Drilling SDS holes

I need to drill 16mm diam holes in a reinforced concrete slab.

14 holes each 150mm deep.

The holes will be used to resin in anchor studs, and then right angle straps are being bolted to slab ... the vertical portion of strap will then be secured to vertical studs of timber frame walls.

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main thing is here is that the holes in the 10mm thick galv straps are in place and fixed, so I can't allow the holes I drill to wander off line.

I have an SDS drill and a new 16mm bit.

When I have drilled SDS holes before they tend to wander about until a cm or so into the material.

Any tips on doing this .... some options I have thought of are :

#1 use a non SDS pilot hole, before using SDS drill ... although I recall someone posting here that SDS bits should not be used with a pilot hole, due to way they work.

#2 bolt straps to vertical studs first and drill through the clearenance holes - risk here is damage to clearance finish, and this is external job so need the protection.

Reply to
Rick Hughes
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#2 should have read ... "risk of damage to galv finish "

Reply to
Rick Hughes

Any drilling into concrete hand held will wander a bit due to the differences in the ballast.

Reply to
Dave Plowman (News)

IMHO a pilot hole is the way to go. For a 16mm SDS that needs to be 6mm or so to properly center the SDS bit. The pilot doesn't need to be full depth just a cm or so to get the main bit started.

Remember with SDS let the drill/action do the work no need to push hard like you do with a normal "hammer" drill, just push enough to stop the bit rattling in the bottom of the hole.

Reply to
Dave Liquorice

Use #2. But don't fully tighten the bolts into the studs. Then if the holes wander you can move the strap slightly or if necessary reposition the strap . Drill a pilot with say a 8mm SDS bit through the hole, then remove the bottom fixing in the strap so you can swing it to away & carry on with a

16mm bit.

Never heard that SDS can't be used with pilot holes.

Reply to
The Medway Handyman

Possibly best to get the hole started with rotary drilling only until you are 20mm or so down.

Maybe make a sacrificial jig drilled off your galvanised parts. Drill the first hole into the concrete and bolt or otherwise fix that end of the jig, then drill the furthermost hole and fix the jig again. Then drill the remaining holes. HTH Bob

Reply to
Bob Minchin

SDS wanders much less than ye olde hammer drill or vanilla rotary drilling. SDS will always be prone to wander in concrete, but wander is as good as zero in a sand/cement only mix IME. So

- sticking to sds is your best bet

- sds will be prone to wander in concrete, full stop

- pilot holes will reduce the odds of wander to some extent, but wont eliminate it

Masking tape can mark the spot, and add 2 long bold lines so no mater where you end up drilling you can see exactly where its meant to be. Now, if any end up off position you can drill them out larger, which isnt a problem with resin fixing.

If for some reason you needed 100% perfect position every time, you could drill out larger and fill with sand/cement mix, which once cured a few days will then drill accurately every time. But it doesnt sound like there's any need for that, resin will take up any slack.

NT

Reply to
meow2222

base plate is neater? The vertical wooden studs run off the wooden base plate.

Reply to
Doctor Drivel

That's exactly what I did to set 40 or so surface mount joist hangers. Made up my jig from drawing around the shape and holes of a joist hanger on an offcut of joist, through holes in jig done on a pillar drill, marked out a batten with the required positions of the joist hangers, screwed batten to laser line on wall, screwed jig to batten in 1st position, sds-drilled holes into wall, moved jig to next position etc. Result - joist hangers set prefectly level to a laser line.

However that does sound a bit overkill for setting strapping. If the OP's diagram is correct, there's plenty of lattitude for "hammer adjustment" to get the strap drilling lined-up over the holes. Why the custom metalwork - why not just use some lateral restraint straps (the type usually used for floor/wall connection)?

If you need something meaty, e.g. :

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Reply to
dom

Why are you trying to fix L brackets to concrete and then affix timber to these? - there is very little, if any strength in doing it that way - far better to build the studding framework and bolt this directly down to the concrete using frame fixing bolts, no resin, no plugs, they just tighten up into masonry and don't budge....you'll need a 10mm bit and the holes can br drilled directly through the timber and into the concrete....you can lay a length of DPC down prior to affixing the studding if you are worried about timber rotting.

Reply to
Phil L

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Rick Hughes" saying something like:

Bollocks to the knowalls. Just drill the first 10mm with the hammer off.

Reply to
Grimly Curmudgeon

Have you ever drilled decent concrete?

Reply to
Dave Plowman (News)

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Plowman (News)" saying something like:

Thousands of times, yes.

Reply to
Grimly Curmudgeon

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Plowman (News)" saying something like:

Fuck. Don't know why I wrote 10mm - 2mm was what I meant.

Reply to
Grimly Curmudgeon

Studs fix to bottom of panel (150 x 50) that rests on a 150 x 50 wall plate that is frame fixed at 450mm intervals to 3 course high dwarf brick walls ... because of wind 'up loading' ..... the biggest risk is wind lifting whole structure off the slab ---- either with the dwarf wall or ripping it off dwarf wall.

The restraint straps fix first into slab and then 2 fixing points into wood - one into the wall plate and one into vertical stud. Take a look at

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was original sketches with Structural Engineer ... gauge had to be increased to 10mm to meet pull out forces.

Reply to
Rick Hughes

Phil see previous answer .... explains why it has been done this way ... also wanted all wood to be at least 150mm up off concrete salb.

I habe 150 x 150 gallow posts for main supports and they are also via resin fixed galv plates, rather than wood to concrete.

Reply to
Rick Hughes

Remember now that the reason given was that for a 'normal' masonry drill, tip meets as an equal angle arrow head. for SDS the angles do not meet, they are off set, and to work correctly the comment was that edge needs to be gripping on concrete .... and putting in a pilot hold first messes this up ? ..... maybe it was correct, maybe not.

Reply to
Rick Hughes

If you hit a re-bar your fu*ked

Reply to
zaax

Don't use an SDS if you need it accurate.

Use a diamond core drill

Reply to
RW

A 2mm SDS drill?

Reply to
Dave Plowman (News)

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