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Masonry type question for Turntable build.
Masonry type question for Turntable build.
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Old 21st June 2010, 01:55 PM   #1
JoshK is offline JoshK  Canada
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Default Masonry type question for Turntable build.

So, I have a bit of a conundrum. I bought a prototype slate plinth for my Teres. The armboard is slate as well. The armboard was drilled for my Rega RB300, however the mounting post is not long enough to reach all the way through the armboard, so I need to countersink from the back side so that I can attach the nut.

I've been told that slate drills relatively easy with masonry bits. However, I have no clue what kind of bit can be used for such a counter-sink job where the hole is not going to go all the way through. Any ideas? I need the hole to be ~ 1.5-2".
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Old 23rd June 2010, 03:49 AM   #2
Golana is offline Golana  United States
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I found these at a decent price, and would recon its what you need.Lowes or other box stores will also have 'em. I have drilled 100"S of these holes. Keep it wet, reel wet. and draw a black marker line at how deep you want, around the core bit. Slate is a layered stone, take a screw driver etc..., and stick it in the newly cut crevis and twist. It should break cleanly away. Keep your screw driver against the most meat.
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Old 23rd June 2010, 05:03 AM   #3
40 watt is offline 40 watt  Canada
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Good deal on those bits. They will drill a nice hole for sure...however, since the hole you want does not pass all the way through it will be tricky removing the slate core and not damaging the rest of the armboard, or breaking it. It can be done, though. Perhaps a small SDS bit would be good for removing the core or perhaps placing the slate on a soft surface like a pillow and using a small stone carving chisel and hammer to chip the core down enough. Smoothing the bottom of the hole will be interesting as well, unless a smooth inside bottom of the hole is not really necessary.

Welcome to the DIY Stone Age...

A tungsten carbide SDS bit mounted in an SDS hammer drill will remove ALL of the material inside the hole diameter from the get go, but finding an affordable big enough one will be a challenge.

I have a Bosch SDS rotary hammer drill and my largest bit is 1 inch and cost like a hundred bucks. I use it for drilling through stone for wire and plumbing and other uses like fireplace damper adjustment handles, etc. Not tungsten but cobalt steel for the cutting insert that is permanently mounted at the factory. On these drills you can usually adjust with a lever how much hammering action the bit sees, right down to just spinning and no hammering.

SDS example here...

Last edited by 40 watt; 23rd June 2010 at 05:28 AM.
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Old 23rd June 2010, 01:21 PM   #4
JoshK is offline JoshK  Canada
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I have one of those diamond encrusted hole saws. I was just thinking that it wouldn't remove the core and since this isn't going all the way through, it wouldn't be helpful, but I can try a small depth first.

McMaster-Carr has 1.5" SDS type bits for $29, so I picked one of those up. Shipped to me in less than 24 hours.

The bottom doesn't have to be completely smooth, it won't be seen and just has to hold strong enough to keep the arm in place.
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Old 23rd June 2010, 01:57 PM   #5
bear is offline bear
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Masonry type question for Turntable build.
your absolute best bet is to have it done professionally.

find a quality dealer in stone, it will be a simple job for them.

who does stone? lots of places. second best bet is a place that does a lot of granite kitchen counter tops...

Slate is somewhat soft for stone, but not for the average person to make the sort of hole you need.

Short of that, i'd make a new armboard out of Corian or another solid surface material... at least you can drill and cut that with carbide...

Btw, you are not going to hand hold a 1.5" bit. You definitely do not want to hand hold.
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- every once in a while I say something that makes sense... ]

Last edited by bear; 23rd June 2010 at 02:01 PM.
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Old 4th July 2010, 08:18 AM   #6
Top Shelf is offline Top Shelf  Canada
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Try a carbide forstner bit with water on a drill press, make sure the material is well clamped. Slate is really soft. I have done lots of slate cutting and that method works for me. Practice on some cheap slate tiles first!!!!!!
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I like it loud, BUT NOT TOO LOUD!.... Hey do you hear that high pitched ringing sound ?
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Old 4th July 2010, 02:16 PM   #7
homebuilder is offline homebuilder  United States
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Default drilling slate

I agree with post #2, if you actually want to attempt this yourself. I would suggest one small additional detail: after you bore with the larger hole saw, go back in and drill the center out to a larger size with another masonry bit to giveyour screwdriver a bit more area to manuever in. Then place a small block of wood under your screwdriver to prevent it from cracking the slate due to fulcrum pressure.

I've drilled lots of holes in old marble for sinks, and this has worked. Marble is soft, but does not "flake out" like slate does.

Whatever you do, don't try to hand-hold this...do it in a drill press or mill.
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Old 13th July 2010, 01:25 AM   #8
dazed2 is offline dazed2  Canada
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I maybe completely wrong here, but what about a router?
Will it work on slate? Your best bet to cut a recess is with that, otherwise I don't know how it would be possible.
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Old 13th July 2010, 03:55 AM   #9
sreten is offline sreten  United Kingdom
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Location: Brighton UK

Visit your Rega dealer. I had a similar problem and was given an extended
arm nut for free, it they do not have it I'm sure they could get it for you.


Last edited by sreten; 13th July 2010 at 03:57 AM.
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