4" core bit

[MNR]

Yep there the ones. One of the sparks on the last site I was on used to use them. Suppose it was all new build with lightweight block.

 

[UNG]

I've got the blue ones from Screwfix. I've done about 20 holes with my 105mm now and it is getting a bit slow in hard brick. It's still okay in softer materials, so I'm going to get a new one and use that on the harder stuff. Might as well wear out the old one completely and get best value from it.

I charge my customers an extra £10 per hole to cover use of the core bit and wear and tear on the drill (Bosch DRE 26-2). Cheaper than hiring (per hole) and cover my costs, so everyone happy.

If your core bits are slowing down in hard brick find or buy a cinder / breeze block and run the core bit through it to deglaze the diamond cutting edge I was told that by a hire shop manager many years ago and they have blocks in the yard to deglaze the hire bits to stop complaints if the previous hirer has polished the diamond in a hard wall

I've done a couple by stitch drilling and knocking out. But I've done a hell of a lot more with core drill and diamond cutter there is really no contest. Not used them before but tct core bit worth having a look at?

TCT bits are best used with a medium to large rotary hammer with a built in clutch, small machines fail very quickly with TCT core bits. There is also more risk of injury with TCT cores in my opinion when they jam

For the few TCT bits I have when drilling stuff the diamond cores won't touch I have one of these MAKITA HR3850K ROTARY DEMOLITION HAMMER BREAKER 110v on eBay!it's 20+ years old but still does a good job when needed but a little bit heavy to use it all day


For diamond cores I use a Makita 8406 with various diameters of diamond core bits, Have done a fair number of holes with it over the last 10 years so it has been worth the investment

It's worth buying a machine that is designed to be used with core drills as they are a bit more powerful and have a clutch that reduces the risk of being thrown off a ladder or possibly a broken wrist if the core bit jams

 

[Mark_Burgess]

I use these made by spectrum they breeze through most materials with ease.

 

[MarkieSparkie]

Buy the best quality you can afford. I can recommend "Norton" as I used these a lot in the past. Last year I was unable to obtain "Norton" from my supplier, in the sizes I required for a particular job, I decided to give "Marcrist" a try, what a revelation! Absolutely superb, speedy and efficient cutting, used either wet or dry. I've cut nearly a hundred holes with a "Marcrist" 117 x 165 CCU850X and still have well defined sharp diamond lands.

Core drills generally come in two forms: - 1) The conventional chuck type takes a hex arbour. 2) The threaded tool holder type takes a screw fit arbour. The former, allow you the flexibility of a standard drill. The later, higher torque of a direct drive at the expense of more laboured tool changing.
Of the chuck type the Makita 8406 is fine example, offerings from Dewalt and Bosch are better, but my personal favourite is the Milwaukee DD2-160XE, the Hilti DD120 and 130 being the firm favourites with the majority of my work mates.
Direct drive types are the professional choice however. The Marcrist DDM2 and DDM3 allow wet and dry cutting at fixed speeds. I have never felt the need for variable speeds when using one of these, I find them remarkably efficient when paired with the same make of core cutter, but a few of my colleagues prefer to use the Milwaukee or Hilti models.

What ever you choose to buy, don’t be tempted to use an SDS drill to drive a large core cutter. The SDS tool holder is very inefficient when used in the hammer stop mode, a large core drill will quickly stress and wear the tool holder and ultimately destroy a SDS if it does not have thermal protection.

If you suspect your drill of getting excessively hot, stop drilling, switch to the max speed range and run it flat out for least 5 minutes in free air to allow the motor fan to cool the windings.

 

[Guest111]

quick tip with core drills when they slow down,hit the diamond bit with an old file so it puts a few dents in it and the cutter is good as new.told to me by a chap who has a company that just does drilling and saved me a load.

 

[pennywise]

Hilti DD-110 for me eats through walls, just a little bit cumbersome in tight spots especially with the vacuum cleaner chuck. core bits are 430mm long too so no extension bars needed. REMS do some nice bits too and are half the price of Hilti