Meehanite Size ?

[WALLACEParticipant @wallace]

[WALLACEParticipant @wallace]

Hello all.

Just a quick question about the lumps of cast iron meehanite sold by our regular suppliers.

As it's not exactly cheap, I want to get pretty much exactly the right size -so does it have a hard skin that needs machining off and how accurate is the advertised size ? I've only about 2 or 3 mm over to play with and I'd rather not go up a size !

thanks.

WALLACE.

[John HaineParticipant @johnhaine32865]

I have used the continuous cast bar from CES and found no trace of hard scale, a delight to machine. Remember that “square” bar has rounded corners though. Can’t comment on accuracy but I think they specify a tolerance. Also can supply sawn lumps that of course have sharp corners, but not very square.

[JasonBModerator @jasonb]

Just measured up a few lumps that I have, 40,50, 60 & 70 all 0.2 mm to 0.5mm oversize depending where the measurement was taken, mine were also all from CES and I've not found any hardspots in them.

J

[KWILParticipant @kwil]

If you want to end up with a specific finished size, you can always state this and ask for the next oversize available.

[WALLACEParticipant @wallace]

Thanks everyone – I think for the case of a few pounds, i'll stretch to the next size up – if nothing else, it gives me a smidge more ' mistake' room – so to speak !

W.

[Sub MandrelParticipant @submandrel]

With round bar there is sufficient machining allowance on the quoted size, the square bar has about 1/4" radius corners but is oversize so you don't lose as much as it sounds.

Neil

[JasonBModerator @jasonb]

Not according to what I measured, all 4 sizes of round bar only had 0.2 to 0.5mm to play with. Maybe you are thinking of cast bronze which tends to have 1/32" allowance.

Also just checked some rectangular CI

40×80 nominal measured 40.2mm x 80.6mm and 50×25 nom measured 50.1mm x 25.15mm hardly oversize at all.

J

[WALLACEParticipant @wallace]

I've bitten the bullet – and gone for a lump 90 x 90 x 80. I'll measure it when it turns up and post the results !

W.

[Chris TriceParticipant @christrice43267]

I made up a longer topslide for my lathe using Meehanite rectangular block and although I had a good extra 3/16th all over, I did notice that when cut to length, some of the material inside looked slightly darker towards the surfaces, bit like a rectangular stick of rock. When I machines the outer surfaces down, there was no discernible sense of the material near the surface being any harder but you could still definitely see a very slight patchwork of darker material. I can only put this down to cooling rates at point of manufacture and the iron changing it's form slightly as a result. In machining terms, it doesn't appear to have altered the properties of the material to any degree I can notice.

Edited By Chris Trice on 25/04/2012 22:27:57

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