I seem to recall that when I first got my machine and did a few inlay jobs that when I dry fitted the inlays into their pockets, they fit in there pretty snug without any play.
My last several projects with inlays have all been a little loose when dry fitting them. Each one has been about 1mm (1/32 inch). Here is a 9 second video showing this play.
Below are the two files used to create the pieces in the video. In the files there are two circles, one with a slightly deeper pocket as an experiment. Both plugs are the same size.
Thanks Tod. I have always used the same depth for my pocket and the plug. In theory the plug will bottom out at the same time as the walls make contact. I’ll try making the plug a little shorter then the pocket and see what that does.
If I am understanding Top Gap correctly, this is simply the amount of space between the two faces of woods. As such, it should not have an impact on how well the plug fits into the pocket.
Unless the top gap is too small, and the plug bottoms out before being fully seated.
“In theory…” is what gets you. slop, runout, backlash, deflection, etc… can all contribute to the pocket being wider, or the plug being narrower than designed. With a 30° V-bit, you also have an ample amount of compression in the wood as you clamp it, making it travel further into the pocket than designed.
I’ve advised a few with significant gaps to go Plug Depth: 0.0, Top Gap: 6.0 (per your example), and then measure the actual fit to come up with a “fudge factor” to apply to all future inlays.
Okay, if I’m understanding you correctly… I cut a 3mm deep pocket and then a plug that has a depth of 0.0 and a Top Gap of 6mm. This plug did not actually fit down into the pocket very far. I then measured how much gap was between the two surfaces of my woods. That gap was about 3.5mm. That means 2.5mm of the plug went down into the pocket. Should I be subtracting taht 2.5mm from my plug depth when I go to make an actual inlay?
Yes. It went 2.5mm further than you expected, it “theoretically” should not have fit at all.
So subtract 2.5 from your plug depth, and add it to your top gap.
This seems like a lot (~0.100"). But with a 15° wall, every bit that it’s off gets exaggerated.
It was kind of hard to measure since the round plug was wobbling around on top of the pocket, so that 2.5mm might have been off. I’m going to cut a pocket and inlay using that offset. I’ll glue it up and then cut it in half to see what it truly is. I’ll report back tomorrow afternoon.
I did not take a pic of it before I cut the plug body off, but I think I need to increase my top gap amount. I use a press to clamp the plugs into the pocket and there was almost no gap left between the pocket and plug faces.
