Topic: Drilling Rotors

[754]

The short series drills are allso known as stub drills or stub length, generally come in split points which helps, till you try to sharpen.

500 sounds fairly fast for a drill press w/o flood coolant, even a small decrease in speed can easily double life of a drill. I can get by drilling a stainless rotor with High Speed Steel drills, if using coolant.

once the drill is dull, nothing much will help except sharpening..


If you want to layout holes to drill ( not on the rotors) try this ancient method..layout die & dividers..

[Kev Nemo]

I took measurements first, then did a full scale layout of the patterns in Microsoft Word (you can get very precise when you scale lines to the actual size) and then printed the patterns and applied them directly to the parts with some cheapo gluestick - then drilled the holes. I staggered the hole sizes (symetrically) and then finished them up with a chamfer bit.

What gauge flat stock did you use for the rear stabilzer bar? That's exactly what I'm thinking of doing.

[joeyboy]

I accept criticizm for this question, but what do the lightening holes do?  They sure look really cool.

[Kev Nemo]

Lighten stuff.

[joeyboy]

Oh yeah, that makes sense.  But how much weight do you lose really?  It looks great, but functionality is in question on my behalf.  I am not doubting those who do it, just curious.

[Kev Nemo]

You know, I'm not sure. There's a thread sticky for the CR's and I'm not seeing a ton of lightening holes there. Maybe someone with more info can fill us in.

[ajinreno]

They are more aesthetic than anything else...don't really lose that much weight. If you really want to lighten your bike, start eating more salads and go to the gym.

[Tower]

drilling the brake disc helps prevent warpage and fading, dissipitates heat faster.

[KB02]

drilling the brake disc helps prevent warpage and fading, dissipitates heat faster.

Yeah, on a disk, the holes actually have a function. Otheerb than that, they look cool. Weight wise, you're really talking ounces unless you have so many hole in your bike that it looks like swiss cheese, then you might have save a pound or two and the bike might not be safe to ride. The theory, though, is an increased power to wieght ratio: The more power / the less weight the better.

Don't drill too many holes in your brakes, though, or you risk loosing enough braking area on the disk to acurately stop the bike.

[andy750]

As tower mention drilling the front brake disk helps dissipate heat faster. Rear drum and sprocket cover holes are for looks only. However, drilling the rear drum (and front sprocket cover) has the potential to let in water leading to reduced braking performance on the rear...possible corrosion. Of course if you never ride it in the rain then thats not an issue.

cheers
Andy

[Gamma]

500rpm is the maximum I run cobalts where I work. If you run them too fast the cutting edge can be easily ruined in an instant. 

[pablo78cb550]

the best i've seen.

[void909]

Who did that and how?

[troppo]

looks bloody good, looks like its been milled.

[pablo78cb550]

i can't remember. but one of the guys on here bought one for his bike on ebay.
but yeah, it's milled.

[merc2dogs]

Judging by the radial pattern in the middle, I'd have to say it was done on a CNC mill. The rest could be done on a regular mill, or on a good sturdy drill press with side cutter bits.

Ken.

[bradweingartner]

There is not radial pattern, those are reflections!

[CrisPDuk]

Damn and blast, I thought I'd finished with the polishing and machining, I'm definitely going to have to get my sprocket cover done like that

[eurban]

The GL 1000 rotors on the front of my 78 750k have been significantly drilled.  They were actually an ebay score from years ago but they have been in service for over 3 years and work quite well with solid braking performance.  The holes reduce the weight of each rotor by about 1/3 . . . .

[MCRider]

The GL 1000 rotors on the front of my 78 750k have been significantly drilled.  They were actually an ebay score from years ago but they have been in service for over 3 years and work quite well with solid braking performance.  They reduce the weight of each rotor by about 1/3 . . . .

Those look very nice! As does what can be seen of your bike!

Another additional approach would be to have them thinned as well, knocking off as much as another 30% (from original weight). Less unsprung weight improves braking and overall traction.

[eengler2]

Less un-sprung weight improves steering/handling, not necessarily braking. I would imagine, on the single rotor front ends, thinning would surely result in warping the rotor when trying to stop these behemoths repeatedly without cool down.

[MCRider]

Less un-sprung weight improves steering/handling, not necessarily braking. I would imagine, on the single rotor front ends, thinning would surely result in warping the rotor when trying to stop these behemoths repeatedly without cool down.

Indirectly improves braking through better wheel control and traction, especially on rough surfaces.
http://en.wikipedia.org/wiki/Unsprung_weight

Single rotor perhaps though I would doubt it. The disc is much thicker than it needs to be. Mine is a dual disc admittedly. I had them thinned to the legal limit in 1975, influenced by an article at the time interviewing Yoshimura I think.  I road raced for several seasons, drilled many holes in them and then put at least 50k on the street. Plan to use them again on current project. I am talking about a K2. You made me look and all my newer bikes have thinner discs than a stock K2. But my 76F appears to have very thin discs as well.

The rotors in question (a 76 or later GL1000) may already be thinner, if so never mind. But the early Ks are too thick IMO.

But its a question for each to answer for themselves.

[Accolay]

Has anyone used this guy off Ebay?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=160272391778&indexUR
L=0&photoDisplayType=2#ebayphotohosting

I'm concerned about getting someone who knows what they are doing. Don't want it over drilled and weakened.

[fuzzybutt]

i've seen too many rotors crack between holes. i think i'd much rather have a slotted rotor that drilled and not the slots all thw way through, theyre more like grooves. i ran powerslotted rotors in a mustang lx i used to have and they did make a difference when hauling down from 120 mph+

[Terry in Australia]

Those discs look pretty good, there was another guy on EBay who also "surface ground" the discs to ensure no warping and an excellent braking surface, but I think he was a bit more expensive.

The old SOHC4 discs are so thick and heavy, drilling them is a great way to reduce unsprung weight and disc heat, and improve your bike's braking performance.

I did my own, but it was a shiite of a job, even using cobalt drill bits at super slow speed I destroyed two drill bits and had to sharpen them every couple of holes, so I'd be happy to pay 60 bucks a disc for a good job. Cheers, Terry.