# Drill bit lengths



## 34_40 (Dec 8, 2014)

What's the difference in drill bit lengths?   i.e. - Jobber / Machine  etc. etc. etc.


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## 12bolts (Dec 8, 2014)

Screw machine drill bits are shorter than jobber bits. Also known as stub drills. They flex less, so they are better at keeping centered.

Cheers Phil


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## CluelessNewB (Dec 9, 2014)

Here is a table of "jobber length" bits, number, letter and fractional.  

http://www.drill-hq.com/products/multiple-heads/custom-heads/multiple-spindle-drilling-head-for-different-size-tooling/jobber-length-drill-dimensions/

McMaster-Carr also lists the lengths of their drill bits:
http://www.mcmaster.com/#standard-drill-bits/=uy8equ


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## OldMachinist (Dec 9, 2014)

I can't explain all the different lengths because I just don't remember but here are some of the explanations.

Screw machine, short overall and flute length which makes it more rigid. Originally for use in screw machines.
Jobber, general purpose drills for high production
National aircraft standard, similar to jobber but always has a 135 degree point
Taper length, same length as taper shank drills of the same size but with a straight shank
Extra length, self explanatory, they have a extra long fluted section for drilling deep holes. come in lengths up to 14"

I'm sure there are some I've forgotten but its lunch time so time to go.


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## 34_40 (Dec 10, 2014)

Thanks for making the time to respond. It is appreciated..)


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## mattthemuppet2 (Dec 10, 2014)

I think that there are mechanics length drills too, which are between screw machine and jobbers length


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