Disk Skimming - A4 - how can it be soooo difficult ??

[Tonto]

Guys: really struggling to get a pair of A4 brake disks skimmed;
I've tried some local (Lincolnshire) engineering companies and no one will touch them with a barge pole ! I seem to be going around in circles (unlike my wheels )

Has anyone been through this loop before, and could recommend a reliable source: Cheers Tim

[PAULJAC47]

Al Marshall on here will do them for you drop him a PM

[z1000puddin]

Tonto,
I had an old machinist here in Aberdeen who skimmed 20 thou of my discs.
It depends on how bad your discs are.

He is away for two weeks on hols, so I cant ask him.

You want someone with an old Harrison & who knows how to use it.

Nowadays everything is CNC and you need a computer to work the bloody things.

Stu

[Z1B]

I find it really surprising any half decent machine shop should be able to machine your discs as they are substantial, different if they were modern thin discs mounted on buttons, these are more of a challenge, if my three phase generator was working I would say send them. but it aint, ive done dozens of them over the years, any CNC turner / machining centre operator should also tackle them. Usually two problems with the larger places minimum charge and
operators who are just not allowed to get involved, there is no fancy program required as the discs would be machined by simply using the hand wheels on manual mode
Best place to try are car machine shops that do rebores, discs drums etc, some of these have cylindrical disc grinders which can tackle the thinner discs without deflection, saying that a good skilled manual turner with good tool knowledge can be every bit as good,

What I should point out is if you find someone who is going to TRY them.with a sturdy lathe. tell them that the discs must be machined in ONE set up. no taking them out of the chuck to machine the other side. then it is almost impossible to machine them parallel, your discs will be fcud, best of luck, if no luck. and you are not in a hurry I hope to find the time to repair my genetator next month, hope this helps

[ade woollams]

not sure about the later disc but the z1 type i was told they have to be surface ground .took my disc to a place they said they could do it .got it back it looked shit all lines in it ,i asked if it had been ground and he said no we have a special disc skimmer lathe .why did i bother telling them .its back on the bike but its not as nice as it should be and it sqeals like f##k

[z1bman]

as ade said they should be ground not skimmed in a lathe

[Padders]

Al Marshall as already recommended above He will sort them out for you no problem. If you contact him I can collect and deliver them if you are wary of posting.

[jimmock]

Guyz,

Sorry, but I do not believe in "skimming" discs.

They warped for a reason, ie too much heat.

Skimming is going to make future warping more likely.

[Garn 1]

There is plenty of room for skimming on the early Z1 series.
The cost is always over the top, however, as mentioned earlier, they usually do both sides at once to keep the surfaces parallel. They are often Stainless steel which is tough and often they are glazed which presents a hard skin.

I nearly always asked if they would bring them down to the thickness of Z900 A4's or Z1000's. They never want to go through that min thickness level!

I had my last disk-set ground, it worked out cheaper.
Regardz.

[kev edwards]

Send them to Al Marshall, it's much easier, i tried skimming one once in a big lathe and although i set it up so both sides could be done without removing the disc it sang like a banshee no matter what speed i tried it at, so i ended up with an Al Marshall ground one.

[ZedHead]

Skimming will chatter, surface grinding is the way to go.

[A1John]

Guyz,

Sorry, but I do not believe in "skimming" discs.

They warped for a reason, ie too much heat.

Skimming is going to make future warping more likely.

most people grind/skim discs for cosmetic reasons

[Tonto]

Thanks for the advise guys: much appreciated. Trying to get this sorted has really has been driving me bat-sh1t
Looks like I'll be getting in touch with Al in the near future: Padders - probably will be in touch shortly re you're kind offer.

Cheers Tim

[Z1B]

The noise from the disc can be caused by a number of factors but nearly always cured by tool choice, it wont help if there is wear in the top slide. wrong feeds and speeds or wear in the head bearings, EVERYTHING has to be right for a first class finish. and if it is not happening then there is a reason,

Jimmock, wear is not just caused by heat, old zeds hardly had enough pressure to build much heat (when did you last do a stoppie) pads glaZing, sticking pads, NO pads left, grit and general road crap, were the main causes.

[z1000puddin]

Z1B,
I agree, with your post.
I have had my z1000 A1 drilled discs skimmed as previously mention in the thread.

At my MOT in May this year my front brakes were 95% on his rolling road - the tester actually commented on how good they were.

I dont profess to be a machinist, but the old guy that did mine
(73 years young) new his stuff.

stu