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Cut both sides of a part with a flip

Some parts have features on both faces: holes from the top, a recess underneath. You cut one face, turn the blank over, and cut the other, and the hard part is that the second cut has to line up with the first. RapidCAM does it with two programs and a pair of registration pins. This guide sets one up, previews both sides, and covers the one mistake that quietly ruins the part: putting the pins where the part is.

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  1. Plan the two setups, on a blank with room

    The example is an 80 × 50 mm plate with two 6 mm holes in opposite corners and a shallow recess, cut from a blank 120 × 90 mm and 12 mm thick. Start a New Project with those sizes, bring the drawing in and press Ungroup (see From an SVG to G-code for that part). Your own part works the same.

    Decide what is cut from which side. Side A is the top face, as drawn: here, drilling the two holes. Side B is the face that ends up on top after you turn the blank over: the recess, and then the outline that frees the part. The outline goes last, from the second setup, because a part released in the first setup cannot be turned over and found again.

    The blank is larger than the part on purpose. The registration pins are holes bored through the whole blank, so they have to be in the waste, and the waste is the 20 mm of blank round the plate.

  2. Turn on two-sided and set the pins

    Open the Toolpaths tab. Beside Two-sided, press Set up…, and tick Enable two-sided.

    • Flip direction. Left ↔ right (mirror horizontally) turns the blank over like a page, about its vertical centreline. Near ↔ far turns it about the horizontal one.
    • Registration. Dowel pins bores two holes through the blank and into the spoilboard at the end of the first program; the second program is cut with the blank sitting on dowels in those holes. None (fence / corner) leaves it to your own fence.
    • Pin diameter (6 mm), Pin depth into spoilboard (4 mm) and Pin inset from edge. The pins sit on the flip centreline, so turning the blank over leaves them where they were.
    Two-sided on, with the pins 10 mm in from the blank's edge.
    The Two-sided machining dialog with Enable two-sided ticked, flip direction left to right, registration dowel pins, pin diameter 6, pin depth 4 and pin inset 10

    Set the inset so the pin holes land in the waste. The default is 15 mm. The plate here starts 20 mm from the blank’s edge, so 15 mm would leave a hole 2 mm clear of it; 10 mm leaves 7 mm. Save.

  3. Give each toolpath a face

    Add the toolpaths as usual. Every toolpath dialog now has a Face (two-sided) choice at the bottom: Top (side A — as drawn) or Bottom (side B — mirrored). Top is the default.

    1. Drill the two circles, depth ⊥ stock, face Top.
    2. Pocket the inner rectangle, 3 mm deep, face Bottom.
    3. Profile (outside) the outer rectangle, depth ⊥ stock, face Bottom, added last.
    The recess is a Bottom toolpath. The orange circles on the canvas are the two pins.
    The Add Toolpath dialog for a pocket with the Face two-sided choice set to Bottom, side B, mirrored, and the drawing behind it with two orange pin markers above and below the part

    A toolpath on the bottom face carries a B badge on its card, so you can see at a glance which setup it belongs to.

  4. Look at both sides

    Press 3D, drag in the view to tilt it until you are looking down, and use the Side A and Side B buttons at the top left. Side A is the first setup: your two holes, and the two pin holes the program ends by boring.

    Side A: the two holes and, at the end of the program, the two pin holes.
    The 3D preview of side A: a wooden block with four round holes, the two drilled holes and the two registration pin holes

    Side B is the blank after the flip: the recess, and the groove the outline cuts round the part. Bottom toolpaths are mirrored for you. The recess was drawn to the right of the centre, and here it sits to the left, because the blank has been turned over like a page.

    Side B: the recess (mirrored) and the outline that frees the part.
    The 3D preview of side B: a recess cut in the face of the part, with the outline groove round it

  5. The mistake: pins where the part is

    A pin hole goes through the whole blank, so a pin inside the part is a hole in the finished part. The default 15 mm inset reaches into any part with less than about 18 mm of blank round it. Run this same job on a blank only 100 × 70 mm, with the default pins, and both pin holes land inside the plate. RapidCAM says so before it exports:

    Pins inside the part: move them into the waste (Pin inset from edge) or use a bigger blank.
    A Two-sided setup warning: a registration pin lies inside the part cut by Profile (outside) 1, pin holes are bored through the whole stock so it would be a hole in the finished part, move the pins into the waste or use a bigger blank

    The check compares each pin, and the hole’s own width, with the outline of every Profile (outside) toolpath, on either face. With no outside profile in the job there is no outline to compare, so it has nothing to say.

  6. Generate, and cut in two setups

    Press Generate G-code. Each side is checked on its own, so there are two export checks one after the other, and then you get a single zip with two programs: …_sideA_….nc and …_sideB_….nc. For this job side A drills the holes at X28 Y62 and X92 Y28 and then bores the pins at X60 Y10 and X60 Y80, down to Z -16: the 12 mm of blank plus the 4 mm into the spoilboard.

    The programs say what to do at the machine, in their first lines. Side A: cut this side first with the stock as drawn; it ends by boring the pin holes, so keep the stock clamped. Then put dowels in the two holes in the spoilboard. Side B: flip the stock left ↔ right onto the registration pins; re-zero Z on the new top face; keep X and Y zero at the same machine position. Re-zero Z because the top is now the other face; keep X and Y because the pins put the blank back in the same place. The stock thickness in RapidCAM must be the real thickness, because side B is measured from it.

    Set your zero for the first setup as in Set your zero.

    Before you run it: run side A with the blank clamped and stay with the machine; unclamp only after the pins are bored. Wear eye protection, and check the blank is seated on the dowels before side B starts.

Open RapidCAMRelated: hold the part down with tabs

Checked against RapidCAM on 2026-10-05. If something here no longer matches what you see, the app has changed and this guide is behind: please tell us.