I am no good at cutting a straight line, never have been. So, these long skin trimmings are troublesome for me. Maybe with enough practice on this plane, I'll be better on the next one! Anyway, if this post works right, look at the picture. This is typical of cut edges. I have smoothed out all the serrations, nicks etc. from cutting. No snags to the finger or a cloth. But there are these little "dents" or irregularities from the scissors. They are smooth and very small.

Will these propagate cracks they warn about?

How can I prevent this?

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Hi Chris

I discovered the Olfa P800 knife which is fantastic at cutting through the aluminium on long cuts. I mark the line, clamp a metal ruler along it and then score the metal 3-4 times with the knife and it makes a real clean cut. I have a picture of it on a blog here http://www.zenith.aero/profiles/blogs/2606393:BlogPost:171712

 

It's pretty cheap, could be worth a trial run, but I'm not going back to the snips for long cuts.

 

Paul

Hi Chris,

I second the recommendations here for the Olfa knife for cutting a long straight cut.

http://www.olfaproducts.com/ProductDetail.jsp?LISTID=C030000-115272...

I always finished the edge of those cuts with a vixen file layed down parallel to the edge.

Regards,

Dave

Chris,

I can't answer your question but I suffer from them same problem as you. I cut oversize anything that has an outside radius and then run against my disc sander to trim to my line. This, I do carefully to avoid building up heat to remove the T6 temper. Don't ask me what that temp is but if I can't hold it comfortably I back off. On straight cuts I use an Olpha knife, then file the edge. I know that this doesn't answer your question but hope it helps.

Chris,

I agree with the previous fellas. I never cut with a hand shears to make straight cuts. I always clamped a straight edge and cut with an Olfa P800 with multiple scores, broke the piece off and then filed and sandpapered the edge till smooth.

I could never achieve an edge smooth enough to satisfy myself with the shear.

Even on curved pieces, I would cut way oversize and file to my line to achieve the desired contour.

Best of luck.                                                                                                                                                   Jerry

Chris - If you are using the traditional left/right cutting snips; my experience is that they are not the best choice. So I bought a pair of snips with a long cutting edge; much better results. Also do not cut all the way to the end of the cutting edge this can leave a nasty little mark. But all-in-all you should not experience any adverse affects from the edges you are showing. More than likely there is a line of rivets between that edge and the rest of the plane. The metal will be more stressed on the plane side of the rivets than on the cut side of the rivet line. It may not look all that good but should not cause any cracking problems. Paul describes a good technique but you must be very careful when scoring the metal. Try to keep each score on the same line. A circular saw with a guide and thin grinding blade could also be used; a relatively quick travel speed cannot buildup enough heat to affect the metal. But move to slow and you could end up with warping problems. I would try on a piece of scrap first.

Chris

Thanks for the responses. I've learned something here! I saw Olfa knife in the recommended tools list, but I got the wrong one. Correct Olfa knife will be ordered and I will practice scoring for a cut.

I can offer two tips on using scissors.  Don't cut all the way to the tip.  Second, I always make 2 cuts, one leaving between a quarter to a half inche of material, then the second cut.  On the second cut all the bending goes into the wasted part as it curls up, leaving the part with a nice smooth line.  

 

I cut everything with them and I think they come out pretty good.

For really long or repetitive cuts, I have access to an industrial quality shear. For shorter cuts, say a foot or two at most, I mostly use a very heavy-duty set of straight snips and as recommended, don't snip to the end of the jaws.

Now, however, if I'm cutting a reasonably short piece where the cut can be made parallel to a known straight edge, I more often than not use my recently acquired bandsaw with a fence. I bought a "metal cutting" blade to use with it, but quickly discovered the 6 tpi wood cutting blade did just fine. You do have to file or clean up the edge a bit, though. There are at least two EAA videos with some great tips on cutting aluminum with a bandsaw.

Don't forget that wood working tools work great on aluminium. If you are not happy with the straightness of your cuts with an olfo knife or other cutters, use a small electric planer designed for wood. This will give you a finish just like that of Zeniths CNC router.

 

Phill

I've never used one, but have always wondered how a sheet metal nibbler (manual or pneumatic) would work on aluminum for nibbling out square holes (I've always used a file to square the corners of a rectangular or square hole). Do they cut cleanly or do they bend/beat-up the edges of the hole?

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