I want to drill a hole for an aerial cable to come in through a window sill. It's about 20cm long. What kind of drill bit should I use for this? All the ones that I've seen that are that long are the flat bladed kind and are too big.
In theory of course I could drill from both sides but I feel sure that would go horribly wrong.
An 8mm auger would be the logical thing, run at low speed.
I would stay well away from the cheap flat bits, they make a messy end result and can behave badly along the way. Their only plus is theyre cheap and can be made easily from scrap.
I'm not so sure drilling the sill is the best option though.
The best drill bit is a long auger bit, provided you have a drill capable of driving it - a diy cordless ain't going to do it.
The tricky bit will be getting the hole to come out exactly where you want, the slightest wrong angle on entry will be hugely magnified as wrong position on exit.
Is there no thinner part of the window frame you could drill?
If your walls are soft stone (e.g. limestone) an SDS drill and bit will be an easier task to get right, if you have granite walls then window frame is best - but find a thinner bit of frame.
Hole though the window frame looks unsightly inside and out. Professional aerial installers will go through the wall lower down - through a brick not a mortar joint.
A 400mm(16") 8mm diam masonary drill will probably go through both inner and outer walls in one go, enabling the cable to be easily be fed straight in across the air gap. Don't forget to leave a small drooping bit of cable on the outside so the rain drips off that rather than runs down the brickwork.
If you are set on drilling the wood, the cheap tool shop here stocked Rolson brand long wood drills of the lip and spur type, set of three: 6, 8, and
10mm x 300 long, for 1 UKP.
I don't know what cable you are using, but if its the high grade PF 100 satellite quality cable then an 8 mm drill is sufficient but if its the older poor quality brown stuff then 10mm drill will be needed.
I once bought 3 long bits for =A31. Against my better judgement, I think curiosity got the better of me. What ensued was a drilling nightmare. Such bits might be ok for drilling holes in butter, but for anything else I'd avoid them. Even on soft building material they managed less than one hole per bit.
I bought a £3.96 50mm TCT coredrill last week to make a hole for a waste pipe. At that price I considered it disposable. It seems none the worse for wear, and saved a lot of hammering (cursing) and time that would have ensued from using hammer and chisel, or even ordinary (smaller) drill.
Well worth th outlay.
This may (will) not be true for all cheap tools. Caviat emptor.
One hole per bit in *very* soft wood- that was my experience too. Hard wood - useless.
My task was to run a cable from one room into another through the wall. Drilled hole with ordinary drill in skirting on one side and followed up with masonry drill through the brick. That left me upagainst the backside of the skirting in the other room. The masonry drill would not cut through the wood, and as I didn't know exactly where the hole would come out I couldn't use an ordinary drill to start from the other side.
The long wood drill through the hole was the answer but as you say, even 15 mm of skirting defeated these cheap bits and the task had to be finished off with another sharper masonary drill.
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