[GutsyGibbon]

Originally Posted by SB08121980

I don't understand.
Are you implying that a drill machine which can drill a 10mm hole in, say, regular hot rolled MS ( mild steel ), can easily drill a 30mm hole in concrete or wood? If Yes, what type of drill bits are we talking about?

Regardless of the quality of drill bit, using a smaller diameter drill bit to make bigger holes cant be safe. (if that is what was meant here) The bits for metal, concrete and wood are all different. Using something meant for one material on other, just ruins the bit and the job.

With power tools, most jobs should be like hot knife through butter. If it requires too much strength you are either impatient, or you are trying too hard.

[SB08121980]

Originally Posted by GutsyGibbon

Regardless of the quality of drill bit, using a smaller diameter drill bit to make bigger holes cant be safe. (if that is what was meant here) The bits for metal, concrete and wood are all different. Using something meant for one material on other, just ruins the bit and the job.

That's not what I meant .

What I meant was what kind of parallel shank drill bit can be fitted in a 10mm Jacob style chuck ( keyed or keyless ) that can drill a 30 mm hole in concrete ?

To my knowledge there are no parallel shank masonry drill bits above 8 mm . Above 8 mm all are SDS plus or SDS Max style drill bits . You cannot fit SDS style bits in a jacob style chuck ; your machine needs to have a SDS chuck .

As per using different types of drill bits for different material , I use HSS ( Bosch HSS-G ) for mild steel . Brad point bits for wood and SDS Plus bit for concrete .

As for technique, to drill in MS , you need to keep the RPMs lower than 400 and apply a lot of downward force and use cutting oil ( I use old engine oil ). I have a Ibell electric screwdriver , which serves as a drill too . To drill holes of size 10mm , I drill a pilot 4mm hole and then enlarge it with a 10mm HSS bit .

For wood , same Ibell drill and brad point bits and full speed .

For concrete , SDS Plus Drill machine in hammer mode and SDS bits , full speed and necessarily ear protection .

So reeling it back in , to my question , I was interested to know how can drill machine which has a 13mm jacob chuck ( and probably a 550 -600 watt motor ) , no decent hammer action, drill a 30mm hole in concrete ?

[Aroy]

Originally Posted by SB08121980

That's not what I meant .

What I meant was what kind of parallel shank drill bit can be fitted in a 10mm Jacob style chuck ( keyed or keyless ) that can drill a 30 mm hole in concrete ?

...............................
So reeling it back in , to my question , I was interested to know how can drill machine which has a 13mm jacob chuck ( and probably a 550 -600 watt motor ) , no decent hammer action, drill a 30mm hole in concrete ?

There are portable drill machines with upto 25mm capacity that use parallel shank drill bits - check the professional ranges.

Coming to drilling capacity, the old time nomenclature was for the capacity to drill in mild steel. So a 10mm wold be good enough to drill holes in 10mm and 25mm for 25mm holes in steel. So that you do not overload the drill, the chucks would accept bits upto the rated capacity only.

Tapered chucks are mostly used on stationary high capacity drills, rarely for portable machines.

For concrete and masonry drills now a days use the "hammer mode". This mode will cut and dislodge the concrete/masonry rubble. This mode is useless for steel and other homodenous materials which require brute force to cut (unlike masonry that both cuts and shatters material).

Regarding paralell shanks. As masonry requires less power than steel, bits of higher capacity are made with the lower portion that is 10mm to 12mm for the first 50mm or so and then full width for the rest. I have various diameter masonry bits - 4, 5, 6, 8, 10, 12, 20mm diameter and 80mm to 300m long. The bits 12mm onwards have 10mm shank at te end and then full diameter later

[Thad E Ginathom]

Originally Posted by Aroy

For concrete and masonry drills now a days use the "hammer mode". This mode will cut and dislodge the concrete/masonry rubble. This mode is useless for steel and other homodenous materials which require brute force to cut (unlike masonry that both cuts and shatters material).

Indeed. Worth mentioning that steel and some other metals work-harden. Using a drill in hammer mode would be just awful. Actually, one would probably break the drill bit?

(I have not drilled steel with a hand drill. I've made holes in it with bench drills. It was fifty years ago --- but I still remember how difficult the stainless-steel batches were!)

[sagarpadaki]

The metal drill bits that come in the Bosch drill kit are utter crap. All of them just broke with mild pressure on mild steel.

Got the Addison branded drill bits from local hardware and they held up well. I do not know if they are the best, but they did the job well!

[Thad E Ginathom]

Originally Posted by sagarpadaki

The metal drill bits that come in the Bosch drill kit are utter crap.

I once bought a boxed set of "Bosch" drills from Amazon.in. Yes, they were rubbish. The wood drills would not even cut wood.

[Jeroen]

Originally Posted by sagarpadaki

The metal drill bits that come in the Bosch drill kit are utter crap. All of them just broke with mild pressure on mild steel.!

Could well be, I have experienced something similar. Mind you the trick with small drills, especially in steel, is to use really high RPMs. And to use cutting fluid liberally.

Even so, I stock a lot of spare drills, especially the smaller diameters. Which are a lot of drills. For my model engineering I need just about all sizes in 0,1mm increments. And my mini mill, lovely as it is, can only run about 1500RPM, which is way too slow.

Mind you, I use HSS drill bits most of the time and I also use them on different materials, such as steel, brass, aluminium, cast iron. Technically you should keep each drill bit for a different material and they require different sharpening for different materials. If I need a really precision hole in any metal I would use a drill and a reamer. Works really well.

Jeroen

[sagarpadaki]

Slightly offtopic, but I always wondered why there is a forward and reverse (Clockwise/AntiClockwise) rotation option on drills. Is there any drill application that makes holes in counterclockwise direction?

I have never used the reverse direction in any of my corded drills. For impact drivers, yes it makes sense to fasten/unfasten. Never understood this usage of drills?

[Thad E Ginathom]

Originally Posted by sagarpadaki

I always wondered why there is a forward and reverse (Clockwise/AntiClockwise) rotation option on drills.

I use it.

I do not do enough DIY to make it worth having an electric screwdriver. I use the drill. Backwards rotation to unscrew,

For the pedantic ...

Yes, there are bits with a reverse thread. They are used for extracting broken bolts. The idea being that hopefully they will cut into and grab the broken piece and unscrew it.

Please ask youtube for the details. Or our Engineer Jeroen probably knows?

[sagarpadaki]

Originally Posted by Thad E Ginathom

I use it.

I do not do enough DIY to make it worth having an electric screwdriver. I use the drill. Backwards rotation to unscrew,

For the pedantic ...

Yes, there are bits with a reverse thread. They are used for extracting broken bolts. The idea being that hopefully they will cut into and grab the broken piece and unscrew it.

Please ask Youtube for the details. Or our Engineer Jeroen probably knows?

Don't you find using a corded drill with its bulk and weight, cumbersome to use for unscrew? Heck, I tried once to fasten a PH2 screw into the wood using corded drill and ended up stripping the head. It felt so ungainly! Or maybe I was doing wrong!?

[Aroy]

Originally Posted by sagarpadaki

Don't you find using a corded drill with its bulk and weight, cumbersome to use for unscrew? Heck, I tried once to fasten a PH2 screw into the wood using corded drill and ended up stripping the head. It felt so ungainly! Or maybe I was doing wrong!?

I bought a Wolf electric screw/bolt driver, ages ago (~1975). It is basically a hand drill (13mm size) with gearing and both forward and reverse direction.s.

[Thad E Ginathom]

Originally Posted by sagarpadaki

Don't you find using a corded drill with its bulk and weight, cumbersome to use for unscrew? Heck, I tried once to fasten a PH2 screw into the wood using corded drill and ended up stripping the head. It felt so ungainly! Or maybe I was doing wrong!?

Not really, but nor do I find it ideal. It is a compromise. My drill and I have been together for maybe thirty years.

My drill has finely adjustable speed, so I am always doing this very slowly. I understand that dedicated screwdrivers are able to apply a lot more torque. I will always be using a good old manual screwdriver to loosen or fully tighten a screw.

For mechanical screws, like wall switches, I have an 4*AA-powered electric screwdriver. Cheap, great within its limitations. I first had one of these at a time when I was assembling a lot of PCs, and it helped hugely with case screws etc.

[OPMaurya]

Interesting discussion on drilling
We were taught on actually calculating the RPM required for drilling. This is dependent on the drill material, workpiece material as well as the drill geometry.
Not going into the theory part, in general, smaller the drill bit size, higher the RPM.
Also, never force the drill. The drill should go freely by itself - smoothly. If the drill is forced, it means the cutting edge is gone and it will rub and not cut, liable to break, if smaller size. Heck, I have seen drill bit of 20mm breaking like this, when someone was being too impatient.
This is true for other cutting tools, as well; like hacksaw. Don't force the tool. Be considerate of the tool. You'll feel at a peace and enjoy the actual experience
If someone wants to go in detail- try looking up metal cutting theory. There is plenty of stuff on the internet.

Drilling speed calculator that I got through Google search : https://krankengineering.com/drilling-speeds/

[Jeroen]

Originally Posted by sagarpadaki

Slightly offtopic, but I always wondered why there is a forward and reverse (Clockwise/AntiClockwise) rotation option on drills. Is there any drill application that makes holes in counterclockwise direction?
?

The counterclockwise rotation is in case you want to undrill a hole. Clockwise drills the hole, counterclockwise in drills the hole. ��

Originally Posted by Thad E Ginathom

I use it.

I do not do enough DIY to make it worth having an electric screwdriver. I use the drill. Backwards rotation to unscrew,

For the pedantic ...

Yes, there are bits with a reverse thread. They are used for extracting broken bolts. The idea being that hopefully they will cut into and grab the broken piece and unscrew it.

Seriously, most people use the reverse for unscrewing. The theory of reverse with a drill bit, is the drill bit is pulled from the hole more cleanly and precisely. I don’t think anybody does that in practice.

I am trying to remember if we reversed the drill string on oil rigs when extracting. Don’t think so.

There are reverse or left drill bits too! They are used in combination with these extractor bits.

https://www.amazon.com/reverse-drill...rse+drill+bits

I have a set of these extractor bits. I have used them a couple of times, but they never worked for me. Always had to resort to different techniques from getting a broken bolt out of something. The idea is you use the reverse drill bit, to drill the hole on which you will be using the extractor.

Jeroen

[Jeroen]

Just to add to my previous post. I decided to look up my little set of extractors. I found these, but I could have sworn I had a different set.





These have a left hand (!) drill bit on one side and the side is the extractor, which also needs to be turned left (CCW).





Lots of YouTubers about who will show how easy it is to use these things. But they don’t work particularly well for me.

Jeroen