liam.mccaffrey
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| posted on 2/8/14 at 09:21 AM |
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Drilling and tapping
I'm having trouble tapping a hole, its a 3/8" bsf into a mild steel component. I've used a good quality 8.3mm tapping drill and it
cut beautifully when drilling. When I've fed the taper tap (with cutting fluid) in it was quite stiff even at the start and got progressively
worse, I abandoned before I snapped the tap. When I withdrew the tap the thread forms were flattened and deformed.
Do you think I might have a soft tap, the component is really nice it turned and drilled really well.
Or should I try with a slightly larger tapping drill
[Edited on 2/8/14 by liam.mccaffrey]
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40inches
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| posted on 2/8/14 at 09:34 AM |
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Probably a cheap carbon steel tap. You need a HSS one.
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Brian R
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| posted on 2/8/14 at 09:46 AM |
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Zeus says 8.25mm for the tapping drill so you're on the money there.
You're either trying to tap material which isn't mild steel or your tap was manufactured by Cadburys. :-)
I have a set at work I inhereted which are carbon steel chinese knock offs and they won't cut for toffee. All new ones I'm replacing them
with are HSS which are far superior.
Go for the likes of Hall, Dormer or Goliath and you should't go far wrong.
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designer
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| posted on 2/8/14 at 10:18 AM |
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As said, you have a low quality tap.
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redturner
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| posted on 2/8/14 at 01:11 PM |
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Are you sure the tap is 3/8". I have used some really shi**y taps in my time but never known one fail in mild steel. If it is seizing after a
couple of threads then it would seem to be more than the tap. A good tap would probably go through without lube but you are struggling with...
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