Edge Finishing - How much is enough?

[rapid_ascent]

So this is a newbie question.

I've been working on my new HS and I'm wondering if I'm over doing the edge finishing. Here is what I've been doing.

1. File edges to remove punch marks.
2. Use cut and polish wheel to polish edge and remove burrs.
3. Touch up sand the spots that I couldn't get to using the wheel with 240 grit emery cloth.
4. Do a final quick sand with 400 grit fine sand paper.

This gives me a really nice edge finish, but it takes a while. I'm just wondering about the general process that is used by other builders and whether I could simplify this process and save some time.

[rv9aviator]

I used a flat file to take the punch marks disappear so the edge felt flat all the way down then used a v groove deburr tool to chamfer the corners. I then hit the chamfers with the flat file to round them a little and finished with .240 sand paper. Was pretty quick and looked and felt nice. I don't think going to 400 paper is really necessary. This was done to the larger flat pieces of sheet aluminum. Try several methods that others have used and you will find one that works for you and is pretty quick. Hope this helps.

[JHines]

Originally Posted by rapid_ascent

So this is a newbie question.

I've been working on my new HS and I'm wondering if I'm over doing the edge finishing. Here is what I've been doing.

1. File edges to remove punch marks.
2. Use cut and polish wheel to polish edge and remove burrs.
3. Touch up sand the spots that I couldn't get to using the wheel with 240 grit emery cloth.
4. Do a final quick sand with 400 grit fine sand paper.

This gives me a really nice edge finish, but it takes a while. I'm just wondering about the general process that is used by other builders and whether I could simplify this process and save some time.

I just file to remove punch marks, then finish with a Scotchbrite wheel. This produces a surface that feels smooth and won't cut your finger if you press down and run it along the edge.

[mike newall]

Unitised wheel, knock the edges off - if you read Van's guide, it merely says if you run a finger over the edge, it shouldn't draw blood !!!!

Get a 6 " Oregon flat chain saw file from Home Despot - they are very cheap and cut beautifully for the bigger bits.

[L.Adamson]

I used a air....angled die grinder & 2" scotchbrite wheels. The bluish colored ones. Easily works on parts, that don't fit easily around a large scotchbrite wheel on a grinder. A 1" belt sander mounted to the bench, was also a great tool to have.

L.Adamson --- RV6A

[terrye]

Two reasons to finish the edges:
1. To remove the transverse tool marks from the CNC punch. If left in the part these will act as stress raisers and cracks can initiate from these sites.
2. To remove the wire edge left from the first operation so that cracks do not initiate from these very thin edges and more important so the wire edge does not initiate a cut in your skin and cause a leak.

A file works well for 1) and a V-groove deburring tool works well for 2) but be careful not to introduce chatter marks which negates the whole process.

A scotchbrite wheel (6" on a grinder) will do both 1) and 2) especially if you set the edge of the part in the groove formed by previous edges. Only drawback is it removes quite a bit of material especially the corners of the flanges.

I have also used a Cratex Kit 777 polishing set of wheels and points in my Dremel tool for getting into very small areas. Also for corners of flanges in ribs etc. the 3M Mini Mandrell 935 is useful.

http://products3.3m.com/catalog/us/e...er/output_hTml

So how much is enough? I would say when there are no more transverse marks on the thickness of the part and when the edges of the part no longer feel sharp when you run a finger across them.

I think 240 paper is too coarse, but using a file, scotchbrite wheel, V-groove deburring tool, Mini Mandrell 935, I very seldom use paper. If I do it is usually 400 grit.

[rv9aviator]

Maybe I should explain a little more on the 240 sand paper. I primed most everything so I washed everything with soap and water using a red scotchbrite pad which smoothed out the 240 marks some.

[Flying Scotsman]

My processes:

For thinner sheet metal,
1. Sand with 220 grit on a sanding block, or with a "free" sheet for interior corners, etc.; round all sharp exterior corners slightly
2. Run a fine grit sanding sponge over all edges to get a perfectly smooth edge.

For thicker metal parts (say, 1/16" and larger),
1. Use scotchbrite pad in a die grinder, or sand with a belt sander/disc sander to remove shear/punch marks and rough spots;
2. 1 and 2 from above

In either case, every edge, lightening hole, corner, notch, flange, etc., is somehow cleaned to a perfectly smooth edge. If I get any cracks, by god, it won't be for lack of trying!

[aarvig]

As you can see above there are several methods to edge finishing and deburring. Basically, do what you find most easily and rapidly makes a smooth edge. You will be doing this a lot so find a way to become efficient at it. For me, I hit everything I can with a 3M scotchbrite wheel and thats it. Smaller spots I work out with either a small jewelers file set or 220 followed by 320 sandpaper. It goes quick. What used to take me 30 minutes to hand file and sand a rib now takes less than 3 minutes. You are building a plane. Efficient production methods save time and make the project more enjoyable. The 3M scotchbrite wheel (available through many suppliers including Cleaveland Tool) will make the job easy and painless. Have fun!

[rapid_ascent]

Thanks for all the feedback.

I'm pretty happy with the process I've been using so far. When I finish with the cut and polish wheel it just seems that there are still some small surface scratches. The final sanding with the fine sand paper is very quick, but still it does take time. I pretty much expected the range of answers that I got. I think I'll try using 320 grit after the scotchbrite wheel and see how it looks. Its probably normal for new builder to over do this in the beginning.