Re: [Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[Gregg Eshelman]

On 1/25/2016 6:28 AM, Peter Blodow wrote:
> Erik,
> better let's be it as it is with metric thread values. If you are
> selling things over here containing non-DIN/ISO threads (and other
> things), you will be liable for all damage that could occur with them in
> ordinary use and you will have to prove that your threads are just as
> good as DIN/ISO, which isn't easy and not cheap either. You participate
> in a call for tenders, the first thing you have to sign is that you will
> keep all existing DIN/ISO norms and standards.

I'd like to know that the standard is to get threads that are FTTL or 
Finger Tight Tool Loose. ;)

Every mechanic has run into the situation where a nut or bolt fits just 
tight enough that it's impossible to unscrew with fingers but even the 
highest quality, freest ratcheting ratchet will just wiggle the fastener 
back and forth without ratcheting.

So you either have to somehow get a finger on something to provide 
enough drag to force the ratchet to do its job, or you're stuck 
constantly swapping and flipping two different open end wrenches because 
the #^#%^# people who designed the thing only allowed enough room for a 
tool to swing 5.6 degrees, and the fit is that tight all the way up 3 
inches of thread.


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Re: [Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[Erik Christiansen]

On 25.01.16 18:50, Gene Heskett wrote:
> On Monday 25 January 2016 18:34:10 John Figie wrote:
> 
> > Why not reference the Machineries Handbook?
> >
> I have a copy of #27.  Its been less than Biblical to me.
> 
> 1. Hard to find in the index.
> 
> 2. Once you THINK you have found the proper table, the column heading 
> abbreviations are quite often so terse as to be worthless.  It should be 
> called "tap drill size" "body drill size" etc. I forget what sort of 
> shorthand they use, but its not always readily translatable to a 
> native 'Merican reader who was taught phonetics 75 years ago.

Thought I was lucky when I bought an old one in a secondhand book shop.
Couldn't find the section I needed - another hundred page section had
been duplicated there instead. Dunno if the section I was looking for is
somewhere else in the tome - I gave up at that stage.

Erik

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Re: [Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[tom-emc]

> On Jan 25, 2016, at 10:45 PM, Gregg Eshelman  wrote:
> So you either have to somehow get a finger on something to provide 
> enough drag to force the ratchet to do its job, or you're stuck 
> constantly swapping and flipping two different open end wrenches because 
> the #^#%^# people who designed the thing only allowed enough room for a 
> tool to swing 5.6 degrees, and the fit is that tight all the way up 3 
> inches of thread.

That is often the time when an extra long fastener is used just to twist the 
knife around a bit ;-)
-Tom


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Re: [Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[Gene Heskett]

On Monday 25 January 2016 22:45:18 Gregg Eshelman wrote:

> On 1/25/2016 6:28 AM, Peter Blodow wrote:
> > Erik,
> > better let's be it as it is with metric thread values. If you are
> > selling things over here containing non-DIN/ISO threads (and other
> > things), you will be liable for all damage that could occur with
> > them in ordinary use and you will have to prove that your threads
> > are just as good as DIN/ISO, which isn't easy and not cheap either.
> > You participate in a call for tenders, the first thing you have to
> > sign is that you will keep all existing DIN/ISO norms and standards.
>
> I'd like to know that the standard is to get threads that are FTTL or
> Finger Tight Tool Loose. ;)
>
> Every mechanic has run into the situation where a nut or bolt fits
> just tight enough that it's impossible to unscrew with fingers but
> even the highest quality, freest ratcheting ratchet will just wiggle
> the fastener back and forth without ratcheting.
>
> So you either have to somehow get a finger on something to provide
> enough drag to force the ratchet to do its job, or you're stuck
> constantly swapping and flipping two different open end wrenches
> because the #^#%^# people who designed the thing only allowed enough
> room for a tool to swing 5.6 degrees, and the fit is that tight all
> the way up 3 inches of thread.
>
And that situation is quite near the top of my pet peeve list, Gregg.  If 
you ever find the guy that designs things that way, let me know, and 
I'll bring 2 piss-elm (or white ash) clubs so we can both help educate 
the miscreant.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[Peter Blodow]

Erik,
better let's be it as it is with metric thread values. If you are 
selling things over here containing non-DIN/ISO threads (and other 
things), you will be liable for all damage that could occur with them in 
ordinary use and you will have to prove that your threads are just as 
good as DIN/ISO, which isn't easy and not cheap either. You participate 
in a call for tenders, the first thing you have to sign is that you will 
keep all existing DIN/ISO norms and standards.

These standards are like laws in industry, handcrafts and trade. No 
discussions, no use to calculate anything, just use the tables, DIN/ISO 
13 in this case. Anybody involved in mechanics can rush down the numbers 
when you wake him up in the middle of the night. I have run a machine 
shop with up to twenty workers for 36 years and I never heard about 
percentage of engagement etc. When you order a box of drills for thread 
cutting, you will get exactly the bits needed for the M-threads, that's 
all. They are often sold separately this way to save the lives of the 
ordinary drill bits in the all-purpose cassettes, increasing by 1/10 mm 
from 1 mm to 10.

Peter


Am 25.01.2016 09:36, schrieb Erik Christiansen:
> On 24.01.16 14:16, tom-...@bgp.nu wrote:
>> OSG, referenced earlier by John Thornton, has this tool
>> (http://www.osgtool.com/Technical.asp?tid=1=1) that calculates hole
>> size given Major Dia, Pitch, and Engagement (% of Thread).  Their
>> numbers seem to be slightly different than Erik’s though, but they
>> suggest 60-70% engagement for deep hole tapping.
>


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Re: [Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[Erik Christiansen]

On 25.01.16 14:28, Peter Blodow wrote:
> I have run a machine shop with up to twenty workers for 36 years and I
> never heard about percentage of engagement etc.

Peter,

On the 10.2mm hole for M12x1.75, given in the table you posted
yesterday, engagement is 84% - very strong, but hard on taps.

Industry standards are necessary, and we rely on bought bolts
conforming to them when we tweak % engagement in the tapped hole to
receive them. 

Please have a look at: https://en.wikipedia.org/wiki/Screw_thread
under the heading "Thread depth". You will discover that nefarious
tapping practices are institutionalised beyond anyone's ability to
eradicate. ;-)

The text at the OSG calculator, cited upthread:
http://www.osgtool.com/Technical.asp?tid=1=1
is also relevant. To wit:

»
To minimize tapping problems and lengthen tool life, use the largest
drill possible to produce a minor diameter that will result in the
lowest percentage of full thread consistent with adequate strength. A
minor diameter that provides a 55% to 65% thread is sufficient for most
requirements, but in some cases a higher percentage of thread may be
necessary to conform with the minor diameter limits of the thread class
specified.
«

Seriously, once we buy an ISO bolt, we can use it as circumstances
permit. In industry, you just need an engineer to sign off on that.

Would you like to post the drill size your tables specify for M12x1.5,
and we'll check the engagement on that? (The table from yesterday
included only M12x1.75, so does not help Tom, or allow comparison with
our preferred hole size. )

Erik

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Re: [Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[John Figie]

Why not reference the Machineries Handbook?

https://www.google.com/search?q=diyhpl.us+%E2%80%BA+papers2+%E2%80%BA+27_Thread_09A=diyhpl.us+%E2%80%BA+papers2+%E2%80%BA+27_Thread_09A=chrome..69i57.1787j0j4=ms-android-att-us=chrome-mobile=UTF-8
On Jan 25, 2016 4:33 PM, "Peter Blodow"  wrote:

> Erik,
> right tomorrow morning I'll copy another table (fine threads) for you,
> for today I have had sufficient wine for not attempting (I found a 30
> year old bottle this afternoon in our rarely used basement room).
>
> In case you need the size still tonight: the formula: diameter minus
> pitch is always correct for metric threads, also for fine threads as M12
> x 1,5, as long as they are 60 degree, als Andy stated. I admit that they
> get easier to cut and breakage is less likely as the prefabricated bore
> is larger, with the limitation of bore diameter equal to outer thread
> diameter.
>
> Good night
> Peter
>
> Am 25.01.2016 16:07, schrieb Erik Christiansen:
> > On 25.01.16 14:28, Peter Blodow wrote:
> >> I have run a machine shop with up to twenty workers for 36 years and I
> >> never heard about percentage of engagement etc.
> > Peter,
> >
> > On the 10.2mm hole for M12x1.75, given in the table you posted
> > yesterday, engagement is 84% - very strong, but hard on taps.
> >
> > Industry standards are necessary, and we rely on bought bolts
> > conforming to them when we tweak % engagement in the tapped hole to
> > receive them.
> >
> > Please have a look at: https://en.wikipedia.org/wiki/Screw_thread
> > under the heading "Thread depth". You will discover that nefarious
> > tapping practices are institutionalised beyond anyone's ability to
> > eradicate. ;-)
> >
> > The text at the OSG calculator, cited upthread:
> > http://www.osgtool.com/Technical.asp?tid=1=1
> > is also relevant. To wit:
> >
> > »
> > To minimize tapping problems and lengthen tool life, use the largest
> > drill possible to produce a minor diameter that will result in the
> > lowest percentage of full thread consistent with adequate strength. A
> > minor diameter that provides a 55% to 65% thread is sufficient for most
> > requirements, but in some cases a higher percentage of thread may be
> > necessary to conform with the minor diameter limits of the thread class
> > specified.
> > «
> >
> > Seriously, once we buy an ISO bolt, we can use it as circumstances
> > permit. In industry, you just need an engineer to sign off on that.
> >
> > Would you like to post the drill size your tables specify for M12x1.5,
> > and we'll check the engagement on that? (The table from yesterday
> > included only M12x1.75, so does not help Tom, or allow comparison with
> > our preferred hole size. )
> >
> > Erik
> >
> >
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Re: [Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[Peter Blodow]

Erik,
right tomorrow morning I'll copy another table (fine threads) for you, 
for today I have had sufficient wine for not attempting (I found a 30 
year old bottle this afternoon in our rarely used basement room).

In case you need the size still tonight: the formula: diameter minus 
pitch is always correct for metric threads, also for fine threads as M12 
x 1,5, as long as they are 60 degree, als Andy stated. I admit that they 
get easier to cut and breakage is less likely as the prefabricated bore 
is larger, with the limitation of bore diameter equal to outer thread 
diameter.

Good night
Peter

Am 25.01.2016 16:07, schrieb Erik Christiansen:
> On 25.01.16 14:28, Peter Blodow wrote:
>> I have run a machine shop with up to twenty workers for 36 years and I
>> never heard about percentage of engagement etc.
> Peter,
>
> On the 10.2mm hole for M12x1.75, given in the table you posted
> yesterday, engagement is 84% - very strong, but hard on taps.
>
> Industry standards are necessary, and we rely on bought bolts
> conforming to them when we tweak % engagement in the tapped hole to
> receive them.
>
> Please have a look at: https://en.wikipedia.org/wiki/Screw_thread
> under the heading "Thread depth". You will discover that nefarious
> tapping practices are institutionalised beyond anyone's ability to
> eradicate. ;-)
>
> The text at the OSG calculator, cited upthread:
> http://www.osgtool.com/Technical.asp?tid=1=1
> is also relevant. To wit:
>
> »
> To minimize tapping problems and lengthen tool life, use the largest
> drill possible to produce a minor diameter that will result in the
> lowest percentage of full thread consistent with adequate strength. A
> minor diameter that provides a 55% to 65% thread is sufficient for most
> requirements, but in some cases a higher percentage of thread may be
> necessary to conform with the minor diameter limits of the thread class
> specified.
> «
>
> Seriously, once we buy an ISO bolt, we can use it as circumstances
> permit. In industry, you just need an engineer to sign off on that.
>
> Would you like to post the drill size your tables specify for M12x1.5,
> and we'll check the engagement on that? (The table from yesterday
> included only M12x1.75, so does not help Tom, or allow comparison with
> our preferred hole size. )
>
> Erik
>
> --
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Re: [Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[tom-emc]

As is often the case with data in Machinery’s Handbook, the specific 
information one is trying to find is difficult to locate.  After many minutes 
of scanning I found the tolerances of a class 6H internal metric thread M12 1.5 
thread:  Minor Diameter - Min:10.376 Max:10.676.  So, this says that as long as 
the Minor Dia is no bigger than 10.676 I am in spec (of 6H class)…And it says… 
In the section on tap drill sizes for metric coarse threads:

"When relatively soft material is being tapped, there is a tendency for the 
metal to be squeezed down towards the root of the tap thread, and in such 
instances, the minor diame- ter of the tapped hole may become smaller than the 
diameter of the drill employed. Users may wish to choose different tapping 
drill sizes to overcome this problem or for special purposes, and reference can 
be made to the pages mentioned above to obtain the minor diameter limits for 
internal pitch series threads."

That says to me that if I use a 10.7mm drill bit as Erik has suggested that 
when finished my (soft) brass may indeed be within 6H spec (10.676) after all.  
But that 10.7 will give me some relief on the required torque.
I couldn’t find a table for anything other than metric coarse and MH appears to 
punt:  "Reference should be made to this standard BS 1157:1975 (1998) for 
recommended tap- ping hole sizes for other types of British Standard screw 
threads and pipe threads.”

-Tom

> On Jan 25, 2016, at 6:34 PM, John Figie  wrote:
> 
> Why not reference the Machineries Handbook?
> 
> https://www.google.com/search?q=diyhpl.us+%E2%80%BA+papers2+%E2%80%BA+27_Thread_09A=diyhpl.us+%E2%80%BA+papers2+%E2%80%BA+27_Thread_09A=chrome..69i57.1787j0j4=ms-android-att-us=chrome-mobile=UTF-8
> On Jan 25, 2016 4:33 PM, "Peter Blodow"  wrote:
> 
>> Erik,
>> right tomorrow morning I'll copy another table (fine threads) for you,
>> for today I have had sufficient wine for not attempting (I found a 30
>> year old bottle this afternoon in our rarely used basement room).
>> 
>> In case you need the size still tonight: the formula: diameter minus
>> pitch is always correct for metric threads, also for fine threads as M12
>> x 1,5, as long as they are 60 degree, als Andy stated. I admit that they
>> get easier to cut and breakage is less likely as the prefabricated bore
>> is larger, with the limitation of bore diameter equal to outer thread
>> diameter.
>> 
>> Good night
>> Peter
>> 
>> Am 25.01.2016 16:07, schrieb Erik Christiansen:
>>> On 25.01.16 14:28, Peter Blodow wrote:
 I have run a machine shop with up to twenty workers for 36 years and I
 never heard about percentage of engagement etc.
>>> Peter,
>>> 
>>> On the 10.2mm hole for M12x1.75, given in the table you posted
>>> yesterday, engagement is 84% - very strong, but hard on taps.
>>> 
>>> Industry standards are necessary, and we rely on bought bolts
>>> conforming to them when we tweak % engagement in the tapped hole to
>>> receive them.
>>> 
>>> Please have a look at: https://en.wikipedia.org/wiki/Screw_thread
>>> under the heading "Thread depth". You will discover that nefarious
>>> tapping practices are institutionalised beyond anyone's ability to
>>> eradicate. ;-)
>>> 
>>> The text at the OSG calculator, cited upthread:
>>> http://www.osgtool.com/Technical.asp?tid=1=1
>>> is also relevant. To wit:
>>> 
>>> »
>>> To minimize tapping problems and lengthen tool life, use the largest
>>> drill possible to produce a minor diameter that will result in the
>>> lowest percentage of full thread consistent with adequate strength. A
>>> minor diameter that provides a 55% to 65% thread is sufficient for most
>>> requirements, but in some cases a higher percentage of thread may be
>>> necessary to conform with the minor diameter limits of the thread class
>>> specified.
>>> «
>>> 
>>> Seriously, once we buy an ISO bolt, we can use it as circumstances
>>> permit. In industry, you just need an engineer to sign off on that.
>>> 
>>> Would you like to post the drill size your tables specify for M12x1.5,
>>> and we'll check the engagement on that? (The table from yesterday
>>> included only M12x1.75, so does not help Tom, or allow comparison with
>>> our preferred hole size. )
>>> 
>>> Erik
>>> 
>>> 
>> --
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Re: [Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[Gene Heskett]

On Monday 25 January 2016 18:34:10 John Figie wrote:

> Why not reference the Machineries Handbook?
>
I have a copy of #27.  Its been less than Biblical to me.

1. Hard to find in the index.

2. Once you THINK you have found the proper table, the column heading 
abbreviations are quite often so terse as to be worthless.  It should be 
called "tap drill size" "body drill size" etc. I forget what sort of 
shorthand they use, but its not always readily translatable to a 
native 'Merican reader who was taught phonetics 75 years ago.

> https://www.google.com/search?q=diyhpl.us+%E2%80%BA+papers2+%E2%80%BA+
>27_Thread_09A=diyhpl.us+%E2%80%BA+papers2+%E2%80%BA+27_Thread_09A
>s=chrome..69i57.1787j0j4=ms-android-att-us=chrome-mobil
>e=UTF-8
>
> On Jan 25, 2016 4:33 PM, "Peter Blodow"  wrote:
> > Erik,
> > right tomorrow morning I'll copy another table (fine threads) for
> > you, for today I have had sufficient wine for not attempting (I
> > found a 30 year old bottle this afternoon in our rarely used
> > basement room).
> >
> > In case you need the size still tonight: the formula: diameter minus
> > pitch is always correct for metric threads, also for fine threads as
> > M12 x 1,5, as long as they are 60 degree, als Andy stated. I admit
> > that they get easier to cut and breakage is less likely as the
> > prefabricated bore is larger, with the limitation of bore diameter
> > equal to outer thread diameter.
> >
> > Good night
> > Peter
> >
> > Am 25.01.2016 16:07, schrieb Erik Christiansen:
> > > On 25.01.16 14:28, Peter Blodow wrote:
> > >> I have run a machine shop with up to twenty workers for 36 years
> > >> and I never heard about percentage of engagement etc.
> > >
> > > Peter,
> > >
> > > On the 10.2mm hole for M12x1.75, given in the table you posted
> > > yesterday, engagement is 84% - very strong, but hard on taps.
> > >
> > > Industry standards are necessary, and we rely on bought bolts
> > > conforming to them when we tweak % engagement in the tapped hole
> > > to receive them.
> > >
> > > Please have a look at: https://en.wikipedia.org/wiki/Screw_thread
> > > under the heading "Thread depth". You will discover that nefarious
> > > tapping practices are institutionalised beyond anyone's ability to
> > > eradicate. ;-)
> > >
> > > The text at the OSG calculator, cited upthread:
> > > http://www.osgtool.com/Technical.asp?tid=1=1
> > > is also relevant. To wit:
> > >
> > > »
> > > To minimize tapping problems and lengthen tool life, use the
> > > largest drill possible to produce a minor diameter that will
> > > result in the lowest percentage of full thread consistent with
> > > adequate strength. A minor diameter that provides a 55% to 65%
> > > thread is sufficient for most requirements, but in some cases a
> > > higher percentage of thread may be necessary to conform with the
> > > minor diameter limits of the thread class specified.
> > > «
> > >
> > > Seriously, once we buy an ISO bolt, we can use it as circumstances
> > > permit. In industry, you just need an engineer to sign off on
> > > that.
> > >
> > > Would you like to post the drill size your tables specify for
> > > M12x1.5, and we'll check the engagement on that? (The table from
> > > yesterday included only M12x1.75, so does not help Tom, or allow
> > > comparison with our preferred hole size. )
> > >
> > > Erik
> >
> > 
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[Emc-users] Calculating thread engagement [Was: Rigid tapping speed advice]

[Erik Christiansen]

On 24.01.16 14:16, tom-...@bgp.nu wrote:
> OSG, referenced earlier by John Thornton, has this tool
> (http://www.osgtool.com/Technical.asp?tid=1=1) that calculates hole
> size given Major Dia, Pitch, and Engagement (% of Thread).  Their
> numbers seem to be slightly different than Erik’s though, but they
> suggest 60-70% engagement for deep hole tapping.

It agrees generally, then. But we need to understand the difference in
the decimals. The OSG calculator's internals are unknown, so we need to
use its behaviour to theorise on where it goes wrong.

> For example:
> 
> > On Jan 23, 2016, at 7:31 AM, Erik Christiansen  
> > wrote:
> > 
> >   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.
> > 
> >

Your observation that the OSG calculator differs a bit made me check the
value of k = 0.613 for ISO Metric.
https://en.wikipedia.org/wiki/ISO_metric_screw_thread says it is 0.614.
That insignificant bit of rounding difference doesn't explain anything,
though.

> > 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.
> 
> The OSG tool gives 10.7mm at 66% engagement (for 12mm 1.5).

Looking for clues here: The ratio of the results, 66/70.6 = 0.93, which
is near as damnit 0.92, so if we dumb down the formula I use, to omit
thread height/pitch correction:

E ~ (12 - 10.7)/2 = 0.65

we are off almost exactly as much as the OSG calculator. (Well within
rounding tolerance for display purposes in a web app.)

It may be that the imprecision is deliberate. The OSG page says
"Drills generally cut holes larger than their diameters. In the form
bellow, the probable percentages of full thread were determined by the
average amount oversize the various drills are expected to cut."

We have no way of knowing what a black box on the internet is doing.
I think I'll stick with a visible calculation, so that I have an
understanding of where the value comes from. Whether it's accidentally
or deliberately inaccurate, the OSG calculator can't know when I'm using
a reamer, or a dowel drill:

Drilling Accurate Sized Holes:
Grind matched  0.4 - 0.8 mm radii on the cutting wings (corners) of a
new or good quality drill. Ensure the radii are even, and have
clearance, so the drill will cut easily. This forms a dowel drill, used
by toolmakers. Drill 0.3 mm undersize first. Run the dowel drill 30%
faster, and feed quickly, using cutting fluid. (AME 90:45)

Erik

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