Microstops for Aircraft Seat Tracks: WES396 and WES596-ER Extended Reach

A microstop countersink cage sets countersink depth by resting its skirt on the work surface while the cutter feeds through it. On an aircraft seat track the skirt must fit inside the track channel before it reaches the work surface, so the skirt's outer diameter and length decide which microstop can clear the channel and start countersinking.

The WES396 fits most seat tracks. It is built for tight spaces, with smaller cutters and a smaller footprint. Where the channel is narrower or deeper than the WES396 will take, the WES596-ER extended reach series reaches deeper into tight areas and hard-to-reach sections of an airframe or structure.

New to microstops? Start with Choosing Your Microstop Countersink Cage.

Why Microstops Matter for Seat Track Installation

Standard seat tracks use countersunk (flush-head) rivets. The track channel must stay completely clear inside, so seat fittings and cargo locks can slide and lock safely.

Using protruding rivets instead causes two problems:

• The rivet head interferes with track fittings as they slide through the channel.
• The surface no longer gives the flush profile the track needs.

Countersinking keeps rivet heads below the surface so fittings slide past. A microstop holds the same countersink depth on every hole.

How to Choose a Microstop for Seat Track Work

Step 1: Check the skirt diameter against the seat track clearance

Measure clearance around the hole at the narrowest point of the channel. The skirt must clear the channel walls while the footpiece sits flat on the work surface. This measurement, not the hole size, determines which microstop you can use.

The two series meant for this work are:

Note: WES396 series should fit most tracks. Swap to WES596-ER if the WES396 won’t fit.

Step 2: Check the skirt length against the seat track depth

A deeper channel needs a longer skirt. The WES396 skirt is 0.88″ long, and the WES596-ER series ranges from 1.25″ to 5.00″. The selection table below lists each skirt length.

Step 3: Check the cutter thread

Check what your cutters are threaded for before you choose a microstop. Thread options by series:

Note: Cutters with a 1/4″ body usually have 10-32 threads, and the WES596-ER8 is built for them.

Step 4: Match your shank to your drill motor

Pick the shank that fits your drill motor's chuck:

• Round (Blank): A standard shaft that fits a standard 3-jaw chuck.
• Tri-Flat (TF): Also fits a 3-jaw chuck. Built for heavy countersinking on tougher materials, where the application needs a better grip. Preferred when a round shank would slip in the chuck.
• Threaded (TS): Fits chucks that receive a 1/4″-28 thread. This option is only available on the WES396 series.

A Quick-Change (QC) system is also available. It needs a QC chuck adapter, such as our WES1750 Series, mounted on a threaded drill motor. This is mostly required at Boeing facilities and their subcontractors, where QC is the standard.

Microstop selection table

Have these two measurements ready before you use the table:

• The smallest clearance point of the seat track
• The height from the upper bracket of the seat track to the work surface

Use these to find the largest OD microstop that fits the clearance, then confirm the skirt length is long enough to reach the work surface without the microstop body touching the track.

CCPhoto: Wescon Industries Inc., CC BY 4.0

Every Wescon microstop countersink cage is made in USA.

Order the cage that fits your track from the WES396 series or WES596-ER series page | Contact our engineering team