Mushroom Fixings Bending

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So this this is really frustrating and I never had problems with the 110mm ones, but since I switched to 8 x 140s they're often jamming and bending when an inch or so is left to drive (happened with 4 so far) Problem isn't caused by the obvious things. I'm using an 8mm bit that isn't worn (checked with calipers). I drill the hole an inch longer than required (10mm recommended) so dust isn't packing up at the bottom. I run the bit in and out a few times to clear any jags in the hole walls and to rake out dust, then I hoover out any dust remaining. I'm not hitting the head off centre, and just in case that was the cause, I drove the fixings with a short piece of brush handle which acts as a punch, so the head isn't impacted directly. Once the shaft of the fixing bends the slightest amount, they're finished. Managed to get three out though using an "extraction system". I'm drilling into solid 9 inch concrete walls and the only thing I can think of is that unlike concrete blocks, there isn't much "give" in the solid concrete, so any jaggy bits in the hole walls are catching the tip of the fixing. I've seen pieces removed from these walls and some of the stones in the concrete are fist sized.
 
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So this this is really frustrating and I never had problems with the 110mm ones, but since I switched to 8 x 140s they're often jamming and bending when an inch or so is left to drive (happened with 4 so far) Problem isn't caused by the obvious things. I'm using an 8mm bit that isn't worn (checked with calipers). I drill the hole an inch longer than required (10mm recommended) so dust isn't packing up at the bottom. I run the bit in and out a few times to clear any jags in the hole walls and to rake out dust, then I hoover out any dust remaining. I'm not hitting the head off centre, and just in case that was the cause, I drove the fixings with a short piece of brush handle which acts as a punch, so the head isn't impacted directly. Once the shaft of the fixing bends the slightest amount, they're finished. Managed to get three out though using an "extraction system". I'm drilling into solid 9 inch concrete walls and the only thing I can think of is that unlike concrete blocks, there isn't much "give" in the solid concrete, so any jaggy bits in the hole walls are catching the tip of the fixing. I've seen pieces removed from these walls and some of the stones in the concrete are fist sized.
Mate I'm not reading all that...I'd fall asleep..are you a diyer or a courser monkey? Your posting threads everyday about shite? Just saying
 
So this this is really frustrating and I never had problems with the 110mm ones, but since I switched to 8 x 140s they're often jamming and bending when an inch or so is left to drive (happened with 4 so far) Problem isn't caused by the obvious things. I'm using an 8mm bit that isn't worn (checked with calipers). I drill the hole an inch longer than required (10mm recommended) so dust isn't packing up at the bottom. I run the bit in and out a few times to clear any jags in the hole walls and to rake out dust, then I hoover out any dust remaining. I'm not hitting the head off centre, and just in case that was the cause, I drove the fixings with a short piece of brush handle which acts as a punch, so the head isn't impacted directly. Once the shaft of the fixing bends the slightest amount, they're finished. Managed to get three out though using an "extraction system". I'm drilling into solid 9 inch concrete walls and the only thing I can think of is that unlike concrete blocks, there isn't much "give" in the solid concrete, so any jaggy bits in the hole walls are catching the tip of the fixing. I've seen pieces removed from these walls and some of the stones in the concrete are fist sized.
 
Sorted the problem anyway. Fixings are pretty crappy compared to the previous ones I used. Tips aren't tapered all the way around, just one side so I reckon they're snagging on the hole walls. Blowing dust out with a piece of air line helped also.
 
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