Steel for machining

[JasonBModerator @jasonb]

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 HarrisParticipant @adamharris13683]

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 HarrisParticipant @adamharris13683]

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

[Adam HarrisParticipant @adamharris13683]

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 6Participant @chrisevans6]

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 HarrisParticipant @adamharris13683]

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

[Marcus BowmanParticipant @marcusbowman28936]

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.

[BazyleParticipant @bazyle]

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 PooleParticipant @mikepoole82104]

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

[HopperParticipant @hopper]

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 GilliganParticipant @michaelgilligan61133]

Adam,

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

Aciera F3 Milling Machine

MichaelG.

[Martin WParticipant @martinw]

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 to extract it.

Martin W

[JasonBModerator @jasonb]

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 CParticipant @iansc]

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

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

Ian S C

[BaldricParticipant @baldric]

For a foundry within Oxfordshire, there is Swan in Banbury, not used them personally but I know they do castings for preservation.
Baldric.

[duncan webster 1Participant @duncanwebster1]

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

[not done it yetParticipant @notdoneityet]

Posted by Baldric on 05/10/2018 09:27:59:
For a foundry within Oxfordshire, there is Swan in Banbury, not used them personally but I know they do castings for preservation.
Baldric.

Within 100 miles of Oxfordshire would cover about half of England, or more? There must be dozens of possibles?

[Adam HarrisParticipant @adamharris13683]

I am totally unfamiliar with casting, and yes google has just shown me there are loads of companies able to do it within 50 miles of Oxfordshire. So far I am getting a price idea of about £3 per kg of ductile iron (plus cost of pattern which is anywhere from £400-£1000 I am advised but £0 if i make myself). A billet of EN1A or EN8 150x150x600 I suspect is a fair bit more than that, but then i would have the use of a nice lump of offcut for the future. While the original would be hollow, mine would be solid from billet but I am looking into casting with a hollow space to reduce weight as advised here! Thanks

[JasonBModerator @jasonb]

Not the best shape to start with but 200mm round EN8 or EN3 which you can get 5×6 out of can be had for about £200 based on a 100mm length price so should be less if buying 530mm in one bit.

Ductile iron is not a nice to machine as a grey iron being more like steel. £3/KG sounds good, as I said some castings I got a month ago cost the supplier £10/kg.  Make sure they are happy to do lost foam then all you need is a sheet of 25mm polystyrene from a DIY shed and glue up 5 layers to make the basic L shape. No need to worry about draft angles etc.

Edited By JasonB on 05/10/2018 13:10:11

[Adam HarrisParticipant @adamharris13683]

Thanks Jason. That sounds a great idea for the pattern. Someone earlier advised ductile iron – what material do you advise?

[Adam HarrisParticipant @adamharris13683]

Best price I have found for square billet in EN3B is £490 for 150x150x550. Looks like casting is very much the way to go! Thanks

[Adam HarrisParticipant @adamharris13683]

Baldric many thanks for the pointer to Swan in Banbury – conversation and price looks promising.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Adam Harris on 05/10/2018 13:38:40:

Best price I have found for square billet in EN3B is £490 for 150x150x550. Looks like casting is very much the way to go! Thanks

Very annoying because steel is a lot cheaper in bulk. It's trading at about £500 per ton at the moment. We pay a lot more because of shipping, storage, retail, tax and other overheads. Trouble is, buying steel wholesale at the gate just ain't practical unless you have comprehensive facilities. Chaps with access to an employers scrap heap live in paradise! Buying steel in small quantities from my local retailer always makes my eyes water.

Dave

[Adam HarrisParticipant @adamharris13683]

Aluminium 6082T6 priced at £330 for a billet 150x150x550 with AALCO. Not really considered using aluminium for obvious reasons but in fact the Aciera high speed head uses a ram made from Aluminium to mount onto! Maybe this milling support arm could be satisfactorily made out of aluminium if kept chunky since it does not need to move once clamped into position….

[Bill Davies 2Participant @billdavies2]

Some of the 'smaller' mills used at my college (long ago) used aluminium castings as the overarm. This was a box section. Probably not used on production mills (Young's modulus, wear resistance and all that).

Use by apprentices knocking out vee blocks and other practice pieces, including a few rare mistakes like work slipping in the vice jaws and 'climb milling' through the steel block, punching the HSS teeth into the steel as it went, and bending the 1 inch arbour. Needed a new arbour, but no apparent damage to the overarm.

Other mills (some may recall) used a pair of large steel bars for the overarm. However, that would need a new arbour support in this instance.

Bill

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