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View Full Version : Beveling a 30 deg edge with a hand file?



Serceflyer
10-27-2007, 02:40 PM
What's the trick to creating a nice 30 degree beveled edge on a piece of 3 X 2 x 3/8 steel plate?

Is there a way to do it with just hand tools like a file and vise? Would I need to scrape the surface?

Thanks,
George

BillH
10-27-2007, 02:52 PM
Start filing!

tony ennis
10-27-2007, 03:05 PM
It really depends on how wide the bevel is going to be.

For a large area, seriously, I'd find a mill.

For a small area, I'd calculate the intersection of the bevel on the adjacent faces, put on blue markup stuff, and scribe the lines on the two faces that show where the bevel ends.

Start with a course cutting file, switch to finer files as you get close to the lines. At the end I'd wrap a bar in progressively finer sandpaper to remove the scratches.

I'm sure there are fixtures out there that can help.

SGW
10-27-2007, 03:10 PM
How accurate does it need to be? Is it for appearance only, or is the angle critical to functionality?

Forrest Addy
10-27-2007, 03:14 PM
When you get close rig up a gizmo like a saw filing guide at the proper angle. If you want to bevel the edge completely like it was a cutting edge hacksaw leaving a little stock and file the final angle.

Serceflyer
10-27-2007, 03:18 PM
It needs to be pretty accurate--- it's for dovetail mating surfaces. What do you mean by a saw filing guide-- something like a mitre saw?

Thanks

tony ennis
10-27-2007, 03:27 PM
If you mean dovetails such as in woodworking or like making a part that slides within another, then you need seriously mad skillz or tons of patience.

The issue is that the cut you need to make is more difficult to cut than a bevel. There will be an inside corner that will be very entertaining to file :eek:

What machines do you have access to?

Can you post some drawings?

jkilroy
10-27-2007, 05:08 PM
If you want a dovetail jib, google up Leigh dovetail jigs. They make anyone a master.

Paul Alciatore
10-27-2007, 05:13 PM
There may be other types, but I have seen filing guides that positioned hardened steel rollers on each side of the work for the file to ride on while filing a flat surface determined by their position. Since the file can not ever go below the rollers, a good flat is produced. It needs to be firmly mounted with respect to the work.

Another thought. Cabinet makers use a small, simple plastic tool with a tungsten carbide blade mounted in it to finish the edges of Formica. It is just dragged over the edge and it cuts a nice, uniform edge. If your bevel is small, perhaps you could use a similar tool with a HSS or TC blade. Or add a guide block that rides on the two sides of the work to a file. Or to a Dremel tool with an abrasive wheel. You would still hand file to get it close and then finish with the cobbled up tool.

Serceflyer
10-27-2007, 05:34 PM
Here's what I'm working on:

http://www.vintageprojects.com/machine-shop/lathe-modelling1.pdf

It's got to be the cutest, simplest homemade lathe ever! I'd love to build it with just hand tools.

George

SGW
10-27-2007, 09:30 PM
Oh -- it's for Bragging Rights. Then by all means, have at it.

I tend to like Paul's idea of the rollers, though I haven't thought it through just how you'd want set it up.

Al Messer
10-27-2007, 09:55 PM
Draw file it. Make a simple wooden jig until you get the hang of the correct angle.

mechanicalmagic
10-27-2007, 11:22 PM
I love a minimalist. Brings out the inventive side.

OK, so you are trying to make a metal dovetail, and matching parts.

Start with a flat 2" wood block and make an angled vise. The block is a quite a bit wider than any of the parts, allowing for clamps. Saw it at 30 degrees, a table saw would be nice, but not required. Using a piece of sandpaper, on a surface plate (float glass, one piece marble tile), lap the the cut sides flat, then together, removing the saw irregularities. These are the jaws, the angle may be approximate.

To file your first dovetail angle, (the inner part):
Screw the back jaw to a pair of parallel, flat boards (base), enough space between for your dovetail. Clamp your (to be dovetail), lightly clamp the front jaw to the base, insert the dovetail stock, and clamp the front jaw so it sandwitches the dovetail. Tighten all clamps. With a thin cardboard protector, on your jaws, hacksaw off the excess. Tap up the dovetail and using cardboard protectors again, file to a flat surface. Draw filing would be my choice for the last passes. Very light tap up, and sand using the inverted surface plate and sandpaper.

Second angle, (inner part):
Scribe a parallel line to the proper width of the dovetail, insert in the above angle vise, allowing for the height of cardboard. Repeat.

Same for the outer dovetail parts, including the gib, remove the excess stock later.

Well, I hope you get the idea, make an angled vise with a top surface that guides all your tools. The tools can't damage the top surface during use.

When it comes time to make the inner dovetail perfectly parallel, I'd probably put sandpaper between the gib and the dovetail, and then use lapping compound.

Just my off the top answer, probably forgot something, maybe confusing, but it sounded good to me.

Rich Carlstedt
10-27-2007, 11:38 PM
Make sure you go buy a new 12 inch or larger file
Two of them would be better yet. One course and one smooth.
Too many guys grab an old file and make it a tough job, because it is wiith a dull file. It can be a fun project, keep it that way.
Rich