shot blasting

[michael howarth 1Participant @michaelhowarth1]

Has anyone had any success with the cheap shotblasting guns available in the £20 price range? I only have a small compressor…4.5 cfm, 115psi and a 6 litre receiver. From what I have read so far it sounds as if it is probably too low on capacity. I only need to shotblast small parts. Any advice welcome.

Mick

[michael howarth 1Participant @michaelhowarth1]

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Mick, I have a cheap one, it's the sort where you stick the suction tube into a bucket of shot (although I used sand in a bag) I had two of these 6 litre things connected into another little receiver through none return valves. It worked well cleaning up the outside of a small worm reducer, which was about 6" x 8" x 4", but both compressors were running all the time more or less, and I felt I had to give them a rest every 20 minutes.

Shot blasting does use quite a high volume of air, even with these cheapies.

I haven't used it for a long while now.

Regards Nick.

[Jeff DaymanParticipant @jeffdayman43397]

Hi Mick,

I think you are right about the capacity of your air system being too small. You will need a lot more storage than 6 litres for much sandblasting. I have an 8 cfm / 125 psi compressor with a 90 litre tank. It will allow sandblasting with reasonable force for about 3 minutes with a cheap gun having a .100" dia nozzle. After that the blast is weak and I have to wait for the compressor to catch up. I have added some "air pig" style auxiliary tanks of 50 litres each, which adds to the duration, but really my compressor and tanks are too small for large sandblast jobs. On small parts say 6 x 6 x 6" it's practical but beyond that it really isn't, and I take anything bigger to a local pro sandblasting outfit who have very large diesel powered compressors and a couple of 20 foot high air tanks.

Just my $0.02. Your mileage may vary.

JD

[Sub MandrelParticipant @submandrel]

You can get tiny ones that look like airbrushes. Try chronos.

Neil

[HomeUseParticipant @homeuse]

Hi – If you can "Wet" sand/shot blast and have a pressure washer then try the sand/shot blasting nozzle which is available at many retail outlets – Matchine Mart being one. – Have been using one for quite a time with dry patio sand on small metal parts – make sute you dont blow the item away or cut holes in it as the abrasive power is very high.

[Phil PParticipant @philp]

Please stop using sand and get some proper blast media.

http://www.silicosis-injury-attorneys.com/pages/sandblasting_risks.html

I work for a company that makes these machines, so I do know…….. stop using sand !!!!!!!

Phil

[John ShepherdParticipant @johnshepherd38883]

Mick

I use one of these :
http://www.axminster.co.uk/axminster-hand-held-grit-blaster-prod22989/?searchfor=grit%20blaster

Its air requirements are quite modest at 5 cfm and 25L tank capacity but too high for your compressor I think.

Whatever you use, keep the compressor as far away from the work as possible to avoid the grit getting into it. Also wear a mask and goggles to stop the grit getting into you.

Regards

[michael howarth 1Participant @michaelhowarth1]

Thanks for all the advice gents.

I do like the look of the axminster product John but I fear that my setup will not have the guts. Having said that, the parts I only need it for paint preparation and the parts are quite small gauge 1 loco stuff…,is it worth a punt do you think ?

Neill…..can't find the airbrush on the Chronos site. I shall give them a ring on Monday.

 

Mick

Edited By mick H on 09/12/2012 16:26:42

[John ShepherdParticipant @johnshepherd38883]

Mick

I think the one I mentioned might work if you are only doing small parts and not in a hurry. I have used a gun that needed more air than this one on a small compressor in the past, it was not ideal in that I had to do small bursts rather than continious blasting but it did work.

Axminster do an airbrush type: http://www.axminster.co.uk/badger-260-mini-sandblaster-prod873608/?searchfor=sand%20blaster but a bit pricy at £50.00ish.

I am not a salesman for Axminster honest!

[michael howarth 1Participant @michaelhowarth1]

John……had a look at the airbrush…..as you said, a bit pricey for what it is.

How does your one operate…..does it suck up the media through a tube or is it contained in the body of the gun?

Mick

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Phil P on 09/12/2012 16:09:59:

Please stop using sand and get some proper blast media.

http://www.silicosis-injury-attorneys.com/pages/sandblasting_risks.html

I work for a company that makes these machines, so I do know…….. stop using sand !!!!!!!

This isn't a problem when using wet sandblasting with a pressure washer.

Russell.

[John Stevenson 1Participant @johnstevenson1]

Shove it in a cement mixer with a load of wet sand

[RJWParticipant @rjw]

Mick, your rig is nowhere near big enough!
I have a 15CFM twin cylinder compressor with a 200 litre tank, and using a standard machine mart gun of the type you stick in a bucket of grit, it practically ran non stop when I was blasting!

Blasting is Not a fast process either, in fact it's infuriatingly slow at times, and if anything on the surface you're blasting is soft or oily, especially soft paint, it won't get it off, it cushions the grit!
You will also find it creates a fair amount of water in the air feed system, so if you don't have a water trap, you'll need one!

I used my guns in two different situations,
(a), I made my own blast cabinet, modelled on a big floor standing Guyson type with filtered extractor, in which I've blasted everything from small suspension components to Aston Martin & Ferrari V8 and Jaguar V12 cylinder blocks using everything from aluminium oxide, to glass bead and walnut,
(b) the same type gun with a hose stuck in big bags of grit to blast hundreds of square metres of stone wall on an C18 French farmhouse – I wore thick overalls, ear defenders and gloves, plus an air fed helmet ……. and a goodly supply of visor lenses, they frost up in a heartbeat!

One of the biggest annoyances with the hose feed type gun for me, was grit plugging the hose in the hopper, so I'd be forever sticking a thumb over the nozzle to back pressure the plug out!

The gun did a cracking job in each case, but the consumption of air (and nozzles) was astronomical, and in some instances when really going for it, consumption outstripped what my compressor could turn out, and it was New, and as grit rapidly wears the (tungsten) nozzles, they get bigger and use more air!

Whatever you use to blast, Do make sure you protect your lungs, ears and, eyes especially: grit in any form, dry or wet, is bloody merciless on skin tissue wherever it hits, get it wrong and in your face, it's Very nasty, and the dust even from an accidental lungful will have you coughing for days, any sort of grit is nasty stuff no matter how small the components you're blasting!

Whenever you blast media against hard material under pressure, it degrades and creates dust in varying degrees of fineness, and the really fine dust if breathed in, acts in a similar way to diesel particulates, your lungs cannot filter it out and it goes straight into your bloodstream where the body's natural defences attack it with antibodies, so at best, you end up with flu like symptoms and you won't feel good …………trust me, I've been there, fortunately my lungs are still giving 100% oxygen (check up at the quacks last week)!!

If you're going to try blasting some parts, I would strongly recommend you use a cabinet and extractor to contain the dust and, use good ear nd eye protection and at least valve equiped face masks!
I can't say whether wet blasting would work any better because I've never done it, but the grit in the feed will still go every which way when it hits the target, and you'll have some cleaning up to do, unless you contain it!
…………and make sure no stray pressurised grit Ever gets near glass or paintwork on your car or house or anything you value in your workshop, it will at best cover it in fine dust, and at worst if close enough, etch it, and if you carelessly wipe that dust off your car or anything polished, you'll make a wonderfully indellible imprint of that wipe, it's incredibly abrasive, so keep it well away from machinery!

If you're not doing much blasting too often, I'd recommend shopping around engineering shops in your area to see if any of them have a cabinet and offer to cross their palms with silver to have them do it for you!
Basically, it is a ball achingly slow, noisy, filthy, gritty job that will have you standing around for an age getting back ache while you run up a big electricity bill and, probably pee off your neighbours with the racket, compressors hammering away and high pressure air hissing for a long time gets a tad irritating to others, and can cause tinitus if you're close up!

Personally, unless you can do it yourself properly equipped, I'd forget it!

Just my 2p's worth!

John

[SiddleyParticipant @siddley]

A 20% solution of phosphoric acid will clean and lightly etch steel parts very nicely without the hassle of blasting. If it proves difficult to buy the acid then DEB sell a tile cleaner which is basically diluted phosphoric acid and does the same job ( can't remember the name of it though, sorry )

[michael howarth 1Participant @michaelhowarth1]

Once again, thanks for the sound advice gents. I cannot accommodate a larger compressor so I think the alternatives suggested make more sense. Wet blasting, phosphoric acid and sand tumbling all sound practicable as does seeking out a workshop with the right gear.

Mick

[RJWParticipant @rjw]

Mick, if you could give us a better idea of the sort of parts you will need to clean and the material they're made from, it might help folks suggest more appropriate means of cleaning!

Some materials don't take too kindly to acid in any form, or blasting for that matter, Mazak (Monkey metal) for instance!
Also an idea of scale would be a big help, 'small parts' could be anything from jewellery items to loco castings!!

Wet blasting might be ok for bits with some substance, but there's a lot of power in a pressure washer, so if it's a 2" diameter cast iron loco wheel, you'd have to nail it to a plank first, otherwise you could end up fetching it from your neighbour's garden!

I have a jewellery tumbler here, which works great for cleaning and de-burring small items, and can be done wet or dry, but it's a slow process, days in some cases, although this does depend upon the grit used and the finish you need!
The drums range from about 6" diameter x 3" long up to about 9", but we don't know if the stuff you're proposing to clean would fit in one!
Drums are costly to buy individually, but complete kits can be had at reasonable money, I picked my set up still boxed and virtually unused at a car boot for a fiver!

John.

[Ian S CParticipant @iansc]

The last time I was in a foundry, i noticed that they usedordenary concrete mixers for tumbling their castings. Ian S C

[SiddleyParticipant @siddley]

The DEB product is Janitol Altrans – 30% phosphoric acid with a tiny bit of detergent
One thing I should mention is that you need to keep the steel completely submerged – use it as a bath.

As acids go phosphoric is pretty benign and I don't think there are any safety issues beyond the usual common sense.

[michael howarth 1Participant @michaelhowarth1]

Siddley….thanks for that. I have googled it and it seems to be widely available.

RJW (John)……I bought Christopher Vine's book, "How not to paint a locomotive" and he recommends sandblasting as excellent preparation for painting. I am building a Gauge 1 "Green Arrow" and the frames are nearly ready for painting. So not a very big job really, as the frames are only about 15" long by 3.5" wide by about 2.5" deep. I don't think that the frames would take kindly to tumbling but it might be effective for other parts. I quite like the idea of the phosphoric acid treatment.

Mick

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