Cast iron – 160mm dia

[FatWelshBoyParticipant @fatwelshboy]

[FatWelshBoyParticipant @fatwelshboy]

Can someone please tell me of a place I can get some 160mm diameter cast iron? I want to make backplates for a couple of lathe chucks but I'm struggling to find raw stock to make my own. There's an Ebay supplier listing 160mm diameter meehanite cast iron but I've messaged him and its 160mm before taking the crust off so will be undersized once machined. If I can't find cast iron is there a suitable steel to use? There's a seller on Ebay that does Mild Steel Black, EN8, EN19HT or EN24T but I'm not sure what would be most suitable, if any at all?

[JasonBModerator @jasonb]

M-machine do 170mm CI bar which will give you something to clean up though you could probably get away with a 168mm finished size if using 160mm stock.

[FatWelshBoyParticipant @fatwelshboy]

Posted by JasonB on 03/07/2019 20:19:56:

M-machine do 170mm CI bar which will give you something to clean up though you could probably get away with a 168mm finished size if using 160mm stock.

Perfect, I'll order a couple of inch pieces of the 170mm stuff tomorrow. I'll also order some other material from them for other projects I have in mind. Glad I asked now as I've never heard of them.

Thanks.

[Nigel Graham 2Participant @nigelgraham2]

College Engineering Supply is another, from whom I've purchased materials at their exhibition trade-stands.

[Mark RandParticipant @markrand96270]

When the family ran it, College Engineering did back plate castings amongst other things. Unfortunately the lads that bought the business from them only seem to do materials.

 

Note:- the Ebay supplier that advertizes 'meehanite' won't provide Meehanite certification with the material (I asked them). Therefore it ain't Meehanite, which is a trade marked manufacturing method that involves certificaton.

Edited By Mark Rand on 03/07/2019 22:27:18

[Alain FooteParticipant @alainfoote90915]

United Cast Bar in Chesterfield

[Mark RandParticipant @markrand96270]

Are they happy to sell less than bar lengths Alain?

[Alain FooteParticipant @alainfoote90915]

Yes definitely Mark, but I am not sure if there is a minumum order or not.

[not done it yetParticipant @notdoneityet]

Might be worth checking out Southwestern steam? They may have selectable over-size offerings (or it may encourage them to offer slightly larger diameter pieces). Not a customer, but have heard/read good reports of them.

[Henry BrownParticipant @henrybrown95529]

From experience there can be some imperfections in the centre of cast bars, probably not an issue for you but just be aware of that…

[KWILParticipant @kwil]

Imperfections, such as??

[Henry BrownParticipant @henrybrown95529]

Posted by KWIL on 04/07/2019 10:35:43:

Imperfections, such as??

Inclusions or voids, usually in the centre up to around an inch, if this is being machined out then it doesn't matter.

If I remember correctly its something to do with the way the cast iron is processed in manufacture. The Co. I worked for occasionally used it for end housings when they had run out of dedicated castings as it was a certified product and had to be made from cast to match the main housing. As a shaft ran through the centre it was ok for that use.

Maybe something to check when ordering?

[Brian WoodParticipant @brianwood45127]

The largest diameter cast iron I have bought from M-Machine was 140 mm diameter, a slice of 2 inch thickness to make a 63 tooth gear of 12 DP.

It was clean, no blow holes or central imperfections and being continuously cast material I would expect that to be typical of all the sizes they sell.

Regards

Brian

[Ian S CParticipant @iansc]

When I got a 160 mm 4 jaw chuck to supliment the 200 mm chuck that came with the lathe I used hot rolled steel, I got a 9" round that had been flame cut from a 3" sheet, that was quite a bit of metal to turn away, it worked out well, and it's handy having a smaller chuck.

Ian S C

[John HaineParticipant @johnhaine32865]

These people do laser cutting and say they can do up to 30mm. Normal structural steel would be fine I'd think.

[FatWelshBoyParticipant @fatwelshboy]

It was Southwestern steam that had the CI on Ebay that was 160mm with the skin on. I bought some CI off them a while ago for my collet chuck and it seemed really good quality with no blow holes and machined beautifully. I gave Ebay one final check and found a lump of meehanite cast iron at 170mm dia and 90mm long for £38 posted. I've ordered it and will have a local metal supplier I use cut it into 3 pieces for me.

[old martParticipant @oldmart]

I made a 6 3/4" backplate out of a piece of meehanite which started at about 200mm. There was a hard bit on part of the OD about 1/4" deep, just like an interrupted cut. I was glad to get through it, and doubly glad to have a variety of TNMG16 inserts. I drilled and tapped the CI to fit on a faceplate and did the od and face so it would fit in a four jaw for the rest of the turning. The mess was incredible, despite having magnets set to catch the cast iron dust.

If I ever have to do something like that again, I will try to get a piece of SG iron.

 I bought a 160mm ci blank from a well known supplier for a 160mm chuck and it was under size. It would have cleaned up at 152mm, but I left a bit uncut at 155mm. I contacted the supplier, who immediately refunded my money and said keep it. I reckoned that the three 8mm rear mount screws would be too near to the edge for comfort, so I simply drilled and tapped for six 6mm screws to hold the chuck instead, they could be on a slightly smaller pcd as well as being smaller diameter.

Edited By old mart on 04/07/2019 23:15:37

[Mark RandParticipant @markrand96270]

Banging the drum again! If it had hard spots it wasn't Meehanite…

[John MCParticipant @johnmc39344]

Seems that from the above posts cast iron is the preferred material for chuck back plates, why is that?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John MC on 05/07/2019 07:37:52:

Seems that from the above posts cast iron is the preferred material for chuck back plates, why is that?

.

Stability

The obvious alternative [Steel] is likely to release inbuilt stresses whilst being machined to this shape.

Other stable materials are available, but cast iron is probably optimum on a cost/benefit basis.

MichaelG.

[HopperParticipant @hopper]

Posted by John MC on 05/07/2019 07:37:52:

Seems that from the above posts cast iron is the preferred material for chuck back plates, why is that?

Cast iron is more rigid than mild steel. And it machines very nicely when cutting the thread in it, if a screwed spindle type. But for practical purposes, mild steel will do the job if need be.

[Anonymous]

Posted by Hopper on 05/07/2019 07:47:10:

Cast iron is more rigid than mild steel.

That's odd, because cast iron seems to have a rather lower Young's modulus than low carbon steel.

Andrew

[HopperParticipant @hopper]

That's where theory deviates from practice. Maybe it's because Young's Modulus measures deformation under tension whereas cast iron's greatest strength is compressive? Or its superior resonance damping properties? Either way, I've never had much luck bending good grey cast iron. It usually seems to want to break before it will bend. Never managed to break a chuck backplate though. (One of the few things I have not managed to break over the years )

Edited By Hopper on 05/07/2019 12:15:07

[Ian S CParticipant @iansc]

Cast iron reduces resonance in machinery so I'v been told, my mild steel back plate , about twice as heavy as one used on a lathe such as a Box Ford, or Myford.

Ian S C

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