Lotus Elan

What blasting medium best for calipers?

PostPost by: robertverhey » Thu Dec 29, 2011 10:36 am

Hi all quick question, I have removed and dismantled the front calipers (and rears will follow)

Have removed pistons and seals, but have not split the halves.

I intend to give them a blast in the cabinet to remove all paint and rust. Can anyone recommend what sort of blasting medium is best? Should I avoid sand and grit and use beads? Or is grit followed by a good clean acceptable?
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PostPost by: twincamman » Thu Dec 29, 2011 12:17 pm

Most rebuild shops I have had experience with use a stone filled metal barrel that rotates. Blasting has static electricity that will prevent the residue sand from ever being cleaned off or out of places....like a nude day on the beach ....Ed
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PostPost by: CBUEB1771 » Thu Dec 29, 2011 12:22 pm

I assume you have standard iron calipers, if so there is nothing wrong with sand or grit. I would not split the calipers before blasting to make sure the mating surfaces are not touched. Also plug both hydraulic ports with bleed screws and make sure the cylinder bores are well protected so that they are not exposed to the blast medium. Regarding Ed's response, I have used a variant of the device he describes, one with a vibrating drum using stones and a liquid medium. Many machine shops use these for deburring machined parts. They produce a very nice finish but the stones have a fairly large diameter, greater than 5 mm. This means that lots of concave radii on parts are never touched by the stones and are never cleaned or deburred.
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PostPost by: Tonyw » Thu Dec 29, 2011 12:51 pm

I have no qualms about using garnet or glass beads, I only use glass beads myself as I use it for Aluminum as well as all sorts of steel. The trick of course is to make sure you get the residue blasting medium out before you try to assemble them again. The best method of course is to use a soda blaster as the soda will dissolve in water, soda blast and put them through your dishwasher job done.

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PostPost by: memini55 » Thu Dec 29, 2011 3:02 pm

One more vote for glass or soda blasting, just be careful as Russ has described the process very well. I have access to glass as the easiest choice.
I have done may rebuilds and have had no issues to date. I have also found a really tough paint made by 3M, finish is kind of a crackle Aluminum color and is rock hard when dry.

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PostPost by: Elanintheforest » Thu Dec 29, 2011 8:32 pm

Sorry guys, but soda won't touch the rusty bits...it will just polish the surface of the rust!

Soda isn't abrasive, but the crystals 'explode' on contact, which sorts out paint and cuts through grease and oil but absolutely no good for rusty metal.

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PostPost by: memini55 » Fri Dec 30, 2011 1:12 am

Thanks Mark, I forgot I use the soda on the fiberglass and too polish chrome parts and it also cleans the glass!

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PostPost by: robertverhey » Fri Dec 30, 2011 8:30 am

Thanks all for responses. Looks like consensus is grit or beads okay, provided all passageways fully cleaned and piston bores and passageways protected from the blaster
Last edited by robertverhey on Fri Dec 30, 2011 11:45 am, edited 1 time in total.
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PostPost by: mikealdren » Fri Dec 30, 2011 11:17 am

I had a large selection of old parts sand blasted along with a chassis a few years ago. I put bolts in the calliper threaded holes and left old pistons (with seals and dust covers) in place.

The callipers came back in great condition. I subsequently took the callipers apart and there were no signs of dust ingress.

Having said that, I would use probably bead blasting nowadays.

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PostPost by: Tonyw » Fri Dec 30, 2011 2:59 pm

The only further advice I would offer is that if you are going to use an abrasive medium make sure that you tap out any threaded holes as the blast medium dust will remain in the root of the thread no matter how well you try to clean them.

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PostPost by: CBUEB1771 » Fri Dec 30, 2011 3:55 pm

mikealdren wrote:II put bolts in the calliper threaded holes and left old pistons (with seals and dust covers) in place.


Bolts are fine, I mentioned bleed screws because you can run them all the way in and not have to worry about damaging the flare seat at the bottom of the hole.
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PostPost by: robertverhey » Fri Dec 30, 2011 11:23 pm

Thanks, all good tips. In hindsight maybe I should have blasted before dismantling....Aaah well.
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PostPost by: DeanG » Sun Jan 01, 2012 1:26 am

I did all 4 calipers a few months ago. They were all split, taped off then glass beaded. They look marvelous.
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