Dimension change after grit blasting
11-23-2012, 03:40 PM, (This post was last modified: 11-23-2012, 03:48 PM by TomasCro.)
Dimension change after grit blasting
Hello everyone. I have one question about grit blast. Is it possible the diameter of piston is changed if the piston before grit blast is lets say 79,50 and after grit blast 79,55-56? Is it possible that the grit blasting add additional mm
11-23-2012, 04:05 PM,
RE: Dimension change after grit blasting
Hi TomasCro

Sign0016 to the Surface Engineering Forum.

Slight increases in diameter are possible due to fact that your measuring from the peaks in the grit blast texture. There is no increase in volume, in fact grit blasting may reduce volume. Thin section tube I suppose could increase in diameter slightly due to induced work hardening compressive stresses.
11-25-2012, 11:25 PM,
RE: Dimension change after grit blasting
Hi Tomas,

there is a useful pdf at the following link :


It covers the requirements etc for surface preparation, it shows the effects of the steel when Grit Blasting using different pressures, grit type and spray distance

When you grit blast steel the it causes the steel to lift slightly and as Gordon mentioned you measure the peak to valley height so it would appear that there has been stock added to the surface but it is not the case.

Hope that helps ?


11-26-2012, 11:36 AM,
RE: Dimension change after grit blasting
ty on response.. Reason im asking because some aluminum tubes after grit blast got 0.10 increase in diamater .. so from lets say 59.65 after grit were 59.75
11-26-2012, 10:46 PM,
RE: Dimension change after grit blasting
That would be correct as Aluminium is a softer material therefore the impact of the grit will raise the profile of the aluminium.

Try reducing your air pressure slightly see what effects that has. Another thing to watch for is grit entrapment due to the soft substrate, its a good idea to brush down the surface after blasting with a CLEAN nylon brush and blow down with compressed air.


11-27-2012, 04:28 AM,
RE: Dimension change after grit blasting
Increases/decreases in OD and ID occur after blast preparation as the surface is ripped up and the 'mechanical fingers' (peaks) for bond interlock are created and add thickness.

The degree of which is down to substrate material, type/size of blast media used and blast pressures. The differences are measurable, relevant and need to be considered especially when spraying thin coatings or thickness specific top coats to size or dimension.

Remember that measuring a blasted/ready for spray component will make this area shiny so coating adherence in this area may be compromised. If dimension deviation is relevant then it is better to anticipate the dimension change of the un-blasted component dimension before.

With Aluminium the best blast profile will be achieved with low nozzle air pressures. Normal blast pressures will result in over-blasting and a poor mechanical key. Low air pressure means less interface contamination (grit entrapment) but as Kev says doesn’t hurt to clean by brush or blow down with clean shop air or Nitrogen. You will need to spray ASAP with this material as it oxidises quickly.
Len Wood
Ph: +64 9 4730705
Fax: +64 9 4730706
Email:: len@metal-monster.com
11-27-2012, 09:12 AM,
RE: Dimension change after grit blasting
Thanks guys for reply Smile You helped alot . Cheers

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