cutting shared lines

[mattnb]

What is the best way to go about cutting MDF where two pieces of the cab share the same line (such as in Lusid's Plans)? I don't want pieces to be 1/16th off when I go to put it together! 

[Shape D.]

The best option is to clamp them together and cut them at the same time.

If that's not doable, make a template, cut it closely, and touch it up with a router.

Either way, put the two together when you're sanding.

[mattnb]

I think you misunderstood my question, upon second reading I don't blame you.

I mean what is the best way to proceed in this situation.

[sstorkel]

I mean what is the best way to proceed in this situation.

Use a sawboard? Honestly, I'm not sure what you're asking. Do you want to know how to make a straight cut? How to account for the saw kerf? Something else?

FYI: if you can get you cuts accurate to 1/16th of an inch, you'll been doing as well or better than the majority of fine furniture makers! Hardwoods will expand and contract by twice that amount just due to changes in humidity from one season to the next...

[jhabers]

i understand what your saying, cut the line for the cab bottom, then measure after you do the cut on the remaining for the cab back. Dont draw all your lines at once because you will run into what you are saying

[fjl]

Saw Blade Kerf is something you need to consider. My first wood project, I was off on all my cuts and didn't realize till afterwards that it was because I was cutting in the center of the line. You're supposed to cut to the side of the line. The side that is scrap.

As for your concern of sharing lines, I wouldn't go by Lucid's plan on drawing all the pieces to cut at one time. Instead draw the first piece, cut it out then draw the next piece.

[mattnb]

Saw Blade Kerf is something you need to consider. My first wood project, I was off on all my cuts and didn't realize till afterwards that it was because I was cutting in the center of the line. You're supposed to cut to the side of the line. The side that is scrap.

As for your concern of sharing lines, I wouldn't go by Lucid's plan on drawing all the pieces to cut at one time. Instead draw the first piece, cut it out then draw the next piece.

Good plan. I think that's exactly what I'll do! Thanks

[javeryh]

I'll second the "one piece at a time" approach.  If you draw one line shared by two panels even the most accurate cut will be off by the width of the blade.

[fixedpigs]

I'll second the "one piece at a time" approach.  If you draw one line shared by two panels even the most accurate cut will be off by the width of the blade.

unless of course you compensate for the kerf of the blade...

[bvicarious]

As long as there is room around the edges to compensate, start from one corner and work your way to the other drawing the lines as you go. If you draw all the lines before you cut, you're going to be doing a lot of erasing, and if you draw all the lines at once and compensate for the kerf, you'll probably find your pieces 1/32" off here and there and need to run them through again or sand. That happened to me quite a bit.

[Franco B]

What I would do (and what I have been doing since I have learnt) is to draw all the pieces at one go but allow for the kerf of the blade plus a little extra.

Say the kerf of the blade is 2mm. Leave about 5mm or so between each pencil line for you to jigsaw/handsaw/circus circsaw between (leave more or less depending on the kerf of the blade and how closely you feel you can cut in the gap.)

Once you have your panels cut, clamp something straight to your pencil line (I use some 32mm square planed pine I have) and then use your router with a flush trim bit to remove the rest of the material and leave you with some lovely straight edges

I would also recommend marking the lines from one datum rather than incrementally marking each line from the previous one, that way any inaccuracies when marking wont be compounded.

*Edited for spelling, I dont think you can fit a circus in a 5mm gap, well maybe a flea circus