Hi,
I noticed on Toolstation's web site that they sell a small guide bit for use with TCT core drills and a long guide bit for use with diamond core drills. Why is there a difference in length?
I bought a TCT core from them (I couldn't afford a diamond core nor the drill to spin it LOL!) but I would like to use a longer guide bit so that it goes through the brick and marks the centre, allowing me to drill from both sides. Is there any reason I cannot use the longer guide bit?
TIA
I would say the answer is because the length of the guide drill bit is related to the length of the core and the TCT cores tend to be shallow (for cutting holes in tiles and cutting shallow holes in brickwork for electrical accessories, etc), whereas the diamond core drill bits tend to be long (for cutting holes all the way through masonry).
There's no need to buy a special long guide bit, just use an ordinary SDS drill bit to drill the entire guide hole before you even get the Core drill out of it's box. Just make sure your pilot hole is the same diameter as the guide drill that comes with the core drill.
Thanks. I didn't know TCT was for tiles. I thought it was for people like me who couldn't afford the diamond ones! BTW, what is special about diamond drills, other than the safety clutch? Why do diamond cores need their own special drill?
I thought of that after I posted. OTOH if you are lazy, having a long guide bit, would save you having to swap bits ;)
TCT will do softer bricks and blocks etc, but probably won't last long an something very hard.
Depends on the size of the core. My 720W Makita SDS is just on the limit with a 107mm core if you take it gently and get the hole nice and straight. Push it too hard and the clutch lets go. For bigger cores you will need a "core drill" - basically a powerful drill with low speed box, long side handle, and a clutch set to hang on a bit tighter!
On many blocks you will find the guide slows you down if you try to drill a guide hole as you do the core (no hammer action on diamond cores remember). So either pilot right through and use the guide drill just to follow the hole, or just use it to get the core sunk a few mm into the wall, and then take out the guid - the cut will keep the core on centre once its started.
Yes. I've bashed a 70mm wide one through a concrete floor on hammer. Got
2" in, then had to SDS a load of small holes round the circumfernece. Then finished the next 2" with the core again. That took about 30 minutes. Did it nicely (for a new mains water pipe) but the TCT was a little the worse for wear.You want one of these:
Yes, I think I had read that before but for one or two holes, I think TCT is the cheaper option for the occasional DIYer.
I bought a 110mm TCT core and have used it twice to drill for 4" fan ducting. It went through breeze block inner and brick outer, though obviously you have to stop now and again to clear the core.
I hadn't realised that a diamond core of that size could be used in a sds drill, I thought a special drill was essential. I think Aldi do diamond cores; are they any good? For one or two 4" holes they may be worth a go as branded cores that size cost a fortune. I wonder if they also sell a drill to spin them ;)
BTW, I left the core attached to the arbor for months between uses and really fought to take it off. What do you use as a tommy bar to fir through the core? The only bit of metal I could find long enough to go through the 100mm core was a bit of earth rod. It did manage to loosen the core but the rod was bent useless in the process!
TIA
BTW, what do diamond drills have at the end? Do they have a traditional chuck that takes a hex shank? I see that the catalogues offer an sds or hex arbour, so I am guessing the hex is for diamond drills? Surely it can't be for "traditional" drills, as I didn't think these had a clutch?
Google found some old posts from this very group on one of those web sites that "borrows" content from usenet. Someone suggested blue spot cores from Amazon as a cheap source of cores. Are they any good?
I see that "traditional" drills are still being sold. Why would anyone want one when there is sds? Woodworking?
TIA
Oops, forgot to ask: are the arbours all standard diameters or do you need different arbours for different makes of core? Thanks again.
You pick the arbour(s) of choice depending on what drill you have...
The hex one will go in any 13mm or larger chuck. As you rightly suppose, designed for the purpose core drills will have a clutch. However there is nothing stopping you sticking it in a normal chucked drill if you are feeling brave!
Not tried them.... I have used a few different brands and not really noticed much difference between them on hard walls. If going for a 4" one then I would recommend 107mm over 102 however - since the 102 is often not a big enough hole for 4" duct that has anything other than very thin walls.
Smaller, lighter and hence easier to get into some spaces. Higher rotation speed which can make them better for some operations like grinding or wire brushing.
I guess however, most are sold to people wanting a drill, but who are not aware of the advantages of SDS or who don't want to spend the money to buy a decent cordless.
Well - the same applies with the longer cores - although you can sometimes get once complete leaf out in one hit. Depends on how "snaggy" the material is.
According to the makers specs, 107 is beyond the capability of the drill. However experience suggests otherwise if you take it slow and keep a nice straight line.
Toolstation do a basic diamond core at £15 or so...
The core usually has a hex nut welded to the back section. I if it gets stuck too well, then gripping the arbour shaft in a vice, and using a self gripping adjustable spanner (you know the things like a cross between an adjustable spanner and mole grips) on the nut with a few taps of a mallet will sort it.
Winding a few turns of PTFE tape on the thread of the arbour first also helps later removal.
They seem to be standard for most cores. You may need something different for very small ones though. (having said that, a drill bit is probably better once you are down to 25mm)
Small diamond such as 20-22-28mm have a hex end usually, they can have an enlarged end to take an arbor though. Larger diamond such as
38-152mm have an arbor end, with push-fit pilot drill (use the drift to remove it).Amazon do Blue Spot diamond core bits cheaply, and they resell ok too. They can be "extremely good" or "just good" depending on the luck of the draw, and at the price (=A328 for 152mm?) are very good value.
A diamond core drill has a reduction gearbox to give the huge starting torque - note that the "start" tends to be "instant quick" so make sure you go very gently on uneven brick surfaces because you do not want to shear a tab off. This is one reason to buy a core drill bit rather than hire - breaking the tab off a 152mm Hilti bit is likely to be very expensive and is chargeable.
You can pick used diamond core drill up on Ebay, 110V & 240V, but they seem to look rather the worse for wear. If you have a lot to do (bathroom shower toilet 107mm, dryer 107mm, kitchen extractor 152mm, kitchen fan 152mm, wall mounted HVAC 70mm) it can work out ok. A note re kitchen extractor, go for 152mm because you can sleeve down. BES do a brown gravity flap for 125mm & 150mm which has the same 200mm outside "form-factor-n-holes" so you can just fit a 5" tube through to spigot & wall plate on the inside, if you later go to a bigger cooker hood it is easy to upgrade as needed. Do sleeve the cavity properly, a relative had a slip tube since 1996 and it never sealed properly on a dryer - duct tape unwinds even amalgamating didn't bond fully, going to be a long weekend or two sorting that mess out when we go cool weather again.
Most fun of all, if you have not met diamond dust, you will soon - it makes a mockery of IP66 due to particle size :-) 110V TX vary from pig heavy (1.5kVA) to plain misery (3.3kVA) so you may want a 110V extension if doing a lot of stuff.
A pity no-one has done a "hybrid" SDS drill with 2:1 gearbox or similar. Diamond core drills are rather expensive for what they are - unremarkable motor rating, just a reduction gearbox and heavier duty clutch assembly, =A3300 for a Makita. I believe some are 2 speed and some a re 1 speed (all those I have hired are 1 speed which is rather inappropriate). Big core means very slow & small core means somewhat quicker but not quick. Let the bit do the cutting and keep it straight because they do like to wander if one brick is hard and another very soft. True engineering takes... time to drill thro and cheap core bits will just spark due to "too much glass and too little diamond", screeching is the first indicator.
A final comment is "getting started" with small diameter but very long bits (22x350mm), these lack a guide drill and can wander particularly on textured brickwork. It can be worth having a short small diamond bit to machine a "pocket starter", Ebay do 20mm from Hong Kong (7-8 working days) which are fine for this in a cordless drill. I used a stub 20mm core drill one today to start off a very long 22mm bit (sleeving through a cavity) and again to enlarge the 22mm ends to take
20mm conduit bell-bush (silicone flex to halogen does not like sharp edges). I also used a stub 20mm core drill to create a cutout perimeter for a 152mm bit which was "skipping around" despite pilot drill due to one very hard & uneven brick surface, the 1-speed makita core drill would not soft or slow start enough with such a huge "barrel of a core drill bit".Wonderful tools with no breakout compared to SDS (you can screw a plank the other side and stitch drill, it needs care to avoid a bell- mouth effect with the middle too small and outer too large). Wear goggles & mask or you will need a JCB to clear your nasal passages out.
I have the cheapy sparky core drill - and it is not really much better than using the Makita SDS. The clutch lets go a little later - but not much later, and it in theory has about another 300W of power. But if you get an awkward hole, you can still find it difficult making progress without the clutch kicking in frequently. I think with hindsight, buying cheap cores is ok, but its worth spending more on the drill.
Cutting a matching hole in a lump of ply can also help - that can be either held against or screwed to the wall to provide cantering.
And the worst job is holding one overhead to cut a boiler flue exit hole near a ceiling...!
Very much so unless you are a hire firm :-) With even a cheap diamond core drill it takes a very long time to wear the tabs off, but just a mistake to break one. Generic are about 60% of the speed of Marcrist & Hilti, but it can take a bit to wear in and take the glaze off.
That does not bear thinking about.
I think the best solution for mains diamond tools is plastic sheet the floor, walls, ceiling - and yourself. Use the tool, slip out of the bagged room, use a vacuum not to pick up the dust, but compress the bag down to something small and bin :-)
I had a look at TS but hadn't found these. It seems they are hiding in the clearance section and there aren't many of the big ones left. The TS search isn't very good imho as it never seems to find what you search for.
So much of TS stock used to be Silverline. Did someone here say there was a link between the two companies? I had a look in the Silverline power tools section but I couldn't see a core drill listed.
This was a Silverline TCT core and it didn't have a nut on the back; just two holes on opposite sides, so I guess you were supposed to but a bar through. There were flats on the arbor so that you could hold it with a spanner.
Thanks for the tip, I will try it next time.
A bit like with hole saws then.
Ah, I was wondering why I hadn't seen anything for 15mm and 22mm pipe sizes. That explains why.
I guess I should get a core for 32mm and 40mm wastes but I think they are internal diameters IIRC and also vary between push fit and solvent weld, so I never know what size to get.
Thanks again.
I do have an old green bosch with two gears that never gets used now that I have got an sds drill. Perhaps that's something I could use if for (in low gear) but I'd only use small cores: it wouldn't be nice if a 107mm core stuck in it!
That's reassuring. I will try to get a silverline or blue spot if there's no real difference between those and ones that cost four times as much.
Noted, thanks. Looks like there's not much room for error if you go with 152mm for 6" ducting though.
But how do you explain the corded blue bosch models?
Thanks.
Is it much worse than any other type of drill dust?
Or buy 240v?
Oops. Too late. Just ordered some cheap ones!
No breakout at all? Can you drill just from the inside and not worry about ruining your brick wall? That sounds too good to be true!
Were your comments about sds on hammer? I used a TCT core without hammer action but even that punched the face off the brick and I had to replace the brick and do it again properly from both sides ;)
Thanks again.
Well, drill dust is large particulate and tends to fall IME close to the drilling. Same with holesaw in plasterboard. Bit messy but doesn't hang in the air.
Angle grinder and sanding output is far worse - finer particles which tend to float in the air for ages.
I can see diamond grinding could produce an even finer dust, so I would expect much evil.
Think I'll stick to TCT cores - bit messy, but the crap is similar to drill dust and tends to fall fairly quickly into a pile on the floor. Certainly doesn't fill the room.
Think custard powder, jewellers rouge, talc powder, some is actually akin to smoke.
Remember nearly all drills (even cordless) are fan cooled, which results in a blast of air near the drilling site so as to propel a virtual "smoke" particulate size into convective air streams where it will carry for some distance.
It does depend on what you are drilling into and size of the bit. Large bits create a substantial amount of "smoke & talc", incredibly soft to your fingers and clumps very much like custard powder.
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