Specialized rear shock "Brain" rebuild with pictures & now forks too

link1896 said:
Started working out how to make schrader valves from scratch. I've the taps and dies but can't for the life of me find a tool for cutting the valve seats.

Going to file/turn a drill bit into a form tool for the 16 degree valve seat.


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First attempt would have made Homer Simpson proud. Not a smooth surface to be found on the 17 degree seat. Tricky stuff.
 
link1896 said:
First attempt would have made Homer Simpson proud. Not a smooth surface to be found on the 17 degree seat. Tricky stuff.
Click to expand...

Started works on a new, carefully ground form tool, using diamond files I'm getting there.

Getting the back relief right, and both cutting tips on the same angle is the challenge.
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Specialized rear shock "Brain" rebuild with pictures & now forks too

Tada

Happily holds 300psi. Bloody tricky bastard to machine.

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You have done well to figure out all of this. Your machining skills are very fine. Good work sir :)

Sent from my F5121 using Tapatalk
 
Thanks gents.

Next trick is to make a replacement for the bottom of the forks Brain cartridge with a schrader valve and thread.

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slowmick said:
that's a whole lot of dedication to solve problems sir. love your work. :thumb:
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nah, we're into the mod/fun region now.

The lower rod with a schrader valve lets me tune IFP pressure. But my real motivation for mastering schrader valves is so I can make dual air piston assemblies for a bunch of forks that never had dual air.
 
ok - i'll bite - that's an awfully deep hole or a hole at the end of a very deep recess. or maybe you've run out of room in the shed and you have to drill from outside...

Idiot in suspense. :madgrin:
 
slowmick said:
ok - i'll bite - that's an awfully deep hole or a hole at the end of a very deep recess. or maybe you've run out of room in the shed and you have to drill from outside...

Idiot in suspense. :madgrin:
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Plan is to drill a 135mm deep hole. Couldn't t find any 4mm x 200mm bits so found this 4mm x 350.

Will probably cut it down to 200 long and reshape the cutting edges for less aggressive profile.
 
It is exceedingly difficult to accurately do deep holes with a long drill. 135mm/4mm is almost a 34:1 ratio. If drilling a blind hole your accuracy will be terrible. If enlarging an existing hole you may have more success and drilling half way from both sides (if it's through hole) may also help. Shortening the drill will be a must, but re-grinding the end so it cuts straight will be no mean feat in itself. With the workpiece in the chuck and a 4mm drill in the tail-stock hanging out say 150mm you can probably measure some droop to the tip of the drill just under gravity. As you put pressure on the drill to start cutting it will also bow.

Can you make the through hole larger in diameter? Can you get some hollow section (tubing) that'll get you close and then machine end caps? Like the way the older RS steel rebound rods are done?
 
Hey good to see you're about summitfever

With 150mm long 5mm bits, if I start my hole with another short bit, then swap to the longer bit, I'm happy with the accuracy. One way to find out with 4mm.

Working with 2011 ally, it machines very nicely and I can go very slowly

I've a drill bit doctor that achieves very accurate drill bit sharpening/resharpening, should be ok shortening the bit, I managed to shorten a cobalt bits with it and kept the symmetry.

If one solid piece cannot be machined, I will be looking at two/three part assemblies.

The part I'm trying to recreate is four post up next to the ruler.
 
Sweet. What goes in the 4mm hole? Just an air passage or will it have an adjuster rod going through? If its an air passage then drill 1/2 way from both ends and the run-out in the middle won't matter.

2011 is great machining but we've never had any trouble with the other alloys. Use metho as a cutting fluid (just brush it on little by little using small paint brush) and you will achieve the most amazing finish. 2011 contains lead and bismuth which actually melts as you machine it to facilitate chip breakage, but both are toxic so take care with the shavings etc.

Keep up the good work...
 
SummitFever said:
Sweet. What goes in the 4mm hole? Just an air passage or will it have an adjuster rod going through? If its an air passage then drill 1/2 way from both ends and the run-out in the middle won't matter.

2011 is great machining but we've never had any trouble with the other alloys. Use metho as a cutting fluid (just brush it on little by little using small paint brush) and you will achieve the most amazing finish. 2011 contains lead and bismuth which actually melts as you machine it to facilitate chip breakage, but both are toxic so take care with the shavings etc.

Keep up the good work...
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Just air, this is to bring the IFP charge out to a schrader valve at the bottom of the fork.

I will be drilling from both ends, my ebay purchase of a 100mm long 4mm bit arrived, the 350's go on the shelf as a novelty for now. Yah for Chinese cnc ground cobalt bits, astounding quality for 5 AUD.

Thanks for words of caution regarding the safety of the swarf, had not considered the health concerns.
 
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