Changing Hinge Mortise Radius
Hinges used for pre-hung doors are available with two different corner radii. There are
¼” radius hinges and 5/8” radius hinges. There are valid reasons for using one over the
other; however the most common is 5/8” radius.
Mortise radius is determined by the diameter of the router bit being used. A 1/2”
diameter bit will produce a 1/4” radius and a 1-1/4” router bit will produce a 5/8” radius.
Some Magnum users will be able to choose one radius and process all of their doors
accordingly. Most users however will need to do some quantity of both.
This document will help you understand the different options for changing hinge mortise
radius and help you decide which is right for you.
Option One: Use a Corner Chisel
Norfield makes a corner chisel that will change a 5/8” radius corner to a ¼” radius. This
is for the shop that does mostly 5/8” radius and needs to do the occasional ¼” radius.
These corner chisels are available for 3 ½”, 4”, and 4 ½” hinges.
Option Two: Add a Second Butt Router Carriage
The Magnum can have a second butt router carriage installed on it. There are several
reasons to have a second router on your machine. The most common reason is so you can
have one set up for ¼” radius and the other set up for 5/8” radius.
This is a good option for shops that do a lot of both radii every week.
Norfield makes several different butt router assemblies, if you are interested in adding a
second router to your Magnum, contact Norfield with your serial number and we will
help you get the assembly that is correct for your Magnum.
Option Three: Convert the Router Carriage You Have
The Magnum butt router carriage can be set up to do either ¼” or 5/8” radius. The
change over will take about ½ hour to an hour.
This option is good if you run mostly one radius and occasionally need to run a bunch of
doors with the other radius. Or, if you are changing your standard radius.
If the router carriage is going to be changed from one radius to another, the following
procedure should be used.
1. Change the router bit.
Because the mortise radius is determined by the diameter of the router bit being
used it is necessary to change the router bit.
Butt routers that have vacuum will have a vacuum shroud that needs to be
changed. The vacuum shroud is a white plastic part that surrounds the bit.
2. Reset the Stop Bolt Mount Blocks.
The stop bolt mount blocks support the stop bolts that limit the side to side motion
of the router. (See the illustration below)
There are two sets of holes that these mount blocks can be bolted to. The
illustration shows the blocks mounted using the inner set of holes. This is the
correct position for ¼” radius. For 5/8” radius move them to the outer holes.
3. Change the Backset into Door and Jamb.
The Magnum butt router has two sets of stops that control the backset into the
door and jamb. There are the turret stop screws and the flat jamb attachment.
You will first need to determine which system you are using to control the
backset.
To change the Flat Jamb Attachment from ¼” radius to 5/8” radius screw both
adjustment bolts in 3/8”.
To change the Flat Jamb Attachment from 5/8” radius to ¼” radius screw both
adjustment bolts out 3/8”.
If you are using the turret stops you will need to change the stop bolts. For ¼”
radius use 10-24 X ¾” long flat head screws.
For 5/8” radius use 10-24 X 1” long flat head screws.
Adjust the stop bolts as necessary.
If you will be changing from one radius to the other frequently, you may want to consider
buying another turret or flat jamb attachment and presetting them for the different radii.