Pilot hole size for M5 coach screw?

[disco_monkey79]

Hi

Is there a rule of thumb for coach screw pilot holes? I've not used them before, and will be putting them in to well-seasoned oak.

I have drilled umpteen pilot holes for regular screws, but these aren't as sharp as "normal" screws.

Thanks

 

[Noel]

Pilot hole should be the size of the shank, the non threaded portion of the bolt/screw..

 

[Droogs]

find out the diameter of the inner circumference ie the valleys of the thread and drill that, then the coach/lag screw will do the rest

edit as I deleted a needed bit

 

[toolsntat]

Pilot hole should be the size of the shank, the non threaded portion of the bolt/screw..

That'll be a clearance hole Noel.
Cheers Andy

 

[disco_monkey79]

Thanks all

find out the diameter of the inner circumference ie the valleys of the thread

...cue callipers and unnecessary Welsh accent...

 

[Cabinetman]

The threads on Coach screws are pretty course and into oak you might struggle a little so as was said above plus a bit, it can also help to drill the hole twice just to enlarge it a fraction, a bit of candlewax on the threads will help as well. Ian

 

[MikeK]

I had to look up coach screws, and learned these are what I know as lag bolts. I was taught to drill a lag bolt pilot hole one half of the external diameter of the threads for soft wood, and three quarters of the diameter for hard wood. For wood screws, I was taught to drill the pilot hole the same diameter of the screw shaft between the threads.