TIP: How to avoid "tearout"

[bzb]

This has probably been covered before (wow there's a lot of tips in this forum!!) but I haven't noticed it on any of the guides I've read or watched on YouTube.

 

One of the things you become aware of when building furniture and other woodworking is called "tearout".  Basically, the nice looking piece of wood you see is very, very thin.  Underneath is generally plywood of various species and qualities.  Needless to say, you want to see the nice wood, and avoid revealing the plywood.

 

Well, same thing was happening to me when I was trimming my parts - especially parts that have sharp corners or turns.  Tearout was occurring on the back side, which could continue on into the visible parts if you're rough when trimming.

 

Most guys have suggested that you score a few times, and then just snap it.  This generated some tearout for me:

 

 

Instead, I scored, then cut relief lines at the top of the shoulder.  In this photo you can see the 1" piece at the top has already been removed, since it snapped off cleanly.

 

 

Then fold on the line.  Some parts may snap cleanly, but mine mostly would just fold over and will not separate by bending either way.

 

 

After the fold, I would unfold and run my blade along the inside edge to make a nice line.  The blade follows the folded part really nicely.

 

 

Then the cut piece basically just falls off when you touch it.  Nice clean lines with zero tearout.

 

Edited January 18, 2014 by bzb

[TK bondservnt[501st]]

sandpaper works to help even out the edge and round the shape so that it's not sharp.,

[bzb]

Oh definitely - I'm following up after the cut with the sandpaper on every piece in my build.

 

I'm just getting to cutting up the initial pieces, and the score-and-snap method isn't working great for me.

 

This method takes a little more time since I'm essentially scoring both sides, but it's producing way cleaner lines with less worry about a piece having to be replaced.

[kaa1304[TK]]

If score and snap isn't breaking on first bend, you just need to score a little deeper and then sandpaper. I don't think I've ever seen this tearout tbh and I've nearly finished 5 months of scoring and snapping on a (nonTK) project.

 

I'd be concerned about scoring both sides simply because, what happens if I dont get the cuts exact? That could get real messy.

[bzb]

I'm scoring each part 3-4 times.  There are some parts that are indeed breaking apart when I bend.  Others chip out.  Not badly, but enough that I wanted to do something about it.  Perhaps it's a bit of perfectionism that I don't need to have on this build - but it may save someone else's cutting.  It's just something I'm going to be doing on the rest of my build and anyone else's I might help with in the future.

 

There shouldn't be any worry about where the cuts on the opposite side are.  The bend lines are pretty clear on the white ABS.  See reference photos above.  You can see the line that the bend created, where my blade is following.

 

To me, it's better than getting chipout, especially near corners (which hasn't happened yet, thankfully, but *could* from the randomness that I've gotten tearout.)

 

Interesting part to me is that no one else seems to experience this.  I had a considerable amount of chipping when I was assembling tweeter arrays with ABS piezos.  In that case, though, I never worried about it because the homemade ABS glue would fill in any holes and the entire thing was painted.

[TK bondservnt[501st]]

one of the other ways to get accurate and sleek lines on armor is to use a handheld belt blade sander and simply cut the armor out with sheetmetal shears

and then followup with the use of the blade sander.

 

http://www.harborfreight.com/1-2-half-inch-bandfile-belt-sander-92158.html

 

[toybiz[TK]]

BZB

 

I'm having too have to follow what you are experiencing as well. Perhaps its the ABS of the MTK kit is somewhat more flexible than other kits. Without another maker to compare to would be difficult to say with any certainty.

 

Just keep trimming slowly but surely.

Edited February 7, 2014 by toybiz