Morse Taper Drills

At what size of drill does the taper increase from a No 3 to a No 4? I appreciate it probably varies a bit from manufacturer to manufacturer but
what is the norm?
AWEM
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Andrew,
Machinery's Handbook shows drills up to 27.0 mm and 1 1/16" take 3MT, and those from 27.50 mm and 1 5/64" upwards take 4MT.
Since I've got the book out and found the right page, for anyone else who might be interested, here are the maximum sizes for each MT:
1MT --- 11.8 mm/15/32" 2MT --- 19.5 mm/25/32" 3MT --- 27.0 mm/1 1/16" 4MT --- 38.0 mm/1 1/2" 5MT --- 76.0 mm/3"
This is for regular shank drills, some longer or shorter ones switch at a larger or smaller diameter.
Of course, this is a largely US-oriented book, so Europe may do it differently.
David
--
David Littlewood

Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Nov 7, 1:53 pm, "Andrew Mawson"

British makes mostly went to 1.1/4" dia but one did an 1.5/16" on a No3 MT 7/8" for No2. 17/32" for No1.
Add pictures here
✖
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.