Erik, I don't know wat table you were glancing at, but here is the table
from Europes No:1 tool seller, Hoffmann Group
(http://www.gewinde-norm.de/metrisches-iso-gewinde-din-13.htm), listing
metric ISO / DIN13 threads:
Thread Pitch Core diam. bolt Core diam. nut
Drill size mm Wrench size mm
Gewinde
Steigung
Kerndurchmesser
Bolzen
Kerndurchmesser
Mutter
Kernlochbohrer
Schlüsselweite
(Sechskant)
M1
0,25
0,693
0,729
0,75
-
M1,2
0,25
0,893
0,929
0,73
-
M1,6
0,35
1,171
1,221
1,30
3,2
M2
0,40
1,509
1,567
1,60
4
M2,5
0,45
1,948
2,013
2,10
5
M3
0,50
2,387
2,459
2,50
5,5
M4
0,70
3,141
3,242
3,30
7
M5
0,80
4,019
4,134
4,20
8
M6
1,00
4,773
4,917
5,00
10
M8
1,25
6,466
6,647
6,80
13 / 14
M10
1,50
8,160
8,376
8,50
17 / 16
M12
1,75
9,853
10,106
10,20
19 / 18
M16
2,00
13,546
13,835
14,00
24
M20
2,50
16,933
17,294
17,50
30
Greetings
Peter
Am 24.01.2016 10:18, schrieb Erik Christiansen:
> On 23.01.16 12:27, Gene Heskett wrote:
>> Now we are getting more precise than we can drill with the typical drill
>> bit, which usually drills oversize because the tip flats are
>> un-avoidably off center. Even to a small extent for pricy carbide bits
>> in the smaller sizes. Yesterdays finished tapping looked great, but I
>> think I could have used the next larger #drill. Yeah, my back of a
>> napkin said a .089 drill, kcalc says 0.0984251968503937008 for a 3mm.5
>> screw.
>>
>> No wonder I felt like I should peck it, the hole WAS too small.
> Ahem, it was WAAAY too small. ;-)
>
> Just a glance at the table upthread shows that 2.6mm (0.102") gives 65%
> engagement, which is as much as I ever want on M3, to avoid busting the
> tap. Even kcalc's 2.5mm (0.098") drill is too small, giving a dangerous
> (to small taps) 82% engagement.
>
> And that .089 (2.26mm) gives an engagement of:
>
> E = (OD - Drill_Size)/2kp
> = (3 - 2.26)/(2*0.613*.5)
> = 120%
>
> That has the tap drilling as well as tapping!
> You did superbly to not break the tap, Gene.
>
> I tried a 2.5mm (0.098") drill for M3. Once.
> Although the tap didn't break, I went straight out and bought a couple
> of 2.6mm drills. Now I can tap M3 without my hair standing on end.
>
> Erik
>
> ------------------------------------------------------------------------------
> Site24x7 APM Insight: Get Deep Visibility into Application Performance
> APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month
> Monitor end-to-end web transactions and take corrective actions now
> Troubleshoot faster and improve end-user experience. Signup Now!
> http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140
> _______________________________________________
> Emc-users mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/emc-users
>
---
Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft.
http://www.avast.com
------------------------------------------------------------------------------
Site24x7 APM Insight: Get Deep Visibility into Application Performance
APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month
Monitor end-to-end web transactions and take corrective actions now
Troubleshoot faster and improve end-user experience. Signup Now!
http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140
_______________________________________________
Emc-users mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/emc-users
