Subject: Jobbers length drills?

From: <[email-masked]>
Date: Fri, 7 Oct 1994 15:31:50 CDT

I've checked all the usual references, but I can't seem to find a
definition of what is meant by the term 'Jobbers length' when
applied to drill bits (actually, I've never seen the term applied
elsewhere).  What are Jobbers length drills?

I want to buy a set of general purpose drill bit for use on
aluminum and steel. Should I get 'jobbers length', HSS, Cobalt,
or what?

As always, many thanks for your help.

- Christopher Wieczorek
  [email-masked]

---

From: PAUL <[email-masked]>
Date: Sun, 9 Oct 94 10:16:49 -0500

>aluminum and steel. Should I get 'jobbers length', HSS, Cobalt,
 
Hi again Chris,
Jobbers length is a salesmans buzz word for "standard Length" as opposed to
Long drills. They are general purpose drills for allmost all materials.
unless you are dealing in some sort of exotic material, or drilling thousands
of holes , a good brand of these drills will be fine. Cobalt drills are sharp-
ened at a shallower angle and have a "split Point" in the center to make up
for the fact that the web in the center between the 2 flutes is much wider
than that of a jobber drill. Consequently, they are somewhere between difficult
to impossible to resharpen when they become dull. Do not waste your money
buying bargain brands of drills. A good american brand will save you alot of
time and
aggrivation when it comes to sharpening. Sears sells a drill guage for this
purpose. It is about 6" long, with a 4" ruler on it and a head that looks
somewhat like a Pelicans head. It also has a rotating beam affair that is
marginally useful for measuring angles. learn how to use this tool, and your
set of drlls will last you years! Good Luck!
Paul

---

From: [email-masked] (Stuart Friedberg)
Date: Mon, 10 Oct 94 20:54:59 GMT

>elsewhere).  What are Jobbers length drills?

"Jobber length" is the common name for normal length twist drills.
"Taper length" is the common name for the standard "long" length, and
"Screw machine length" is the common name for the standard "short" length.

If you need the actual table of standard lengths per drill diameter,
consult Machinery's Handbook, or something similar.

You can also find non-standard "long boy" or "aircraft" drills
in 12" or 18" lengths, etc.

>aluminum and steel. Should I get 'jobbers length', HSS, Cobalt,

Jobber length HSS should be quite sufficient.  Actually, carbon
steel should be sufficient, but most drill sets advertised as
"high carbon" are collections of trash.

Stu Friedberg ([email-masked])

---

From: [email-masked] (Bruce Holder)
Date: Tue, 11 Oct 1994 00:29:30 GMT

: - Christopher Wieczorek -- [email-masked] wrote:
: I've checked all the usual references, but I can't seem to find a
: definition of what is meant by the term 'Jobbers length' when
: applied to drill bits (actually, I've never seen the term applied
: elsewhere).  What are Jobbers length drills?

>From  the FAQ:
   - Machinery's Handbook
     A standard reference book for machinists, available from most
     distributors of machines or tools.

  Where the term came from I don't know, but as far as meaning, it means
"regular length".  If you go into a generic hardware store and buy a
generic set of 1/16th to 1/4th inch drills, they will be jobbers length.
The actual length varies with the diameter, but the ratio of diameter to
length and the ratio of flute length to overall length will be
approximately the same for each drill size (or at least a fairly smooth
function).
  There are two other standard lengths (that I know of).  Screw machine
length is shorter, taper length is longer.  Machinery's Handbook gives
actual measurements for a huge number of drill sizes rather than describing
the ratios.
  As far as material, it depends on how many holes you intend to drill,
what material you are drilling in and how much extra money you have just
lying about.  Cobalt drills have given me noticeably better mileage than
high speed steel.  I like titanium nitride (TiN) coated even better, but
someone who re-sharpens drills might disagree.
  Point geometry is a whole 'nother complication.  I like split points a
lot.
--
Bruce Holder		[email-masked]
			(303)530-8739

---

From: [email-masked] (Paul Jones)
Date: 11 Oct 1994 12:21:33 GMT

-Newsreader: NN version 6.5.0 #26 (NOV)

 >elsewhere).  What are Jobbers length drills?

Machinery's Handbook doesn't define it specifically but does offer
three classes of length...Jobbers, Taper, and Screw Machine.
Jobbers runs all the way from #97 (.0059") to 1" diameter.
Taper and Screw Machine kick in at about #60.

For a given diameter, Taper length is longest, Jobbers next, and Screw
Machine shortest. 

Screw Machine length has its own table going up from 1" to 2" diameter.

There are also the different shank types, straight and taper.

 >aluminum and steel. Should I get 'jobbers length', HSS, Cobalt,

I would think Jobber's length ground (not forged) cobalt, 118 degree
point angle would do just fine.  I would stay away from 135 degree split
point unless you have a *really* good drill press or a mill.  I have
found that the 135 deg. walk pretty badly on my cheap Taiwan drill press. 

Be sure to get numbered *and* fractional bits if you can to enable
you to get the closest tolerances you can.
--
------
Paul Jones,  Motorola MCG                           [email-masked]
1101 E. University Ave.                             Voice: (217) 384-8529
Urbana, IL 61801, USA                               FAX:   (217) 384-8550