Cleaning up castings

[John Wood1Participant @johnwood1]

Up ’till now I have cleaned up new castings using normal hand tools but this can sometimes be hard work. I have just started work on my latest project, a Redwing hit-n-miss engine, and find the castings have a lot of flashing to be removed as well as a good amount of finishing, so I thought it about time I got mechanised.

 

I have had a look at disc sanders, disc and belt sanders and the hand (file) type 1″ sanders, mainly in the Axminster catalogue, all of which no doubt would do some or all of the job but I would very much appreciate the advice of those who do have a method of cleaning up castings without too much hard work.

 

Many thanks, John

[John Wood1Participant @johnwood1]

How’s best to do this job?

[JasonBModerator @jasonb]

A die grinder is the best thing to get the flash off either electric or air if you have a big enough compressor. A Dremel with grinding bits also works well.

 

J

[The Merry MillerParticipant @themerrymiller]

I use a Dremel with carbide burrs.

 

Len. P.

 

 

[Gordon WParticipant @gordonw]

Iron castings used to be tumbled, in sand/ gravel. You could try putting them in a tub with gravel in the back of the car, if you have a car and roads like mine. Or make a drum on rollers with a motor drive (friction wheel) as a model of the real thing.

[John Wood1Participant @johnwood1]

Thanks for that. I will investigate die grinders although I don’t have an air source. I thought of the Dremel but, to be honest, I have a couple of these mini grinder type sets, one from a holiday in France (some obscure make I reckon) and the other is a Black & Decker. I find that neither of these have much power and the motor slows to a stop with very light pressue on any tool. My question now is does the Dremel have reasonable power to actually do any sensible work? as I am reluctent to buy one only to find it is no better than these others.

 

Not an easy question to answer of course because I can’t quantify the power of mine but some indication would be helpful. I guess the only real way is with the hand tools.

 

Thanks, John

[JasonBModerator @jasonb]

I fettled all the iron castings on my 2″ Fowler and the recently completed IHC hit & miss engien with my Dremel without any real problems. Though I think I may inverst in a Makita or DeWalt electric Die grinder when I start on teh 2″ ploughing engien as there is quite a bit of moulding flash to come off.

 

If you look at the photos of the IHC crank case in my first post in this thread you can see where I have been grinding around all the various bosses to tidy them up and get them concentric to teh drilled holes. It was also used to blend the bosses on the cylinder head in a later post which you can see were quite rough after milling as true as possible.

 

They are also good for dressing welds when you start fabricating larger parts that are beyond silversoldering.

 

J

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Its much easier to do it backwards if the castings are small . Arrange a fixed motor to carry a grinding point and just manipulate the casting against it . Doing it this way you can have ovewhelming drive power , use any of many different shapes of grinding point available commercially and be able to see what you are doing .

 

Improvised wooden fences and jigs can be used if (eg) you want to dress along a particular line or follow round a curve though you can do most things freehand quite successfully .

 

Its not actually nescessary but a coolant drip makes cutting more free and keeps the dust down .

 

A well supported piece of thick perspex is good as a safety screen and safety glasses are a must for any grinding work .

 

MW

 

 

I

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

You can of course also use small regular grinding wheels , flap wheels and wire brushes with same set up .

 

There where once on the market properly made drive spindles for this kind of work – often with a regular grinding wheel one end and a chuck for holding grinding points et al at the other end – and all arranged with versatile work rests and good guarding .

 

MW

Edited By MICHAEL WILLIAMS on 17/01/2012 22:44:48

[Martin CottrellParticipant @martincottrell21329]

Hi John,

 

I use a variety of small grinding wheels, diamond grinding wheels and flap wheels either in my Dremel chuck for fine detail work or mounted in my pillar drill chuck. The pillar drill is ideal, just raise the table up until it is just clearing the grinder/flap wheel and you have a nice firm base from which to fettle your casting against the grinding tool. I’ts advisable to wear a good pair of gardening gloves as finger nails can inadvertantly be trimmed to excess in a very short time if you’re not careful (don’t ask how I know this)!! Goggles are essential and some form of breathing mask is advisable as using this method you tend to be working with your face in close proximity to the action.

 

Hope this helps, regards, Martin.

[BERTOParticipant @berto]

Hi John .

I have in the past used a wood router (ozito) with the base removed to serve as a die grinder and it has plenty of power plus it is speed adjustable .

Not sure if all routers can have the base removed as mine clamps on and is very similar to an electric die grinder in shape with the base off .

The collet for this is 1/4 inch and my carbide burrs are the same .

Try the cheapest one you can find at the local hardware store .

 

Ian

[JasonBModerator @jasonb]

I can see the fixed motor working for small or regular shaped items but at the moment I’m working on a 1/2 scale Domestic hit and miss engine, the base casting for that must weigh about 10kg. Trying to move that sort of weight about for any length of time with any accuracy could be interesting. As for when you get onto the traction engien models what happend when you need an engine hoist just to lift the cylinder casting?

 

As for seeing what you are doing I think it would be hard to see whats going on 2-3″ down inside the casting cavities.

 

J

[Peter Wood 5Participant @peterwood5]

I met a chap at the Warwick show who had made the same model as me and had also had to deal with poor castings with considerable flashing.

He told me that he had dumped them in conc. nitric acid!! Apparently they came out perfect. Sadly not a practical solution in these H&S obsessed times.

[John Wood1Participant @johnwood1]

Many thanks to one and all, you have given me several good ideas to go at and it’s a real help to know what others do. It looks like I don’t need to chuck money at it really so that can be kept for something else.

 

Right then! it’s goggles on, dustmask and gloves on and wait for a mild day when I can do it outside so as not to spread iron dust all over the workshop.

 

Thanks again, John

[DMBParticipant @dmb]

Nitric acid probably works very well on sandy castings since sand be used as the basis for glass making and I believe that Nitric attacks glass. So what do you store it in? Also how would you dispose of it? Pouring down the drain is NOT the solution! Very nasty stuff.

[Sub MandrelParticipant @submandrel]

> So what do you store it in?

Lead vessels IIRC.

“All I have to do is combine these two liquids and I will have created the ultimate solvent – but what would I store it in?” <evil laugh>

Neil

[TerrydParticipant @terryd72465]

Posted by John Coleman 1 on 18/01/2012 11:41:41:
Nitric acid probably works very well on sandy castings since sand be used as the basis for glass making and I believe that Nitric attacks glass. So what do you store it in? Also how would you dispose of it? Pouring down the drain is NOT the solution! Very nasty stuff.

 

I used to get Nitric from the School labs when I needed to mix with hydrochloric to make ‘Aqua Regia’ for various nefarious purposes. It was stored in glass Winchester jars. The really nasty acid, which is most reactive with glass is, I beleive, hydrofluoric.

 

 

T

 

 

[Deltic007Participant @deltic007]

Hi John,

 

Try a metal tin preferably square (Old oil tin) with gravel in and a little machine coolant and spin slowly in a lathe for about 2hr or until fettled.

 

Mike

 

[JasonBModerator @jasonb]

A question for those that suggest acid or tumbling.

 

How does the acid/gravel know the difference between moulding flash, steps due to mould misalignment and fine cast detail such as raised lettering?

 

The way I see it neither the gravel or acid can be aimed at the bits of metal that want removing and will just attack the whole surface in the case of acid and all the high spots in the case of gravel and missing any internal corners.

 

Your comments awaited, Jason

[Gordon WParticipant @gordonw]

Jason, tumbling was done when I was a lad, in large ,rubber lined drums. We made the drums for sale also. I think the medium was steel shot. The idea was to knock of the sharp, thin, flash and the sand etc. Timing is possibly important, ie. 1 hour or 5 hrs?

[Gordon WParticipant @gordonw]

Jason, tumbling was done when I was a lad, in large ,rubber lined drums. We made the drums for sale also. I think the medium was steel shot. The idea was to knock of the sharp, thin, flash and the sand etc. Timing is possibly important, ie. 1 hour or 5 hrs?

[ronnie barkerParticipant @ronniebarker18785]

i have also built a redwing and as john says the castings are very rough, on myown model the worst area was round the top of the hopper which i got out with a angle grinder.

 

the flywheels were also very bad so i filed off the flash and high spots and then used good pimmer filler paint to fill the worst of the pitting.

 

on models such as hit and miss engines the full size castings were not very smooth and perfect some worse than others so shouldnt we put this into our models, but i understand you dont want flashing or great holes or pitting .

 

i wouldnt like to use any sort of acid on model castings it would worry me that the paint wont stick after

 

jonathan

Edited By ronnie barker on 20/01/2012 13:42:50

[Sub MandrelParticipant @submandrel]

When Stan Bray wrote up making an RLE he described how he changed his mind and didn’t fill the casting in order to make it more in keeping with the real thing.

 

Neil

[Ian S CParticipant @iansc]

You can always say that the rough surface is there to give greater surface area, for better cooling!! Ian S C

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

There is a definate distinction to be made between the process of cleaning off foundry dirt , sand and odd bumps and the process of removing substantial amounts of metal such as remains of runners , heavy flash and large distortions .

 

Just cleaning the dirt off has been well covered already . I’ll just add that in industry its often just as horrible and improvised a process as it is in home workshops – the tools are just bigger .

 

As regards removing more substantial amounts of metal :

 

Modern practice in industry is to incorporate this into the actual machining of the part . In the automotive industry in particular the entirely automated machining processes incorporate cycles which machine all round the problem areas . No distinction is usually made as to whether there is or is not any flash (or whatever) at a particular location – the process just machines to a dimension and in so doing sometimes machines metal and sometimes air .

 

So carrying this back to the home workshop suggests that in some cases at least heavy cleaning up can be done more easily by controlled machining than by improvised grinding .

 

MW

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