Topic: Cross drilling and surfacing rotors questions

[ncstatecamp]

While perusing through the services section on here I saw the cross drilling surfacing offered and thought that's looks interesting but have a few questions.

An I right in guessing, other then aesthetics, it's to reduce weight and dissipate heat?

While this lightens the front end a bit isn't that slightly disadvantageous on a cb due to the already wobbly (potentialy due to how skinny/light the forks are) front end?

How much does this weaken the steel?

Does the pattern matter all that much or do different ones effect differently?

What are, if any, the disadvantages to this?

I was also wondering if anybody could provide me with minimum specs for rotor thickness.

I ask these questions bc my shop teacher loves when we bring in our own projects. Id like to utilize access to a shop while i have it.

[wrenchmuch]

Many have drilled rotors with no problems. It helps displace water which makes wet riding a bit safer. These are stainless rotors and disk lathes won't do much. They need to be surface ground.

[DJ_AX]

I'm in the process of doing mine right now. I'm going with the simple "Lay it out, center punch, and drill method.
(my drill press goes down to 300 rpm so that'll be fine )
For resurfacing I'll just give it a good (but careful) stoning. It's flat... just glazed.

[flybox1]

While perusing through the services section on here I saw the cross drilling surfacing offered and thought that's looks interesting but have a few questions.

An I right in guessing, other then aesthetics, it's to reduce weight and dissipate heat?  and to clear debris and water to improve braking

While this lightens the front end a bit isn't that slightly disadvantageous on a cb due to the already wobbly (potentialy due to how skinny/light the forks are) front end? if your front end is wobbly, you need to service those systems - proper tire mount/balance/truing, spokes, fork fluid flush, fork springs, steering bearings, etc...

How much does this weaken the steel?  as long as you dont turn your rotor into swiss cheese, i wouldnt worry about it. 

Does the pattern matter all that much or do different ones effect differently? nope, but you want a pattern which allows the whole brake pad surface to be swept.

What are, if any, the disadvantages to this? too many holes= less braking surface

I was also wondering if anybody could provide me with minimum specs for rotor thickness. specs for yours might be stamped on your rotor hub. 

I ask these questions bc my shop teacher loves when we bring in our own projects. Id like to utilize access to a shop while i have it.

you'll also want to rebuild your master cylinder, front caliper, and upgrade your brake hoses to get the most out of this system.

[oldbob]

This was my approach the last time that I drilled a bike rotor.

1. I worked up a pattern with a CAD program and printed it.
2. Glued (using rubber cement) the pattern to the rotor.
3. Center-punched through the paper pattern.
4. Drilled 1/8" pilot holes.
5. Drilled 3/8" (with a cobalt-tipped bit).
6. Chamfered (I think that's the correct term) the 3/8 holes with a 1/2" bit.

Bob

[ncstatecamp]

Many have drilled rotors with no problems. It helps displace water which makes wet riding a bit safer. These are stainless rotors and disk lathes won't do much. They need to be surface ground.

Ok i definately like the water displacement part, is there anything that can be done to help drum brakes do the same? Mine always seem to lock up in wet conditions.

we have a surface grinder too do might get to use that. This is probably a stupid question but, what's the difference between a disk lathe and a large metal lathe?

[ncstatecamp]

This was my approach the last time that I drilled a bike rotor.

1. I worked up a pattern with a CAD program and printed it.
2. Glued (using rubber cement) the pattern to the rotor.
3. Center-punched through the paper pattern.
4. Drilled 1/8" pilot holes.
5. Drilled 3/8" (with a cobalt-tipped bit).
6. Chamfered (I think that's the correct term) the 3/8 holes with a 1/2" bit.

Bob

This is essentially the method I was thinking about just with a mill (need more practice and more accurate)

[lostinthe202]

we have a surface grinder too do might get to use that. This is probably a stupid question but, what's the difference between a disk lathe and a large metal lathe?

I doubt surface grinding these would work, since the hub of the rotor is offset so you couldn't really grind one side without hitting the hub. 

I'm surprised to learn these are stainless since most kinds do funny things when they get hot.  What kind of stainless are they made from?

A brake lathe has two cutters mounted so that it turns the front and back side simultaneously to ensure two parallel surfaces.

[ncstatecamp]

we have a surface grinder too do might get to use that. This is probably a stupid question but, what's the difference between a disk lathe and a large metal lathe?

I doubt surface grinding these would work, since the hub of the rotor is offset so you couldn't really grind one side without hitting the hub. 

I'm surprised to learn these are stainless since most kinds do funny things when they get hot.  What kind of stainless are they made from?

A brake lathe has two cutters mounted so that it turns the front and back side simultaneously to ensure two parallel surfaces.

O that makes sense about the grinder, damn... Well how do other do it? Face one side on the lathe and surface grind the other side?

[stockscreamer]

Majority of braking on motorcycles and cars is used up front, its where majority of the weight is (goes in terms of motos) there for its more effective, the rear brake will lock up quite easily regardless unless its locking with slight braking pressure in which case somethings wrong.

[70CB750]

I'm in the process of doing mine right now. I'm going with the simple "Lay it out, center punch, and drill method.
(my drill press goes down to 300 rpm so that'll be fine )
For resurfacing I'll just give it a good (but careful) stoning. It's flat... just glazed.

Drilling SS requires certain minimum speed, you can harden it by going too slow. Basically you want to drill the hole before the disc heats up.

[lucky]

we have a surface grinder too do might get to use that. This is probably a stupid question but, what's the difference between a disk lathe and a large metal lathe?

I doubt surface grinding these would work, since the hub of the rotor is offset so you couldn't really grind one side without hitting the hub. 

I'm surprised to learn these are stainless since most kinds do funny things when they get hot.  What kind of stainless are they made from?

A brake lathe has two cutters mounted so that it turns the front and back side simultaneously to ensure two parallel surfaces.

Brake discs are manufactured using 400 series stainless, ferritic stainless.
High iron content.

[754]

 They can be ground, and are gound at the factory. There is ways to grind them, but it is not simple. Turning them is tricky as well.

 If better rain performance is your main cosideration, cutting a few radial grooves will take care of that..