Tapping - is this just the way it is?

Could have sworn I left a comment here. Weird. Well I must have replied to someone else's thread on accident. I bet they think I'm off my rocker. Anyways, that's a neat looking part. I don't have any advice though.
 
Maplehead said:
I ordered four spiral taps.
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Be careful with the nomenclature here. There are spiral flute taps and spiral point taps - very different things. See pics below (shamelessly stolen from McMaster Carr's website).

Spiral flute have spiral flutes just like a drill bit. They are for blind holes, they bring the chips up out of the hole so you don't have to stop and reverse to break chips as you do with a hand tap. However, they are more fragile than hand taps and need to be used with care.
sp-fl.png
Spiral point taps have a short spiral section ground at the very tip. This pushes the chips forward. They can't be used in a blind hole (unless the hole is very deep and you don't mind leaving it full of chips). But they work great in thru-holes. Don't reverse to break chips - just keep turning and a continuous chip will be ejected out the bottom of the hole. Spiral point taps have a little more beef to them than a hand tap (flutes are shallower) and are a bit less likely to break. That combined with no need to reverse and break chips mean they are the bees knees for thru-holes.
sp-pt.png
I use spiral point wherever possible. I haven't bought a hand tap in years, spiral points are only little more expensive and so much nicer to use.

McMaster Carr sells a plain HSS spiral point #6-40 for $7.41, or a TiCN coated one for $10.91. If your part is steel I'd spring for the TiCN.

As others have mentioned, a tapping head would really work great for this project. Of course you need a spiral point tap if you are using a tapping head - using a hand tap in a tapping head is pointless, the chips won't break and the tap will. A tapping head will set you back a few hundred bucks but if you are making lots of these it will pay you back pretty quickly.

Also very important - make sure you are using a suitable lubricant or tapping fluid!

One final thought - the tap drill chart is a recommendation, not a gospel. For a #6-40, the chart says #33 drill, and says you'll get about 75% thread depth. Do you really need 75% thread depth in your application? Maybe going one size larger with the drill will make it tap easier, and still be plenty strong for your parts. Try it out on a piece of scrap and see.
 
I go for 50% thread in steel, especially stainless, makes tapping so much easier and I've never had a thread fail (touch wood)
 
It appears that a new Tapmatic tapping head is around $700. Are the used ones on eBay considerable? I usually shy away from used as you never know how much the wear effects operations/results. However, used is $350 down to $75. Your thoughts?
 
Maplehead said:
It appears that a new Tapmatic tapping head is around $700. Are the used ones on eBay considerable? I usually shy away from used as you never know how much the wear effects operations/results. However, used is $350 down to $75. Your thoughts?
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There is a uk brand (old second hand only) that is even cheeper , I think the tapmatics have a reduction gearbox which the type I have doesnt. Uses some sort of fiber (aparently card not asbestos :) ) for a friction clutch.

Payed about £35 some times worth a punt on s/h if it's a massive saving.


Stu
 
If that is a guitar bridge I think you would be much happier with a linear adjuster for intonation.
This design looks like it would make intonation adjustment rather difficult.
There you go; no more hole tapping problem!
 
Maplehead said:
It appears that a new Tapmatic tapping head is around $700. Are the used ones on eBay considerable? I usually shy away from used as you never know how much the wear effects operations/results. However, used is $350 down to $75. Your thoughts?
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Like most tools, the used, provided they have been taken care of, are just as reliable and robust as the new ones. Often, used may also mean made in USA or Japan or the like instead of China or India.
 
My earlier designs had linear adjustment but they were a PITA. The whole idea of this bridge is that it's tool-less for adjusting action and intonation. It works and sounds really good.
 
Good deals can be found on eBay, You have to read the description carefully and ask questions if necessary. Also be sure the seller offers a refund. Many years ago I bought a couple of used tapping heads at an auction. They came from a production shop and looked like they had heavy use. I opened them up for a good cleaning expecting to find a horror show, but I was surprised to find the oil clean and the gears showed almost no wear. I still use them without any issues.
 
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