Pocket cuts are smaller when cnc'd than in carve?

Heya all-

Pretty new to CNC here (just took the class) but have lots of vector and laser experience.

I have a design that has several pocket cuts and several thru cuts.

When the CNC was finished, I noticed the pocket cuts were meaningfully SMALLER than they were meant to be. Design below (magenta are the pockets):

When I go back to V-carve to double check, the vectors are appropriately sized. When I measure the entire piece that I cut out, it is the correct size. Only the pockets are incorrectly sized (.6630" instead of the .7035" they are meant to be).

Any ideas?

Any ideas?

What do you mean smaller? Smaller in width, or shallower? Could it perhaps be the setting you have chosen for where the bit rides along the vector? You can choose inside the line, outside the line, or right on the line, and that may make a difference. If it was shallower, then perhaps your z zero is set incorrectly, or there is a .04" deviation in the machine bed?

There is a small chance that if your bit was not tightened enough, or if you plunged too rapidly, the bit could have slipped .04" back into the collet and invalidated the z home position…not sure how likely this is though.

Sorry that was a little muddy/rushed. The magenta spots (pockets) were supposed to be .74" tall and ended up smaller. All of the cuts were right on the money.

(this happened right after I realized that importing a certain version of SVGs into Vcarve results in them getting shrunk by 30% or so-- I resolved that issue but never figured out this one).

When I tried the magenta areas a SECOND time as CUTS instead of pockets, they were the correct size. Pretty strange! I’ve got a workaround but I’m curious if anyone has any ideas on what I might’ve done wrong.

Did you have a value put in the pocket allowance box?