RequiredOutside Diameter to Cut 5/16 BSF Thread

[Danni Burns]

On Danni Burns Said:

In conclusion, a 1″ dia Die for cutting a fresh 1/2″ thread is way too small. Lesson learned.

As illustrated by this manufacturer:

https://www.avontapdie.co.uk/bsw-1-2×12-split-circular-die-hss

There is a saying for tools: buy quality, buy once.

Julie

[Clive Brown 1Participant @clivebrown1]

I’d be very reluctant to cut a 1/2″ Whit. thread dirctly with a die if I could possibly avoid it, especially a fairly long thread and in steel. Screwcutting in the lathe would be my choice and maybe using the die to take a final fine cut to size. Apart from being easier, the thread should be more accurate, particularly wrt concentricity.

[JasonBModerator @jasonb]

On 25 March 2025 at 20:57 Danni Burns Said:

In conclusion, a 1″ dia Die for cutting a fresh 1/2″ thread is way too small. Lesson learned.

 

I agree with Clive 1/2″ Whit is quite a coarse thread and needs a lot of effort to cut with a die. Even if you had a larger diestock chances are the work would spin in the chuck. Screwcut fully or at least do 75% and then finish with the die.

I’ve cut finer 1/2″ or 12mm threads with 1″ dies without problem so it is more the pitch and therefore amount of metal to come off that determines how much force is needed to cut the thread rather than it’s diameter which in turn determines the size of diestock you need to get the leverage

[Danni Burns]

On Danni Burns Said:

 

Nick, maybe those kits are OK for little taps/dies that don’t need any real torque. You could easily make your own tap wrenches using square bar and some cap-head allen screws. Maybe even rubber/nylon pipe on the handles. They’ll last your lifetime.

Hi Danni, I probably could have made my own tap wrench, but it would’ve cost more in material and electricity, than the price I paid for the No. 0 one, plus cap-head screws standing out, would be most uncomfortable to use, as I only hold the body of the wrench using such small taps, and I very much doubt that I will ever have enough time to wear this one out.

Regards Nick.

[Julie Ann]

On Julie Ann Said:

On Danni Burns Said:

In conclusion, a 1″ dia Die for cutting a fresh 1/2″ thread is way too small. Lesson learned.

As illustrated by this manufacturer:

https://www.avontapdie.co.uk/bsw-1-2×12-split-circular-die-hss

There is a saying for tools: buy quality, buy once.

Julie

Julie

Is ATP a manufacturer or reseller of the same I can find elsewhere online?

If UK manufacturer, I would happily support them, but I’m guessing they’re a reseller and charging for this Die at least £5 more than others I’ve found (11 and 15) online.

 

 

[Danni BurnsParticipant @danniburns84841]

Clive, I also agree 100%.

Screwcutting should be a painless choice for me. It’s too painful even to talk about it.

cheers all

 

[noel shelleyParticipant @noelshelley55608]

I would always use a split die, it gives some control of the thread OD. NEVER buy a really cheap set, I was given one, some of the threads were so far out of true there was plainly NO QC. The WPS “Metal Workers Data Book” No42 DOES give the OD for threads and I hope all of us have a copy ? It is a mine of all you need to know on many subjects. Whilst the OD of a thread MAY be it’s size, there are plenty where this is not so, BA, some small American threads, Hydraulic and pipe threads are some. BIG threads, 7/16″ up are to big for a 1″OD Die and if a coarse thread the more so. 1 5/16″ OD is the next size, then 1 1/2″, there is a 2″ but that is Not a model engineering size ? Tool steel may not be cheap but a split die that is in 2 pieces is not much use to most of us. In my case a 12mm die 1″ OD broke ! Most small BA and ME threading dies are only 13/16″ OD, this size is good to 1/4″. Remember that a bigger die and stock will have longer handles and give more leverage in use. Noel.

[bernard towersParticipant @bernardtowers37738]

Danni, a few hours of practice with ref to (screwcuting in the lathe) will pay dividends for years to come and when you have mastered it you will wonder what all the fuss was about. It opens the possibilities of any dia with any thread( and if you repair old stuff you won’t need hard to find taps and dies)

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