Drilling rotors

[racerdave]

Family time today, maybe tomorrow. I only need a rear done. I have a drill press and all needed bits. It 's the actual template I'm having trouble with. I opened the link for the pattern, and then went into my printer, I can't find anything that says reduce to 90% or anything along those lines.

 

[kvanderploeg]

Open the template with Adobe Reader. Go up top to "File", then "Print". Next to where it lists your printer, click the "Properties" button. On my HP printer, there is an "Effects" tab. Under the "Effects" tab select the button for "% of Normal Size". Enter 90 in the box, print 4 of them out and see how they line up. 90% worked well for me, but you may want to adjust.

Kent

 

[racerdave]

I don't have that option in my HP shop printers toolbox . I have another newer printer in the house, I'll see if that has it.

 

[jd750ace]

Guys, if possible, when drilling an iron rotor, keeping the speed below about 430 RPM maximizes bit life, and reduces the risk of smoking the bit. At the proper speed and feed, any decent High Speed Steel bit will work. Drill pilot holes first, somewhere around 3/32 to 1/8 inch. Guides the bigger bit, and reduces heat build-up. My understanding is deburring or chamfering the holes causes them to retain debris in the holes, and can make gooves in the pads. If you drill part-way through each hole from each side, there will be almost no burr on the hole. That's how we drill acrylic on aircraft windows, to avoid big burrs, and a crater type blowout on the back side. Not much danger of that with an iron rotor, but it makes a nice clean hole edge on both sides, no deburr required!

 

[tonyc]

I used masonary drill bits.

 

[jd750ace]

I suppose that masonry bits will work, but that's more of a rotary chisel than a drill bit! If they have a tungsten carbide lead plate, it probably does just fine, but certainly not a first choice for me.

 

[tonyc]

I also use them on spring steel.

 

[mitchp]

Vice grip makes a clamp like that. It has a stud and eye nut on the bottom so it's easy to move around in the table slots, Mine is always on the drill press.
IIRC the recommendation is don't chamfer rotor holes.

I have drilled several project bike rotors and have always done a light camfer on the holes, but i cant give a good reason why i perform this bit of extra work. AS for performance they seem to work fine. Heck chamfering gets rid of a few extra grams of unsprung weight. , Mitch

 

[mitchp]

I don't have that option in my HP shop printers toolbox . I have another newer printer in the house, I'll see if that has it.

Dave, I have done several rotors out my home shop. As for the pattern i use a drawing created on a drafting table, useing a basic drafting tools. I take the pattern on the paper and transfer it to a thin sheet metal ring that matches both the inner and outer diameters of the rotor, useing a light punch. Start with a small bit and work uo bit size till you end up with a desired hole size. By the time you complete your job, you will have an oily mess of drill shavings to clean up. Its also loud as hell (ear plugs) and the sound can remind you off the fingernails on the chalkboard. Mitch

 

[52Chevy]

I'm glad there are patterns out there for this, I have been considering it myself. And I like your choice of the holes getting smaller as you go outward

 

[DirtyErnie]

These rotors should be stainless.

I think I drilled mine with a 1/4hp and very old drill press. 1/8" pilots and 1/4" final. Just keep the heat out of the bits and it will all work out. Both bits I used are still plenty sharp, just doused the 1/8" in water between holes. With the 1/4" I drilled two holes, shut the press off and wrapped a wet rag around the bit until it stopped hissing.

 

[jd750ace]

If the chips start turning brown, a blue squealing bit ain't far behind. 400 RPM or less for steel. Low speed, medium feed.

 

[DirtyErnie]

These rotors should be stainless.

I think I drilled mine with a 1/4hp and very old drill press. 1/8" pilots and 1/4" final. Just keep the heat out of the bits and it will all work out. Both bits I used are still plenty sharp, just doused the 1/8" in water between holes. With the 1/4" I drilled two holes, shut the press off and wrapped a wet rag around the bit until it stopped hissing.