutting through butter. Key selling points are no need for cutting fluid and only 10kg down-force needed.

To put it nicely I'd say that video is showing "best case".(whats the "coolant" he is using? WD40? makes for great pictures)
Having said that, for $20 if it gets you out of a corner its worth a shot.

Stuart

Thanks everyone for your contributions to this thread, it has been most interesting. I have a couple of questions though or points I would like to have clarified. The commercial version leaves a small disc as it cuts through, which implies either a cutting tool sharpened so that it is lower on the outer tip when viewed as illustrated in Joes drawing of the tool, or alternatively the broached square hole for the cutter tilts down so that the cutter cuts the outside edge lower than the rest, without special grinding to achieve that result. I just wonder which way it has been done.
The other question I have is also concerning the broached square holes. On your sketch Joe, they both appear to be centred on the axis of the boring bar, but I would have thought that they should have been offset, so that the cutting edge of the cutter was on a radial centre line if that makes sense. That would mean that the 4.8mm cutter would be offset 2.4mm so that its cutting edge was on centre. I may just be imagining problems that aren't there, and making the whole process more difficult than need be, but would appreciate the groups thoughts on this. Thanks,
Rob

Originally Posted by Ropetangler

The other question I have is also concerning the broached square holes. On your sketch Joe, they both appear to be centred on the axis of the boring bar, but I would have thought that they should have been offset,

I dont see that it matters where the cutting edge is V the center of the boring bar. It may even be a good thing to be off centre as the end corner of the cutter could be negative rake(well at least "not positive"), the cutting edge would also be a little longer, though how much these things matter I dont know.
I've been wrong before though

Stuart

Originally Posted by Stustoys

I've been wrong before though

Stuart

You and me both Stu, at least once or twice.

Originally Posted by Stephen H

I'm tempted to give it a go as they have a 30mm for $20.

That's cheap.. usually you'd pay 3 times that just for a decent arbor, and then still have to buy the holesaw itself.

Ray

Sorry I didn't address the question of angled square holes: they are at right angles to the axis in mine and other I have seen. And they are centred, not offset. Clearance angles are ground front, bottom and periphery of the cutters.
Used my now Morse taper equipped one today: much more rigid and works like a charm. I also tried it in an existing hole, boring it a couple of mm bigger in diameter on the drill press. Not something I would have attempted chuck-mounted. Work piece clamped of course. No problem!

Thanks Joe, it looks like I would have over engineered it, although with the holes tweaked a bit, the cutters may be simpler to get and maintain the correct geometry. For the time we would spend resharpening cutters though in the hobbyist workshop, possibly not worth the extra bother.
Rob

So who put their hand up to make batch???? I'm sure someone did

Originally Posted by Anorak Bob

Or use a left hand tool. My whizzo boring and facing head's arbor will unscrew itself if run in reverse. Photo 2 shows a left hand set up, the only thing left about it is the orientation of the square cutter. Looks simple enough.

Ahh, Anorak Bob. Nice boring head. The idea is sound and looks relatively straight forward to make.

That being said, of all the boring heads you could post, you had to post a Kaiser. I was actually going to post a "Call out to Anorak Bob" thread (given you are a prolific and capable machinist) a few weeks back with a challenge to make a "poor mans" Big Kaiser - yep the digital boring head! http://youtu.be/ZReeMReAi8s?t=18s

I am desperate to make one of these. I have been trying to think of how to do the DRO part. I am thinking about buying a digital micrometer and tearing it down and trying to retrofit the screw mechanism into the boring head screw. The only issue is the cheap ones worthy of wrecking all have huge LCD's! Ugh!

I might have to create a new thread dedicated to it..

Originally Posted by variant22

Ahh, Anorak Bob. Nice boring head. The idea is sound and looks relatively straight forward to make.

That being said, of all the boring heads you could post, you had to post a Kaiser. I was actually going to post a "Call out to Anorak Bob" thread (given you are a prolific and capable machinist) a few weeks back with a challenge to make a "poor mans" Big Kaiser - yep the digital boring head! http://youtu.be/ZReeMReAi8s?t=18s

Mmmm... Very nice boring head, but I doubt that they make one to suit a Hercus mill or even BTs big Schaublin 13! Keep us posted with pics if you make your version of it though, it will be a mighty nice acquisition when you pull it off, assuming you find suitable donor parts,
Rob