measuring stuff

[kec-10238]

Since I was an accountant for 28 years then turned signmaker/engraver for the last 8-9, I learned the secret of making things. Measurements! Not any measurements - ACCURATE measurements. Not being a woodworker or even handy for that matter, I learned that virtually nothing you get today comes already cut square. It's close but over an 8 foot span can differ by up to .25" sometimes more if the saw guy had a bad day. Therefor, I cut every piece of wood square (3 edges) when ever I do anything. Having said that, CNC has thrown a new dimension at me - "thickness". So my question is this - Should I want to make a box using so called 1/2" wood and I need some 1/4" deep pockets in them ie. shelf SHOULD I be measuring the thickness of the wood with a digital caliper since we all know it is likely not a 1/2" to make sure the pockets get milled .25" deep. Common sense says yes since the wood might actually be .42" thick and you would gain an extra .08" of milling depth even though it was milled .25" you pick up the extra .08 you counted when the wood thickness was .5" (since z was set at surface).

I have designed a box and would like to cut it AND I think I have accounted for all measurements to include tool sizes (D) for cut thru's, where (inside/outside/on cuts) and how they should be milled, size of wood (HxW). The only thing I have not accounted for is the thickness of the wood. Again when I piece it together having milled 1/2 inch pockets .25" deep on the side edges (2 pieces) to fit the other 2 sides. I am afraid if the wood is not .5" thick and I stick the non milled edge side to a milled edge, they will not perfectly meet. So do you adjust for the wood thickness using a caliper before cutting or do you just get it close and finish the edges so they meet like they should. I can't imagine they measure the thickness of every piece of wood in a high production environment (which I am not in). Whats the dealio - How do you guys do it?

[aforww]

In a production environment, they use engineered wood these days for this very reason. That's why almost all furniture is MDF or particle wood. Is pretty damn consistent.

With real wood this is why I own so many tools lol. If I wanted to make something from a 2x4 for example my process would be rough cut length, run one edge and one face on jointer, them take it to the planer for final thickness, then cut to final length.

So in closing, yes measure the thickness of every piece of stock if you want it as accurate as possible lol.

[kec-10238]

Oct 16, 2017 14:38:02 GMT aforww said:

In a production environment, they use engineered wood these days for this very reason. That's why almost all furniture is MDF or particle wood. Is pretty damn consistent.

With real wood this is why I own so many tools lol. If I wanted to make something from a 2x4 for example my process would be rough cut length, run one edge and one face on jointer, them take it to the planer for final thickness, then cut to final length.

So in closing, yes measure the thickness of every piece of stock if you want it as accurate as possible lol.

that sucks - and I think I'm through with that mdf stuff (at least in my engraving room) - the dust is just too nasty.

[aforww]

Oct 16, 2017 14:44:50 GMT kec-10238 said:

Oct 16, 2017 14:38:02 GMT aforww said:

In a production environment, they use engineered wood these days for this very reason. That's why almost all furniture is MDF or particle wood. Is pretty damn consistent.

With real wood this is why I own so many tools lol. If I wanted to make something from a 2x4 for example my process would be rough cut length, run one edge and one face on jointer, them take it to the planer for final thickness, then cut to final length.

So in closing, yes measure the thickness of every piece of stock if you want it as accurate as possible lol.

that sucks - and I think I'm through with that mdf stuff (at least in my engraving room) - the dust is just too nasty.

It has its place. But controlling the dust is hugely important with that stuff?

[Derek the Admin]

I agree on measuring. Thicknesses are almost always off from advertised. On the matter of pocket depth, though: If you model the piece that is 0.42" thick as 0.5" thick with a 0.25" pocket, when you zero to the stock top and run the program you'll still get a 0.25" deep pocket. The contour will just be 0.08" into your spoil board. Perhaps I misunderstood what you were saying though.

[Hommer Woods]

It might be critical on the pockets where you join the parts. If you want the pocket to be .25 from the outside for assembly to work and your stock is only .42 vs .5 you would need to make the pocket only .17 deep to maintain the thickness under the pocket.

I experience that with hole drilling for cribbage boards. My holes are set to 3/8 deep so I can't use stock much less that .5 to avoid punching through.

Hope that makes sense.

[kec-10238]

Oct 16, 2017 17:07:20 GMT Derek the Admin said:

I agree on measuring. Thicknesses are almost always off from advertised. On the matter of pocket depth, though: If you model the piece that is 0.42" thick as 0.5" thick with a 0.25" pocket, when you zero to the stock top and run the program you'll still get a 0.25" deep pocket. The contour will just be 0.08" into your spoil board. Perhaps I misunderstood what you were saying though.

Same thing you said....lol. when you assemble the box so that the outside edges meet - you are actually moving the entire sides back (by the difference in wood thickness if set wrong) thus adding that difference to the pocket depth (altho milled out .25" it is set back further thus leaving room at the back of the pocket) for each side(changes interior of box dimensions. Otherwise the outside edges would not meet perfectly and they would be needed to be sanded down to do so changing your box's exterior dimensions. WOW so easy to visualize so hard to verbalize.

On another note, I measured a piece of plywood thickness up (.48") to give it a test run with my box design (which I adjusted for thickness) to see how things would go. Used 2 operations (change in tools). Man - O - Man, I am super impressed on the job this machine did. Not impressed with the results due to the wood used (not your best piece of ply)!....Can you say HAPPY CNC FACE! ....I messed up on 1 of the profiles (told vcarve to cut on the line instead of outside of it) - so 2 sides were a tad higher than the other two sides. And I couldn't make a cut all the way through with my 1/16 end mill as the taper was going to contact the wood surface if I let her ride. I need a longer 1/16 end mill for cut throughs on 3/4" hardwood. Other wise - outside edges aligned damn near perfectly (awesome accuracy of this machine). Pleased as punch! Now I need to get some real wood and do some real things - Confidence is up.

[Derek the Admin]

Thanks for the compliments on the machine! It sounds like you are progressing quite nicely with the overall skills required to operate.

And yes, with all those words.... I think we are saying the same thing on the thickness.