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Joel OF

Drilling slotted holes in masonry

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Hi folks,

Is there a dark art to drilling slotted vertical holes in masonry, or is it just a case of drilling a series of vertical holes? Nearly all of my clients have period buildings with old red brick piers, never block work and rarely new brickwork.

I have attached a few doodles of a hinge pins forged from 25 x 8mm flat bar, they could even be 25 x 6mm now thinking about it for the light weight I'm working on. I have also drawn in a couple holes in the wing(?) for resin to key into, it may also require some chiselled teeth.

Is there a rule of thumb for oversizing holes for resin?
Cheers

58e9cd948b09d_Hinge1.thumb.JPG.3d55b09536586a3fec2eba754abaef1f.JPG58e9cd97e88bb_Hinge2.thumb.JPG.c04bea6f3cb04b9c53035b4d9710644d.JPG58e9cd9a6888a_Hinge3.thumb.JPG.448522c9d4dfc4d6fbe662a16ab1e286.JPG

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I don't have an easy answer about drilling slots in masonry.  I can tell you that Headed Anchor Studs are commonly used in applications where new steel meets existing masonry.  They are generally epoxied or grouted into a drilled hole and the exposed end is welded to whatever you're trying to attach. 

Hilti makes a range of epoxy kits designed to match headed anchor studs.  As memory serves, some are like a capsule that is inserted into the hole before the embed is hammered home.  The capsule breaks, the epoxy does it's thing, and everything's locked down.

None of that stuff is "rule of thumb", the capsules are engineered for a specific stud in a specific application.

 

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Add 3 millimeters (1/8") for epoxy. Series of holes and a chisel. 

Super important that you thoroughly clean the hole for epoxy to be effective.

You could also weld the hinge arm to a plate and bolt the plate. 

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I wouldn't slot it at all.  I'd use a dry cutting diamond hole saw (they make them to fit on VS angle grinders) and cut into/mostly through the brick portion.  That'd create a nice clean hole and give you a bit more front/back clearance in order to align the hinges in a vertical plane.  Cost in the US is about 40 bucks for the bit assuming about 25 mm. (several on amazon)

Once you pop out the first brick "plug", you could go deeper with a standard concrete hammer drill--not having to be quite as careful because you are well into the brick by that point and won't mangle the front surface.

I'd use hydraulic cement to fill the bulk of the hole and mount the bracket, leaving the cement a bit shy of the face.  Hydraulic cement has a VERY short working time so you have to get it right in about 4 minutes.  It slightly expands rather than shrinking.  Then I'd use a portion of that brick plug to create a fascia which could be epoxied (or a simple tube "glue" for brick) on the face parts to make it virtually disappear if you worked it right.  With a little care, the work would be hard to see unless you really look closely.  You could even used crumbled brick and a clear epoxy mix to create that front cosmetic fill (light sanding to remove any potential gloss once it's set up).

Slots are hard--holes are easy.  Basically, find ways to make a hole look pretty instead and you'll save a ton of aggravation.

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