What Metal is this?

So a few years ago (before I new better) I picked up some random bits of metal from the local scrapyard.

One was a shiny round bar 100mm across and about 200mm long.

Messing with it, to see what I could do, I stuck it in my mini lathe and managed (idiocy) to catch the end with a tool at some speed.

It did in the plastic gears and replacing them and the strip down and rebuild blew the controller and damaged the spindle.

All is now well, I hasten to add - bigger transistors, new spindle and metal gears. I should say thankyou for the learning experience!

So it sat there being a paper weight until recently when I decided to make a surface gauge and it seemed like a good place to start from.

So I chopped 35 mm off and put it in the lathe to face and clean up.

The facing went OK with a carbide tool, however the outside struggled with carbide (several tools) and hss. Part of this was that it was a mildly interrupted cut, The lathe was stalling (various speeds but around 300 rpm - any lower and there's not the power).

Just about to give up I tried it with an insert for aluminum a few thou at a time and that has produced a brilliant finish.

I also passed the tool over the face. I was taking cuts of around 2 - 4 thou and getting very thin yellow (hot) stringy swarf. The finish passes being faster, perhaps 800rpm for the spring (is that the word?) passes.

The finish is phenomenal.

I'd like to know what it is. It hasn't a touch of rust, it is slightly magnetic (that is a magnet sticks to it). It has an apparent density of about 6.8gm/cc,

Which puts it as some kind of stainless steel?

The next step is to chop quite a lof of it out in the mill (carbide tools again) and I'm wondering if it's the sort of stainless that work-hardens and if I need to use any particular techniques?

Iain

Edited By Iain Downs on 19/11/2020 17:21:51

Its unobtanium, are you sure of the density?

Diameter ~89mm (radius 4.45 cm), height 35.5mm (3.55cm), weight 1.7kg (1700gm)

volume = pi r squared h = 4.45*4.45*pi*3.55 = 221 cc (cm3)

1700/221 = 7.69 g/cm3 (sorry copied the first one wrong).

which according to Engineer's edge is in the range for stainless steel.

Iain

I was kind of hoping it was unobtanium, I would then sell it and buy a real surface gauge... And a new Lathe

Iain

The only Stainless that I’ve ever used that was slightly magnetic was also of unknown parentage. I assumed it to be one of the 400 series stainless steels?

There's a couple of candidates in here @ 6.8 gm/cm³, but they would seem unlikely, except maybe cast iron.

Bill

Edited By peak4 on 19/11/2020 17:53:49

I now mainly use inserts for aluminum on most materials now, aluminum inserts are also very good on stainless.

Sounds like a bit I got from a scrappie, 150mm in my case, by about 8 inches

It's not hard hard, it's like soft hard, not steel, no rust, shiny, and it's really tough

I made a couple of circular vices out of mine, used the shaper with cobalt and slow speed backgear with cobalt tools on the lathe to work it, especially for interrupted cuts

When I cut it at high speed it was goldy coloured and tools soon lost their edge so I only finished off at high speed, 500 rpm for me

It drills ok but laffs at HSS and cobalt on the lathe at high speed, I think it deforms before it cuts, like stainless

Like you say though, if you can work it it makes great gear and has a lovely finish

Perhaps it's a type of machineable stainless steel

Edited By Ady1 on 19/11/2020 18:58:39

Peak4. I got the first calculation wrong. It's a bit more dense (see 3rd post).

My feeling when machining it was 'sticky'.

When I cut it on the bandsaw (over an hour in bits!), something had slipped so it was not straight. I ended up milling the worst surface flat it it took decent cuts (1mm) with a 63mm indexable face mill. So I have some hopes for chopping it on the mill!

Ady, I don't suppose your scrappie was near Ripon?

Iain

Edinburgh, 5+ years ago, I also recall there were 3 tapped holes in a triangular pattern about 12mm thread at each end, so it was like a giant insert/support for going between parts on some huge machine

When I saw it I had to have it... but could barely lift it

Knew I had a piccy somewhere, took me days to cut it up

In the last picture you can see how thin the vice base is, but that's not an issue because it's a really tuff metal

Wouldn't dream of doing that to my shaper again but back in the beginning it was a case of needs must until I built up some kit

Edited By Ady1 on 19/11/2020 19:55:04

Stainless steel varies in its magnetic properties and very much in its machinability. I have to tap a 4.5mm thread in a piece of non magnetic SS and even with a brand new British made tap, I'm not looking forward to it.

Some sort of bearing steel is my guess. Going by my very technical method of looking at it. 😋

We have some large pieces of Stainless steel laying about at the museum, I avoid them as the swarf comes off like razor wire, only sharper.

316?

I have a piece of steel lucking under my bench, glaring at me every time we meet.

It,s about 45mm dia, dirty grey in colour, and as hard as a H------r,s boot.

No idea what it is, but I,m not about to let it anywhere near my lathe.

Perhaps it work hardens?

Some stainless versions are slightly magnetic.

Heaven forbid that it is Manganese Steel. That does work harden, and how!

Howard

I've cut the other end of the piece in the 4 jaw using the Ally carbide insert, in steps of maybe 3 thou and it's turned out very nice again.

The limiting factor seems to be the power of the lathe. If I take much more off the lathe struggles (550W CJ018A type) and I don't want to put too much hurt on it.

Tomorrow (or possibly later) I will be trimming the sides on the mill - taking about 10 -12 mm off each side. This will be with a carbide insert face mill (steel inserts, could afford the ally as well) and it will be interesting to see how it goes. I will keep you posted.

Iain

Yesterday I too roughly 15mm off each side wiht a 50mmface mill as above (about 1.5mm deep cuts at 800rpm). This went really well with rather lovely golden chips coming off. I did have some tearing on the first side, but I'd been cutting dry. Side 2 I used cutting fluid and got a great finish.

Then it started to go wrong. Here's a drawing of what I'm attempting

The next item on the work list was to mill out the channels under the lugs at the back. 21mm deep and about 14 wide.

This was slow going. I assumed if I could cut 1.5mm off a 40mm surface, I could cut 3mm deep with a 10mm carbide mill. The result was a slot that tapered upwards as the cutter was pushed up into the collet, and the metal at the end turn pale gold.

I kept at it with smaller cuts and took the speed down from 2000 to 1400. At one point I noticed that the cutter was glowing red and took this as an indication that I was working it too hard and slowed down. The cutter was still being pushed up into the collet, regardless of how tight I'd clamped. That is until it decide to pull itself into the trough rather suddenly and stalling the mill (I think it managed to spin the tool in the collet first, but not so sure of that!

I got to the bottom size I'd aimed for and decided to move out. (about 0.5mm cut). this sometimes worked and sometimes dug the channel deeper. So I tried cutting higher up, with the aim of a( or several) clean up passes. The last one I tried on this pulled the cutter down about 5mm towards the end of the slot and took a bit out of the foot.

I have some latitude with the design of this so I can make the slot deeper or wide so I can clean up my mess. However, I still have the other side to cut and it's clear that I'm approaching this quite wrongly.

The only 2 thoughts I have are :-

1. to change the orientation and cut in from the side, leaving the lugs solid until the end.

2. Follow the example of Joe Pie and drill the material out first and then take a VERY fine finishing pass.

Any more educated ideas would be most welcome.

Oh I started off with a 4 flute mill, but noticed that it was a bit chipped so swapped out to a 2 flute mill which seemed a little happier (and I don't SEEM to have broken it yet).

Iain

ColinG (outside this post) had two recommendations:-

Don't piss around with metal you've no idea about. He's right. By the time I've broken a few more tools it would have been cheaper to buy a nice piece of cast. On the other hand I am learning things, albeit by getting things wrong.

Put the end mill in an ER32 collet. This has a lot more bits of metal touching the tool and so will reduce the risk of it being pulled out. It turns out that my R8 10mm collet is actually about 10.06 and the cutter is slack fit, so even less touching. I have tried this and the results so far are positive.

Now to work out how to tidy up the mess I've made so far.

Thanks Colin.

Iain

On the other hand, one can be lucky with " pre-loved " metal from the local New-To-You Metals Stockist.

I one bought some stainless-steel (identified by it not being rusty) for a very unusual task for a friend. Whatever its grade it machined beautifully on an elderly IXL lathe, with HSS tools.

The task? My friend ran a regulatory-conformance business, and wanted two probes for testing items like motor-fan guards to ensure real fingers cannot go where fingers should not go. One was a straight rod with tapered end, as if representing the trespassing screwdriver; the other was jointed, a 1:1 model finger.

The drawing such as it was, was the EU / ISO- supplied generic one for the appropriate Regulations, so did not specify material, but the jointed probe had absurdly tight dimensions on an awkward profile officially therefore unconvincingly representing human finger-tips. My friend advised as near as I could would be fine. After all, Nature does not grow body-parts to 0.2mm and 0.1º tolerances, so I turned a blunt cone as closely as possible, and filed it to match the drawing.

For good measure I added something the EU had not suggested - a plastic handle and a 4mm banana socket to the rod probe, for low-voltage testing distance-isolation from bare electrical parts.

+++

As for the sort of machining problems many of us encounter with come-in-handy metals, a look in the insert-manufacturers' catalogues show a bewildering variety, but many are to cope with exotic alloys at terrifying but carefully-calculated swarf-making rates. Typically, tool-life for these is quoted in figures like 20 minutes.