Author Topic: Drilling Rotors (Read 69084 times)

kaceyf2 · « **Reply #50 on:** May 19, 2006, 02:18:33 PM »

Hya guys, aint it just great when a tool that you purchase totally surprises you with its performance??
Like a tool that dont break, bend, go blunt, or snap?? WELL, I sure bought a few last week!! And I gotta tell you all about them!
I wanted to drill holes in my rear disc AND my front ones on my F2 sohc cb750 (what else eh?)
I knew the discs were gonna be TOUGH big time! ANd I knew that the rear disc would be THE toughest (being twice as thick as the front ones) So.....
Just for fun (and a stupid,repeat STUPID vain HOPE ) I thought I would see what my "normal" Hss twist drill would do......so I tried on the rear disc..OW, OOOH, horrid SQUEALING (that made the dog run under his bed ! and SHAKE big time!) and the result was a blunt drill IN nano seconds!!! (as expected) Then i bought an "ALLEGED" repeat "alleged" 5% cobolt drill.....Hmmm, even with cooling fluid it must have had the thinest coating of cobolt in the world, because it lasted 1.5mm deep in the first effort and promptly died, all the cutting edge chipped and broken.....USELESS!!!!

THEN, i came accross a guy that was selling cobolt drills purloined from the aircraft industry, he assured me that they were up to the job, and that they were for drilling STAINLESS, TITANIUM, and other "hard as F*** metals" that one may come accross.....
"Hmmm" I thought, " Hope hes telling the truth, cos if he is, thats what i need!! I thinks to myself....
Well, I had made up a template (for were the holes were supposed to be if I found a drill that could cope etc etc) and had glued it on the disc with upva adhesive (any "white" wood glue will do,the stuff thats water soluble!)
I had then centre punched the holes with a centre punch, (believing the template would peel off and get totally messed up with the cooling fluid, but as an aside it didnt,because the oil I used as a cooling fluid didnt affect it!!)
ANYWAYS, Then came the moment of truth,
into the chuck on my pillar drill went the new drill , rear disc was clamped to the drill table, and can of oil in hand I started me drill........WOW, like the proverbial hot knife through butter!!!

I must admit, I went in about 2mmm, then back out, oiled and then back in 2mm or so,oiled, and went on like this, lots of oil, lots of gently backing off and checking,
I didnt let the drill squeal for lack of oil, i didnt let the drill get hot, And I had my piller drill on the slowest speed, which on mine is 600revs per min.
SEVENTY TWO HOLES LATER, yep, thats SEVENTY TWO HOLES LATER IN ONE OF THE HARDEST BITS OF MY BIKE, AND THE DRILL BIT IS NOT EVEN MARKED!!!!!

MY god, something thats OUT PERFORMED ALL expectations, something that does MORE than it says on the label/ tin!!!

I was so happy, i got me misses to take pics for you guys should you be interested!!!
I was so happy, I carried on and did my front discs, but as these are twice as thin as the back one, i only gave them thirty-six holes each as opposed to the rear discs seventy two!

This has really given me faith back in things, as lack of funds has persisted over the last year or so,and made a mess of my biking plans!
I wanted the discs drilled for both water dispertion, BUT also more for asthetic reasons, and I could not afford the machine shop to do this work!!! GREAT< CHUFFED< HAPPY AGAIN!!!!
if anyone is interested, i put up some photos on photo bucket of the job here is the link to them....

http://s83.photobucket.com/albums/j294/kaceyf2/

scunny · « **Reply #51 on:** May 19, 2006, 02:35:20 PM »

good job, might have to try that myself

cb650 · « **Reply #52 on:** May 19, 2006, 02:47:42 PM »

Thats how i did mine but with a regular hss drill. We have a decent sander to sharpen them.

Terry

SteveD CB500F · « **Reply #53 on:** May 19, 2006, 11:58:08 PM »

Kacey (welcome back by the way...)

Did you champher the holes? If so, with what?

Terry in Australia · « **Reply #54 on:** May 20, 2006, 06:20:30 AM »

Nice job Karl, has your dodgy mate got any more of those "purloined" drill bits? Ha ha, Cheers, Terry.

Tim2005 · « **Reply #55 on:** May 20, 2006, 02:04:20 PM »

Any idea what make that drill bit is? Sounds too good to miss out on.

historicjake · « **Reply #56 on:** May 21, 2006, 04:49:59 PM »

Just about done with my weekend dual disc brake conversion project that I started two months ago....now the question is should I drill my discs or not? How much difference does it make? Do it myself or farm it out? Those discs must be pretty hard, what bits are needed? Anyone done this recently...

caferacer550 · « **Reply #57 on:** May 21, 2006, 04:57:44 PM »

I say drill them for sure.
The weight issue and they look cool.

Seems like drilling stainless steel is a bit of a pain.
I sent them out to a machine shop.

cbjunkie · « **Reply #58 on:** May 21, 2006, 05:03:34 PM »

do a quick topic search - there is a brand new thread, as of two days ago, about best practices drilling rotors...

ProTeal55 · « **Reply #59 on:** May 21, 2006, 06:23:35 PM »

Drill em....

HondaMan · « **Reply #60 on:** May 21, 2006, 09:34:47 PM »

With dual discs, drilling rebalances the braking pressures and tends to reduce the locked-disc tendency. Be sure to chamfer the holes, both sides. You will lose some braking efficiency, but in the wet, they will grab a little sooner because the water wipes out faster, into the holes. You will also experience shorter brake pad life.

cben750f0 · « **Reply #61 on:** May 21, 2006, 11:48:07 PM »

drill them m8, if for no other reason than it looks coolll...peace

Steve F · « **Reply #62 on:** May 22, 2006, 02:37:04 AM »

Need I say any more?

KB02 · « **Reply #63 on:** May 22, 2006, 05:08:50 AM »

Drill 'em!

The holes help cool the disk faster during heavy braking thus reducing brake fade.

And, I mean, besides... Take a look at Steve's picture. How you could you not[/i] when they look that cool?

ProTeal55 · « **Reply #64 on:** May 22, 2006, 06:59:26 AM »

Here's mine

cben750f0 · « **Reply #65 on:** May 22, 2006, 01:22:19 PM »

ok heres a pic of mine....

..peace...BTW its the same pattern as the CBR's... and i have an autocad profile if you whant to chuck it on a CNC machine..peace

Peter · « **Reply #66 on:** July 28, 2006, 10:30:55 AM »

I am cutting weight anywhere possible, and I know that I can drill "speedholes" in the drum cover, but has anyone drilled the actual braking surface in the rear. I can't imagine a couple well placed holes would hurt anything (if like the front rotor it would improve braking), but I have never heard of anyone doing this. Feed back is eagerly awaited.

marvsho17 · « **Reply #67 on:** July 28, 2006, 10:37:10 AM »

meh, I wouldn't do it. Drilling holes in the rotor surface decreases the surface area contact pad with the rotor. Cross drilled rotors are mostly for looks.

KB02 · « **Reply #68 on:** July 28, 2006, 04:46:03 PM »

Plus, drilling the rotor helps the disk to cool better and thus reducing brake fade when they get hot.

I've never hear of anyone drilling the drum... Don't know that I would recommend it...

OldSchool_IsCool · « **Reply #69 on:** July 28, 2006, 05:43:55 PM »

I wouldn't drill it ether. And not because of reduced breaking power.

Dynamic frictional force is a matter of weight/pressure and the coefficient of friction of the materials in contact. Surface area has nothing to do with it.

Prove it to yourself. Get a spring scale, some string and a small brick. Tie the string to the brick (not over the surface in contact with the table). Measure the dynamic friction (force needed to drag the brick over the table, take your measurement once the brick is moving). Retie the brick so a different face is in contact with the table. You will see that dragging the brick takes pretty close to the same amount of force no matter which face in in contact with the opposing surface.

Again, I wouldn't drill the drum. That's because I trust that the Honda metallurgical engineers knew just exactly how thick/strong to make the drum to handle the expected forces. They too knew that a lighter bike would make for a faster ride (acceleration = force/mass ... less mass, more accretion!) Like any good engineer, some margin of error (over-engineering) was added, I'm sure, but we're also talking 30+ years of use and fatigue on these parts.

A few ounces of saved weight are not worth the risk of part failure to me. no, I wouldn't drill the drum.

merc2dogs · « **Reply #70 on:** July 28, 2006, 06:51:02 PM »

It used to be a very common mod for offroading, many how-to write ups in magazines, primarily used to allow water, sand, and mud get out of the drum. typically the holes were drilled in a 'spiral' pattern from one edge to the other, not in straight lines.
Quick search brought up a couple examples, here's one:

http://www.chtopping.com/CustomRod4/

Hard to say exactly how much weight it could remove, but the technique is supposed to improve braking to some extent, mostly it's faded out because of the cheap availability of disk brake conversion kits. I think if weight were the reason it''d be easier to remove the fins than to try and pull weight by drilling. Do know that the holes are not very large at all, but I'd assume that since the hub is thicker on the bike it means more weight will be removed per hole.

Ken.

Peter · « **Reply #71 on:** July 31, 2006, 05:49:39 AM »

Thanks a ton for all of the insight.

eldar · « **Reply #72 on:** July 31, 2006, 06:55:45 AM »

Drilling the hub along where the pads contact would be a very bad thing. I am whipped after this weekend of moving in 100 degree heat but i know it has been mentioned on here that people have had their hubs crack on these bikes. You go drilling holes and you will increase the chances of cracking. I dontr know about your but I have a hard time finding parts anyways without having to try and find a whole hub. besides that, what if you are going down the road fast and have to hit the brakes hard and thats when you hib decides to fly apart?

If you decide to do this, can you put me in your will?

One other thing to remember, I have never seen a 500+ pound dirt bike.

Bodi · « **Reply #73 on:** July 31, 2006, 08:08:09 AM »

I've seen this done on period race bikes. I don't know why, I doubt if much cooling air could get through since most of the drum is covered by the shoes. Possibly for weight reduction?
The "speedholes" in the cover and opposite cace of the hub are for cooling, not so much for weight reduction. They do accelerate corrosion of the iron and steel parts inside - the drum, springs and actuator cam. You need to do regualr inspections and lubrication if you allow easy water entry.
I would not drill the drum face though, mostly because the holes will allow water to get at the iron/aluminum interface where the hub was cast onto the brake drum. I don't think encouraging corrosion there is a good idea.

nippon · « **Reply #74 on:** July 31, 2006, 08:17:45 AM »

what an idea.

But if you like and you have not drilled it until yet.
You can drill the rear brake panel like Carpy did it or like
it's on the CR750 race bike.

nippon

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Author Topic: Drilling Rotors (Read 69084 times)

caferacer550

Peter

marvsho17

Peter

eldar