Threading questions

Two questions please from of novice at metal working.

[1] I have been recommended to use a high pressure lubricant (Break Free TF) when tapping holes in steel and it seems to improve the thread form compared to non-lubricated tapping, but the fluid stops the swarf dropping out of the flutes of the tap so I wonder if it is actually counter productive. What are your opinions on tap lubrication? [2] I never seem to get a decent thread form using a die on steel or brass rod. The top of the peaks are rough and flattened no matter how much I reduce the initial diameter of the work. The lubricant mentioned above seems to help but not solve the problem. Is it my technique, or is it the quality of the tools? ( I use taps & dies made by Presto.)

Cliff Coggin Kent UK

Reply to
Cliff Coggin
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i would sugest Rocol RTD compound, but the stuff you have should be more than good enough

firstly.... try opening the die up a bit in the die holder, to vut an oversize thread, and then adjust the die to size and re-thread

try backing the die off one full turn every 2 or so full turns down the bar, this will reduce "ripping"

brass should die realy well, but steel is a different matter, it all depends on the grade EN1A (bob standard mild steel) can be prone to ripping when using a die, better quality steel EN8 will be less prone



Reply to
Tim Bird

I also use ROCOL RTD and find that it cuts down the rejection rate enormously.

When forming a thread with >=1mm pitch I find it most beneficial to take a starting cut oversize (roughing), then a finishing cut to the correct Major Diameter. step 1 is usually accomplished by diehead, step 2 using a split die. Takes a tad longer, but I can't sell anything with a torn thread!

Light oils and paraffin are Kiss-of-Death to good threads! Avoid!

Have cut thousands of threads on A2/A4 stainless this way.

Festina Lente


Reply to
Mark Pinkney

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