Tom, please read the last part. Going to a 10.7 mm drill for M12 x 1.5
is a good move, and may fix the problem.
On 23.01.16 11:48, andy pugh wrote:
> On 23 January 2016 at 11:28, Erik Christiansen <dva...@internode.on.net>
> wrote:
> >
> >> The OSG online tool recommends a 27/64” (10.7mm) drill, so I am very
> >> close (0.008” difference).
> >
> > That only gives 60% thread engagement, if counting on my fingers is
> > working for me.
I was wrong there, see below.
> Most digital calipers seem to have a table on the back. Mine says
> 10.2mm for M12 x 1.75
> (Which is no help, as this is M12 x 1.5)
> M10 x 1.5 is given as 8.5, which ties in well with the 10.5mm
> suggested for M12 x 1.5.
This is what I use:
----------------------------------------------------
Metric Coarse | BS 4168 Clearance hole:
| | Type of fit:
Size Drill E Core | Close Medium Free
----------------------------------------------------
M2 1.70 61% 1.51 |
M2.5 2.15 63% 1.95 | WARNING:
M3 2.60 65% 2.39 | 3.2 3.4 3.6 2.5mm drill -> 82%.
M4 3.40 70% 3.14 | 4.3 4.5 4.8
M5 4.40 61% 4.02 | 5.3 5.5 5.8 With a nut length of
M6 5.20 65% 4.70 | 6.4 6.6 7.0 1.5 * diameter, 50%
M8 6.90 72% 6.47 | 8.4 9.0 10.0 engagement is stronger
M10 8.70 71% 8.16 | 10.5 11.0 12.0 than the external thread.
M12 10.50 70% 9.85 | 13.0 14.0 15.0
M16 14.25 71% 13.55 | For CI and thin sheet,
-------------------------------------------------- stick near 75%.
Or in general: # d is full thread depth.
Drill Size = OD - (E*2d) # E is e.g. 0.65
# d = kP , where P is thread pitch.
Or transposed for E: E = (OD - Drill_Size)/2d
k is: ISO Metric 0.613
UNF/UNC 0.613
# British Association BA 0.600
# BSW, BSF, ME (32 & 40 TPI), Whitworth forms 0.640
# BSB, and BSP parallel.
----------------------------------------
So for M12 x 1.5:
d = 0.613 * 1.5 = 0.9195
E = (12 - 10.5)/(2 * 0.9195) = 81.5%
That's too much, especially for a deep hole. The 10.7 mm hole:
E = (12 - 10.7)/(2 * 0.9195) = 70.6%
would give Tom's spindle a fair chance.
(In my previous post, I forgot that the above table is for Metric
Coarse, i.e. 1.75 mm pitch @ M12. :-(
What would Andy's 10.2 mm hole give with M12 x 1.75?:
d = 0.613 * 1.75 = 1.07275
E = (12 - 10.2)/(2 * 1.07275) = 84%
That's hard on the tap and spindle. Much better is:
E = (12 - 10.5)/(2 * 1.07275) = 70%
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
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
