Maximum hole diameter - drills

[diy_fun_uk]

I'm looking to buy a new drill (cordless) and I notice in the blurb it gives a maximum hole diameter for the drill e.g. masonry 10mm, metal 12mm, wood 30mm. However, taking masonry as an example, surely if you weren't abusing the drill by exerting too much pressure you could be using a larger masonry bit? And the same surely holds true for metal and wood?

If I'm correct, what are the manufacturers basing their (somewhat conservative) sizes on?

 

[Deleted member 174758]

The sizes are only recommended so deviating slightly won't be a killer (other than drill.bits having too big a shank to.fit in the chuck). The metal drill size you can generally take as the maximum physical size of drill shank the chuck will accommodate, but not always. One thing to understand is that if you exceed these recommended sizes, on cordless drills at least, you risk overheating the motor and the battery of the tool. This could mean bye bye motor, but is more likely to either see the battery off or at the very least cause the protection circuitry to kick in in order to save the aforementioned motor and/or battery. The bad news, though, is that this electrical protection whilst fitted to modern (I.e. last 5 to 8 years) professional level kit is either rudimentary or completely missing from DIY, Chinese knock-off and older professional gear. So, caveat emptor!

What I have found is that using far too large a drill bit results in often horribly slow drilling with everything getting a bit warm. I haven't cooked a motor yet, but I have cooked batteries (in the days before protective circuitry). The biggest killer was always a combination of underpowered cordless drill, large hole saw (100mm and above) and especially warm flat roofs (2 or 3 layers of torched-on felt over 100mm plus of mineral wool over hardwood plywood).

In case you are wondering , selecting too small (motor power) corded drill then running a massive oversized drill bit in it will also potentially result in a cooked motor. Smelled a few of those in my time. Once again the manufacturers generally fit a chuck to suit the largest metal drill bit the motor can sustain without overheating the the motor. It isn't arbitrary (unless, of course, you are buying Chinese stuff where seemingly anything goes)

One other point to note; many DIYers (and not a few trades) seem to always want to select the maximum speed the drill will run at, a practice which can blunt bits and even reduce cutting rate This isn't always the best - always match the drill speed to the diameter of the tooling

 

[diy_fun_uk]

The sizes are only recommended so deviating slightly won't be a killer (other than drill.bits having too big a shank to.fit in the chuck). The metal drill size you can generally take as the maximum physical size of drill shank the chuck will accommodate, but not always. One thing to understand is that if you exceed these recommended sizes, on cordless drills at least, you risk overheating the motor and the battery of the tool. This could mean bye bye motor, but is more likely to either see the battery off or at the very least cause the protection circuitry to kick in in order to save the aforementioned motor and/or battery. The bad news, though, is that this electrical protection whilst fitted to modern (I.e. last 5 to 8 years) professional level kit is either rudimentary or completely missing from DIY, Chinese knock-off and older professional gear. So, caveat emptor!

What I have found is that using far too large a drill bit results in often horribly slow drilling with everything getting a bit warm. I haven't cooked a motor yet, but I have cooked batteries (in the days before protective circuitry). The biggest killer was always a combination of underpowered cordless drill, large hole saw (100mm and above) and especially warm flat roofs (2 or 3 layers of torched-on felt over 100mm plus of mineral wool over hardwood plywood).

In case you are wondering , selecting too small (motor power) corded drill then running a massive oversized drill bit in it will also potentially result in a cooked motor. Smelled a few of those in my time. Once again the manufacturers generally fit a chuck to suit the largest metal drill bit the motor can sustain without overheating the the motor. It isn't arbitrary (unless, of course, you are buying Chinese stuff where seemingly anything goes)

One other point to note; many DIYers (and not a few trades) seem to always want to select the maximum speed the drill will run at, a practice which can blunt bits and even reduce cutting rate This isn't always the best - always match the drill speed to the diameter of the tooling

Thanks for the detailed reply. I've been using a basic corded Black & Decker that I've had for around 25 years if not more. Still works, I've never hashed it. However need to do work under my house including screwing home multiple screws, so a cordless will save me taking the corded down there and tiring myself with manual screwdriver. I don't need the best, neither do I want to buy cheap tat, so I'm going to settle on this:

Bosch GSB 18V-55 18V 2.0Ah Li-Ion Coolpack Brushless Cordless Combi Drill | Combi Drills | Screwfix.com

 

[ETAF]

However need to do work under my house including screwing home multiple screws,

you may want to look at a Impact driver - kit , and use that for doing the screwing, just an idea - i like the dewalt 3 speed impact driver as you have control over the impact and mine came with a combi drill in a kit from screwfix, for £119 with 2 batts
BUT i'm a DIYer so no expert here

 

[lostinthelight]

Oops! I may have overdone it a little

 

[JohnD]

wet?

 

[lostinthelight]

wet?

Dry, cut kept clear with air gun

 

[SFK]

,don't need the best, neither do I want to buy cheap tat, so I'm going to settle on this

Whichever drill you get, I suggest you get it with two batteries. You can then charge one whilst using the other.

Cheaper to buy in a pack, so in your preferred Bosch case an extra £30 at £129.99 gets the second battery version.

https://www.screwfix.com/p/bosch-06019h1170-18v-2-0ah-li-ion-coolpack-cordless-combi-drill/714fv

If you want/need/afford an impact driver I would get the one of the dewalt packs that comes with a drill and driver and two batteries for about £170 and £180.

https://www.screwfix.com/c/tools/kits-twinpacks/cat830712

Also avaliable from other suppliers.
Also try www.ffx.co.uk

Sfk

 

[SFK]

If brand name is not an issue, At the moment these might be considered as better deals than the Bosch you are looking at (one is cheaper, one has bigger batteries).

https://www.screwfix.com/c/tools/combi-drills/cat830832?modelno=m18_bpdn_402c|dcd778d2t_sfgb

 

[foxhole]

Some cordless drill have a smaller Chuck size and won’t accept some hole saw arbours .

 

[Notch7]

I find auger drill bits with a screw tip to be the killer

I use them with a Milwaukee 18v drill with 4ah battery and even the struggles with bigger sizes.

Wrist breakers too.

 

[Deleted member 174758]

I find auger drill bits with a screw tip to be the killer.

At least with them the shank size generally precludes the use of lower powered drills because it is so big.

In terms of torque you might find a standard keyed chuck fitted onto a cordless SDS is more capable of handling it than a cordless combi drill. The only solution I can think of for wrist snapping (as a result of a snatch) on a combi drill, albeit a poorish one, is to use one of those extra long side handles seen with the heaviest combi drills.

 

[diy_fun_uk]

Guys ... I've got a confession to make.

Yes I started this thread but ...

I've decided just to drill the pilot holes using my corded drill (with extension lead) and bought a £20 cordless driver to drive the screws home.

Me? Tight?!? How VERY dare you

 

[SFK]

£20 cordless driver

Nothing wrong with using a Corded drill to make holes.

But if on a budget I would have suggested the following over a powered screw driver to screw screws.
Simply because it will get used more often on more jobs, and has a torque setting so can minimize breakthroughs, has variable speed (easier to start at slow speed and faster to finish), and battery lasts a lot longer (£20 screw diver might only get a few screws in the wall before requiring recharging).

£30
https://www.toolstation.com/bauker-12v-cordless-drill-driver/p83914
or
£45
https://www.toolstation.com/bauker-18v-cordless-drill-driver/p91867

(but note that neither have hammer function, you need £50 for that).
SFK

 

[Deleted member 174758]

I've got to concur about corded tools. At the bottom end (in price terms) you are almost always going to get more bang for your buck than you will get from cordless. As a tradesman I need to use cordless simply because it avoids having to cart around a girt great transformer or massive numbers of extension cables. These aren't issues a DIYer needs to worry about all that often