Broken masonry bit

[Jonathan Webb]

Today I have mostly been drilling through a number of pieces of 2" slate. I was about 80% of the way through one and saw glowing coming from the hole of the current piece. On lifting the drill, I realised that the bit was rather shorter than it should be & had been glowing as the broken parts rubbed.

I need this hole where it is and have tried drifting the broken bit out from the other side, but it has presumably at least partially melted in situ. I'm afraid to crack the slate as it's longish & narrow (about 14" x 4" x 2").

I tried various dremel attachments to try & relieve the broken piece but no joy.

I wondered about melting it with my arc welder, but worried that it would probably cause extreme spalling at best.

I had a half-hearted go at drilling into the old bit, but it was getting late & I was hacked off - will an HSS bit drill into a masonry bit?

There aren't any decent tool shops near from which I could get exotic tools, just Screwfix & Wickes and no time to mail order as I need to submit this by the end of Wednesday :-)
Any ideas?
Many thanks

 

[Dcal]

The drill bit probably overheated and melted the braze holding the cutting tip to the drill shank, so you will have a bit of carbide stuck in the hole which won't be easy to drill out.
Can you drill from the other side and force / push the broken bit out?
Is it a SDS bit or just a standard drill on hammer?
Masonry bits need a good hammer action to work properly.

HSS bit will have no chance drilling a small piece of carbide out , the slate dust will trash the bit anyway.
Don't touch it with your welder you will make it worse.

Only other option I can think of is a wet diamond core drill and even that will struggle with carbide, but if you can use a bigger bit it might go over the broken drill bit and get your job done.

 

[Kent]

Think given the size of the slate I should just replace it.
Have you used a thermic lance?

 

[Jonathan Webb]

I read around before starting and everything I read said that as slate is soft, masonry bits were up to it. I went that way also as it's only an 8mm hole and diamond holesaws start somewhat bigger than that. Most of the slate is pretty soft and it has been no problem, although there have been a few hard areas and this must have been one...
The drill is a Tauco pillar drill on slowest speed with water lubrication.

There is about an inch of shaft in there, not just the carbide tips.
I've drilled through from the other side and tried drifting it out, but no movement with the impact I was prepared to administer.
I've got no exotic workshop tools like a thermic lance.
Edit
I'm off to Screwfix to buy misc bits... A small cobalt bit to try & drill the shaft and I've seen a 17mm diamond holesaw that I might try to cut thing out as a plug.

 

[Matrixx]

Can you drill in from the other side with a slightly larger bit ? as its soft I wouldn't use the hammer stetting just slow with lots of water? or you could use a tile drill bit? then drift it out from the other side.

 

[Alan Reynolds]

Spark eroder or Metal Disintegration Machine.

 

[jordan1]

Can you drill in from the other side with a slightly larger bit ? as its soft I wouldn't use the hammer stetting just slow with lots of water? or you could use a tile drill bit? then drift it out from the other side.

X2

 

[Hitch]

I'd try and drill from the back using a slightly larger than the bit that's stuck, then try and punch it through from the top face into the bigger hole.
What sort of bit was it? Don't think I've ever managed to snap a masonry bit, loose a tip, yes, but never snapped off!

 

[Jonathan Webb]

It's a win.
Small diamond holesaw £7 from Mr Screwfix did it. Tapped through as Hitch suggested.
It was a standard SDS masonry but. Only Erbauer: I was given them and prepared to wear them out on this job. Broken part on the rock. Some thin strata on this are pretty tough.
Thanks.

Onwards!

 

[Kent]

I read around before starting and everything I read said that as slate is soft, masonry bits were up to it. I went that way also as it's only an 8mm hole and diamond holesaws start somewhat bigger than that. Most of the slate is pretty soft and it has been no problem, although there have been a few hard areas and this must have been one...
The drill is a Tauco pillar drill on slowest speed with water lubrication.

There is about an inch of shaft in there, not just the carbide tips.
I've drilled through from the other side and tried drifting it out, but no movement with the impact I was prepared to administer.
I've got no exotic workshop tools like a thermic lance.
Edit
I'm off to Screwfix to buy misc bits... A small cobalt bit to try & drill the shaft and I've seen a 17mm diamond holesaw that I might try to cut thing out as a plug.

Slate is soft but it's also prone to getting hot because of all the dust when mechanically drilled or cut. This is why they do it wet.

 

[Jonathan Webb]

Slate is soft but it's also prone to getting hot because of all the dust when mechanically drilled or cut. This is why they do it wet.

I did it wet from the start.
Post mortem showed the TCT teeth missing so my guess is they failed and the thing couldn't rotate and it snapped.
I must have put a bit too much pressure on a particularly hard section-mistvwas soft but parts definitely weren't.
If I do this again, I'll buy in some small diamond drills I've since found.
Interestingly, I also got trace amounts of oil now & then. Black stuff got washed out occasionally which I assumed was just darker dust even though it looked like oil a bit. I finally stopped drilling to investigate when a small pinhead sized blob floated around and i got it onto my finger. I know shale beds can contain oil and this was obviously residue from the shale to slate pricess.

 

[Dcal]

Good to see you got it sorted, what size of tile drill did you end up using?

They are probably a good option if you are worried about damaging the slate but you need to keep them well doused with water and ream it out often to clear the hole, don't expect to get too many holes out of them though.

A big advantage of the diamond core drill is the water is introduced down the center of the drill and brings the drill arises out as it escapes out of the hole so you don't get a slurry that jams the drill.

I went that way also as it's only an 8mm hole and diamond holesaws start somewhat bigger than that

see below for a 8mm diamond core drill, they do exist!

 

[Jonathan Webb]

I didn't have a lot of time as I let it slip somewhat. One of those things that's weeks away, then suddenly it's two days...
I subsequently found these, down to 6mm. I actually need a 10mm hole, although enlarging a smaller hole isn't too gruelling for a masonry bit.
https://www.atsdiamondtools.co.uk/product/electroplated-diamond-holesaws/

 

[Jonathan Webb]

Good to see you got it sorted, what size of tile drill did you end up using?

They are probably a good option if you are worried about damaging the slate but you need to keep them well doused with water and ream it out often to clear the hole, don't expect to get too many holes out of them though.

A big advantage of the diamond core drill is the water is introduced down the center of the drill and brings the drill arises out as it escapes out of the hole so you don't get a slurry that jams the drill.



see below for a 8mm diamond core drill, they do exist!

View attachment 154645

That's interesting to know about the core drill & water. Thanks.
I've never drilled stone before so this is another learning curve. Keeps life interstingi.

The bit was 17mm. I brought it up & flushed it quite a lot and had to break the core off on the deep side. I only needed it for this task and don't have any other expected use for it any time soon. For £7, I'm happy enough.

 

[eLuSiVeMiTe]

Was going to suggest diamond tile bits.
They would have been my first choice for drilling thin slate.

Usually keep a sponge next to the bit and squeeze occasionally. Most have a wax core for dry cutting anyway but porcelain is a pig tp drill.

Glad its solved.

 

[Jonathan Webb]

Was going to suggest diamond tile bits.
They would have been my first choice for drilling thin slate.

Usually keep a sponge next to the bit and squeeze occasionally. Most have a wax core for dry cutting anyway but porcelain is a pig tp drill.

Glad its solved.

Thanks.
This is 2" thick, so not sure if that counts as thin - as it is lumps of rock it could have been 10"+ thick.
This was a wet drill - seeing as I had water set up it made no difference and it was cheaper.
Are the dry ones as good as wet? What happens when the waxl goes?

 

[eLuSiVeMiTe]

There convenient when drilling tiles on a wall. Not sure how lifespan will stack up against normal.

Yeah 2 " isnt thin. Must have been full depth of the bit.

Was recommend these a while back . Might be worth a try. Never got around to buying any
https://www.screwfix.com/p/bosch-x-...gclsrc=aw.ds&dclid=CPu08emE190CFa6lUQodKDEBkg

 

[Jonathan Webb]

There convenient when drilling tiles on a wall. Not sure how lifespan will stack up against normal.

Yeah 2 " isnt thin. Must have been full depth of the bit.

Was recommend these a while back . Might be worth a try. Never got around to buying any
https://www.screwfix.com/p/bosch-x-...gclsrc=aw.ds&dclid=CPu08emE190CFa6lUQodKDEBkg

Yes, I had to break off the internal stump, like using a wood plug cutter.
I bought a couple of 6mm Bosch masonry bits whilst I was in Screwfix, as I had another rock to drill. Not sure if it was these. I don't need impact ability as I think having hammer set on a loose rock wouldn't end well and I was wanting to use my bench drill (no hammer available).

 

[Kent]

That's interesting to know about the core drill & water. Thanks.
I've never drilled stone before so this is another learning curve. Keeps life interstingi.

The bit was 17mm. I brought it up & flushed it quite a lot and had to break the core off on the deep side. I only needed it for this task and don't have any other expected use for it any time soon. For £7, I'm happy enough.

You didn't go straight in with 17 mm did you?

 

[Kent]

Yes, I had to break off the internal stump, like using a wood plug cutter.
I bought a couple of 6mm Bosch masonry bits whilst I was in Screwfix, as I had another rock to drill. Not sure if it was these. I don't need impact ability as I think having hammer set on a loose rock wouldn't end well and I was wanting to use my bench drill (no hammer available).

Other than just getting the first dimple always use hammer. Just hold back on the pressure. If the stone is loose it need sorting before hand because it's not even going to be strong enough to take the load asked