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Steel for machining

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Involute Curve04/10/2018 18:23:04
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328 forum posts
86 photos

Material Cast Iron, my guess is the original will have been hollow, in order to make to manageable.

Shaun

Adam Harris04/10/2018 18:25:41
438 forum posts
19 photos

original is solid not hollow

Adam Harris04/10/2018 18:35:39
438 forum posts
19 photos

Or at least the early one (the more curvaceous one) is solid . The later model has a more angular and slightly more bulky one which may or may not be hollow

Neil Wyatt04/10/2018 19:06:32
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16655 forum posts
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Bloody 'ell!

I thought you were planning something like this:

For a lump like that, it's possibly worth making your own pattern and getting a casting done. I doubt the price difference will be huge as that will mean so much less metal.

Neil

JasonB04/10/2018 19:12:06
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Not so sure Neil, recently picked up some castings and the foundry were charging £10 a kilo, Alibre tells me a basic L shaped blank will be 40Kg and you won't have any offcuts to use for something else.

Adam Harris04/10/2018 19:16:08
438 forum posts
19 photos

Ha Ha Neill! That would indeed be a job! No this is quite a simple affair albeit more voluminous. Are you still recommending EN1A pb?

Adam Harris04/10/2018 19:18:15
438 forum posts
19 photos

Or if casting, what spec of material and anywhere recommended to do it within 100 miles of Oxfordshire?

Adam Harris04/10/2018 19:22:29
438 forum posts
19 photos

I thought a common commercial size billet cut down to rough size with my Rapidor saw which I hardly ever get a chance to use, would be the cheapest way but if casting is cheap then I am all ears...

Chris Evans 604/10/2018 21:52:59
1489 forum posts

Make a simple pattern from polystyrene which will be burnt out of the sand box. This is how I made my new lathe cross slide. Speak to Nigel at Coventry Castings.

Adam Harris04/10/2018 21:59:09
438 forum posts
19 photos

Thanks Chris, I will call him tomorrow. And what spec of material would you recommend casting with?

Marcus Bowman04/10/2018 22:25:54
162 forum posts

The ideal material for a real machine tool would be Meehanite, which dampens vibration, but I imagine that might be a tad expensive. In that case, spheroidal cast iron ('ductile' iron) would still give good results. I have no experience of specifying grades, but this site gives advice:

**LINK**

and I guess a foundry would advise. There seem to be plenty of companies advertising that they either cast from patterns, or sell large section bar. West Yorkshire Steel, for example, sell bar. I have no connection with them.

Bazyle04/10/2018 22:47:30
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4761 forum posts
187 photos

I doubt the original would be solid. The big Elliotts use a hollow cast iron overarm with a hollow alloy drop arm (the bit Neil pictured) The drop arm is hollow to provide an oil reservoir.

Mike Poole04/10/2018 22:54:26
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2147 forum posts
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Posted by Bazyle on 04/10/2018 22:47:30:

I doubt the original would be solid. The big Elliotts use a hollow cast iron overarm with a hollow alloy drop arm (the bit Neil pictured) The drop arm is hollow to provide an oil reservoir.

I was able to pick up the overarm for an Adcock and Shiply 1ES and install it so I think it was hollow, it would have been v heavy if solid.

mike

Hopper04/10/2018 23:28:09
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3743 forum posts
76 photos

Carving that "L" out of a solid lump is madness. Waste of material, time and machine/cutter wear. Much easier to fabricate it from two pieces of 5" x 2" flat bar, or whatever the size is. The end piece could be either bolted and doweled in position, or even welded on before machining.

The original would have been cast iron because it's more rigid than steel. But steel would do the job in most cases.

You should be able to mill the dovetails to a suitable finish for this purpose. It is not a moving surface under load, like say the ram on a shaper or even the table on a mill. One trick to milling dovetails nice and smooth is to do your finish cuts using only one surface of the cutter at a time. This involves machining to almost final size, then drop the mill table a few thou so the cutter cuts the angled face of the dovetail only for one pass. Then raise the table so the cutter then clears the angled face and cuts only on the flat end face of the cutter and take another pass to machine that face. Yes you end up with a couple of thou in the very corner of the dovetail that is not machined but the mating dovetail should have the matching corner relieved for clearance here so it does not matter.

Michael Gilligan04/10/2018 23:37:50
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14139 forum posts
616 photos

Adam,

I feel sure that you are familiar with the machine, but others may find this page useful for reference: **LINK**

http://anglo-swiss-tools.co.uk/aciera-f3-milling-machine/

MichaelG.

Martin W05/10/2018 00:09:02
792 forum posts
29 photos

The overarm for the F3, see Michael's link above, is quoted to weigh 16kg or in old money 35lbs which is considerably lighter than the weight Jason calculated of 40kg for an L shaped blank. So either I am looking at the wrong thing, Aciera have machined a vast amount off the casting or it is possibly hollow as suggested by other posts above. It is also stored at the bottom of the illustrated tool cabinet as shown in the catalogue, no fork lift in sight wink to extract it.

Martin W

JasonB05/10/2018 06:55:07
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16448 forum posts
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Three clues to it being hollow and scraped as I said earlier

Edited By JasonB on 05/10/2018 06:55:39

Edited By JasonB on 05/10/2018 06:55:58

Ian S C05/10/2018 09:17:18
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7447 forum posts
230 photos

I'd say hand scraped, and hollow for that Jason.

If i was making it I'd fabricate from steel plate.

Ian S C

Baldric05/10/2018 09:27:59
142 forum posts
10 photos
For a foundry within Oxfordshire, there is Swan in Banbury, not used them personally but I know they do castings for preservation.
Baldric.
duncan webster05/10/2018 11:00:09
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2255 forum posts
32 photos

Cast iron is not stiffer than steel, in fact it's Youngs Modulus in tension is considerable less. Considering that the load is put into the overarm via the much smaller arbor it is quite obvious that high tensile steel is not required, as others have said the original would have been cast iron. Using a 'better' grade of steel will not reduce elastic deflection. Making this out of one piece is just making life difficult, Neil's suggestion is far more sensible. I would just make it out of 2 pieces of EN3 (070M20) or S275, but the latter would not machine as well. If the OP really must have it from solid then a plasma cut blank would be a better starting point

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