I noticed the rotors don’t seem to have a sonex part number. Does anybody have dimensions for them? In particular the thickness, so I can buy material.
Hi Bryan,
My new rotors are .245” thick and 4.494” diameter.
Best,
Paul
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Thanks Paul! I’m either going to try making a set on the lathe, or maybe the Bridgeport. I have a rotary table. The other thing I need to know is the bolt size. I think they were 1/4” but I’m not sure. I will need to buy tooling for the countersink.
Cotton’s law strikes again 
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ACV-B01-24
Machined Stainless Steel Brake Plate for Hydraulic Brake
ACV-B01-15
Alloy Steel Flat Heat Socket Cap Screw, 5/16"-18 Thread, 3 1/4" Length, Black Oxide
I used the countersink below to clean up the new discs I got from Sonex, but so far haven’t cut any new discs. MMC parts below, and my dxf file attached.
Rusty
brake disc.dxf (10.4 KB)
From McMaster-Carr I ordered the following:
Cobalt Steel Countersink
for Screws, 82 Degree, Uncoated, 3 Flutes, 3/4" Body Diameter
3285A482
each 43.62
Black-Oxide Alloy Steel Hex Drive Flat Head Screw
5/16"-18 Thread Size, 3-1/4" Long
91253A597
packs of 5 5.83
High-Strength Steel Nylon-Insert Locknut
Black-Oxide, 5/16"-18 Thread Size
97135A416
pack of 20 5.44
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Awesome, thanks Rusty! I think I’ll try to make some practice parts in aluminum, just to get the sequence down. Then stainless - and I may try titanium as well.
I worked all that out a few years ago, but wouldn’t have posted it while they were still selling them.
Note that the bolts I got from MMC are maybe 1/8" shorter than the ones I got from Sonex, but I do recall that there was some extra on their bolts. I’ll be changing my discs and pucks in April during the annual. I’ve worn well into the tapered bolt heads.
Rusty
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I mostly need a set for myself, but may do a little production run to fill the gap in the community. Assuming nobody buys the company and restarts production, I wouldn’t want to compete.
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Here’s my tooling to make rotors.
Here’s the sequence as I see it. Clamp up stock in the vise, skim it if needed, drill a 5/16” hole in the center to slide on the dowel pin. A half inch away, drill a 3/16” hole for the hold down AN bolt.
The rotary table will need to be centered, and then when the plate is bolted down it will need to be centered as well. Then indicate the back edge of the plate and turn the rotary knob to make the plate edge aligned with the X axis.
Drill the 5/16” wheel bolt holes, and countersink them. Use short flush screws to bolt the stock to the plate.
Cut out the two circles with the end mill - the outer one, and the inner one.
Face off the braking surface on the table - flycutter stationary and spin the rotary table.
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