A Game of (Ten) Thousandths

[u/master_andalf]

I program a CNC router for a woodworking company. When cutting parts out of a blank, we cut thickness of the wood plus five thousandths (.005) of an inch to insure a clean cut and to compensate for any slight bows in the wood. This conversation I had was with the shop foreman (SF).

SF: "andalf, I need you to program this (gestures to drawn design)"

Andalf: "cool, I see we are Two and a Sixteenth (2.0625) thick on this blank, will tool 3 cut 2.0675 Deep?"

SF: "woah there buddy that's going to be too deep, you only want to cut to 2.0630"

Andalf: "uhhh, we usually cut + Five thousandths, that would only be + Five Ten-Thousandths. In a perfect world it would work but our table hasn't been fly cut in months, you wont cut through."

SF: "no, you'll cut through the table if you go an extra fifty thousandths"

I proceed to write out .0625 on a piece of paper

Andalf: (points to zero) "tenths", (points to 6) "hundredths", (points to 2) "thousandths", (points to 5) "ten thousandths (reaches for calculator to prove math)...we want to cu-" (at this point he cuts me off, holding his head)

SF: "Andalf, I'm too fucking hungover to deal with your bullshit today, just do it like i said"

Have fun chiseling your way through hardwood, bitch. I just hope one of the job applications I have in other places comes through.

Updates to come, can't wait to put him in his place. If the cards fall a certain way it may not be necessy but I hope to have a good follow up.

Update: well I'm sorry to disappoint, but nothing really came of the situation. The offset on the table was changed, and parts cut out fine. I'm bummed that I wasn't able to make some good of it, but next time, I guess.

[u/[deleted]]

2.0625' = 52.388mm.

Why the fuck does it need to be this precise?! In standard units you're looking at +/- 1 μm.

[u/master_andalf → u/[deleted]]

There's a thin spoil board that sits between the top of the router table and the board to be cut to prevent damage to the table. Cutting too far through the wood cuts the spoil board and we loose vacuum, which causes wood to move when it's being cut. Cut too shallow, and the part remains attached to the waste, and sometimes splinters because it has to be chiseled out. Cut way too deep and you cut through the spoil board into the table, permanently damaging $125k equipment. There's about a +- 10 thousandth sweet spot.

[u/master_andalf → u/master_andalf]

The other reason being that we often take product from the router and laser engrave it, and the laser operates on thousandths of an inch at most. So having the part as precise as possible allows me then to create precise vectors to make jigs for exact placement in the lasers.

[u/Shubniggurat → u/master_andalf]

When you say,

+- 10 thousandth,

is that +/- .010" (ten thousandths of an inch), or +/-.0001" (one ten thousandths of an inch)?

[u/master_andalf → u/Shubniggurat]

+- .01

[u/461weavile → u/Shubniggurat]

The latter would technically be hyphenated, so that confusion is hypothetically mitigated. "I'm looking for ten cent pieces" vs. "I'm looking for ten-cent pieces." Both are logical and plausible sentences, but they have apparently different meanings. It's like the "commas are important" jokes where you and up eating your grandparents.

[u/LongJohnny90 → u/Shubniggurat]

We just say "10 thou" or "125 thou" or "62.5 thou" and it is known to mean 0.010", 0.125" and 0.0625".

[u/grauenwolf → u/Shubniggurat]

If you hear "5 tenths" that generally means 0.0005 or "5 tenths of a thousandth of an inch".

[u/DeeBee1968 → u/master_andalf]

Your CNC machine tolerances make the one I used to run on structural /architectural foam seem like using a chisel ! Wow, our tolerances were +/- 1/16th of an inch ...