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Old 06-29-2017, 04:14 PM
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digidocs digidocs is offline
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Default Best way to cut 0.050" 4130

What are your preferred methods for cutting brackets out of 4130 0.050" plate?

I have a "high-speed" bandsaw that I use for aluminum, a jigsaw, angle grinder, and standard hand tools. I'd love to use the bandsaw, but I think it may run a little to fast for steel. Perhaps the jigsaw or angle grinder might be a better choice?

Thanks for the help,
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Old 06-29-2017, 04:22 PM
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BillL BillL is offline
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For long cuts I use a Bosch jig saw with metal cutting blade, but mostly a hack saw and a bench vise.
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Old 06-29-2017, 05:30 PM
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vernon smith vernon smith is offline
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The rule of thumb for any metal and a toothed blade is you want at least three teeth in the metal. Obviously, that would require a very fine blade with .05 sheet. Also, whacking blade teeth into the metal from a ninety degree angle guarantees a rough cut. I have yet to see a reciprocating blade (jig saw) cut metal well.

If you have a sheet metal shop, roofer or spouting outfit near by they can cut you long strips to various widths. Below is a link to a cheap cut off "chop" saw with an abrasive cut off wheel from Northern Tool. This will give you a nice straight cut ready to deburr. Better still is a table saw with an abrasive wheel. With that you can cut from large sheets with great results. I assume I don't have to go into the safety glasses and gloves speech on this forum but will until I learn the customs
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Old 06-29-2017, 05:35 PM
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hgerhardt hgerhardt is offline
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Fiber cut-off wheel in an angle grinder, preferably pneumatic.

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Old 06-29-2017, 05:40 PM
painless painless is offline
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How long of a cut? The die grinder would work fine on short cuts. Cut close to your desired dimension, then fine tune with a vixen file.
Jeff Orear
RV6A N782P
Peshtigo, WI
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Old 06-29-2017, 05:46 PM
TFeeney TFeeney is offline
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Default Me 2

This sounds like the rudder cable links F-10104 step 1 (38-10)? I've got the same question.

I'll go a bit further - how did you create the R1/4 for the outside? I can grind it down to be close, but that seems crude. Since its connecting a flight control, things start floating around in my mind like overheating material or removing too much material (especially if my hole wasn't perfectly centered ).

Is there a nicer way? Something more elegant?

Sorry if this is thread drift.
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Old 06-29-2017, 06:01 PM
Robert Anglin Robert Anglin is offline
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Default Band saw.

I cut a peace today with a 32 tooth per inch band. Just cut it on the outside of the line and file it smooth. Just what we do. Yours, R.E.A. III #80888
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Old 06-29-2017, 09:50 PM
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hgerhardt hgerhardt is offline
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Originally Posted by TFeeney View Post
This sounds like the rudder cable links F-10104 step 1 (38-10)? I've got the same question...
If it's just cutting a narrow strip to length, use a cold chisel with a vise. If the chisel is reasonably sharp and you hold it at the right angle, it will make a clean cut. The part cut off will have a bit of a curl to it, but the vise will flatten that out nicely. After cut to length, you can angle the strip in the vise and cut off the corners too. Less work with a file that way.

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Old 06-29-2017, 09:59 PM
lr172 lr172 is offline
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Originally Posted by TFeeney View Post
things start floating around in my mind like overheating material or removing too much material (especially if my hole wasn't perfectly centered ).
Most of the 4130 on an airplane is welded. Pretty sure you won't see more than 2000* with a cutoff tool :-). Reasonable heat is not an issue for most non-treated steel. I use abrasive wheels; Mostly a cutoff tool and occassionally a chop saw.

N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019

Last edited by lr172 : 06-29-2017 at 10:02 PM.
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Old 06-30-2017, 08:19 AM
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DanH DanH is offline
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A bandsaw is fine for .050 4130 sheet, given enough teeth and low blade speed. The chop saw is reserved for heavy tube and angle sections, or as Larry said, an edge that will be subsequently welded. Mostly I just use a hacksaw.

If you must use abrasive cutting tools (or a laser), remember it doesn't matter how hot you make the part. Given the section thickness we use in light airplane construction, what really matters is how rapidly you cool the part. 4130 is an "air-hardening" steel. Cool it rapidly and it becomes very hard and rather brittle. How hard mostly depends on the cooling rate. Conduct an experiment; warm a piece of 4130 scrap to dull red, then cool it rapidly (dunk it in a water bucket, squirt it with an air hose, or just wave it around in the air). Now try to drill it, or file it.

When cutting a 4130 part with a abrasive tool, the cut edge is heated near red, then quenched by the mass of adjacent cool metal. As a result, the edge is hard and brittle, while the balance of the material remains ductile. We want most of our airplane parts to be ductile, meaning they bend, stretch, and otherwise deform long before they actually break. The problem here is that a quenched edge is not ductile, and the edge is where cracks start. Think of it as a strong but brittle crust on a softer center.

So, good home shop practice says to use toothed cutting tools on 4130. Can't get hot, so it can't be quenched, so it remains ductile, and as a big bonus, easy to edge finish with hand tools.

If you must use a cutting method that heats the material, your goal is slow the cooling process. One way is to heat the whole part so it can't quench itself. Given something like a laser cut part, simply remove the quenched edge with the belt sander (you were going to edge finish anyway, right?). Do it while holding the part in your hand (rather than with a gripping tool), a sure way to make sure the part doesn't ever get very hot.

The same quench rules apply to welding. Cool slowly. It also applies to drilling. A novice will spin the drill fast, as he would (correctly) for aluminum. It will work on 4130 if the bit is fresh and sharp, but if it's dull, or not enough pressure is applied, friction makes the material under the tip of the bit get hot. Since the drill isn't cutting well, our novice stops drilling for a short break, or to change bits, and the hot material is immediately quenched. When he resumes, the new bit won't cut, because the bottom of the hole is hardened. It's all very amusing to the experienced, unless of course the novice happens to be using your drill bits
Dan Horton
Barrett IO-390

Last edited by DanH : 06-30-2017 at 08:22 AM.
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