scoho

I've got 8mm track ends and a hub with a 10mm axle. Replacing the hub/axle isn't an option.

So, any advice about grinding out the track ends? I've got a flat file, a round file, and a Dremel-style rotary tool with a metal grinding attachment.

I'm especially concerned about getting a flat, even result, both for aesthetics and performance, and I don't have any particular ideas about how to achieve that.

dabac

That's a hand-eye coordination thing. A method that yields a tolerable result for me might not do it for you.

I wouldn't use the Dremel. It's a fair bit of metal to be removed and it'll take some time with the Dremel.
Ideally I'd use a rat tail file with the same diameter as the desired slot width. Hold the file not parallel with the axle, but pointing along the bike as much as possible.a Align with slot and file away.
You can use something like a fine point permanent marker, support the tip and draw a guide line along the inside edge of the dropout.
If I wanted the job done faster, I'd inscribe some help lines, then reach for the angle grinder.

scoho

Given decent hand-eye coordination and a lot of patience, do you think the file method has a fair likelihood of producing a solid result? Would the Dremel be useful for smoothing and fine-tuning at the end?

dsaul

My advice would be to remove all the necessary material from the bottom of the slot. This way the surfaces the axle rests on(top of the slot) will remain parallel to one another, regardless of how accurate you are with your filing.

scoho

Ah, nice point. I had envisioned going half and half, but this makes a lot of sense.

unterhausen

it depends where the extra material is, if there is any. I have never heard of an 8mm slot, is this some kind of historical oddity?

If you cut only on the push stroke with a file, it's a lot easier to make a smooth cut. That's the proper technique anyway. A flat bastard file is what you want, it might be worth going out to Home Depot and getting a new one. The Nicholson files in the green packaging are supposed to be better than the red white and blue packaging files.

scoho

Some (mostly older) Japanese track frames have 8mm slots, plus 110mm rear spacing where the standard is 120mm. Going to have to cold set and align the rear too, but that seems reasonably straightforward.

Didn't know about cutting on the push stroke. Thanks for that.

Andrew R Stewart 

I'll be the contrarian here and take the side of do least harm to the hardest tp replace item, the frame. Sure the slots can be filed down, many of us have done as much to one degree or another to attain best alignment. But that's a lot of filing and once done there's only very costly paths or reversing the results. Instead I would strongly suggest the OP consider filing two 1mm flats on the axle on both ends. Far less filing, you're changing a far less costly part to replace, no need for an real alignment concerns. To my this is a no brainer.


Remove axle from hub if possible, or at least the outer lock nuts. Secure axle in vice or restrain it's spinning if still in hub. Run file over the thread tops at the location the axle will fit within the drop outs. There is a pretty good guide for the amount of material removal needed in that the threads are slightly less then 1mm deep. So file to when the thread just disappears on tow opposing spots of the axle. Test fit in the frame then if more filing is needed only work on one flat, this way the axle's fit up against the drop out's upper face is more easily held symmetrical. The only real challenge is to "clock" the two ends' flats WRT to each other. But since the filing is a slow process the "take a couple of strokes and check" method will work well if a small amount of care is taken.


And to head off comments about the axle/hub's claim of not being replaced... why is that the case? Any other wheel (or hub laced back into this wheel) will work in the future, so why the claim of not being replaceable? Andy.

tuz

The main challenge in filling/grinding the dropouts would be in properly securing the frame. You would need tapered tube blocks and a vise to hold the chainstay as close to the dropout as possible. Otherwise the frame will just vibrate as you work on it. And 2mm is a lot of material to remove, and keeping the cut parallel is difficult.

I second Andy's sugestion to work on the axle as long as it's not hollow.

Edit. I also agree that you should file the bottom of the track ends. But it it has a raised relief it'll look assymetrical. If you know someone with a lathe they could cut a groove in the axle with a parting tool. Just make sure the groove overlaps the locknut and track nut.

CliffordK

With some practice, I can do fairly precise filing (flat file for work like this).

Trying to file between the stays will be a pain, limiting the ability to do full strokes.

I'm mixed about taking off from the bottom only vs top & bottom. Another advantage of only shaving the bottom is that it is less likely to throw the dropouts out of alignment.

Is your rear axle QR or solid? I like Andrew R Stewart's idea of shaving the axle threads, although for a solid axle, you'll have to make a slot between the locknuts and the retention nuts which would be odd, but shouldn't structurally affect it too much.

fietsbob

File sharp and relatively New? Got a file card to clean out the chips?

Bench vise to hold the part at a good working Height?

Longer the better for the file.... and a good handle on the tang?




'/,

scoho

I just meant that I've got to work with the (new, expensive) hub I have now. I can't, for example, return it or put it aside and get a new one with an 8mm axle.

Thanks to everyone for the advice. Andy's points about filing the axle itself are well taken, and my axle is solid, but I'm still leaning toward attacking the slots, since: 1) This is going to be my wife's bike, so I'm confident that I'll be more patient than I would be for my own bike. If it can be done well, I'll do it well, and I don't mind spending the time. 2) Modifying the slots will make the frame amenable to any standard hubs in the future, whereas modifying the axle risks creating an awkward fit between this hub and any future frames. Plus, since I'll have to reset this frame to 120mm regardless to fit the current hub hardware, leaving the slots at 8mm would create a mismatch between slot spacing and slot diameter for any future hubs. (The standard for rear fixed gear hubs is 110mm/8mm or 120mm/10mm for those who aren't familiar).

I'm not sure what I'll do about securing the frame. I had just planned on straddling it and clamping with my knees, but it seems that might be insufficient and I'll need to get more creative.

Andrew R Stewart 

I'll just end my part of this thread with a few pointers.


A year from now you can still file the drop outs if you wish. A year from now replacing the axle or hub will likely be NBD. I've learned that time has a way of shifting our bases and what we feel are the must dos or can't haves. My suggestion of chasing the least permanent change, still retain all the current parts and reduce the work effort to achieve the goals offers the best solution. Others will disagree.


But I'm both a Dr's kid (where doing no harm and bowing to the insurance cartel controlling what can be paid for rule) as well as a life long LBS wrench. Both side of my experience say to do the least first. Greater and far more invasive solutions can always be done in the future. Andy

scoho

After posting I took a file to the threads of a spare bolt to see what that process would be like. Pretty easy indeed.

Aside from my concerns noted above, I've got one outstanding reservation about that method. As dsaul pointed out, filing the excess material from the bottom of the slot would leave the contact points between axle and slot unaffected, so there are no potential alignment issues. I'm worried that filing the axle reintroduces the potential for alignment problems. Andy doesn't seem concerned about this, though, so I wonder if I'm misconceptualizing something. Any words of wisdom?

Andrew R Stewart 

As I tried to explain in my first post keeping axle alignment control is easier then dropout slot control. The axle has a "go/no go" gage of sorts, the threads. Or more to the point the thread roots. Filing one flat on the axle to this thread root, an easily seen aspect as the thread bottom becomes less and less, helps maintain the axles' alignment foundation. Then filing the other set of flats, diametrically opposite the first pair, to fit the drop out slot allows the axle to slide in the frame.


The axle/drop out slot has some tolerance in fit. The frame has some alignment tolerance. The rider has some steering tolerance. Which is the greater amount? You tell me which every time and I'll we'll be rich (well, at least comfy as the bike business make very few rich people). The seeking out of perfect alignment can be a holy grail. In the trenches of the LBS we deal with "what's good enough" frequently. My advice here, besides involving all the least harm stuff I mentioned before includes this pragmatic aspect. What's good enough, what works, what can be redone. Andy.

fietsbob

Single cut mill-bastard file should leave the surface adequately smooth.

JohnDThompson 

+1 this.

fietsbob

Largely what a Sturmey Archer 3 speed axle is.. . flattened ..

NB if your axle is Heat tempered almost as hard as the file . It may spell the end of the file. ..

Canaboo

Clamp the dropout itself in a vise and support the rest of the frame. You can do very precise work with the right file.

JohnDThompson 

In that case, use a grinder, or Dremel-mounted grinding stone.

RidesaCarlton

Lets back up a little on the conversation. If you try to file the forks, you will never get it perfect. Talk to a frame-builder. They will tell you it is next to impossible for us to get right. Filing the axel of the wheel may work, but be careful how you do it because you still want to insert the axel into the wheel after the filing has been done??? It may be hard to install cones over the filed part. OK, How about purchasing a replacement front fork from your LBC. You get to the size you want. You also get to change your mind if you ever find the correct wheel, and want to use the old fork. You also keep your bike intact, because some day, it will be worth a million dollars. (That ought to be enough for 2 Starbucks.)

RidesaCarlton

Sorry for my 2 cents worth about filing front forks. It has been ponted out to me that you are talking about rear fittings. Sorry.