Tapping a 1/4″ BSPT Thread

[Brian AbbottParticipant @brianabbott67793]

Hello everyone, could anyone offer some advice on this,

Drawing calls for a Rc1/4 x 15dp hole,

Am i right in thinking this is a 1/4″ bspt x 19 – 15mm dp

How do i go about tapping this.

Can i drill a core size of 11mm then just tap the hole?

Thank for any advice.

Brian

[Nigel Graham 2Participant @nigelgraham2]

The Tracy Tools chart I have, advises 11.5mm, not 11mm, for the tapping size.

Otherwise a straight tapping-size hole would be used, though is that 15mm depth enough for the fitting?

Might be worth testing on a scrap of the same material.

[noel shelleyParticipant @noelshelley55608]

Can’t see a problem. drill tapping size and tap. As it’s a taper thread don ‘t go too deep. Noel.

[Neil LickfoldParticipant @neillickfold44316]

It will depend on the style of tap that you have. Some are quite long, and depending of your fitting may need to be drilled 20mm deep.

Sutton from Australia make a nice series of BSPT taps Rc range, that are shorter, and when taped to nearly full depth is about right for most fittings.

With a 1/4BSPT I use an 11.8mm drill 15mm deep at full diameter. To the point of the drill will be 17 to 18.5mm deep depending on the drill point angle.

[ChrisLHParticipant @chrislh]

Something to be aware of if the tapping is intended for an elbow pipe fitting is that it is not straightforward to get the thing pointing in the right direction and tight at the same time. A bit of trial and error required.

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