How to Ream MS Hinges

(rev. 03-01-2006)

 

As mentioned earlier, most hinges will fall on the larger end of the tolerance range.  Therefore the reaming operation will not be removing a lot of material.  In most cases, it will be more like a deburring process, removing material only at the ends of each hinge segment.  

 

The Reamer

The reamer is made up of two parts, both available from McMaster-Carr:  A chucking reamer with a .0955 diameter and a piece of stainless steel capillary tubing, OD 2.0 mm, ID 1.5 mm.  The reamer is ground down to a diameter of 1.5mm.  The capillary tube is held in place with retaining compound.  I used Loctite 609, also available from McMaster.  You’ll need about .05 inches ground down to a uniform diameter for a secure bond.  If too much gap develops, the Loctite will not cure properly.  Shoot for a slight press fit.

 

Above:  Ground reamer installed on capillary tubing

Below:  New reamer

(Click for larger image)

 

The Reaming Operation

Clamp the hinge piece to be reamed in a vise or to a table top so that both hands are free.  Keep the reamer lubricated with oil.  Spin the reamer with very little forward pressure.  Using a light weight drill works well.  You want to be able to feel how much pressure is being applied so that you can avoid high torque.  This could separate the tubing from the reamer if you happen to have a weak joint. 

After reaming, use shop air to clean out any left over debris.

 

 

Reamer making its way through a hinge segment

(Click for larger image)

 

Inserting the Pin

The hinge pin is 3/32” Stainless Steel welding rod.  I used 308L.  If you have the opportunity, check the diameter with a micrometer.  Of all the batches I have purchased over the years, only one deviated from the nominal 0.09375” by more than just a few ten thousandths of an inch (0.0001). 

 

Here are some tips to avoid difficulty inserting the hinge pins for the first time. 

  1. Make sure the end of the pin is rounded and completely deburred.  Remember that the clearance may be less than .002”. 
  2. Make sure the ID of the hinge is completely clear of any reaming debris and keep the part well lubricated as you go.