18 replies to this topic

[mattcave]

I fitted 7.5” Cooper S disks / callipers a while back. I noticed today that the screws that hold the drive flange I the disk are not recessed enough (not countersunk sufficiently) and have left dents in the mounting face of my rims. Anyone seen this before? I assume the fix is to machine the drive flange so the countersink is deeper?

[nicklouse]

that is A fix the other is to check that the screws are correct.

[mattcave]

Screws came in the kit from Mini Spares so I assumed they were correct...

[GraemeC]

Something doesn’t sound right - they normally sit noticeably below face

[mattcave]

Here are pics. Anyone spot what is wrong?

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•  DSC_0720.jpg   43.72K   1 downloads

[nicklouse]

that screw has not been seating correctly. something is not right.

[mattcave]

Does the machining for the screw hole look uneven / not square to you? Does to me.

Edited by mattcave, 20 June 2018 - 01:26 AM.

[nicklouse]

i am more interested in the witness mark on the screw stand it on the head and photo straight down to show the pattern on the taper face.

[GraemeC]

How tight was the screw when you removed it?

It’s hard to tell, but the drive flange doesn’t look to be seated as far into the disc as I’d expect.
Put a washer and plain nut on each stud and wind them up - see if it pulls the disc and flange closer together. Then put the screws in tight.

Edited by GraemeC, 19 June 2018 - 08:30 PM.

[mattcave]

Here are the marks on the screw....

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[mattcave]

Screws were tight. Like, driven in with a ratchet rather than a screwdriver, and needed a ratchet to remove them again.

 

The other side of the car doesn't have the same problem, and the machining for the countersunk screws is visibly wider (and hence deeper)...

[nicklouse]

rather poor resolution but i would say it is central. but i would say the countersink angle is possibly wrong. as there should not be a witness mark like that if it was face on face and not face on edge.

 

i would run a quality countersink tool in to the current ones to rectify the issue.

 

someone like Spider would confirm the angle etc.

[GraemeC]

The witness marks on the screw would suggest the drilling is too large and the angle of the countersink too shallow, so the screw is seating on the edge of the hole, not on the countersink. I must admit the cut of the countersink looks like it was done with a blunt tool.

The flange could be badly made. Where are they from? If they are from MiniSpares you could PM Simon on here and see if he is willing to exchange and take that flange back for investigation.

[sonikk4]

The countersink looks like its been chattering in the hole when it was being cut. This is normally down to the hole being too large for the pilot on the countersinking bit. So i would suggest the countersink is slightly offset. Next you need to find out whether that is a 100 or 90 degree countersink.

 

Judging by the hole it does not appear to be knife edged so still a bit of meat left to cut a fraction more off.

 

So if you are going to touch that you need to accurately measure the hole and the degree of cut.

[mattcave]

Thanks everyone. From visual inspection the angle of the countersunk seat looks to be noticeably wider than the angle of the screw (eg countersink is ~100 degrees, screw is 90?). That would explain the marks on the screw. 

 

I've PM'd Simon@minispares to see what he thinks.