Drilling and tapping hubs/discs

[flat]

So, If I understand correctly, you are redrilling stock 4-130 drums/disks to Porsche pattern? There isn't enough meat in the new holes to tap for the 14mm wheel bolts. I spotface the back and then press in the studs. It's the only way I do 'redrills', helps me sleep at night.

Lanner

[zeroaxe]

I didnt understand the term "Spotface" so I did a Google and found this. As I understand another word for it is "Countersink", correct? From what I can see on the net regarding spotface tools, is that instead of using a normal drill and do the countersink, one uses a 'flat' drill (like in the pic below) to do a nice and flat 'countersink', correct?


Thanks!

[wrenchnride247]

You got it :agree: . They also make counter bores w/pilot. The pilot goes in the hole as a centering tool so, the tool doesn't "walk" on you.

[zeroaxe]

Wheyhey, at last I am learnign something!

So....This is what I think the order of drillinig should be, please correct me if I am wrong.
1. Drill pilot holes according to new stud layout. Use the appropriate size drill, same as the pilot drill on the Spotface tool.
2. After drilling, spotface the holes making use of the pilot drill.
3. Drill final holes, 14mm.

This method seems the most logical to me. The way I see it is that if the pilot drill is much smaller as the drilled hole, the spotface bit can still 'walk' a little?

Cheers!

[Brad_gt]

In the aircraft business the term counter sink and spot face are totally different . A spot face is a flat seat , and a countersink is a beveled hole for a flush fastener .
See ya , Steve

[flat]

zeroaxe,

Yeah, you've got the procedure correct.

Brad_gt,
You're right. Spotface is when the machining is perpendicular to the hole. Countersink is for flat head screws or rivets, so that the fastener is not above the surface. The holes on rotors for the disk-retaining screws on most cars are countesunk holes.

[ricola]

spotfacing is just used to get a flat surface, normally involves skimming the top off a cast surface..
Rich

[zeroaxe]

Flat,

Thank for the ocnfirmation. I will note this down in my 'tech book'

Brad_gt,

Yes, sorry, I should've clarified myself. Countersink is done with a normal 45° drill bit.

It has been confirmed by Flat, and elsewhere with a picture about the webbing problem at the back of the hub/disc. So the tapping idea will probably be scrapped. I guess I would just have to make up my mind and stick with Porsche pattern No wheel swapping here anymore...

I appreciate the input from everyone. Anyone know where a jig can be had from?

Thanks!