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Thread: Breaking taps !
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29th Oct 2020, 12:32 AM #1
Breaking taps !
Hi Guys,
How to break a good tap ! Drop it onto a tiled floor I haven't broken a tap in years !
I've now managed to do this trick twice over the past couple of weeks ! Both carbon steel taps, one a "Goliath" and the one this morning a "Sagasa" M6, Indian I think.
As it happens I've just bought a new set of M6 X 1 HSS ones from Avon Tap & Die here in the UK.
28-10-2020-001.JPGBest Regards:
Baron J.
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29th Oct 2020, 09:55 AM #2
We all break taps. Its how we break them that will vary.
In my own case, the ones I seem to break in the manner you have described above are those special ones.
They are the one offs ,those reserved for a special job taps, those same taps that are that more difficult to source and obtain.
This especially applies if those taps are more expensive than the run of mill taps I own.
Grahame
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29th Oct 2020, 10:38 AM #3Most Valued Member
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- Apr 2012
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You can spend days or even weeks on a job and the last process is often tapping a thread, that is when i break them.
4mm and under is always a worry for me.
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29th Oct 2020, 11:14 PM #4
I bought a cheap set of m3-m8 spiral taps and have done hundreds of holes with them using tapping my tapping goo always.
There starting to get a bit blunt now but will buy the same ones again over and over.Using Tapatalk
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30th Oct 2020, 12:45 AM #5
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30th Oct 2020, 01:39 AM #6
As we age, it is not, if we are going to suffer a Bumblefinger attack, it is when.
Grahame
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30th Oct 2020, 08:35 AM #7
Yeah I painted a small piece the other day and siliconed some rubber channel around it.
The sun came out so I picked it up to take it outside and of course it was a little slippery with a thin film of silicone and I dropped it scratching the paint.
Took probably half an hour to get all the silicone film off so I could repaint that side. I almost gave up as it would have been quicker to make a new one.Using Tapatalk
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28th May 2023, 08:57 PM #8Still learning ..
- Join Date
- Jul 2005
- Location
- Melbourne
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- 15
tapping woes
I was about to start a new thread but the subject is exactly what I find. In the past month I must have broken 4 taps, two each of 3mm and 4mm and it is invariably the last tapped hole in the part. Almost 60 years ago when I was a nipper I was taught one turn forward and 1/4 turn back to break the chips but it is the chip breaking part that, in my case, causes the breakages. Has tap design changed as I watch with envy those people that can power tap and they just go straight through. I have both spiral and traditional taps but have as many broken broken of each type and of all quality imports and sutton. Is it my age and growing impatience or am I missing something? How do all you fellows get on?
Mike
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28th May 2023, 10:27 PM #9
Breaking taps !
Only HSS taps, no carbon steel unless I am just cleaning threads.
I usually use the mill spindle or lathe tailstock to ensure the tap starts straight. I even bought drill and tap guides for free hand drilled/tapped holes.
Using the appropriate size tap handle matters because I need the sensitive feel while tapping else I tend to break the tap.
The right cutting fluid helps as well.
I avoid blind holes for such small diameters and I specifically bought a set of drills from 1mm to 6mm in 0.1mm increments because i wanted to ensure I get very close to the recommended hold size.
6mm and above doesn’t bother me much but I still stay as focused as I can.
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28th May 2023, 11:02 PM #10Most Valued Member
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- Jul 2010
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- Melbourne
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I was taught the 1/4 turn back thing but I think its partly dependent on material. I was also taught spiral taps where for power tapping and you wanted the chip to spiral out of the hole, so reversing those seems like a bad idea.
Biggest thing to me is hole size. Most of the charts use drill sizes that give a pretty high thread % which doesn't help all that much with the strength of the thread but increases the torque required by 100% and more. Do you really need that thread %? There a calculators online.
Ok typed the above then went looking. They said it much better than I did.
https://www.guhring.com/Tech/tapdrill
"Many variables affect the performance of threaded holes and the taps used to generate them. One very important factor is the drill size used to produce the hole that will be tapped. Most tap drill charts call out only one tap drill size, and that will produce an approximate 75 percent thread. In general, tap tool life can be increased significantly by using a lower percent of thread and we suggest using values between 60% and 70% for most applications. Thread strength is not directly proportional to percent of thread. For example a 100% thread specification is only 5% stronger than a 75% thread specification but requires 3 times the torque to produce."
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29th May 2023, 02:10 AM #11Most Valued Member
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- May 2011
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With the small taps, I usually go the next size up drill bit, if a metric size is required, I then look at the imperial size, that extra .2mm can make all the difference.
KrynTo grow old is mandatory, growing up is optional.
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29th May 2023, 05:52 AM #12
Hi Guys,
One trick that I've used if I've only got a tapping size drill, is to grind a touch off one side cutting edge. This pushes the point off center and causes the drill to make a larger hole ! This works a treat if you are tapping a harder material. Though if you forget and use that drill in say aluminum or a soft material, you can easily get an oversize hole.Best Regards:
Baron J.
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29th May 2023, 11:48 AM #13Golden Member
- Join Date
- Dec 2007
- Location
- Adelaide
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- 574
To select a drill size for tapping, most of the time I use the free version of a mobile app 'TapDrillTool' the interface is a bit clunky but it's very convenient to use - not sure if it is in the app store - Google Play - but it can be found with an internet search and installed as an APK, it always defaults back to imperial threads 1/4" 27tpi and 65% on startup which can be a bit annoying if you put your phone down for a minute and then pick it up again you'll have to make your selections again - it's worth a look.
Screenshot_20230529-094727_TapDrillTool Free.jpg Screenshot_20230529-095031_TapDrillTool Free.jpg
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