Carbide Face Mill & 0.003" Cut in Cast Iron?

[SteveHGraham]

I am still working on my $15 Harbor Freight hand plane. I realize it's not worth it, but it's a fun project.

The sole of this thing has a big dip in the middle, and by "big," I mean less than ten thousandths. Close by the mouth, where you really want flatness, it's worse. I should not be surprised that the Chinese craftsmen put the biggest defect in the place where it would cause the most aggravation. I have been working it with sandpaper, but the more you flatten something with abrasives, the slower the abrasion gets, because more flat surface is in contact with the abrasive.

I am planning to whack it with a carbide insert face mill. I want to take as little off as possible. Say three thousandths at a time.

Question: is there any hope that a carbide tool will cut cast iron well at this depth? I know carbide likes deeper cuts. The inserts are nearly new, having cut only one other object.

I don't really care if I ruin the plane, but I would rather not try something that has no possibility of success.

It is sitting very nicely in the vise. One side of the plane is dead nuts square to the sole, and the other is just barely off. I put the cattywampus side against the vise's movable jaw. Indicating it has turned out to be surprisingly easy, and the test indicator is barely moving at all, which makes me wonder if I'm doing something wrong. I keep working to make sure it's preloaded after adjusting the plane. I would not want the tip to be hanging in space, giving me zero movement no matter what I do.

[SteveHGraham]

I'm going to go for it. Waiting for replies is a bigger inconvenience than ruining a $15 plane!

[GlennW]

The plane has now given you a perfect excuse to buy a shaper!

[stephenc]

I can't comment on the face mill but if you have an old file handy why not spend a few minutes and grind yourself a scraper .

With your new scraper , some Prussian blue , a surface plate of some sort and a little bit of effort you'll soon have a very flat plane .

[tetramachine]

Is the face mill wider than the base, or narrower? Is the mill dead square in tram?
Using a 6" mill in a BP on a cylinder head was very successful, if that helps you. Speed around 200-300 ft/min. There may be an issue at the blade port, so not too slow with the feed.

You should blockup the ends of the plane, that will be critical, Movement will junk the workpiece.

[SteveHGraham]

Putting this thing in a vise is a headache. The sides are a little convex from top to bottom, and they are not what you would call parallel. I tried putting a round piece of stock between the movable jaw and the plane, but it didn't help. I can get the plane level within around 10 thousandths, but that's pretty sloppy.

I will keep fiddling with it. Right now I have to replace my wireless desktop. Guess I should not have let acetone splash on the mouse.

[Richard_W]

You should use a cast iron grade of inserts.

[SteveHGraham]

Thanks, Richard. I don't have any idea what kind of inserts the facing mill came with. They work beautifully on steel, but I can't even guess about cast iron. I have some others I could check.

[Richard_W]

If you don't have the proper inserts, I would give it a try anyway. The inserts migh hold up long enough for one part.

[SteveHGraham]

Sounds like you know my style.

[SteveHGraham]

I see I have a lot to learn about clamping oddly shaped objects. The sides of this plane are convex, and the bottom is not quite square to them (as if it makes sense to say a curved side can be square to anything). I got it within around 5 thousandths and gave up. I ended up removing somewhere between 10 and 15 thousandths from the sole.

I calculated the RPM's and came up with around 300. I was surprised it had to be that slow, but sure enough, the finish was adversely affected when I sped up. Wondering if anyone has any corrections to offer.

The face mill worked great. I'm sure the mill is slightly out of tram, but no one will care when they use the plane or look at something I made with it. I gave it a light sanding after I cut it, and I wiped it down with oil to remove leftover cast iron dust.

I may make new blade adjustment nuts for the plane. The ones it came with are ridiculous.

The plane really does work. Even better than a Shamwow.

[Harold_V]

Richard's advice on carbide grade is spot on. C2 tends to be the correct choice, although you can achieve success with other grades. They just don't hold up as well.

In a case like this, where you have difficulty holding the work piece, especially that you are not restricted from taking a cut or two to bring the item square and/or parallel, there's absolutely nothing wrong with placing the base of the plane against the solid jaw of your vise, leveling to the best possible condition (parallel with the opposite side as best you can) and take a skim cut. Once done, flip the item and do the same thing to the opposite face. Now you have a square piece that can be reliably held in a vise and leveled without concern.

Depth of cut.
So long as you are not cutting the surface of cast iron, it responds VERY well to shallow cuts. However, if you machine a cast surface and remove less than about .05", you can expect poor performance from the cutting tool, as you'll likely encounter trapped sand. That said, I'm assuming that the iron isn't chilled. If it is, all bets are off.

H