nicholas harteau wrote:
Thanks Nicholas,
Decided I needed to do some tapping homework..... Currently enrolled in
Introduction to Precision Machining, Lake Washington Technical College
It's a more extensive subject than I can convey in one post, but here's
some stuff that might
be relevant.
>I can't even believe it. I was tapping some threads into what basically
>amounts to aluminum stock (an aftermarket upper tailgate for my truck)
>and I broke the lovely tap off inside the pillar!
>
>Not only that, it's a brand new tap.
>
What kind of tap were you using? I'm reading Machine Tool Practices for
my class and
I was pretty surprised with the complexity of tap selection.
Here are SOME! of the recommended steps for hand tapping. I've edited
out the ones
that talk about additonal tools for securing the workpiece. ?Set
emergency brake?
1. Select the tap (consider size, fit, and material.)
2. Select the proper drill for the tap using a tap drill chart.
3. Drill the hole. (Speed, feed, coolant, alignment)
4. Countersink to major diameter of the thread.
5. Fasten tap in handle,
6. Use correct cutting fluid
7. Start the tap by turning two or three turns
8. Remove tap handle. Check for square.
9. Reinstall handle without disturbing tap.
10. Turn tap one quarter to one half turn and then
back three quarters to break the chip. Clear chips.
Repeat.
To avoid typing in a long list of tapping problems and solutions I'll
categorize.
Be aware that each category has a lower level of detail.
1. Chip accumulation
2. Tap selection, condition, and usage
3. Hole preparation
4. Speeds and feeds.
>
>The break is on a pretty extreme angle.
>
>I have no idea how to get this out besides take it to a machine shop and
>pray. Any ideas?
>
>
>
The only thing about removal that I see in the book that hasn't been
covered here is the mention
that a high carbon tap can be annealed, then drilled. Probably not a
good idea here as I suspect
the aluminum would be melted once the steel was red hot. Doh!
Hope this helps.
Steve Shipley
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