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mklotz
02-10-2005, 12:45 PM
Recently, someone asked me about the origin of the numbered (wire gage) drills.
A bit of googling revealed that their sizes are based on the Stub's steel
(note, not iron) wire gage.

Of course, this immediately led to the question of the origin of the letter
drills.

Are they based on some particular wire gage as the numbered are? If so, which
gage?

Were 26 sizes selected because the alphabet has that many letters or was it
coincidence that the sizes needed to fill the gaps totaled up to 26?

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.geocities.com/mklotz.geo

Spin Doctor
02-10-2005, 02:15 PM
Well its a good ting they weren't invented in Canada. Otherwise we'd only have one size "A".

Sorry I could not resist

lynnl
02-10-2005, 02:56 PM
Wouldn't that be two: an 'e' and 'h'? eh?

Speaking of which: how long has that stereotype of Canadian speech been around?
I only started hearing that within the last 15 or 20 years. And it seemed at the time I started hearing it, that it was kind of a new joke.
But then, I never lived near the border, so I guess I could've just missed it. ...eh?

Evan
02-10-2005, 03:11 PM
Time for some history eh?

http://www.billcasselman.com/casselmania/mania_eh.htm

lynnl
02-10-2005, 03:22 PM
Actually I kinda like the 'eh'. Sorta spices up the sentence.

I am tho, sick and tired of the "...he goes.." and "... I'm like..", as used in the first of that discussion on the link Evan posted.

(...guess Marv's due an apology for sidetracking his thread. Sorry Marv.)

Thrud
02-10-2005, 04:00 PM
All the numbered and lettered drills are a piss poor excuse at trying to be Metric drills - want a really complete set of drills? Metric in .1mm steps!

I am sure this abortion was the result of Americans refusing to go metric - instead opting for a Phillips screw when the Superior Canadian Robertson screw was already available - just because it was invented in Canada (can't have that or an Avro Arrow flying overhead, can we?) and is still the best screw in town... http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

RANT MODE OFF
reboot RANTING MODE

P.S. the Bomark missle sucked and the only reason you monkeys have air superiority is because of Canadians designing your jets (re:Avro) http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif
(But I still love you crazy monkeys!)

Rant Mode really off now

[This message has been edited by Thrud (edited 02-10-2005).]

Evan
02-10-2005, 04:02 PM
To put this back on track I just submitted the question to the Morse Cutting Tools "Ask the Experts" web page. They say they will get back within 24 hours.

lynnl
02-10-2005, 04:36 PM
Aahh, quit bellyaching Thrud. We like some Canadian things. For example, ...er, ah.., well Canadian bacon is pretty good. ...and hockey. That's gotten real popular down here. http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

pgmrdan
02-10-2005, 07:14 PM
lynnl,

And don't forget all those really hot Canadian women like K. D. Lang. http://bbs.homeshopmachinist.net//biggrin.gif

[This message has been edited by pgmrdan (edited 02-10-2005).]

aboard_epsilon
02-10-2005, 07:41 PM
why dont you ask BILKO

http://www.wilkinsonmachinery.com/ask_bilko.php

all the best.mark

wierdscience
02-10-2005, 08:08 PM
I was told that it is just another set of drill sizes to allow for different percentage threads.Sometimes you need other than 70%.

MJMIKE
02-10-2005, 09:28 PM
I don't know the origin of letered sizes but numbered size diameters are .060" + .013 X #. For example a #10 is .060 + 10(.013) = .190" Who decided on .013????? or decided to add it to .060? This might be interesting history but all they taught us in history class in school was history of governments. I wonder if all governments in their day were considered as screwed up at the time as we consider ours screwed up now?
Oops - sorry to diverge.

------------------
Mike

shaque
02-10-2005, 09:37 PM
Hey Evan, that's a hell of a good expanation why we use eh, eh? http://bbs.homeshopmachinist.net//biggrin.gif
Jim

J Tiers
02-10-2005, 11:04 PM
That "eh" was in fairly common use in Minnesota when I was a kid. But they took Canadian coins without a problem back then also.

They hand out the coins here in Missouri, but they sure don't want them back.....but at least now that we in the US use 25 franc pieces instead of quarters, who can tell the difference? Not the droids running the registers.

Letter sizes don't seem to make much sense. Maybe they advance by a multiplier, but I haven't checked. And a few of them duplicate other sizes. Like A, same as a 15/64, and darn near 6mm.

And, since the metric system was second, it makes sense that it would be set up to avoid the peculiarities of the older systems.

If you think drills are weird, check out old forms of liquid measure. Drachms, Firkins, minims, hogsheads, etc.....and to think the English/Canadians came up with those odd things........



[This message has been edited by J Tiers (edited 02-10-2005).]

Ian B
02-10-2005, 11:26 PM
I recently bought a set of Chinese letter drills - there are 2,000 of them in the set...

Ian

MJMIKE
02-10-2005, 11:59 PM
Excuse my previous post, the subject was drill sizes and I was thinking screw sizes. I would delete the post if I knew how.

------------------
Mike

Excitable Boy
02-11-2005, 01:42 AM
<font face="Verdana, Arial" size="2">Originally posted by lynnl:
...and hockey. That's gotten real popular down here. http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif</font>

Well, actually, not so much so this year it seems... http://bbs.homeshopmachinist.net//smile.gif

John

------------------
Pursue Excellence and the rest will follow.

Doc Nickel
02-11-2005, 01:54 AM
<font face="Verdana, Arial" size="2">Originally posted by Ian B:
I recently bought a set of Chinese letter drills - there are 2,000 of them in the set...

Ian</font>

-Yeah, but you have to combine two or more to get the size you want.

Doc.

madman
02-11-2005, 02:14 AM
Its EH AND ONLY EH EH GOT THAT. EH

Allan Waterfall
02-11-2005, 04:25 AM
Deleted

[This message has been edited by Allan Waterfall (edited 02-11-2005).]

mklotz
02-11-2005, 11:26 AM
Canadian self-congratulation, slang and dumb sports
Somebody with an unquenchable urge to talk about numbered screws in answer
to a question about drills
Feeble attempts at humor

Sheesh! Maybe I should start a ho(c)key thread and see if it degenerates into
a discussion of letter drills.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.geocities.com/mklotz.geo

Allan Waterfall
02-11-2005, 11:48 AM
Marv,

Perhaps the letter drills correspond better to tapping drill sizes,I know a lot of old model engineering plans call for holes drilled with letter drills.
I seem to remember reading that the number drills are now only available in their nearest metric equivelant,and not in the fractional sizes they used to be.I could be wrong in this.

It seems that a lot of topics stray from the original post.

Allan

Al Flipo
02-11-2005, 11:59 AM
Thrud, Mr. Robertson refused to sell his patented screw head design to the Americans.

SGW
02-11-2005, 12:05 PM
I don't think either the number or the letter drills have any really discernable relationship to what one would rationally choose for tapping drill sizes.

My best guess on the letter sizes is that "some company" in the obscure 19th-century past came out with them, based on some notion that may have made sense at the time but in fact was totally arbitrary and not connected to anything. And, in the way that such things will do, they became a standard.

But I sure would like to which "some company" it was, and why.

Ted Coffey
02-11-2005, 12:05 PM
For what its worth, the 1895 Book of Tools, Machinery and Supplies by Chas A. Strelinger states that
"The letter size drills are based on the P.S. Stub's drill rod list of sizes; the decimal sizes are given in table. These drills are used generally, when a size is desired that is between the 64ths in the regular drill list. For example, the letter "E" is 1/4 inch, while the letter "H" is 13/64, the two letters "F" and "G" being between these sizes."
When I look at the list there seems to be a few exception to this description but this is what the common thinking was in 1895.

BillH
02-11-2005, 12:20 PM
What are you talking aboot?

mklotz
02-11-2005, 12:34 PM
Allan,

Glancing at my Imperial tap drill chart:

F =&gt; 5/16-18
I =&gt; 5/16-24
Q =&gt; 3/8-24
U =&gt; 7/16-24

Twenty-six sizes when only four are needed for the most common thread sizes in
that range? Granted, there may be oddball threads that require letter tap
drills, but I don't think that's the answer.

Like most people, I've heard the folk wisdom that the letter sizes were
constructed to fill in the gaps in the fractional series (just as the number
drills do for the smaller sizes). However, the question is what logic (if any,
after all, this is Imperial) defined their sizes and how did it come to be a
total number of drills that just matches the number of alphabet letters?

I'll expand my question. Did the British or the Americans instigate the use
of the numbered and letter series? For some reason, "Stub's (or Birmingham?)
steel wire gage" strikes a British note in my mind, so I'm guessing the
British started the number series and we adopted it.

Ted C.,

Do you have a list of the "Stub's drill rod" sizes? I'd be interested in doing
a comparison to the letter sizes if you do. The Stub's steel wire gage
doesn't agree perfectly with the number drill sizes so I wouldn't be surprised
to see some mild disagreement with the letter sizes.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.geocities.com/mklotz.geo

J Tiers
02-11-2005, 01:14 PM
Sorts sounds like someone's idea of useful interpolated sizes. Maybe they were just the ones that came up for what THEY were doing. Obviously some company with the capability to make drills must have been involved.

Since numbers were already taken, and they weren't fractional, letters "got the call" as identifiers. Might be as simple as some significant company's toolroom identifiers for sizes.

And, they sort of "take over" filling in larger sizes than the number sizes. They even are labeled the "other way", which adds some credibility. (A is 0.234, and they go up)

As for the 26, well, there ARE 26 letters. When you run out, you run out.

Adding double letters, or letters plus numbers, probably didn't make sense at a time when many ordinary shop workmen probably could not read.

Ted Coffey
02-11-2005, 01:58 PM
In the Strelinger book there is a listing of Drill rods. They start at #80 increasing in size to #1 then the next size is "A" , "B", "C", "D", "E", "F", "G", 17/64", "H", "I", "J", "K", "9/32", "L", "M", 19/64", "N", 5/16", "O", "P", 21/64", "Q", "R", 11/32", "S", "T", 23/64", "U", "3/8", "V", "W", 25/64", "X", "Y", 13/32", "Z", 27/64", 7/16", 29/64", "15/32", 31/64", 1/2", then in 1/32nds up to 1" followed by 1-1/16" and 1-1/8".
Some of the descriptive text follows:
"Drill rod is used for Taps, Drills, Punches, Pins, Rollers, Shafts and Rods for marble work. Available in 12" and 36" lengths". "We believe these rods are equal to the Stub's or any imported Rods; and for finish they excel all others. Others sizes then those listed can be furnished to order but not in small quantities"

Lettered drills "A" thru "Z" show the same decimal values as modern day lettered drills.

Numbered drills are slightly smaller in the table when compared to modern numbered drills by 0.001" to 0.005" with no constant relationship to diameter. We are probably using a different standard today for numbered sizes.

[This message has been edited by Ted Coffey (edited 02-11-2005).]

Allan Waterfall
02-11-2005, 03:46 PM
I've just looked in"The Model Engineers Handbook" by Tubal Cain.

The letter drills are specified for tapping Model Engineering and some of the BSF and Whitworth threads.The M.E.threads tend to be only 0.016"in depth and 32tpi or 40tpi

The book also gives the nearest metric equivelant,occasionally they are the same size.Not having a set of number drills I use the nearest metric one.
I ought to get a set of proper number drills,but in six years I have not been desparate enough to warrant the purchase.

I can only assume the letter drills were in use before we started to use the metric sizes.
At least you didn't build a damn tunnel so the French could enter your country easily. http://bbs.homeshopmachinist.net//wink.gif


Allan

spope14
02-11-2005, 04:10 PM
Read in a machining text book they were the percentage of tap drill thread depths an such, as mentioned above. Same with number drills.

Why do they call drive dogs "dogs"? always wondered that one.....

Evan
02-11-2005, 04:30 PM
It has a bend in it, a "dogleg".

Sailor
02-11-2005, 06:04 PM
Howdy;
While you on the subject. Can you reccomend a place where I can find a half decent and resonable priced HSS metric drills in .1 steps from 5.1 to 10mm.


<font face="Verdana, Arial" size="2">Originally posted by Thrud:
All the numbered and lettered drills are a piss poor excuse at trying to be Metric drills - want a really complete set of drills? Metric in .1mm steps!

I am sure this abortion was the result of Americans refusing to go metric - instead opting for a Phillips screw when the Superior Canadian Robertson screw was already available - just because it was invented in Canada (can't have that or an Avro Arrow flying overhead, can we?) and is still the best screw in town... http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

RANT MODE OFF
reboot RANTING MODE

P.S. the Bomark missle sucked and the only reason you monkeys have air superiority is because of Canadians designing your jets (re:Avro) http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif
(But I still love you crazy monkeys!)

Rant Mode really off now

[This message has been edited by Thrud (edited 02-10-2005).]</font>