Run out of tip

[kenb1953Participant @kenb1953]

Any suggestions on when screw cutting and the tip runs out of depth?

I am machining a thread in brass that exceeds 0.050" depth which the max a ceramic tip will machine without the following corner of the tip doing its own machining of the the apex of the thread. I know the smart people will say grind a piece HSS but I'm not that clever unfortuately!

[kenb1953Participant @kenb1953]

[Ian PParticipant @ianp]

I think you need to clarify the problem a little. I dont understand what you mean about the 'following corner' of the tip.

Are we talking internal or external threads?

The depth of thread is determined by the thread type and form. What diameter and pitch are you cutting?

Ian P

[Ian S CParticipant @iansc]

Think I'v an idea what your problem is, I'v had similar sounding troubles. Just finish to almost full depth, thenmove the saddle forward a few thou and take the bit that you missed off. Then resett and finish the depth if required, check it,(remember to allow for back lash when moving back and forth), that thread is proberbly bigger than most people have dies for, and I don't know if any one uses a chaser, although I supose one should if using Whitworth threads. Ian S C ps; I use mainly SAE or metric

[Martin WParticipant @martinw]

Hi

Why not buy an HSS or tipped tool from somewhere like Chronos, usual disclaimer re interests. They are readily available for internal or external threads with either 60 or 55 degree tips. These are relatively cheap and appear to have the clearance you want for a deep thread.

Just a thought and you don't have to grind anything .

Cheers

Martin

[mickParticipant @mick65121]

Like Ian I don't understand what you mean by the following corner, are you cutting the thread with a full thread form insert? If so it sounds like your using one that's ment for a shallower thread form.

[Harold Hall 1Participant @haroldhall1]

If you are using a full form tip then they are pitch specific, that is to say, a tip can only be used for a single thread pitch. If you wish to use a tip to cut any pitch, you should purchase a tip that does not add the radius on the outer tip of the thread being produced.

These tips will of course cut a thread with a flat on the threads outer diameter, because of this, the outer diameter will have to be slightly smaller than normal to prevent it binding in the internal thread

The thread form and intended pitch of a pitch specific tip should be marked on it.

Harold

[Harold Hall 1Participant @haroldhall1]

I should have added, that the tip for any pitch will have a very small radius on its tip so that it can be used for very fine pitches. Because of this, the depth of the thread will have to be greater than normal for larger pitches. This must also be taken account of.

Harold

[chris stephensParticipant @chrisstephens63393]

Hi Harold,

Not quite so. You go in the correct distance, as given in the reference books, then widen the cut by use of the top slide which will compensate for too small a tip radius. This of course requires that you don't subscribe to the old myth that the top slide has to be set to half the thread angle.

chriStephens

[Harold Hall 1Participant @haroldhall1]

Thanks Chris, I had not thought of that idea, not that I use the method, but perhaps one day I will find the need. I always use full form tips or chasers from Coventry die heads.

Harold

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