This belongs in the "Never do this category!"

[Doug Rodrigues]

I took my O-360A1D crankcase to the only business in town that does glass bead blasting. I wanted the exterior of the case blasted so as to have a fresh surface on which to apply paint. I instructed the blaster to focus on the outside of the case only and warned him to stay away from any machined surface inside the case. Two hours late I returned to find everything blasted: the outside, the inside including the main webs and the cam webs!! I freaked and had a few words with the business owner. DivCo in Tulsa said that they can fix it. I sure hope so?

The lesson learned here is to NEVER have ANYTHING done to ANY aircraft engine part by ANY business not specializing in aircraft engines!

[flyboy1963]

ummmmmm, what planet was the blaster from?
I don't think you have to be an aircraft engine expert to know what a bearing journal is!!!!!!
As an education for those of us that may try something similar, wouldn't you also have to put a bolt in every threaded hole, to keep the blasting from buggering up the threads??? I guess that is a 'machined' surface, but there are sooooo many, is it even worth blasting?
Is just a hot-tank type solvent treatment as good, or better?

[ddurakovich]

By the time they "true" the mating surfaces and line bore the journals to factory tolerances, I suspect it will be OK.

As an added bonus, it will come back with a bright gold alodined finish all ready to paint!

[boom3]

The guy probably thought he was doing a great job too.

Kind of like the guy that sanded down all the AN470 rivets on that King Air during paint prep.

[chaskuss]

Originally Posted by Doug Rodrigues

I took my O-360A1D crankcase to the only business in town that does glass bead blasting. I wanted the exterior of the case blasted so as to have a fresh surface on which to apply paint. I instructed the blaster to focus on the outside of the case only and warned him to stay away from any machined surface inside the case. Two hours late I returned to find everything blasted: the outside, the inside including the main webs and the cam webs!! I freaked and had a few words with the business owner. DivCo in Tulsa said that they can fix it. I sure hope so?

The lesson learned here is to NEVER have ANYTHING done to ANY aircraft engine part by ANY business not specializing in aircraft engines!

Doug,
Engine crankcases [auto and aircraft] should never have the insides glass beaded. The accepted blasting media is crushed walnut shells. VW had a rash of problems back in the 1960s due to overhaul shops glass beading their crankcases. The problem is that the glass bead is VERY hard and abrasive. It gets embedded into the aluminum. Once the engine is heated during running, the aluminum expands. This allows the pores in the aluminum to open. When this happens, it is possible for some of the glass bead to fall out. It goes into the oil and wrecks havoc on the engine, as the oil spreads it throughout. You might want to talk to a Lycoming engineer about this.
FYI
Charlie Kuss

[JetMech72]

I would definitely talk to Lycoming on what to do next. I had an auto engine blasted, but not cleaned properly afterwards. Those beads wore away my lifters, cam, and snowballed after that...fodding out the engine with less than 3,000 miles on it. Only plus side was that with a car, you can pull over....

[BikePilot]

A walnut shell blast also removes less materal so is safer on more critical areas (though I'd still never blast a bearing journal). When I worked in a machine shop for a bit we only used walnut shell media on engine parts (car and motorcycle). We used glass or sand on steel chassis parts where contamination and tollerances are generally less an issue (and rust more an issue). I'm not sure how bad glass is on engine parts - I know sand can be very bad, but tdon't know much about glass.

[Geico266]

Originally Posted by chaskuss

Doug,
Engine crankcases [auto and aircraft] should never have the insides glass beaded. The accepted blasting media is crushed walnut shells. VW had a rash of problems back in the 1960s due to overhaul shops glass beading their crankcases. The problem is that the glass bead is VERY hard and abrasive. It gets embedded into the aluminum. Once the engine is heated during running, the aluminum expands. This allows the pores in the aluminum to open. When this happens, it is possible for some of the glass bead to fall out. It goes into the oil and wrecks havoc on the engine, as the oil spreads it throughout. You might want to talk to a Lycoming engineer about this.
FYI
Charlie Kuss

Originally Posted by JetMech72

I would definitely talk to Lycoming on what to do next. I had an auto engine blasted, but not cleaned properly afterwards. Those beads wore away my lifters, cam, and snowballed after that...fodding out the engine with less than 3,000 miles on it. Only plus side was that with a car, you can pull over....

I was going to say something along these lines, but you guys beat me to it. IMHO the case is junk.

[rocketbob]

If Divco says it can be fixed, it can be fixed. Provided that after they align bore and flycut it again you can still get the minimum deck height.

I've heard of this exact thing happening with other engines, a good hot tanking and scrubbing with scotchbrite should get any glass embedded in the case out.

[chaskuss]

Originally Posted by rocketbob

If Divco says it can be fixed, it can be fixed. Provided that after they align bore and fly cut it again you can still get the minimum deck height.

I've heard of this exact thing happening with other engines, a good hot tanking and scrubbing with ScotchBrite should get any glass embedded in the case out.

Bob,
Do you mean "cold tanking"? I had always understood that "hot tanking" was for iron and steel parts, not aluminum. My preferred method of cleaning aluminum parts is to cold [chemical cleaning] tank them. This involves soaking the parts in methyl chloride.
Charlie