Machinist

[Lawrence London <lfljvenaura@gmail.com>]

http://www.practicalmachinist.com/vb/general/tapping-tips-317429/

Tapping hard materials by hand: When you notice the material is difficult to tap try using a plug tap first, until difficult, then switch to a bottom tap until difficult, and then back to the plug tap.
The plug tap creates a lead for the bottoming tap, then the lead is recreated with the plug tap for the bottoming to follow.

I've found the AnchorLube works great on hard materials like 4140HT, and hard stainless, bronze etc.

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Don't hand tap,
Don't buy taps that look like they could have come from a tap set.
Don't use tap sets
Don't buy hand taps
Don't use taps they have the size stamped on them or show the tap drill size.
Don't act like tapping fluids make a big difference unless you're in nasty materials.
Don't worry about coatings unless you're pro.

Use three flute spiral point taps as much as you can.
[Spiral point. Not spiral flute.]
Use high quality taps.

Power tap when possible.
Use a cordless drill when possible.

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Store the taps in a case with the appropriate sized nuts on them.
Makes it easy to size a screw.

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Here's a little trick I use to get the thread started nice and straight using the old SouthBend 13".

The material is 416 SS and the tap in the picture is an old 4 flute. The 4 flute didn't cut so well so we purchased a new three flute from McMaster. Then it cut like a hot knife..

P.S. The tap from McMaster didn't have the pilot hole in the rear of the tap so I chucked the tap and put a pilot into it using a carbide drill. Then the live center can actually center the tap.

Yes, you need to feed the carriage and tap at the same time which is strange but it works.



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Usually the hole size is for 75% of the thread.Hard or gummy stock would be better tapped to 65%.If the hole is deep I will often bore 3 sizes bigger.
Example would be a #7 drill for 1/4-20 threads I may drill with a #4 if the stock is steel.I use Castro Molly Dee for steel ,paint thinner for aluminum.
Nothing for brass.

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You can get spring loaded centers so that you can fix the carriage. I used to do the feed the carriage method, but I've been using the spring loaded thing lately.

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If you are doing the crank the tailstock thing pretty
often you may want to consider one of these gems. It's
a Spring Loaded Tap Guide on Steroids.
80 lbs spring pressure.
Almost 1" of travel.
Hardened and Ground Throughout.
M-2 High Speed Steel Tip.
#3 Morse Taper.
Made In USA
89.00 Each Free Shipping



Works well on large taps and allows the use of
both hand on the tap wrench.

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Put the tap into a keyed Jacobs chuck in the tailstock and power tap that shit. Tap wrenches are for mechanics--not machinists.

Turn on spindle, push tailstock by hand (do not lock it to the ways). Push it in, reverse, pull it out, Done.

Don't reef down on the chuck pressure so the tap can spin in the chuck as to not break the tap if you end up bottoming it out before you throw it into reverse.

If you do not have a large enough Jacobs chuck to hold the tap, mount the tap to a toolholder on the carriage and feed it in and out. Back some 25 years ago, I tapped a LOT of 1/2" NPT holes on an old Mori-Seiki and held the depth within a few thou by watching the Trav-A-Dial go to the zero mark and kit the foot brake, then throw the bitch into reverse, rinse and repeat.

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