Mum's dad worked in the pit. Step dad (the good grandad) worked in the pit fixing and maintaining the electrical equipment.
After reading this post I'm still not sure what your grandfathers did. Is joiner a term for enlisting in the military? I would guess pit is some kind of factory?
My grandfather on my mom's side worked for the electric company on Long Island. He started from the bottom and ended up pretty high up on the chain there when he finally retired. He basically did everything that you're supposed to do when it comes to financial planning so now he owns two very nice houses outright (no mortgage left on either) and has a lot of money.
On my dad's side my grandfather was a WWII vet. He had a purple heart in Germany when he was blown hit by mortar fire I think. Then his ambulance was hit again. According to my dad he woke up a week later in a hospital in Paris. He didn't talk much about his experience there but we know that he saw combat as he operated a machine gun and was at the Battle of the Bulge. Aside from that though he worked for Fanny Farmer candy company driving a truck. We still have a few Fanny Farmer pencils laying around the house because he most have got so many of them while he was working there. At some point he also operated a gas station with his brothers in the Bronx. I unfortunately never met him as he died about 8 years before I was born. My dad is 40 years older than me and my grandfather wasn't too young when my dad was born either so it's not like he died all that young.
There's also someone out there, likely in Florida, that's my biological grandfather on my mother's side. She was adapted as a baby and knows nothing about her biological mother and father. She's only 40 so the guy is probably alive and out there somewhere, which is really weird when I think about it too much.