Topic: Cross Drilling Rotors

[Hockers Choppers]

Here is what mine turn out like. Took a few hour on the press. but I think they turned out OK.

[kghost]

Nice job...I really like that decreasing spiraled hole sizing...very attractive

[Bob Wessner]

I second that, looks very good!

[ElCheapo]

I'm thinking of drilling my rotors myself, but i'm not sure if I have the right machine for it. I have a machine that looks similar to this at work:
.
But it doesn't spin that fast, maybe it's a machine for wood. What RPM is likely to work?

Somebody have a pattern they want to send me?           ivar.eisma@euronet.nl

This is about the size rig I am using. Works very nice for rotors. I see a lot of very nice patterns in this thread.

[SD750F]

I do like the spiral design with reducing hole size! Exactly what I want to do to my 3 rotors (78 CB750F). Okay here is my problem. I am an engineer, so as you can imagine I am a perfectionist! Yeah, I know, sterotype and all. But I would want to drill mine on a end will with an indexed platter so I could do one ring every 40 degrees (9 holes around), then offset let's say 10 degrees, and move the table over 400 thousnads and do the next ring. Not what I would really use as far as actuals but just for the discussion.

So I am thinking a known machine shop, or at lease a friend with the right equipment that would let me use his (or her) stuff. Well, do you think I am overthinking the process??? Or can you guys supply some examples of how you marked the rotors without using CNC equipment...

Scott

[Hockers Choppers]

I used a 12 hole pattern because I used a clock face to lay it out. increased the size on a copy machine untill it was big enouph to fit the rotor. marked out the big holes on the hour marks and stepped down ( just enouph to overlap the holes a little ) for each minute mark.

Also I have an extra set of stainless steel brake lines that will fit a 77-78 cb750f if you want to upgrade?
They work great. I put a set on my bike.

[ElCheapo]

I will be making a "Homegrown" video and providing it on line to help demystify this mod for the new comers. It is not all that hard, and the truth is if one of your holes is only a tiny bit off, the only people who will notice is well is no one..... Unless they are crawling on the ground around your bike with a dial caliper. 

[Hockers Choppers]

yeah, I got off a spot on the rear disc ( the one I did first ) and I can't even find it unless I look for it. I've shown a few people and they don't pic it out. Won't see it going down the road at 120mph I bet

[Jinxracing]

So I am thinking a known machine shop, or at lease a friend with the right equipment that would let me use his (or her) stuff. Well, do you think I am overthinking the process??? Or can you guys supply some examples of how you marked the rotors without using CNC equipment...

Scott

Well Scott, if you're in Southern California I've got a mill and rotary table that you're welcome to use. I'm pretty obsessive about details too, but in this case I'm more concerned with the quality of the holes and chamfered edges from a safety point of view than I am about perfect hole spacing down to .001". A ragged hole or chamfer with chatter marks–even on a very small level–seems to be an invitation for stress cracks (less likely on stainless rotors than cast iron I gather), but man, the thought of a rotor coming apart under braking makes a certain orifice pucker big-time!  I'm not an engineer though, so maybe I'm all wet on this one. 

I think the rotary table method, while certainly precise, isn't the way I'll be going. Just too time-consuming. A quality drill press should do just as good of a job, assuming the table is square to the spindle and TIR ain't too bad. 

I'd take a round piece of 1/2" thick aluminum plate slightly larger than the rotor with a 1/2" hole dead center, then mount a 1/2" pin vertically on the drill press table to act as a center for the aluminum disk. Then it should just be a matter of slapping on a big hunk of double-sided carpet tape to hold down the rotor (also centered) and marking the edge of the disk with a number of increments equal to the number of holes needed. A strip of paper printed on the computer could just be wrapped around for that. Index those marks against a fixed reference point on the drill press and start drilling and turning. 

I've used this method on other projects with success but haven't actually done it yet to my rotors, so like lots of projects this could easily be derailed by reality. 

[kghost]

I cheated 

I found a modern rotor the same diameter with holes in it.

Drilled two holes thru the 750 rotor... bolted them together and went to town 

[Hockers Choppers]

Hey kghost, Forget about the rotors, how in the hell do you pull that big ass wheellie?!!?!?!?!?

[kghost]

Hey kghost, Forget about the rotors, how in the hell do you pull that big ass wheellie?!!?!?!?!?

In a nutshell...I twisted the right grip 

Seriously...proper component selection and assembly when I built the engine.

Theres alot of great posts on this site for making horsepower. Trick is separating the retoric from the useful.

[Hockers Choppers]

Here is what I have planned this winter.
78f bottom end
76 top end
wisco 836 kit
springs & retainers
adjustable cam gear
webcam 63a     .370 lift, 282' duration
cr carbs
dyna ign with coils
mac 4-1

[ElCheapo]

I cheated 

I found a modern rotor the same diameter with holes in it.

Drilled two holes thru the 750 rotor... bolted them together and went to town 

I do this sort of.... I lay out the disc on 1/4 aluminum because that is what I had and basically did the same thing you did only I transferred to the aluminum so I can make the pattern later with transfer punches. Sure makes the whole job go so much faster. 

My question for the wheelie is a how also, but How do you keep fork seals in her doing wheelies?  I have blown two sets this season but I was doing them pretty regular.

[ElCheapo]

One important point that has been over looked.

WEAR SAFETY GLASSES WHEN DRILLING THE ROTORS. 

Better stopping power means nothing if you are blind and cant ride

Very good point. Good to see you back. And I welcome you.

[Hockers Choppers]

Very good point with the glasses. A lot of use take for granted drilling at slow speeds that nothing will fly off too fast. But with the hard stainless little shards of shrapnel will fly of the bit pretty fast and hot!! I'd recommend some light gloves and a long sleeve shirt also.

[cben750f0]

i would not recommend light gloves.... ever seen what happens when a peice of swarf gabs hold of a glove?.... mate of mine is two fingers down b/c of gloves and a drill..... just a though.... would much rather stitches than missin fingers.... BTW and a fitter and turner by trade, and have been for the last 14 years.... so just lettin you know....

peace

[Hockers Choppers]

Yeah, I got to thinking about that after I posted. A long sleeved shirt is not a good idea either unless it is tight fitting and won't get caught in a bit. Another neat idea is running a sewing machine switch ( foot operated ) so you can step off of it to stop the drill if you get in a bind.

[SD750F]

Well I have reviewed all the responses up to date, and I really do appreciate the suggestions. With some of the ideas focused on using a template, I think I have a solution that will work great. I have another friend that owns a water jet cutting business. I will supply him with a CAD drawing of the pattern that I want to use with all holes on the pattern having the same internal diameter. He will cut this out of an aluminum plate with other provisions to center this plat to the rotor. The internal dimeter will be the correct dimension for a drift pin that I will use to mark the holes on the rotor. After this operation, remove the guide plate and use a good slow speed drill press with the correct drill and counter. I will tape over the holes that are not the size that I am currently drilling so to reduce the chance for mistakes. Counter sink and be done...

How many of you suggest that I have the rotors machine shop turned or precision wet grind? I have even seen where someone ground a spiral pattern into the face ( I do not like that myself).

Scott

[ElCheapo]

i would not recommend light gloves.... ever seen what happens when a peice of swarf gabs hold of a glove?.... mate of mine is two fingers down b/c of gloves and a drill..... just a though.... would much rather stitches than missin fingers.... BTW and a fitter and turner by trade, and have been for the last 14 years.... so just lettin you know....

peace

This reminds me of the scene on American Chopper where Rick got his hand ate and wrapped around the drill press head. Just a guess, he would have gotten little more a scare and maybe a nick if he had not been wearing those gloves.

I would reccomend that you have them turned just a little (enough to remove the majority of the flaws on the surface). Just a tickle.

Also turning rotors too thin will cause issues with caliper piston hanging up as it will be over extended. You may not notice this until the pads get a bit on the thin side.

I can not find my min max specs for the rotors right now. Someone please post the specs if you have them.

[super pasty white guy]

looks like the rotor thickness standard value is 6.9-7.1 and minimum is 5.5 mm

dave

[Soos]

Only use cobalt bits!! carbides will not even touch the stainless steel rotors. Regular high speed steel bits will drill 2 to 3 holes at best. COBALT COBALT COBALT!!!!!! at slow speed with some oil, don't let them get hot. You can't go wrong ( hell, I did it ).

Being a machinist who uses carbide on a variety of stainless steels on a daily basis.
I have to say carbide WILL work on stainless including 316,410annealed/HT,416 annealed/HT 420 annealed/HT, alloy20, nimonic, hasteloy, inconel 600, stellite as well as other exotic stainless steels.

IN A MILL!(with SF/m ranging from 100 to 270 SF/m depending on material)

With *LOTS* of coolant(preferable through the tool coolant at 900+psi).


Sorry, i'm bored at work... waiting for machines to end their run.....


Anyway, cobalt does great in most stainless steels at a Surface Feet per minuite(SF/m) of 40-80.
RPM=3.82Xsurface speedXdiameter of drill(in inches)
an example would be - 3.82X40/.312(5/16 drill)=488rpm
                                 3.82X80/.312(5/16 drill)=977rpm
that will give you a good speed to start with.

With little coolant(ie. tap magic or other oils) you want to stay on the lower end of the SF/m (40'ish)
With no coolant/lubricant, try around 15-25 SF/m.(careful not to burn the bit)
                       
thought i'd pitch my .02 in(i know this is an old thread.... )

If you were intoning that carbide will not work on a home drill press, mostly you are right.
Carbide will drill through virtually anything given the right conditions.
It is impossible(or nearly) to emulate the correct conditions to use carbide on a home drill press.
A small knee mill with flood coolant will suffice, but for cost, cobalt is better unless you have access to free bits, and the proper machine.

l8r

-=Soos=-

[JohnG]

Many years ago I was road racing a 1979 DOHC 750 Honda and decided to drill the disks over the winter.  Seemed like a good idea. This was about 1982 or so. At that time, almost any shop did 3 rows of 35 holes (usually 1/8") staggered by 5 degrees on the middle row. The going rate was about $60-$80 per disk and the 750 had two so being a mostly self sponsored rider, I attacked it myself. (if you have done any racing, you never have enough money...)

The people who have responded here know much more about drilling than I do so there is no point in repeating what has been said. I did however learn one thing that I will pass on.

If the disk you are drilling has had a very hard use life, independent of its thickness or condition, it may have gotten hardened and you will have a heck of a time getting through it, no matter the type of drill.  I found that on my inner rows, the going was just awful while on the outer row it was pretty straightforward. I finally investigated the possible reasons and ended up realizing that the heat had case hardened the stainless steel towards the center. I can't even begin to tell you how many bits I went through (carbide was the best) but it was a darned good thing I had all winter! Once I got through the first few thousandths of an inch, the rest of the hole was reasonable...

Moral? If I had to do it over, I would hunt down some low use disks, check out all specs and go from there.  The stock SOHC disk is more massive than the ones used on the '79 DOHC so the problem I ran into may rarely occur, if at all.  But I have to say I will not forget those disks!

              John - MA
         John - MA

[Dragman836]

 For you that dont have all that fancy stuff and want to do your disks. I just used a $59 drill press from harbor freight and made a template from paper using a degree wheel (or use a good compus) .Make your marks on the paper templete , carfully tape the template to the disk using areas of the paper without marks on it and  putting holes in these areas. then take a sharp center punch   (I used a tap from tap and die)and transfer your marks. I then used a reg. high speed 1/8th in. drill and just started into the disk enough to get a drop of oil (syn.) in. then you got your pilot hole and I used both reg. high speed and cement(carbide) tipped to finish the job while using synthetic oil to lube the bits and had the drill press set at its lowest rpm setting (around 600).
You can check out my work on the front of Pro Teals 750 double disk front end.
Also if you plan on doing it more than once transfer that pattern to a sheet of aluminum cut out to a circle w/ a hloe to fit around the center of the disk . And for those good with computer cad programs , use it to make the template
Thank You
Dennis

[KRONUS0100]

a buddy did mine in a machine shop on a cnc endmill.  Broke 5 5/16 bits before he finished all 3 rotors.  we also did not countersink the holes, and 5000 miles later have had no problems. We have since done his sons kz650, his cb550 chopper and are getting ready to do my GL1100. and have not broken any more bits.