Core bit for bathroom extractor hole

[Jupiter01]

I will be using one of these to drill out a hole for the bathroom extractor and wanted to check if it is sensible to start this hole from the inside or the outside please?
I can access the outside quite easily and will be making good on the inside anyway. I wanted to avoid the exterior bricks flying out and making an awful mess.

 

[mrStat]

Personally I prefer to core outside to inside because of the mess and dust.

Depending on the wall type and the finish required, if needed I will pilot all the way through, do 90% of the core from the outside and then finish the core from the inside to get a good finish. However this takes some practice as get the angle slightly wrong and it’ll just be a mess.

 

[dilalio]

Are you buying or hiring the drill and diamond core cutter?
Make sure it's decent kit and that the drill has a proper clutch on it as you don't want it breaking your wrists or chin if it gets bound up.
Don't have it on rotary hammer!
Outside to in means less to clean up inside, but you'll still need to wash down all the dust outside from windows etc and a windy day will send it everywhere.
On really tough walls or where the core keeps wanting to bind, I'll go in a few inches and then break out the plug with the hammer action of the drill and an sds chisel bit... This keeps the core bit free to turn for the next few inches.
Keep the drill true and level.
A decent bit will not blow the bricks if drilling from inside to out.
And finally, do whatever checks you can to make sure you don't hit a pipe, cable, lintel, brick tie etc!
My sparky went straight through a lead main, buried in the wall last week... He got very wet

 

[Jupiter01]

Thanks for the responses.
Firstly, I own a Bosch GBH 2-26DRE SDS Hammer Drill which I was planning to use with a Core Bit that I will hire. I am assuming the hired bit will be good quality and given how infrequently I use this, it probably makes sense to hire this instead of purchasing.

Can someone please confirm that my drill is safe to use for this purpose and has "clutch"? I've seen the safety videos on how the drill should be positioned whilst drilling this out.

 

[Gasguru]

You haven't mentioned what type of core...diamond or TCT and what the walls comprised of...soft brick, eng brick, concrete, ironstone, granite etc. Can you afford to make a mess on the inside or would dust extraction be necessary?

 

[Jupiter01]

Diamond core. I have a brick and block cavity wall to get through. Mess on the inside is fine as I need to make good anyway.

 

[ianmcd]

drill from outside, far less mess and just dont try to force the drill, let the core do the work and it wont make a mess

 

[mrStat]

Thanks for the responses.
Firstly, I own a Bosch GBH 2-26DRE SDS Hammer Drill which I was planning to use with a Core Bit that I will hire. I am assuming the hired bit will be good quality and given how infrequently I use this, it probably makes sense to hire this instead of purchasing.

Can someone please confirm that my drill is safe to use for this purpose and has "clutch"? I've seen the safety videos on how the drill should be positioned whilst drilling this out.

So your drill has a safety clutch, for a standard dry diamond cut it will "probably" do the job, but it was definitely not made for core drills, spec on that says max 68mm (2 1/2"?)... It will do the job in most brick and block, but may take a couple of years off of the drills life and be a bit of a muscle stretcher holding it in place. There are specialist drills out there designed for core bits, I use a GBH8-45, she's a beast, but was made for coring... For a 1 off core you will get away with it, but if you are going to a hire centre, personally, I'd just rent theirs... Of course, price of a core bit and mandrel, if you are only using it once, a quick trip to screwfix will suffice and then throw it in the bin after.

I find it's surfaces like tile and concrete that eat up core bits, std brick (Not engineering) and block can be cored without too much fuss. I know our apprentices get a buzz when they start doing their first core - But halfway through and the arms starting to ache they realise the benefits of letting the drill do the work. Slow and steady.

 

[dilalio]

Thanks for the responses.
Firstly, I own a Bosch GBH 2-26DRE SDS Hammer Drill which I was planning to use with a Core Bit that I will hire. I am assuming the hired bit will be good quality and given how infrequently I use this, it probably makes sense to hire this instead of purchasing.

Can someone please confirm that my drill is safe to use for this purpose and has "clutch"? I've seen the safety videos on how the drill should be positioned whilst drilling this out.

I always use my trusty 240v makita 3in1 sds drill. It's not specific to core drilling but it's lightweight and I have a feel for it and the clutch is very forgiving. I couldn't comment on other brands/models as I don't use them. Your bosch should be up to the job but until you get familiar with how it copes with a 4" core just go nice and steady and hold it in a way that allows you to quickly release your grip.

 

[dilalio]

Diamond core. I have a brick and block cavity wall to get through. Mess on the inside is fine as I need to make good anyway.

Keep it level and true and it should pi$$ through it

 

[Jupiter01]

Thanks for all the help guys. Really appreciate it.

 

[dilalio]

Thanks for all the help guys. Really appreciate it.

Its like drilling porcelain tiles... You'll go through some like a knife through butter and others will have you straining for an hour! Wet walls when core drilling are the worst... even when it's just standard block and brick.

 

[Jupiter01]

will definitely provide a update once I've done it (and survived it!)

 

[mrStat]

Honestly, it's not as bad as it initially seems... You'll be amazed at the dust it kicks up though, so if you are going in-to-out - Keep the door closed.

 

[lostinthelight]

I've had one of those drills for years and in that time have cored scores of holes , some through reinforced concrete and most have been 110mm clearance holes.
One thing you may find is the clutch is too ready to slip so its is softly softly to ease it through