Drilling and Tapping hole newbie question

[ToNkA]

Ok, Am slowly doing the mods to my winch but have a simple question I am sure someone here can answer for me.

I want to drill and tap two holes to put in a drain plug and a breather hose. To make them airtight I want to use the thin style thread found on plumbing/air fittings as opposed to a normal coarse thread bolt.

My question is, how do I go about it? I first drill the hole then use a hand tap to cut a thread or is there another way?

How do I know what thread to cut for the style of fitting that will be used?

Can someone explain this to me?

Cheers

[M&M Custom Engineerin]

Get the fitting from a hydraulic place, they will have hundreds of different fittings to choose from.

Once you have the fitting it is just a matter of getting the appropriate tap, drilling the housing with the correct size drill bit and then screw in the tap. Its best to use some thread cutting lube but a little bit of oil or grease will do.

It is generally best to wind the tap in half a turn and then back it off a 1/4 of a turn.

[GQJonesy]

Well firstly work out the size thread of the fitting you want to use with a pitch gauge. Refer to a tapping drilling chart and find the right size drill the tap the hole accordingly. Just make sure that the air plumbing fitting isnt taperd like the ones on the arb compressor switch.

[Area54]

BSP fittings (tapered thread) are ok, they seal with a few wraps of PTFE tape.

[ToNkA]

Thanks guys!

Made it sound quite simple!

[big red]

you can get an 1/8 gas tap to cut the thread as it is a straight hole, the fitting that screws into it is tapered.
that way you dont need sealing washers.
the hole is roughly 5/16 to 3/8.
or you could go up in size to 1/4 gas which would have a hole around 1/2"
plugs can be bought from a refrigeration part wholesaler, kirbys, actrols or lovelock luke.
shane

[tritonasuras]

u can also use a thread sealer...
Basically like a type of silicon...

Rob

[ToNkA]

All sorted!