On Friday, 6 April 2018 16:45:23 UTC+1, David WE Roberts (Google) wrote:
Just tried to sharpen a builder's pencil and the two wood halves came
apart.

Pencil sharpener for normal pencils is blunt.

I am now considering a propelling pencil with a thick lead for use in
marking up work.

Anyone else doing this?

If so, which lead thickness?

What you want is a "clutch pencil". They often incorporate a sharpener.
Thicker leads are less likely to break.

https://en.wikipedia.org/wiki/Mechanical_pencil

http://www.pencils4artists.co.uk/fab...6b-c2x22173309