Making a face plate, what steel to use?

[savarin]

yep, overnight in vinegar works very well.
get the double strength vinegar and it works faster.

 

[n9viw]

Fantastic responses all around, you all rock, thanks.
@rabler - I was actually going to have the shop pipefitter weld it, same guy as did the stellar job on my Jacobs chuck the other week. So, welding method is up to him. If I do it, it's probably going to be MIG.

@Nesse1 - I'll be shooting you a PM as soon as I finish writing this... you're a prince.

@den-den - Just what I needed to hear, thanks. And definitely on the Nevaseize, no sense in making it a permanent fixture by accident.

@Jake M , @savarin , @francist - also just what I needed to hear. HRS it is, and I was planning on at least 1" if they had it. If the consensus was for CRS, I was going to have them slice a bit more so I could hog it out, but that bit about the hard spots is good info, thanks. And I think we have some of that industrial-strength vinegar, too. A good week or two in an oil pan with a gallon of that, we'll see how it goes.

Again, thank you all for your replies, much appreciated .

 

[durableoreo]

Any weldable steel (low-ish carbon) should work.

Cast iron is preferred for a variety of reasons chief of which may be cost. Galling is a risk with similar metals but as long as they aren't stainless, the risk is manageable. A invisible coating of LPS 3, Fluid Film, or even wheel bearing grease is good insurance.

Face plates are typically not used very often. You would be better served by saving up for a decent chuck.

It is less usual. Many of us have lost the spirit of the early days of garage machining. A man was lucky to have a lathe and a drill press. The olde time model builders used the lathe for all kinds of machine work, often using centers or a face plate. Having a mill with a boring head was very uncommon in a home shop in the 1950s (I gather) but a lathe can do most boring tasks, with enough setup effort. You may need to bolt change gears onto the face plate to balance it, or run at very low speed, but it can be done. The first of the Moore books indicates that many of these practices carried on for some time, even with large die parts. So don't be discouraged. Once you make a few parts, you'll see that there are only 2 types of men---those with a lathe and everyone else. It's a quantum leap in skills. Someday a chuck will make you faster, if this hobby 'takes'.

 

[graham-xrf]

Given the choice between hot or cold rolled I think I would go with the hot. For one; I find it turns a little more predictably than cold rolled which can have hard zones right next to soft spots and two; cold rolled can have a real tendency to warp if you remove more metal from one side than the other. Might make for a nightmare trying to true the face.

If you’re worried about the mill scale, an hour or so in muriatic acid takes care of that nicely. Just do it outside and not near any tools or machines you care about. Supposedly vinegar works too, just slower.

Let's add to that. Muriatic - that is the industrial version of hydrochloric. It is swimming pool pH adjustment acid, and it is very aggressive.
The advantage of going at a metal with any acid is it works reasonably fast, and is handy, and cheap, with easily purchased ingredients. compared to "gentler" more expensive ways like chellation with EvapoRust. Other rust removal acids are phosphoric acid (like Coca-Cola), and citric acid.

BUT... the instant you wash it off, and let the air oxygen see the chemically exposed iron, it will flash-rust right before your eyes, and worse if you used a steam-cleaner. Even after oiling, there seems no way to make it permanently quit. The answer is to de-activate the iron, done quite easily by keeping it wet until you can douse it in something to neutralize it, and then go further, and try to get some hot alkali on it.

Try dissolve a few tablespoons of washing soda, or even caustic soda (carefully !), heat the water some, and leave for maybe an hour. It cools, and then, with some oil after, will have calmed down the raging rust activity.

Even rubbing some wet baking soda over the part can bring the flash rust effect to a stop. Going all the way, and deliberately converting a flash-rust coat to magnetite, and then oil it up, is, I understand, even more effective, but those "conversion" fluids that go purple, and stain your skin, and clothes, are expensive!. The guys who do surface treatment for their guns will know lots more about the ways of deacivating the iron. When I saw it happen, on my lathe bed before I painted it, I was amazed how it could turn orange in only 5 minutes or so.

 

[WobblyHand]

A simple way to convert flash rust to magnetite is to boil it in water. This is one of the cold blue processes. That's how I blued some tee nuts, using hydrogen peroxide and a little table salt to promote active rusting. The loose rust was carded off, and the rusted part boiled. The rust converts to dark blue/black magnetite. It takes 5-10 applications to get a nice deep finish, doesn't take too long, and it's cheap. Nothing fancy needed. Got carried away there, back on topic.

Diluting the acid with water, then neutralizing the acid the way Graham mentioned is good. I wouldn't sweat the rust at the moment - just get the part done. It won't disintegrate to powder in seconds.

Or course one could also use coarse sandpaper to take off the mill scale, or use an angle grinder with a flap disk, like a welder might use. That's pretty fast, and uses no acid. It doesn't have to be pretty at this point because the surfaces will be machined anyways. Lots of ways to get it done, use whatever you have at hand.

 

[markba633csi]

There's something called hydrogen embrittlement which could be caused by using muriatic acid. I doubt it would be a problem for what
the OP is doing, but it is a thing

 

[Nesse1]

Unbeknownst to me until just a few minutes ago, USPS has a Cubic Priority rate option for smallish packages up to 20 LBs. This chuck met the requirements and ships for all of $15. Can't beat that. Big shout out to Pirateship.com

 

[gard]

Welding might distort both the nut and plate, you may want to consider bolting the plate to your nut with 4 or 6 flat head socket screws. My faceplate is 3/4 thick aluminum bolted to a cast iron threaded backplate. You can also purchase rounds of cast iron you could bolt to your nut.
My face plate does not have slots, I just drill holes in it wherever needed for the project a hand.

 

[rwdenney]

Just yesterday I faced a large flat surface on a 1-1/2" mild steel plate. I got the best finish from a CCMT insert, feeding very slowly, after peeling off all the mill scale with a CNMG432, which is a tougher insert. And it was a square, so there were interrupted cuts for both facing and turning. The finish is more than good enough for a fixture plate, and flat within a couple of tenths. The round part that is visible on the top is 7-3/4" in diameter.

Your plan is fine, by the way. Use just a thin wipe of anti-seize compound on the spindle threads before mounting it. And for fixturing, just drill and thread holes instead of trying to machine slots. You can use a lathe dog without the crook and just let it butt up against a stud screwed into the fixture plate.

Rick "easier if it's round to start with" Denney

 

[n9viw]

Last week I picked up two 8" slabs of 1x8" HRS, and on Sunday I cut them into a reasonable facsimile of round with an angle grinder- one the full 8", the other slightly larger than 6" to match the chuck I just received from Nesse. Went through six cutoff wheels. I tried using a 7-1/4" circular saw with a metal cutting blade in it... that was a joke.

My plan at the time was to find center using a cross scribe and, after verifying with edge measurements, weld the nuts I've prepped to the plates, then mount them to the spindle and turn and face them. Now, after thinking about it, I'm wondering if I shouldn't turn a shoulder on the nuts, then use the lathe at work to bore a corresponding hole in the center of the plate into which the turned step of the nut will fit.

This would serve three purposes: first, to more positively anchor the plate to the nut; second, provide a second joint at which I could weld the nut to the plate, and third, set the plate back over the nut by its one inch thickness, keeping the plate more securely over the threads of the spindle rather than sticking out. Suggestions?

And to think, all this nonsense would have been obviated if I had just bought a blank iron backplate and learned to thread come hell or high water...