Steel for machining

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

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

Not the best shape to start with but 200mm round EN8 or EN3 which you can get 5x6 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

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

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

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

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

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....

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

Adam, where do you live?

Our local blacksmith had two lengths of hexagonal cast iron about 80mm across. I have one of them (which I wish to keep) but if you are local / happy to collect I can see if they still have the other one.

They were offcuts from a bespoke lamp column and are' blinkin heavy'!

I can nip out to the workshop and give you an 'across the flats' dimension if interested.

John that is a very kind thought but I am going down the route of casting (with hollows in the pattern)

The overam on my Centec is solid with a separate ''hanger' with dovetail fitting and a bronze bush to support the arbor. There is / was an aftermarket overarm made for the Centec with dovetail slide in the top also and this both raises the vertical head slightly and also allows setting up in horizontal mode without the need to remove the vertical head assembly. This arm is about 100mm wide by 50mm thick and has never shown any indication of flexing, which is why I thought the CI section might just suffice (I have measured it - 90mm across flats). I am sure the height will be good if the width is sufficient to get the vees to match your mill.

(I got my bit for free but that might be because I live locally and am on nodding acquaintance with the blacksmith - there again he may just have a problem throwing 'potentially useful stuff' away!)

Thanks again John but the casting looks like it will be the simplest option and if a pattern with hollows is too complex/expensive then I will make a solid cast and simply bore out some excess weight from the underside.

Keep us posted on the progress and machining Adam, best in a new thread I think.

It will be interesting to see if you can do a core with the lost foam process. More likely you will need to make a traditional solid pattern and a separate "core box" to cast the sand core in.

That's strange that you're Centec overarm is solid mine is a hollow casting .

Thanks

Sean