Cutting Airshaft

FrankV

Active Member
If you're doing this for school and have access to a machine shop and a torch, why not use it as an exercise in how to make a tap? O1 and some scrap material to test it on(whatever the air shaft is made of) and you have a learning opportunity. They're not too difficult to make, just a little time consuming. I was never trying to discourage you from doing it, just wanted to let you know of any potential issues before you jumped into it.
Unfortunately the school doesn’t have quite enough equipment to get that done, definitely not discouraged though and I’ll see what I can get done. My current dilemma is getting the bottom unscrewed. It feels pretty much welded on, this should be fun
 

Rocksrgood4u

Active Member
Unfortunately the school doesn’t have quite enough equipment to get that done, definitely not discouraged though and I’ll see what I can get done. My current dilemma is getting the bottom unscrewed. It feels pretty much welded on, this should be fun
I think the margin of error of yer sag setup would be at least +/- 5mm. Maybe a tad less air...
 

FrankV

Active Member
I think the margin of error of yer sag setup would be at least +/- 5mm. Maybe a tad less air...
Actually one of the reasons I wanted to try this out is because my sag is currently 25%, and adding 5mm will allow me to sag of out to get around 29% sag. Not doing it because I “need” more travel.
 

Patrick

Overthinking the draft from the basement already
Staff member
Get out the metric BF tools!

we'll get it open.

and maybe a torch!

I like this project.

so if you sag that much, with a larger chamber, what will it do to the curve? will it need a bunch of tokens?
 

FrankV

Active Member
Get out the metric BF tools!

we'll get it open.

and maybe a torch!

I like this project.

so if you sag that much, with a larger chamber, what will it do to the curve? will it need a bunch of tokens?
I always have ran my suspension softer, so I usually put 4 tokens up front. I’ll up it to 5 if I increase the sag. Tomorrow will be my attempt to take apart the 150mm airshaft. If I can get it apart I’ll order a 170mm to go ahead with the project
 

jklett

Well-Known Member
If we are rethreading air shafts, the correct tool needed is a die, not a tap. External thread vs threaded hole. Most above-crappy ass level dies are split and somewhat adjustable with a set screw. If the specs quoted are correct you should have more than the 0.004” per side adjustment needed to get to 0.305” dia.

Or just start off threading the new section a few thou undersize, and you’ll prolly come out right on anyway.
Or you could just skim the major of the 5/16” thread a couple thou and file file file nice-a nice-a but that’s the hack way to do it.
This whole job is likely an exercise in futility anyway so hack at it...
The part he wants to shorten is internally threaded. Otherwise you are right about the adjustment on split dies.
Unfortunately the school doesn’t have quite enough equipment to get that done, definitely not discouraged though and I’ll see what I can get done. My current dilemma is getting the bottom unscrewed. It feels pretty much welded on, this should be fun
The stud is red loctited(again, as per the drawing), heat it to break the bond. You will probably need to replace the o-ring, part number and size are listed.

Now I'm really interested in seeing how this works out. If you do need a tap made, there's a way to do one with just a lathe and a pedestal grinder. It won't work for production runs but It'll be fine for a one off like this.. PM me if it comes to that, I might be able to help you out.
 

w_b

Well-Known Member
Ok then, now I see. I looked at a pic of the airshaft online and didn’t realize the end was a stud threaded into it.

We’re talking the thickness of a piece of paper around the OD here. So stick with the 5/16-48and use a conventional (not a bottoming) tap. The red loctite will make it all good in the end anyway.

Unless of course you ever need to get it back apart.

The best answer was to change the air pressure in the fork. Easy peasy, same end result, and best of all, reversible.
 

FrankV

Active Member
UPDATE: Took it apart, heat definitely worked! Appreciate all the feedback as well.
So after being able to take a look at it, there will have to be three things done to the air shaft after it is taken apart.
1. I will have to first take off 5mm from the end of the shaft
2. I then will have to cut threads a few millimeters further, going to check if the school has the tap that is close enough to the original so I can chase the current threads then tap new ones.
3. I will then have to drill a 21/64 recess in the inside to allow room for the seal and metal bit at the beginning of the threads, all is pictured below.

Once I can confirm that the school has what I need, I will order a 170mm airshaft and get started. If there is any flaws you guys see, lemme know!
 

Attachments

Last edited:

Ryan.P

Well-Known Member
Team MTBNJ Halter's
Would it be easier to space a 160 to 165 ? Also have to consider how the positive and negative chambers equalize. I'm not to familiar with fox airshafts but if its not right the fork will have poor performance.
 

FrankV

Active Member
Would it be easier to space a 160 to 165 ? Also have to consider how the positive and negative chambers equalize. I'm not to familiar with fox airshafts but if its not right the fork will have poor performance.
Spacers don’t apply to the new stuff so cutting is the way. Chambers shouldn’t get messed up, they seem to be the same
 

Ryan.P

Well-Known Member
Team MTBNJ Halter's
Spacers don’t apply to the new stuff so cutting is the way. Chambers shouldn’t get messed up, they seem to be the same
I'm not talking off the shelf spacer . Make the anchor that ties the air shaft to fork lower 5mm longer
 

FrankV

Active Member
I'm not talking off the shelf spacer . Make the anchor that ties the air shaft to fork lower 5mm longer
Definitely see what you mean, wouldn’t that just raise the riding eight without effecting travel? The length of the goldish shaft seems to be what the piston is sliding on and dictates travel.
Maybe I’m just confused though
 
Top