Bead-blasting
 

Anyone had any experience bead-blasting gear cogs? Would bead-blasting damage the hardening on the teeth? Ours are a bit rusty, and a rotating wire-brush doesn't properly access all the nooks and crannies.

Bead blasting
 

Hi Andrew,
You could try Soda blasting which is much gentler. Another alternative is to use Molasis which you can get in bulk from the produce store. You then mix with water - I use 1 part molasis and 2 parts water. Leave the item to sit in the mix for about a week. Parts will be back to bare metal and you can just rinse under water. The solution will turn some sufaces a blackish colour - but they will be free of the rust. Hope this is of help.

Regards,

I do not believe bead blasting would do any harm what so ever to your gears. You are talking glass beads, I assume. The stuff is however, harmful to your lungs, if you don't take the pecautions required. It is also very important that your clean up of your parts (to have them 110% clear of any glass residue) is vitally important.
Glass bead blasting can make a component more durable because it tends to eliminate stress points from which fractures start.

Bead blasting absolutely. A friend of mine rebuilds truck transmissions and uses this on gears, especially if they are hard to find or obsolete.

Thanks for that. Re molasses, I am a convert and have had great results with it. I have already used it on the gear cogs and now I want to get rid of the black residue and also some persistent hard-caked grease that is reluctant to dissolve in solvent.

I use molasses quite a lot and this is the result, lovely shiny clean bits.

Attachment 76678

I use a mixture of 10 to 1 molasses to water, that is diluted enough.

I wire brush each item after rinsing it off and then it is ready for priming after a wipe over with a wax and grease remover.

Lynx manual carrier before immersion.

Attachment 76679


The finished item ready for painting after repairing it.

Attachment 76680

DO not put any die-cast items into the solution or you will end up with that a bit of mush.

Any oil or grease will stop the process at that particular point, but will continue to work on the rest of the item.

Regards Rick

So Rick, for the molassess bath, a thorough degrease is in order prior to immersion into the bath for best results?

If you remove any grease beforehand the molasses will work better. At least that has been my experience. I use a 6:1 ratio of water to molasses and if left for about 10 days it gives the excellent results achieved by Lynx42 above. A high pressure water-blaster (mine is 2000psi) is best for cleaning the black gunk off afterwards. However with my gearbox cogs there is still an unacceptable amount of residue that I now need to remove by some other method.

It is surprising how, sometimes the de-rusted steel does not start rusting again immediately after the molasses treatment, while other times it gets an orange "rust bloom" almost straight away. I suppose it might depend on the humidity of the air. I sometimes use a blow-torch afterwards to speed up the drying process and avoid further rusting. Its amazing to me that the molasses method is not more popular, as it does an excellent job, is very cheap, easy, biodegradable, non-toxic and (if you are in a rural setting) easy to dispose of afterwards. As far as I can see there is no down-side to molasses, as long as you plan ahead and are not in a hurry.

Chris, If you use a degreaser the molasses won't work. Just scrape of the excess grease but don't spread it as the solution won't work where the degreaser or grease was. There won't be any rust under the oil or grease and you can put the item in the molasses with the grease on it and clean it off later.

Regards Rick.