Guiding taps

[DPittman]

I'm sure I must be missing something here...

All but my smallest taps have a centering hole that you can use a centre on to make sure they are straight. However the smallest ones are ground to a centre point themselves....how does one use that? And why wouldn't they just keep a centre hole on them all???

Don

 

[DPittman]

ok I just figured out one of the methods.... a spring loaded tap guide! But I still don't understand why they don't just have the female centre point in all of the taps. I've also seen tap handles that have the centre hole but mine do not.

 

[PeterT]

Yes at a certain diameter they no longer have the center drill in the top of the tap shank. Actually, when you put a typical block slider style handle wrench on them, the top of the wrench may extend above the tap so hard(er) to engage a center point into it anyway. I've read somewhere the center hole is a function of how the manufacturer supported it during manufacturing, it just so happens it assist aligning on a point. Not sure if that's accurate but makes sense.

Back to your question. I don't thing the point like the tap on the left can be used, or at least it would be a clunky device. You can either

- put the tap in your chuck jaws, drive it in under lowest speed for a few threads to engage, release chuck & hand tap the rest of the way. This takes a bit of feel, don't do it on your prize possession first attempt

- make a knob tap holder like pic. Here the chuck jaws are just loose enough so you can rotate by hand but its being guided on the shank. These give an excellent feel which is important on small threads. Unless you are tapping really hard steel, there is enough leverage on the knob to cut threads. I'm suspect the tap shank might have to have a new flat ground for the set screw, just with a Dremel or whatever

- an extended shank holder. Similar concept to the knurled knob but with a cross hole for a tommy bar. I'll be making some of these shortly so stay tuned.

- they do make conventional tap holders with an extended pilot rod that you can similarly guide in a chuck or better yet sliding in a collet or holder. They work perfectly fine but they use more Y-axis real estate, probably 4-6" with a tap in there.