Thread: Drilling 30mm hole through 10mm plate

According to the website, Super Drill:

Because the cutters are made from 8% cobalt and the SUPER Drill body is hardened to internationally recognised hardness measure, 60 Rockwell, the SUPER Drill and its cutters is built strong to tackle your toughest drilling.

Joe, Thanks very much for the drawing, a couple of questions if I may.

I assume the diameter of the thickest shaft is 25mm?

I assume the cutters/holes are at some sort of angle from the centre line of the shaft?

As I can already drill 25 mm holes, I might make one that starts at 25mm

Originally Posted by BobL

Joe, Thanks very much for the drawing, a couple of questions if I may.

I assume the diameter of the thickest shaft is 25mm?

I assume the cutters/holes are at some sort of angle from the centre line of the shaft?

From memory, 2 to 5 deg off of 90 deg so the outer tip cuts first. Could probably grind this angle into the tool bit. The ones I've used leave a little disk as they go through, the don't cut from the pilot hole out.

PDW

I see they also have a morse taper version. if your going to make your own wouldn't this be a better option? Knock the chuck out and fit the cutter directly into the spindle. Removes any error from the chuck or risk of damage to the chuck??

I like that super drill idea, it's been on the project list for ages, never makes it to the top however... Thanks Joe for posting it.... (BTW your monitor is ready)

Back to the original problem, I've had to drill a number of 25mm holes in 6mm steel over the last few weeks, part of a sliding gate project. I used a hole saw in an old AEG hand drill on low speed.. no trouble at all...

So, I think if the OP has a half way decent hand drill with 1/2" capacity chuck and a low speed range, forget the Bunnings drill press and do it by hand. Go half way and flip over, will make it a little easier for chips to clear.

While I was drilling the 25 mm holes in the posts, Josh used the mill and a boring bar to drill the 20 mm diameter holes in the 10mm base plates.. I got the easy job.

Ray

Superdrills are an awesome tool.
300RPM should be fine for a 30mm hole. Work on the rule of 1000RPM for a 10mm hole, 500 for 20mm and so forth. I reckon your cheap bunnings drill press will drop enough speed when you start cutting to not overheat the cutter, make sure you use a good cutting lubricant though.

I'm not clear on the difference between drilling and boring. Is it that the boring scrapes whereas drilling cuts?

Both drilling and boring cut, but drilling cuts material away from the bottom of the hole and boring cuts material away from the side of the hole. (Normally you have to drill a hole before you can bore)

Michael

What Michael said, plus a boring bar is a single point cutter, and is used in a boring head that allows the diameter to adjusted very accurately. So when you want a nice clean hole of fairly accurate dimensions, you use a boring bar.

Boring is done on the lathe as well as a milling machine, when used on a lathe, you don't need the boring head, the lathe cross-slide allows to to move the boring bar to adjust the diameter of the hole.

Slow motion boring video...




Then the next much more advanced stage is a boring and facing head... for that topic, I'll hand you back to Michael...

Ray

PS... Bored yet..

I have only ever used a boring head/boring bar for enlarging the ID of a hole.

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

Say I have milled a 100mm square piece of 12mm thick steel flat and I want to have a 4 mm high x 90mm diameter circle on top, could you use the boring head/boring for this as described above?

Hi Gang,

I have had one of these for probably 15years, I had a good chat to the maker, from what I recall they are hardened, but depending on how much use that may not be necessary. The cutting bits are dead easy to sharpen and flipping them you can do holes in timber, upto 3" I think.
there was also a nifty tool for doing hose clamps out of stainless wire, always meant to make one but it ended up on the must do one day list.
Cheers
Bruce

Originally Posted by jhovel

Here it is - as close as I can make it to mine.
The Hex shaft is a mod - based on the shocking wear on mine. Cutting bigger holes is a struggle for a 1/2" chuck to hold this thing. I you can, make it hex. My original tool is mild steel. A better tool steel one would last longer. Case hardening would be even better.

I'm going to have a go at making a new one as well now. I intend to drill the two tool steel holes 6.35dia and then make a crude broach out of some 6.35 square tool steel (turning one end to 6.35 in a 4-jaw chuck and turning a taper from there to maybe 10mm from the other end. Then use my T&G grinder to make some teeth on all 4 sides along the taper). Then push the broach through the hole in my little press with cutting fluid.

By the way, I think the bottom cutter would be better at 4.8 or 5mm square - I have had the grub screw let go because the thread is a bit too short. Both cutters should be HSS.

In use, you drill a 12.7mm hole on the drill press, then swap for this tool and adjust the stick-out of the bottom cutter to the required radius between 12.7 and 25.4. If a bigger hole is required, then set to 12.7 radius and bore through. Then adjust top cutter to required radius.
Put moly grease on the piloting section and use cutting fluid for the cutter. Feed slowly. When you get a continuously curling swarf coming out of the hole, you have hit the 'sweet spot'.

The kit was/is available with bushes/spacers for larger holes still, but in my view the drive spindle diameter is too small for holes over 50mm and a 1/2" drill press not powerful enough.
If you find this useful for bigger sizes, make a bigger one for your mill!

Originally Posted by Big Shed

I have only ever used a boring head/boring bar for enlarging the ID of a hole.

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

Say I have milled a 100mm square piece of 12mm thick steel flat and I want to have a 4 mm high x 90mm diameter circle on top, could you use the boring head/boring for this as described above?

I've never thought of doing it that way? Normally you would use a rotary table and just normal end-mill. Another way would be to mount it up in a 4 jaw chuck in the lathe. I won't mention CNC.. ( just did.. )

One problem that using a boring bar to do that job is that it would be an interrupted cut, on a large diameter that's going to cause problems with the boring head flexing and carrying on. Apart from those sort of problems I guess it might work?

Ray

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?

Say I have milled a 100mm square piece of 12mm thick steel flat and I want to have a 4 mm high x 90mm diameter circle on top, could you use the boring head/boring for this as described above?

Certainly can - you just need to make sure that the tip is facing the right way so that it will cut

Michael

Originally Posted by RayG

I've never thought of doing it that way? Normally you would use a rotary table and just normal end-mill. Another way would be to mount it up in a 4 jaw chuck in the lathe. I won't mention CNC.. ( just did.. )

One problem that using a boring bar to do that job is that it would be an interrupted cut, on a large diameter that's going to cause problems with the boring head flexing and carrying on. Apart from those sort of problems I guess it might work?

Ray

Yes, I have done it like that (both ways), I was just curious whether it could be done with the boring head/bar.

In the (hypothetical) case above it would only be an interrupted cut for maybe 1 or 2 revolutions, after that it would be uninterrupted.

Originally Posted by Michael G

Certainly can - you just need to make sure that the tip is facing the right way so that it will cut

Michael

Yeah, that would help!