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Mild steel wheel blanks

Lath not cutting

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IanT23/05/2020 23:16:37
1507 forum posts
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Posted by JasonB on 23/05/2020 18:46:40:

A lot of the laser cut stuff is S275 which is not the nicest stuff to machine, better suited to teh welding and fabrication guys than machinists, it also has a slightly higher carbon content (0.25% ) which may be what the heat is affecting. The other downsid eis it is a hot rolled steel and does have a thin smooth coating of mill scale, not so much black but a dark silvery grey which can be hard and abrasive to tools.

If getting stuff laser cut then ask for HR4 which is hot rolled so no scale and about 1/3rd the carbon content. Still not a snice as a slice of 230M07 though

Certainly fits the description Jason - mine are dark silvery grey as described above. They were purchased on eBay and I've always assumed that they were a by-product of some other commercial manufacturing process - and that either the company itself has found an additional revenue source, or some enterprising soul has discovered extra income by raiding the company's scrap bin...

Regards,

IanT

Hopper24/05/2020 02:55:18
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Posted by Mike Brett on 22/05/2020 17:35:50:

I was afraid that would be the answer. If I tried to grind the edges it would no longer be a perfect round and I would never get it back in the chuck.

Sure you would. Or you could even use a four jaw if needed. But it sounds like you are proposing to hold the blanks by the OD while you machine the OD, so could be kind of flimsy holding power.

You might be far better off to either mount the wheel on an arbor/mandrel or bolt it to a faceplate. You can drill and tap threaded holes part way through the wheel if you don't want the holes visible on the finished wheel outer. Or make a stub mandrel out of a piece of say 1.5" or 1" bar with a bolt hole in the centre. Bolt the wheel on and hold in position with Loctite or superglue while machining to stop rotation. A blast with the propane torch afterwards will break it loose. Or even a rap from a hammer often does it.

What RPM did you try machining at? For 2" diameter you would need to be down around 100rpm for HSS and maybe 200 or 300 for carbide inserts. Hard if you have one of those small lathes with variable speed motor with no torque at low rpm so your best shot then would be grind off the scale and carry on as above. Use backgear if you have an old banger from that primitive era.

i machine laser cut discs all the time without problem. Our local steel merchant sells the "holes" he cuts out of structural steel work. Very handy and usually machines quite nicely. The hard layer is only a few thou thick so takes not much at all to grind or machine it off.

vintage engineer24/05/2020 10:31:46
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Depending on whether it was made from new mild steel or it was recycled mild steel will affect it's composition. Recycled mild steel can contain all sorts of unwanted crap including boron.

The only mild steel that I know that is made from raw iron ore is structural steel as this has to have a certificate of conformity. Where as run of the mill mild steel doesn't.

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