Taps and dies

[rebekah andersonParticipant @rebekahanderson95322]

[rebekah andersonParticipant @rebekahanderson95322]

Hiya guys,

Another question for yah.

I have been trying to cut a left ahnd thread. Its M3 size.

I turn a bar down to 3mm then cut the thread using a M3 LH. Once i have a good cut i then try and screw it into the female LH thread hole. However it just zips in, no screw required. Obviously not the desired effect. I measured the outer diameter and find that it's 2.5 mm. Again undesirable.

I have cut a normal RH thread doing exactly the same with the correct result.

So I am thinking i have been sold a duff LH die that isn't M3 size.

Would I be correct in my fury or am I being mince and missed something out?

Cheers

Becky

[Chris HeapyParticipant @chrisheapy71135]

Possibly. Is the die a split-die (i.e., adjustable)? If so, it may be you have tightened it within its holder to the extreme minimum size. There are 3 screws in the holder (normally), and when you tighten the center one it wedges the die open making it cut a larger diameter thread, the two screws either side just lock it to the desired cutting size and prevent it springing open further.

[David JuppParticipant @davidjupp51506]

The size will usually be marked on one face of the die. Should allow a quick check.

[rebekah andersonParticipant @rebekahanderson95322]

I may be a bit blond but not that much lmao.

Yes it does say M3 LH lol

[SpringbokParticipant @springbok]

Rebekah,

Use firstly the centre screw only, use cutting oil, check what is stamped/engraved on the die, gently clean up the cut with a VERY fine abrasive once again useing cutting oil, Now loosen centre screw and lightly tighten other 2 then centre, go for 2nd cut then once again clean up.
I am presuming that you have a nut to check tollerances.
good luck (I usualy need it)
Bob

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

A common mistake is to turn the die the wrong way when doing LH threads . Under end load it will still cut but more like a hollow milling cutter than a die – basically reduces bar to core diameter .

MikeW

[Ian S CParticipant @iansc]

You could check the size by putting the shank of a tapping size drill through the die, if it's a split die, it will proberbly need opening. Ian S C

Edited By Ian S C on 26/05/2013 12:58:17

[rebekah andersonParticipant @rebekahanderson95322]

Ian,

you are correct. Although opening isn't easy. Lol

[colin hawesParticipant @colinhawes85982]

You may need to turn the dia. to about 2 thou undersize to get a clean thread. There are some poor quality dies about that will never be capable of cutting on a full diameter. Colin

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