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Shot Blasting


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HI All


Just thinking long term here, who on this forum has a shot blasting machine that they would be willing to hire for a couple of days for people to do their MV's with, obviously they can be brought but for a couple of days rental it might be cheaper and the person who rents it makes some money.


Just a thought

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Given the mess that sand blasting can make, unless you want to blast the whole vehicle, it's usually easier to send parts away to be blasted clean. I use a local farmer, and there are probably people offering a similar service all over the country. That way I get my parts back nice and clean without having to worry about what I'm going to do with several tons of sand.


Smaller parts can be blasted in a cabinet, here at work we have a walk in blaster which I could probably fit a Ferret hull in. Unfortunatley it's used for special materials and I think they might notice if I tried to get them to blast a Ferret for me!



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  • 3 weeks later...

Bearing in mind that forum members are spread around the country, it would not be viable for HMVF to get involved with blasting. You need a good sized compressor to get the volume of air, something like those used for road drills. There are many people with small businesses around the country, just ask around, they may not advertise much as work comes from word of mouth. I use one and he often does car body shells, so is well aware of being careful not to damage the metal work. Believe me it is a lot cheaper to get get the specialist to do it.



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....and are we talking Glass bead or shot or sand ? How big will the compressor be, single phase or three ?


I might be able to shed some light. . . . . . . .Having run and operated a blast cleaning company for several years up to last Friday when I retired from it, the dust, noise, grit in your underwear, heat, cold, etc, etc.


Media - using sand is illegal because of the released silica and silicosis, sand is only used wet therefore. All media comes in different sizes and to different size standards.


Shot is not used for cleaning but to clean up castings and forgings of surplus metal and provide stress relief by the peening action.


Crushed glass is used for mobile, outside and architectural work; the silica is chemically contained and the spent media is like sand for clean-up.


There are many other very application specific media types, garnet, walnut, coconut, plastics et al.


For iron, steel and alloy the industry standard materials are this, chilled iron grit, aluminium oxide and copper slag. Copper slag is cheap and expendible, it is used for outside ferrous work and its a one-shot, its not too agressive. (ie. slow) You have the mess to clear up.


For enclosed work in a blast booth or room, chilled iron is the industry norm. This is iron shot hardened by chilling and then crushed/shattered to produce randon edged grit, the norm is G12 or G17 being around 0.3mm grain size. It is fast and aggressive but some care is needed to not distort the work although sheet steel will move a bit as it does heat it and also stress relieves. It is recycled to the blast machine many times and is very heavy. A bag about the size of a box file weighs 25kg, costs about 20 quid and there are 10 - 12 of those in my pot.


Aluminium oxide is what it says, while iron can be used with care, fine castings are done with the oxide media of a much finer nature, it is much lighter than iron but quite aggressive, it gives a fine matt finish on alloy in the finer grades (F80) and is hugely expensive.


The air (and noise) requirements are vast, I used a 250cfm Ingersoll-Rand diesel compressor (80HP Deutz turbo diesel) with a 3/8" blast nozzle, this would consume up to 25L of red a day and need to be almost flat out when blasting, I could only do a maximum of three pots a day lasting 45mins a pot as this 1/3 ton of grit has to be pushed into piles on the rubber floor and then shovelled/carried into the 4ft high pot, a shovel of cast iron is very heavy. The booth output air has to be extracted at several metres/sec and cleaned from the dust fog of removed crud.


You'll find a 80HP electric motor to be huge and its supply cables also, the rate of rotation of the _three_ meters clocking up kWh on each pase will be something to shock also.


The grit comes out of the nozzle at 300mph, its 95% air and 5% grit.


You need riggers boots so the leather can blast off the toe-caps in short order, second hand heavy hand cotton overalls, last about a month and look like a dirty dish cloth in 30 secs, very expensive breathing air filter and air-fed blast helmet with cape and piles of outer, sacrificial visors (can last just 2 mins), plus a leather apron, Balaclava and ear plugs too. Inner inspection gloves and outer thick rubber chemical gloves are essential and hitting one hand with the edge of the blast stream is exceedingly painful; thanks to all those bringing small parts. . . . . . .


Its a very violent, very noisy and exceedingly dirty operation. Much like spending the day in the dust cannister of your Dyson. . . . . . . . You need to lay in copious supplies of shampoo and shower gel, watching the brown grey mud disappearing is educational, having orange feet and wrists from sweat rusted iron grit is no fun either.


Removing the rusted on grit spots from the bath tub can be a chore also.


Blast cabinets are not really the domain of the hobbyist, there are two types:




Suction cabinets are broadly an expensive waste of time and can only handle light media and then its like painting with a fine artists brush which does a 1/4" disc slowly. It will run on a 3hp compressor and is fine for detailed modelling work only.


Pressure cabinets have a proper blast pot incorporated but with a smaller nozzle, these have to have attendant extraction equipment because of air volumes. A small refurbished pressure cab will be from £4K.


Take it to a pro but remember his work and overhead even if the job takes but a few minutes. eg. A 9.00 x 16 split rim should cost about £25 - £30 in primer. The industry standard is not primed, per se either. It is a carry coat; a light blow-over, for protection while you get it home.

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