In Mozaik (cabinetmaking/CNC software), a full back pocket is a shallow pocket machined into the back face of an MDF door to relieve surface tension and fight warp — useful on near-full-face profiles like a slim shaker where a regular back route isn't enough. Phill Anton Consulting builds it parametrically with formulas (PartL/PartW and Tomm), assigns a back-pocket tool group, then runs it as a flip operation. The process is easy but not intuitive, so the formulas keep it reusable across any door.
When should you add a full back pocket instead of a back route?
Add a full back pocket when warp is a real risk. Depending on the time of year and the material you receive, a regular back route can't always control warping, especially on doors that do near-full-face machining like a slim shaker. The full back pocket relieves more surface tension. It works on any door, not just slim shaker. Trade-off: when you run these you will have to shim the back side. (There's also an advanced version with built-in shims you clip off later with a hand router; this guide covers the basic version.)
How do you start the back pocket on the door?
Get out of the 3D viewer and go to Libraries → Doors. Edit the door (a slim shaker in the demo) and make a copy of it. Phill names the copy with the door's prefix plus the deviation in all caps — e.g. DR (door) + BACK POCKET (or BP) — so any deviation from the standard is easy to spot. Then click on the panel and edit to enter the shape, and switch to the operations tab.
How do you place the pocket with formulas?
You start on the front face; click the arrow to flip to the back face, then add a pocket (Mozaik makes a generic pocket). Rather than anchors, the pro way is to drive the corner points with formulas using Tomm (Tomm = 25.4, i.e. one inch in mm):
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Near corner (XY 0 reference): X =
2.25*Tommand Y =2.25*Tomm— brings the pocket 2-1/4" in from each edge. -
Far side in X: reference the opposite side —
PartL-(2.25*Tomm). PartL is the part length (24 in the demo), so this resolves to 24 minus 2-1/4". -
Far side in Y:
PartW-(2.25*Tomm), because you're measuring from the other direction (PartW = part width).
Apply the matching formula to all four points (Phill copies/pastes the expression). Because every point uses a formula, the pocket stays parametric and follows the door if you later change its shape. Caution: don't drag a point by accident — if the blue formula indicator disappears, that point is no longer parametric. The 2-1/4" inset also leaves room for the hinge.
How deep should the pocket be and what pocket settings does Mozaik need?
Click on one of the pocket's points to set the depth. The demo uses an 1/8" (0.125) back pocket. For the pocket options (available on 13.1 or later), turn on use pocket tool, and always set the cut to inside out and clockwise — this avoids leaving a small "nibblet" in the middle that can break off and need filling. A tool path isn't assigned yet at this stage, so skip it for now.
Why does the corner cleanout matter?
The 3D viewer shows the pocket with sharp corners, but the pocketing tool leaves a radius in each corner. You need a cleanout in the corners, the same idea as cleaning out a shaker/slim-shaker face on the front side, so the pocket finishes square.
How do you build the back-pocket tool group?
Open the optimizer (View → Optimizer), then Libraries → CNC tooling → panel tool groups. Phill's naming system uses prefixes like S00004 (slim shaker) and S004BR (the back route, offset about 1-1/4" because the slim shaker is set to 1"). Make a generic 1/8" back-pocket group so it applies to anything:
-
Copy an existing group and name it so it sorts to the top of the list (he uses something like
S 0 back pocket 1/8 inch). The "1/8 inch" in the name matters. - Put the operation on the TOP face, not the back — counterintuitive, but the pocket operation lives on the back so the tool group must be on top to show on the back side.
- Remove the 30° tool from this group (it's not needed on the back and just adds machine time).
- Keep a 1/2" down shear and the 1/8" down shear; you can substitute a 3/8" or 7/16" down shear by left-clicking twice and pulling one in. Don't go below 3/8" unless you're using a small pocketing tool. The pocketing tool is already assigned to the door, so the group mainly needs the down-shear cleanout tools. Aim to engage the 1/8" down shear roughly 10% of its diameter on the outside of the pocket's inner line (the green line = inside of the stile/rail = inside of the pocket).
How do you assign the cleanout tool group back on the door?
Back in Libraries, open the back-pocket door, panel → edit → operations tab, flip to the back, and carefully click the point (confirm the formulas and the 1/8" depth survived). Instead of applying a single tool, click panel tool group and pick the S0... back pocket 1/8 inch group you made, so the back-pocket depth and the pocketing-tool depth match (inside out, clockwise).
How do you reuse the back pocket on other doors?
This is why every point needs an X and Y formula. In the operations tab, left-click and highlight all four points, then click copy. You can then paste that tool path onto any door in a global library or as a single-door override. If you edit the door's margin later (e.g. change the inset from 2-1/4" to 1-1/4"), reset the door, then re-apply by editing, flipping to the back, going to operations, and hitting paste — Mozaik remembers the copied path as long as it stays open. Note: resetting a door can revert it to a one-piece (not a routed pocket door); if that happens, reset again, select the pocket on the middle panel, edit, paste, and save.
How do you cut it (the flip operation)?
The setup is demonstrated for a Shop Sabre; the operation is about the same on most machines (Homag/Holzher are a little different because of their mirrored origins). Steps:
- Check material (e.g. MDF white HD) and set trim to 0.25 for length and 0.25 for width as a starting point.
- In Optimize, you can mic your material; 3/4" and 1" MDF is usually close, and entering slightly thinner doesn't usually hurt.
- With parts loaded, Batch optimize and automatically flip parts.
- Generate G-code — but do this from View → All patterns, NOT from the per-sheet generate G-code. Choose all sheets, create flip, create primary.
- Add a squaring cut: Mozaik requires a known dimension for the flip op, effectively sizing the sheet so it knows where to place front-side operations. The origin is top-left on most CNCs; after the squaring cut, flip that edge into your pins.
- Run the flip side first, flip the sheet over into the pins, then run the primary.
If a tool shows as a placeholder, it isn't in your tool set — open the panel tool group and pull in the right tool (e.g. the 30°) from your tool set.
Warp tip — spacing parts in the optimizer
If doors warp while cutting, you may have a surface-tension issue. Move parts farther from the edge by setting the width and length trim to one or two inches, and leave two to three inches between each door. Recutting one door is cheaper than losing sheets to bad yield. (There's also a PAC tool-set part-spacing setting you can use for this.)
Flip-op troubleshooting — origin
If flip ops don't line up, the usual cause is the XYZ origin not being set correctly. On a Shop Sabre it's easy: there are often machined 000 marks in the phenolic — bring a 30° (or any pointed) bit over, line it up on both sides, and hit the XYZ button. If there's no dot, square a sheet of material nestled into at least three pins, bring a 60° or 30° bit to its corner, line up both sides, and set XYZ. A small origin error throws off edge boring distance on hinges and can make profiled glass doors look off. (Phill also mentions a 1/8" squaring cut with 1/4" width trim as a working combo.)
Get it done-for-you
You can set this up by hand (above). If you build these regularly, PAC MDF Door Profiles from PAC has it ready in Mozaik. → phillanton.com
Full disclosure: Phill Anton Consulting makes this product.
FAQ
Why add a full back pocket to an MDF door in Mozaik?
MDF doors with near-full-face machining (like a slim shaker) are more prone to warp, and depending on the season and material a regular back route can't always control it. A full back pocket relieves more surface tension. You'll need to shim the back side.
What formulas does the back pocket use in Mozaik?
The near edges are 2.25*Tomm in X and Y; the far edges reference the opposite side as PartL-(2.25*Tomm) in X and PartW-(2.25*Tomm) in Y. Using formulas keeps the pocket parametric so it follows the door if the shape changes.
Why does the back pocket tool group go on the top face, not the back?
Counterintuitively, the pocket operation is created on the back face but the tool group must be assigned to the top for it to show up on the back side, because that's where the pocket operation lives.