oldtuckunder Posted October 24, 2016 Report Share Posted October 24, 2016 Hi Guys May seem a stupid question to some of you, but I have a 1/2" BSP TAP that has virtually no lead in on the nose. In the past I have just used it for cleaning out existing threads, but I would like to cut a couple of threads into an alloy block, and to do so I could do with modifying the tap so that it has a gentler lead in. Do you think I could get away with mounting it in the lathe and very gently taking a bit of material off, or will the tap be too hard to machine? Its marked HSS GRD Alan Quote Link to post Share on other sites
Paul J Posted October 24, 2016 Report Share Posted October 24, 2016 I have often put a tapered lead onto a tap or sharpened the leading edge with a grinder, but machining a HSS tap would be very difficult. Paul Quote Link to post Share on other sites
Hamish Posted October 24, 2016 Report Share Posted October 24, 2016 Would this do ? http://www.partridgeshadleigh.co.uk/hardware/plumbing/taps/outside-taps-and-cocks/brass-hose-union-bib-tap-1-2-bsp/101308a?gclid=CM25y8Ch888CFTco0wodM9cCzA ???? Quote Link to post Share on other sites
oldtuckunder Posted October 24, 2016 Author Report Share Posted October 24, 2016 I have often put a tapered lead onto a tap or sharpened the leading edge with a grinder, but machining a HSS tap would be very difficult. Paul Thanks, I think you have confirmed what I suspected, just not sure that I can set it up for the bench grinder to dress the three flutes evenly, but will see what heath robinson device I can build to hold and rotate it :-) Alan Quote Link to post Share on other sites
TriumphV8 Posted October 24, 2016 Report Share Posted October 24, 2016 (edited) Seems you have a two or three step TAP and from that set the third finishing step. Best is to buy a correct set. No chance to modify that item on a lathe. Maybe Ebay has a used set that can be refreshed with that third proper step..... Edited October 24, 2016 by TriumphV8 Quote Link to post Share on other sites
Lebro Posted October 24, 2016 Report Share Posted October 24, 2016 I have often re-ground taps to give a better lead in, or in some cases to re-sharpen. You don't need a lathe, it would not help anyway, you just need a bench grinder. You not only need a taper on the end, you also need to grind an angle on the 3, or 4 threaded parts so that there is a cutting edge. Bob. Quote Link to post Share on other sites
oldtuckunder Posted October 24, 2016 Author Report Share Posted October 24, 2016 OK course of least resistance, just bought a tapered tap on ebay for £6.50 (including delivery)! Thanks! Alan Quote Link to post Share on other sites
RogerH Posted October 24, 2016 Report Share Posted October 24, 2016 Hi Alan, problem solved but as I was in mid investigation this is my answer. The tap can't be cut. The flutes would cause to much disruption even if you had a tipped tool to touch the HSS. Grinding it down in the lathe would be quite practical - the lead in may not need to be that accurate. Otherwise I would have gone to these people http://www.tracytools.com/ Very quick service and quality products. Roger Quote Link to post Share on other sites
oldtuckunder Posted October 24, 2016 Author Report Share Posted October 24, 2016 Otherwise I would have gone to these people http://www.tracytools.com/ Thanks for the recommendation, good prices, have bookmarked for future reference. Alan Quote Link to post Share on other sites
TR 2100 Posted October 24, 2016 Report Share Posted October 24, 2016 (edited) From someone who knows he doesn't know so much ! Taps come in Nos. 1, 2 & 3 - No. 1 to get you started and No. 3 to cut the thread as fully as you can. So - if you take a No. 3 tap and grind down the start of the thread, you will be left with a longish section of partly cut thread. Unless, that is, you are not tapping a blind thread (I think that's the correct term) but a thread in a plate where you can go right through. Taps aren't that expensive, are they? (No. 1, 2 & 3 threaded taps are to die for!) AlanR Edited October 24, 2016 by TR 2100 Quote Link to post Share on other sites
Waldi Posted October 24, 2016 Report Share Posted October 24, 2016 Hand taps come in a set of 3. There is a clear visual difference between the 3. Machine taps are just 1 per size. HSS = High Speed Steel Quote Link to post Share on other sites
john.r.davies Posted October 24, 2016 Report Share Posted October 24, 2016 +1 for Tracey Tools Quote Link to post Share on other sites
pinky Posted October 26, 2016 Report Share Posted October 26, 2016 Three taps are needed in a blind hole, (a hole wich has a bottom) An open hole you can get away with two taps however three taps are better to tap the hole square Needed with a half inch tap Taping the hole two forward turns one reverse turn plenty of lube No 1 tap lead in No 2 tap intamediate No 3 tap bottoming tap Thin material only no 1. Tap is needed Pink Quote Link to post Share on other sites
oldtuckunder Posted October 27, 2016 Author Report Share Posted October 27, 2016 It appears that 1/2" TAPS are a bit like Buses, hardly any around and then three come along at once. The new First Tap arrived in post today magic. I'm then digging through one of the many machine tool chests I inherited from my father that I haven't opened in years, looking for a large morse taper chuck I remembered, and inside I found a wooden box full of BSP taps everything from 1/8 up to an 1" including of course a set of 3 1/2" ones! Must go through those chests one day and sort out what is there, and what I'm likely to use. Alan Quote Link to post Share on other sites
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