Drilling Hole in Tank in Attic

AleoN

Just another quick question to all you helpful plumbers.

I have to drill a hole (approx 20mm) in the plastic tank in the attic to take a half - inch connector (Think its called a 350) The biggest drill bit I have is 13mm. Do I need to buy a 20 mm drill-bit and if so what type is best for plastic tank? Is there any other way to do this?

Thanks
AleoN

DublinDilbert

AleoN wrote: »

Just another quick question to all you helpful plumbers.

I have to drill a hole (approx 20mm) in the plastic tank in the attic to take a half - inch connector (Think its called a 350) The biggest drill bit I have is 13mm. Do I need to buy a 20 mm drill-bit and if so what type is best for plastic tank? Is there any other way to do this?

Thanks
AleoN

You would be best off using the correct size hole saw, rather than a big drill bit.... you can buy hole saw sets quite cheaply...

There's also a cutter type bit which goes into your drill and can be set up to cut various size holes in materials such as plastic, can't remember what these are called... i always just use a hole saw....

ircoha

u need a hole saw such as a starret,
http://www.starrett.com/pages/4_saw_blades_power_tool_accessories.cfm

u will also need an arbor for the hole saw: this will fit a range of sizes

You may find the plumbing shop sells the correct size already on arbor

AleoN

ircoha wrote: »

u need a hole saw such as a starret,
http://www.starrett.com/pages/4_saw_blades_power_tool_accessories.cfm

u will also need an arbor for the hole saw: this will fit a range of sizes

You may find the plumbing shop sells the correct size already on arbor

Tried in my local hardware for Starrett hole saw but they dont have them. They had the cheaper hole saw type but the smallest size was 25mm.
I was looking at the flat wood drillbit which they had in 20 mm. Would this do for a one-off hole in the plastic tank in the attic?

Thanks for your help
AleoN

311

AleoN wrote: »

Tried in my local hardware for Starrett hole saw but they dont have them. They had the cheaper hole saw type but the smallest size was 25mm.
I was looking at the flat wood drillbit which they had in 20 mm. Would this do for a one-off hole in the plastic tank in the attic?

Thanks for your help
AleoN

The problem with using anything other than a hole saw ,the fitting can leak if the whole is not perfect.

By the way ,I always use a 3/4 350 on the tank and reduce at a 3/4 gate valve.

A 1/2 350 can be very flimsy on a tank.

DublinDilbert

AleoN wrote: »

Tried in my local hardware for Starrett hole saw but they dont have them. They had the cheaper hole saw type but the smallest size was 25mm.
I was looking at the flat wood drillbit which they had in 20 mm. Would this do for a one-off hole in the plastic tank in the attic?

Thanks for your help
AleoN

I guess the wood drill bit would do if you took it easy, your only drilling plastic. There is an adjustable tool for drilling tanks, it wouldn't be that different to how a wood bit would cut it.

If you can't get anything else use the wood bit, but do a test cut on some old plastic material of a similar thickness and see how it goes...

2 stroke

Before everybody had cordless drills and holesaws what was often done was to heat a 3/4 inch pipe with a blow torch and melt the hole in the tank.

311

2 stroke wrote: »

Before everybody had cordless drills and holesaws what was often done was to heat a 3/4 inch pipe with a blow torch and melt the hole in the tank.

I've seen blokes doing that ,talk about gunterism:D