Grub Screws

[mr]

This may be a daft question (sorry) but when fitting grub screws into wood does the predrilled hole for the screw need tapping for the screw thread or do they work in a similar way to a threaded inset ie cutting themselves a grip in the wood as they are driven in?

 

[Dewy]

Grub screws go into tapped holes in metal not wood.

 

[MikeW]

This may be a daft question (sorry) but when fitting grub screws into wood does the predrilled hole for the screw need tapping for the screw thread or do they work in a similar way to a threaded inset ie cutting themselves a grip in the wood as they are driven in?

Hi Mr,

I tap the holes. I use Allen head bolts for some jigs I've built and for all small hinges I use brass flat head bolts of appropriate size and also tap the holes for those.

Take care, Mike

 

[Chris Knight]

Machine screws hold very well in most hardwoods - better than woodscrews according to some research Lee Valley did years ago. However, repeated screwing and unscrewing will weaken the fixing and there needs to be enough thread engaged to provide a firm fixing.

When tapping, do it just like metal and back off the tap a bit each half turn or so. This makes a cleaner thread than just winding the tap in - which you can do in wood, unlike metal. Use a bit of wax for lubrication for a cleaner thread too.

 

[mr]

Thanks all. Questions definitely answered there. Now off to see if I can find a tap set small enough failing that time for a rethink. THanks again.
Mike