Advice drilling 32mm holes in 80mm joists

[Chubber]

A simple hardwood gauge/ template ( like a bench hook with one ledge ) drilled 3mm at the appropriate distance would save a lot of faffing about with a square and pencil. Used to spot-drill the hole position it would increase the likelihood of the distance from the edge of the beams being equal.

Oh, if it's for cold water, add foam pipe insulation as you go even if indoors to avoid condensation of moist domestic air after each time a fresh draw of water* .

(* Ask me how I know...)

 

[robgul]

I wouldn't contemplate a flat bit as the kick-back risk is high, especially when in a confined space between the joists - an auger bit is the best option as it threads itself and self-clears - just run it slowly and steadily.

 

[glenfield2]

Thanks for everyone’s comments really appreciated.
My plan is to thread the pipe through the stair opening
The pipes will be 22mm copper, I don’t use plastic anymore after a pipe leak after a mouse eat through a pipe. I also have an M Press tool to crimp the pipes makes a great job
I guess I could make the holes smaller if I make a jig I was just concerned if the holes were not bang on or totally straight with threading copper through would make them tight.
I have seen an erbauer 90chuck attachment on Screwfix I was going to give that a try.
I fancied the 90 degree chuck for my fein drill but it’s £100

I’ve been through a couple of those screwfix 90o chuck attachments and IMHO they are pretty ropey and clumsy to use. Very awkward to hold everything especially if reaching between joists. Both also had the little magnetic bit holder fall out so the drills keep dropping out. Fun.
I’d buy the cheapest 90o drill. Even s/hand. You can always sell it again.

 

[Jake]

At post Nº3 you stated that the maximum hole size was 25% of the Joist depth. 25% of 250mm is 62.5mm not 31.25mm

I was giving depth for a notch on the underside not a hole (notch is 12.5% not 25% because it weakens the stressed edges of the joist not the more neutral part in the middle).

 

[johnnyb]

100 holes in 400 centres? I'd ponder a better solution up

 

[Herr Nilsson]

Similar to a mason’s line, stretch a piece of string between the furthest points of the pipe run a few mm below the joists! This is your datum for measuring the height of each hole. A jig that references off each joist may not be the way to go if there isn’t a uniform distance between the bottom of your joist and your string line.

*Edited: Oops, just read that ChaiLatte suggested this already at the start of this thread. *