Core drill bit extension

[meddyliol]

My son has to drill a 52cm hole in a wall which is about 50cm thick. He is thinking of getting the Erbauer 52cm bit plus an Arbor. The problem seems to be that getting an arbor long enough is difficult. It must be possible otherwise nobody would be able to do it.
Any advice would be greatly appreciated.

Thanks

Brian

 

[AC Power]

You mentioned a 52cm (21") diameter hole? Do you mean 52mm (2")?

Too, is the wall 50cm (19 1/2") thick?

 

[meddyliol]

The wall is about 50cm thick (a 1847 house). Sorry, I must have had a mind burp, the extractor ducting is 150mm. So the hole will be 152mm if that will be big enough.

 

[AC Power]

Well, if it poured concrete, your going to need to have it cored, wet diamond core saw, by a subcontractor. If it's sandstone, block, brick, or wood, you might manage with portable residential homeowner power tool/s. It would be a long arduous task, but it could happen.

 

[meddyliol]

The wall is (I believe) sandstone. It would obviously need a long enough arbor to get through. Any ideas as to what core bit arbor is any good? There is one on Amazon by Amtech for £9.60 350mm long. I don't know if it is wise to connect shorter lengths together to make up the required length.

 

[AC Power]

I did look, but most of the small residential tool (Amtech) drill extensions are only 1/4" bore. Your not going to find a 6" (150mm) diamond hole saw that will adapt to a 1/4" shaft.....too small.

As a side point, you won't need a core drill for this (provided it's sandstone). Just keep the hole saw wet, low speed. Sandstone is VERY easy to core through. But otherwise.....I can't think of how a homeowner could make a 6" hole through 20" of sandstone without commercial assistance.

 

[meddyliol]

OK, thanks for your help. I think this will take a bit of thought and maybe a professional. What exactly is a hole saw anyway?

 

[meddyliol]

The Starrett BMA4250 Extension Bar Rod on Amazon has 1/2' BSP and the Starrett 24cm adapter should be OK (I think)? What do you think?

 

[AC Power]

It would appear those would work, yes. You might need two (2) of the BMA4250 (screwed together to make 20" long).

What are you using for a hole saw?

What are you using for a drill? (Is it an SDS chuck, or a Jacob's three jaw chuck?)

 

[meddyliol]

Using an SDS drill and don't know yet what hole saw. Found a plumber who said he could do it so will see. Thank you very much for your assistance. If and when we do it ourselves, will let you know the outcome.

 

[meddyliol]

I am going to get one of these Mexco Solid Dry Diamond Core Drill 162mm and the extension parts previously mentioned. What I am not sure of, there is no mention of a pilot drill, so I have no idea what sort of pilot drill would fit. Any help would be appreciated.

Brian

 

[AC Power]

I wouldn't worry about the pilot bit.

Built a scrap lumber rest (forming an "X"), rub some hand soap on the upper cradle of the wood for the hole saw to spin easily. Start your coring....once your 1/4-1/2" into the cut (13mm or so), you won' need the wood anymore, nor would you have needed the pilot bit neither. A pilot bit is just there for STARTING a hole saw's cut. See my picture below?

By the way, you'll find you preserve the diamond in your saw, and increase speed if you keep it wet. Just use a "Windex" spray bottle with water in it, and keep the cutting wet. You should have sufficient water so it runs down the wall. You may have to wet-vacuum, or mop/towel, the puddle as it forms. It makes the job WAY easier, and also keeps the dust WAY down.

 

[meddyliol]

Thanks a lot, what a good idea. I was concerned about the pilot drill but not now.

Ta very much

Brian

 

[AC Power]

Hope it all works our for you.

When your done, take a pic and send it to me somehow, that is, if you want to.

 

[meddyliol]

OK, will do. Have ordered the bits etc, my son is strong (unlike me) so if it can be done he will do it.

 

[AC Power]

Nice. I get my son to do things too. Good Luck!

 

[meddyliol]

Well, we managed to get a hole drilled. I was wrong about it being a 50cm thick wall, it actually measured 48.5cm. The main problems were: The `Titan drill was supposed to have a safety clutch, if it did, it didn't work and my son nearly broke his wrist a few times. The said drill went back to Screwfix and we had it replaced with an Erbauer ERH750. This is about half the weight of the Titan although less powerful. Well, on a slow speed the clutch certainly worked, a little too well. It kept slipping. We decided to have a go with my Bosch drill, even less powerful. This did the same, clutch slipping on slow speed. So he thought, "hell to this and put it on the top speed, lo and behold it solved the problem until smoke started coming out of it. Put it outside to cool off and went back to the Erbauer and did the same thing. The core bit went through quite easily. Hole finished. Another problem is because this house was built in 1847 there is a cavity filled with rubble. This didn't help. By the way, the hole had to be drilled right at the top of the wall even going through the coving.
Anyway we now have a hole.

Thanks again for everybody's help

Brian

 

[AC Power]

I am really glad you came back to tell us how it worked, I was actually wondering about it.

Well, your right in saying "....we now have a hole." Good for you. I TOTALLY know what you mean by overpowered drills...they can be dangerous....I have about three of them (Milwaukee Magnum Hole Shooters), they are small, but MEGA powerful.

Anyways, good on you!