mfk
Tea Maker
Posts: 111
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Post by mfk on Oct 11, 2021 22:16:45 GMT 1
Just wondering what grade discs do you guys use for the likes of dressing up corroded edge on brake discs.
Do you use flap discs or wire style brushes etcs?
Thanks
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Post by valhalla on Oct 11, 2021 23:14:31 GMT 1
I don't use anything abrasive, as the objective is to chip or blast the loose material away, and leave good metal behind.
For the edges of brake discs, you can go a long way with just an old screwdriver (flat-blade, obviously) rested on the caliper carrier as a "toolpost" and just revolve the disc around as the blade scrapes the rust off. This is less likely to remove good metal, but gets all the flaking lacquer off.
For the disc face itself, and this is where I go very carefully, I use a twist-knot angle-grinder wire-brush, a good pair of goggles, and some thick gloves. The risk here is that if you start powering your way across the friction face too carelessly, you write the disk off.
My own preference, but this is beyond the normal DIY route, is to use a needle descaling gun for the outsides of discs, but you have to be very careful about not leaving a load of pock-marks on the friction surface. It is also noisy beyond belief, so totally useless in a shared workshop or where the neighbours work on nightshifts....
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remmington
Apprentice
Owns Spark Eroder
Posts: 4,971
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Post by remmington on Oct 12, 2021 18:18:17 GMT 1
I use a welding scaling hammer on the outside edge of the discs - then a twisted knot wire brush on an air grinder.
If the disc has too much of a "lip" on it - I just sell/fit new discs (as the disc is getting thin!).
If I have to - skim on lathe - it is too late for the disc.
Only thing I really put on lathe nowadays is rear brake drums (hate the job as it needs a four jaw chuck - I hate changing chucks).
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mfk
Tea Maker
Posts: 111
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Post by mfk on Oct 12, 2021 21:14:58 GMT 1
I don't use anything abrasive, as the objective is to chip or blast the loose material away, and leave good metal behind. For the edges of brake discs, you can go a long way with just an old screwdriver (flat-blade, obviously) rested on the caliper carrier as a "toolpost" and just revolve the disc around as the blade scrapes the rust off. This is less likely to remove good metal, but gets all the flaking lacquer off. For the disc face itself, and this is where I go very carefully, I use a twist-knot angle-grinder wire-brush, a good pair of goggles, and some thick gloves. The risk here is that if you start powering your way across the friction face too carelessly, you write the disk off. My own preference, but this is beyond the normal DIY route, is to use a needle descaling gun for the outsides of discs, but you have to be very careful about not leaving a load of pock-marks on the friction surface. It is also noisy beyond belief, so totally useless in a shared workshop or where the neighbours work on nightshifts.... Thanks for the reply. It is really only for the outer perimeter edge. Like you said I have used old screwdriver but thought a grinding disc would clean it up better but not sure what is the correct grade as don't want to damage the disc face. I tend to just rub the discs face with sand paper. If it needs more than that or has a lip its generally time to replace them as remmington has said too. Thanks again.
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oli
Apprentice
Posts: 1,065
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Post by oli on Oct 26, 2021 20:25:24 GMT 1
I’ve just watched a video on turning brake discs on a lathe - he was talking about it in the same historic way you might talk of measuring valve clearance at a service. I remember the old man being charged to have new pads and the discs turned some years ago at one of the more commercial/agricultural garages locally. It seemed daft at the time, given it would have been cheaper to fit new discs but I now wonder if the garage was used to working on commercial stuff that needed to be back out there earning ASAP, rather than waiting a day for new parts, even if they were cheaper.
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