SpudFiles

I'm looking for a way to make a 34mm hole on my lathe. ATM my largest drill is 1". I could drill the initial hole with this and enlarge it with a boring bar but they will be a PITA for large production runs.

So basically, I'm looking for a way to bore a hole in a plastic such as HDPE around 110mm deep. I can make the bit or buy it. Preferably not spending too much. Perhaps a spade bit?

thanks

hmm spade bit would work, but take it slowly

you could also use a Forstner bit, tho spade bit should work

Does the whole drilled need a smooth enough inside wall to seal against?

Depending on the depth, and if its a through hole, look for the appropriate sized hole saw.

A spade drill close to 34mm should do then all you have to do is make a type of reamer to ream it to final size. A reamer 34mm in diameter would be expensive, but you don't have to buy one.
reamers can be homemade here is a pic of some homemade reamers