Accessory Materials

[Colin LLoydParticipant @colinlloyd53450]

Having failed to find a miniature tilting vice for my small Chester lathe/mill machine, I have made one myself using a 1" bench drill vice as the starter unit and then miniaturising the design from large tilting vices. For several reasons – availability in my trash box, ease of machining etc., most of the extra metalwork has been made in aluminium except where it was deemed appropriate to use a harder steel, e.g. the rotating rod (in stainless steel) and where there was going to be constant tightening of bolts. The process raised the following thoughts as to appropriate materials to use when making accessories in the workshop. To my mind, the important point is force. While I appreciate that normal size lathes and milling machines require the extra strength of steel to deal with the forces imparted to work pieces and their holders, is this strictly necessary for mini lathes and milling machines? I don't appear to have problems with making lathe packing plates and bed-stops out of mdf, and vice support plates (as above) out of aluminium. I have avoided running bolts into aluminium where there is constant tightening/releasing of threads that need to be very tight, but have little worry when using steel bolts into aluminium to anchor plates together. How right or wrong am I in this appreciation?

[Colin LLoydParticipant @colinlloyd53450]

[Martin KyteParticipant @martinkyte99762]

Sounds like a reasonable approach. You may like to consider helicoil inserts into aluminium when you do wish to tighten/retighten. I have used Trespa instead of steel or aluminium for machines before now. It's a lot more rigid and durable than MDF and you can machine it with a router or woodsaw. Its a modern version of tufnell really. We use it for Lab benches as it's chemically and biologally inert, stable dense and dead flat. If you can get offcuts cheap its great stuff.

Martin

[Ian S CParticipant @iansc]

A good alloy that can in some situations replace steel in constructions like this is 7075T651 Tool plate, my metal supplier often has off cuts, although there wasn't any the other day when I was in town.

Ian S C

[Neil WyattModerator @neilwyatt]

I have often been struck by the way that American hobbyists (in particular) make vastly more use of aluminium for the structural parts of their tools than Brits. We seem to have an obsession with using steel and cast iron for everything

There are exceptions, of course.

Neil

[KWILParticipant @kwil]

I well remember in my real engineering days testing some equipment on a vibration jig (large). My American colleagues had attempted a similar exercise and had not got such clear results as I had achieved.

When it was looked into, I had used a MASSIVE steel jig and they had used ALUMINUM because it was lighter! It had also be that much easier to twist and bend which had screwed their result

[AjohnwParticipant @ajohnw51620]

There is or was a book about concerning home casting complete machines in suitable grades of al. The ways were plated with mild steel. I visited some one who made an excellent shaper this way. As it can be a relatively dead material like some cast irons it can work rather well for machine frames.

Personally in case such as a vice I would be inclined to bush the the areas that might be subject to wear from say a stainless steel shaft. More stainless or even brass and penny washers under any nuts and bolts.

I was going to mention that Record make an excellent little drill vice that works well on small milling machines and also vertical slides on lathes. Then I checked the current price. The word insane springs to mind. Not much sign of the sub 3in one either only the 4in.

John

–

[Neil WyattModerator @neilwyatt]

Posted by KWIL on 23/06/2015 17:04:35:

When it was looked into, I had used a MASSIVE steel jig and they had used ALUMINUM because it was lighter! It had also be that much easier to twist and bend which had screwed their result

I take your point, but there are many examples of projects made of steel or CI that could happily be redesigned to suit light alloys. A home-cast steady rest frame might be a good example.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 23/06/2015 20:07:43:

Posted by KWIL on 23/06/2015 17:04:35:

When it was looked into, I had used a MASSIVE steel jig and they had used ALUMINUM because it was lighter! It had also be that much easier to twist and bend which had screwed their result

I take your point, but there are many examples of projects made of steel or CI that could happily be redesigned to suit light alloys. A home-cast steady rest frame might be a good example.

Neil

.

It is worth noting that [to a first approximation] the stiffness to weight ratio of 'engineering' Aluminium Alloys is the same as mild steel.

MichaelG.

[Edward BrightParticipant @edwardbright86070]

The late Phil Irving (Vincent HRD, Repco Brabham etc) always argued that duralium with a 20% increase in cross-section was as strong as mild steel to all intents and purposes. If I remember my materials engineering correctly it isn't good in cyclic stress situations, ferrous metals always have lower limit below which fatigue cracking will not occur, aluminium in particular does not.

Edward

[JasonBModerator @jasonb]

Posted by Neil Wyatt on 23/06/2015 15:33:05:

I have often been struck by the way that American hobbyists (in particular) make vastly more use of aluminium for the structural parts of their tools than Brits. We seem to have an obsession with using steel and cast iron for everything

There are exceptions, of course.

Neil

Maybe its the tightness that model engineers seem to have a reputation for. With Aluminium 6082 costing about twice as much as the same section in steel that would put some off and if you went with Edwards 20% increase with 2014 you would be looking at about 3.5 times the price.

What about durability, spend some time getting a nice flat bottom on that new tool and then knock a corner as you put it away in the cupboard and you have then got a dent that will raise a burr and stop it sitting down flat the next time you come to use it.

[Neil WyattModerator @neilwyatt]

What about durability, spend some time getting a nice flat bottom on that new tool and then knock a corner as you put it away in the cupboard and you have then got a dent that will raise a burr and stop it sitting down flat the next time you come to use it.

I was going to mention that, but for once I thought I'd keep my post short and to the point

Not a total answer, of course, but I am looking into anodising for surface protection. I've noticed my hard-anodised Taig/Peatol vertical slide looks as good as new, although it's not had a lot of use since I got a mill, it has been 'knocking around' for about 15 years.

Neil

[AjohnwParticipant @ajohnw51620]

Cast iron was cheap it's also ideal for some things. I have seen model engineer designs in mild steel that will fail at some point due to it's properties. I even have one a Eureka.

Peatol make good use of al and concrete slurry. My Peatol vertical slide has faired well too. Maybe the answer to the vice is to simply fasted some mild steel section to the bottom and chamfer the edges as it too will deform if given a whack. Flat ground cast sections would be better.

I have done a bit of anodising and found the numbers in the workshop book series to be incorrect. I'd guess this might be down to the type of aluminium.

The strength aspects of aluminium is an interesting subject. I have rebuilt several car engines. The heaviest ones for size were easily the 2 that used an aluminium block. On the other hand aluminium pistons and cylinder heads are rather light considering their strength. I feel it all comes down to the alloy that is used and also how parts are made in some cases.

John

–

[richardandtracyParticipant @richardandtracy]

With regard to stiffness to weight, the statement that 'Aluminium and steel are similar' is true, but not the whole story.

If you take into account the depth ^ 4 effect that comes into play when making sections, then aluminium comes in at about half the weight for the same stiffness if designed correctly. If the width remains the same, the section depth is nearly 50% deeper. I have looked into this for lifting beams where the design was stiffness and strength limited (wanting to keep the deflection to 1/250 the span while having a 6x reserve factor on the strength). With the current price of aluminium and steel in the UK being about the same, volume for volume, this makes steel lifting beams heavier and cheaper. Steel lifting beams have a significant advantage, to my mind, though, beyond being cheaper. The difference in yield and ultimate strengths is high in most structural steels, and it will deform up to 40% before failure. This gives much more margin safety when catering for operator stupidity than aluminium's, which deform 10% max, more usually 3-4% between yield & catastrophic failure. That way a steel lifting beam will show it's distressed long before it breaks, and should give the operator time to make it safe before catastrophic failure.

In fact, I hate working with brittle materials. At work we had one box we tested in a shunt test with a 1.3 ton contents to simulate a crane banging it into a building. The contents were held in using LM4 castings (1% max deformation to failure when sand cast). The casting smashed and the dummy we used was damaged. We then used a nominally slightly weaker steel casting to the same shape, but due to its ductility, the contents remained secured. Everyone happy.

It is not really extreme to expect that a crane driver will bang a box into a wall – one satellite interface component box (10ft square, 8ft high) went missing with its contents in JFK airport, and was found upside down in a hanger after 2 weeks searching. It transpired that it had rolled out of a cargo B747, across the loading platform and fallen off the other side, 15ft onto its roof. The contents, worth about £500k, were miraculously OK.

Regards,

Richard

 

Edited By richardandtracy on 24/06/2015 11:16:51

[Colin LLoydParticipant @colinlloyd53450]

You know what I like about this forum – the amount of extra information and knowledge provided as forum members branch off on tangents not strictly to do with the question. This may sound like a criticism – but its not. By talking around the question, you've provided me with a better understanding of stresses, properties of metals and possible alternatives that a straight answer would not have provided. Thanks

Colin

[Neil WyattModerator @neilwyatt]

Yes, some thought provoking ideas. perhaps one thing in favour of aluminium alloys for workshop gadgets is that many (but by no means all) are lightly loaded (e.g. grinders – several components on mine are alloy).

Interesting you mention the Eureka, John. The original specification was EN8 IIRC, but I've heard of a few made in mild steel that have stood up to the very infrequent use most of them get. Even so not having a big lump of EN8 is my excuse for not making one

Neil

[Author]

Posts