Jointing my Menard's Straight Edge

[Paul Simmel]

No joke.

It's aluminum and a 4', and it's crowned just a bit.

I've read here and elsewhere that aluminum can be machined with WW'ing tools. But I don't know for sure what SORT of aluminum that straight edge is.

My jointer's knives are plenty nicked right now, and I'm just about ready to plop in the second set. They are HSS knives, though, not carbide.

I am actually thinking about shaving off a few thousandths to get a straight edge on that sucker. But I'm going to wait until tomorrow morning, AFTER tonight's Norco wears off.

Seriously, though, I'm wondering if there isn't a stronger alloy or something in there, which would possibly change my consideration.

P.S. the SE was purchased for tile work, and has worked like a dream. But wouldn't it be cool if one could joint a cheepo?

[Paul Mayer]

You can do it on your jointer, but not on mine.

I would say you are taking a big risk since you don't know the composition of materials in the straight edge. If you do it, let us know how it goes.

[Dave Verstraete]

Paul

My day job is machining metals but I've never tried aluminum on a jointer. I would stay on the side of caution until somebody that has done it before chimes in. How would you hold it? I think you're right that it might spoil those blades.

[Jeff Wittrock]

I'd tape some sandpaper on your jointer table and just use that to take a little material off. I don't own a jointer, but the thought of those blades touching that aluminum makes me cringe .

-Jeff

[matt dumney]

Do it! But the sandpaper idea seems better,

[Gary Keedwell]

How about using a router mounted on a table with a split fence and using it with a good HSS or carbide router bit? A spiral bit will cut aluminum like butter. Just take small chips.
Gary

[Paul Simmel]

I swear it, people machine aluminum on these forums!

Been thinking about how to hold it. I could make a block or two, no problem. Holding it against the fence would be easy.

I'm not worried about the knives. They are nicked-up, but I have the Makita knife sharpening system with the green wheel. I've a project coming up, and I'm going to be doing the jointer and planer knives anyway.

I've hit aluminum before, not on purpose, mind you, but it is very soft and saw blades and shaper cutters go right through it. This straight edge is only 1/8" or so thick... not a lot of resistance there.

But I'm going to see who chimes in... good advice. (Laughing) But I'm probably going to do it anyway! Just a hair should do it.

[Gary Keedwell]

How about using a router mounted on a table with a split fence and using it with a good HSS or carbide router bit? A spiral bit will cut aluminum like butter. Just take small chips.
Gary

Thought I would bump my answer down since we posted the same time.

Gary

[Mike Heidrick]

On my jointer the blades cost a lot more than a really nice lee valley straight edge. Doubt I would do this on mine.

[Jason Roehl]

There are a lot of silica-rich woods out there that do far more damage to your jointer knives than a Menard's aluminum straight-edge. I'm gonna take a wild stab and say that it's not some exotic aircraft-grade alloy. Do a test--take a utility knife and scrape the edge you intend to machine--I bet you at least polish it, if not, take a small shaving. Then you'll know it's not too much for your soon-to-be-retired jointer knives.

[J. Z. Guest]

Use a carbide-tipped straight router bit. Carbide is much harder than your HSS jointer knives.

One basic concept of machining is that the harder the material, the slower the cutter needs to be turning. Therefore, cut aluminum slower than steel but faster than wood.

Slow the router bit down as fast as you can, even with a smaller diameter bit. Be careful to hold the aluminum steady and feed it slowly, so that it doesn't get grabbed by the sharp edge.

[Chris Bruno]

If you're not worried about your jointer knives, then you should be good to go if you can hold the straight edge safely.

I use HSS endmills in my Bridgeport all the time to mill aluminum. Unfortunately, the difference is that I can slow down my cutter.

Be careful on the speed - part.. Too slow would be bad too. What's important when you are machining metals - particularly soft metals such as aluminum - is to keep the chip load per tooth at a certain value. If you're spinning the bit faster, you actually need your feedrate to be higher to maintain the proper chip load. This is one of the reasons that High speed machining works so well. If you feed too slow, you'll gaul and mash the aluminum instead of cut it, and your surface finish will be terrible. Now, all that said, ideally you'd want to take extremely shallow passes with really sharp knives... probably on the order of .020" - if you can even set up your jointer bed that accurately. If you're knives are as knicked as you are suggesting, it might be worth while to run a honing tool over them.

Last thing I might suggest is to wipe a little oil on the edge of the aluminum to help the jointer knives out... I've used HSS endmills, but they're almost all spiral bits and not straight edges..

Good luck! And make sure to tell us how it goes! (But please don't do it if you can't hold the stock safely!)

-Chris

[Paul Simmel]

If you're not worried about your jointer knives, then you should be good to go if you can hold the straight edge safely.

I use HSS endmills in my Bridgeport all the time to mill aluminum. Unfortunately, the difference is that I can slow down my cutter.

Be careful on the speed - part.. Too slow would be bad too. What's important when you are machining metals - particularly soft metals such as aluminum - is to keep the chip load per tooth at a certain value. If you're spinning the bit faster, you actually need your feedrate to be higher to maintain the proper chip load. This is one of the reasons that High speed machining works so well. If you feed too slow, you'll gaul and mash the aluminum instead of cut it, and your surface finish will be terrible. Now, all that said, ideally you'd want to take extremely shallow passes with really sharp knives... probably on the order of .020" - if you can even set up your jointer bed that accurately. If you're knives are as knicked as you are suggesting, it might be worth while to run a honing tool over them.

Last thing I might suggest is to wipe a little oil on the edge of the aluminum to help the jointer knives out... I've used HSS endmills, but they're almost all spiral bits and not straight edges..

Good luck! And make sure to tell us how it goes! (But please don't do it if you can't hold the stock safely!)

-Chris

Chris! You are da' man. That's great advice. I can set my beds up in such a way to just barely scrape a few thousandths off. I am definitely going to try this and I am going to report back.

Jason, also great advice, and will do!

[Pat Germain]

As I understand it, you can use woodworking tools to safely cut and machine nonferrous metal (those which do not contain iron). This would include aluminum, brass and copper.

I learned this from David Marks and watched him do it, in case that helps in the credibility area.

[Eric Haycraft]

The problem that I see here isn't that it won't cut it, it is that the results probably won't be good. The jointer would have to be perfectly flat AND perfectly adjusted to get an acceptable level of accuracy out of it. Also, the straightedge can easily flex in the machining process, so it may not end up straight at all even on a perfectly tuned machine. At best, I foresee a menards straight edge in the garbage...at worst I foresee a souvenir mounted on the wall as a reminder to never try that again. If you really want to use the jointer for this experiment, I would suggest attaching the straight edge to a larger board and jointing both..that will take any flex in the straight-edge out of the equation.
If he really wants to do this, the router suggestions are the best.