# File to fit disc brake mount for bronze fillet brazing?



## illcomm33 (May 10, 2006)

Hey all. 
Do you file/mill your disc brake mount for a closer fit on the seatstay?

I have done it with varying degree of success (lots of frustration) in the past but feel it might be a time waster. I remember seeing a Spot frame with the mount almost hanging off the stay. 

I do typically file down hydroguides, stops, etc for a better fit/more surface contact on the frame for silver brazing.

I attached a couple pics to show how the mount is sitting on the seatstay.





















Thanks!


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## Walt (Jan 23, 2004)

Good enough. Just tack in 4 spots and check alignment, if you're good, finish it up.

Better fit will help with alignment, keep the load evenly distributed over the seatstay better, and be be easier to braze up/look nicer. But what you've got there is IMO just fine. 

-Walt


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## illcomm33 (May 10, 2006)

Thanks for the quick reply and explanation Walt. Hope Salt Lake is treating you well and glad you were not in Boulder during all that rain.
Travis


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## calstar (Mar 26, 2013)

Looks like a nice simple jig, please post a few more pics of the jig on the dummy axle if you have the time. thanks, Brian


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## afwalker (Apr 26, 2012)

I've been filing for a tighter fit, but brass would fill that and maybe I just expect to do hours of manual labor to put in my time
cheers
andy


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## Eric Malcolm (Dec 18, 2011)

I notice the comment Silver Braze. I have been experimenting with techniques to address various non-lugged frame applications using silver. In this case I suggest using 35% silver as it fillets better and would nicely fill the upper edge. You have to heat the mount to a more Red colour than you would for higher % silver as it has a slightly higher melt temperature. Also, the big one to make this work well, add detergent to your flux @ 10:1, it helps the flux from running away so much so you can get the nice fillet. If you get it right, you will not need to file up at all.

Eric


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## Rody (Sep 10, 2005)

Travis,

My answer would be absolutely fit the tab to the tube... to leave a tab with potential unsupported area is sloppy and may create long term durability issues for the structure.

If you've put that much effort into the frame, why would you not finish it with the same degree of care?

Here's a tab mitered and the blog posting on forks it came from...








Groovy Cycleworks 330-988-0537: It's FORK week...ti and steel flavor!

cheers,

rody


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## Walt (Jan 23, 2004)

I'll quickly play the contrarian here: what I see in the picture won't have alignment or durability issues, assuming the seatstay is beefy enough and the joinery is done decently (which, based on the appearance of the other fillets, it will be - looks nice!) 

If you are more of a process person, knowing that there is a tiny gap filled with bronze will probably drive you crazy. If you are a results person, as long as the mount is where it's supposed to be and the bike holds together, you'll never think about it again. 

Another way of looking at it: there will *always* be some gap, though it might be really small. It's not *ever* going to be a perfect fit no matter how long you spend filing to try to keep a single air molecule from being stuck between the pieces. So you can draw the line on when it's satisfactory anywhere you want once you've got it to the point where it's functional. How close you want to get to "perfect" is up to you. As I said, a better fit will be easier to join and look nicer with less finish filing. But what I see is plenty good enough to braze up and ride. 

-Walt


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## illcomm33 (May 10, 2006)

Thanks everyone for all the discussion and insight. (Walt: I don't want to jinx myself but thanks for the nice words on the brazing...that seriously made my day.)

Rody, I am happy to see a disc brake mount that looks like that! I swear I would hand file for hours to try and get a closer fit, look at what I ended up with, shake my head and think to myself that there w no way I was doing it right! Good to see my approach was in the right direction 

As for the seatstays for this frame I am using straight gauge 4130 Steel Tubing 5/8 X.035 from Aircraft Spruce (Part #: 03-03600) and bending it (single bend). Hope it will be thick enough for this 170mm spaced Fat Bike frame (S/M)

Calstar: I attached a few pics of the disc brake mount JIG I made. It isn't pretty, or even well designed (hey I am honest), but works good enough to let me know where the mount should be. I used a Specialzed Stumpjumper rear triangle/disc mount and kinda reverse engineered where I would need to place the mount.
The dummy axle is just all-thread from Home Depot (5/8 I believe) I use it for all my axle spacers. Again it isn't 100% perfect (I just hand filed the slots for the dropouts, using a lathe would lead to a much better end-product). The steel that holds the mount is just mild steel scrap I had around drilled to the ISO standard.

Honestly, if you have Anvil dummy axles just buy the feng shui Don makes. It would be easier to use and setup. The one I made doesn't have a thick enough base and wants to tip to a side.

I truly appreciate all the guidance/thoughts/ideas/best practices. I will definitely keep them in mind when I am tasked with the next disc brake mount! The previous mount I did was on a 132.5mm spaced cyclocross frame, with the basic Nova seatstays, so the seatstay tubing was smaller and angle was worse (hence the filing to make a better fit/more surface area) This most recent frame stumped me because the mount seemed to sit ok..but I could see where a little filing might help.

For this frame (#13) I went with Walt's recommendation and bronze brazed with no filing. It was early, I saw his reply, and ran to the torch. 





















Thank you everyone!
Travis


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## Rody (Sep 10, 2005)

Walt,

Not that I disagree with your perspective, but as professionals and mentors, is it not our goal to continue to refine process and reach for the highest level of fabrication quality?

I hope to never reach the point where I feel that my work is "good enough"...the desire to improve fuels me in the shop and is why we are all here contributing.

Although Travis and many readers are not at a professional status, ie...selling frames to consumers, the drive to improve on each effort should be encouraged.

That being said, yeah, I agree his tab will be fine...just gotta keep holding the flag high


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## jay_ntwr (Feb 15, 2008)

Yeah, I'd file it. It would be just fine without it I'm sure but I like stuff to fit tightly before I join anything. Filing this shouldn't take more than 5 minutes to have it near perfect. I get where Walt is coming from and I agree--it's not going to cause any issues one way or the other but I also get where Rody is coming from and skipping it just because you can isn't a good reason to skip it IMHO.


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## shiggy (Dec 19, 1998)

illcomm33 said:


> Hey all.
> Do you file/mill your disc brake mount for a closer fit on the seatstay?
> 
> I have done it with varying degree of success (lots of frustration) in the past but feel it might be a time waster. I remember seeing a Spot frame with the mount almost hanging off the stay.
> ...


I would--and have--do a small amount of filing for a bit closer fit, then fill(et) and file. Will look and function of a piece.
Would use a stay brace, too.


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## TrailMaker (Sep 16, 2007)

Hey;

There are definitely differences in outlook, intent, and business model at play. Those who are more production oriented, and working at earning a living doing something (hard to do sometimes!) will not take the time to do a lot of fiddling because it does not further the goal of being efficient and profitable within whatever constraint there is on the budget. Solid, reliable, and functional is the goal, and that is fine. These folks are building a tool, for someone else. That is what production is. That is not to say that they cannot, will not, or even do not enjoy doing the fussy work. It's just not the general goal.

I tell my customers that I will work on their car like it is my own. When I am satisfied, they can have it back. When I work on someone's car in my shop, and especially if it is a creative project, I make it quite clear that I am doing the work to please myself, and that their idea of what it should cost has to fit around that. Not to say that I do not take their budget into consideration, but there is only so much I will compromise for the sake of their wallet. It takes what it takes to do it right, the way I envision and want it. I build most everything the same way, no matter what it is. Invariably, even if a project ends up costing more than they had bargained for, they are in the end very happy with the results, satisfied that they got their money's worth (usually more), and pleased to own something of enduring quality and craftsmanship. Sometimes this takes a while to settle in for them, but it always does. I often end up doing stuff that "I don't get paid for," but that is the price YOU pay sometimes for pleasing yourself.

Taking something away from both outlooks is a really good idea. If you're doing it for yourself, PLEASE yourself. If you're trying to earn a living from it, MAKING MONEY is pleasing. If you can do both... wow! Yur a lucky dood!


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## Walt (Jan 23, 2004)

Hey Rody -

I think we're just at opposite ends of the function/form spectrum. Obviously we both care about both but I'm much more function oriented - many of my customers seem to be pretty indifferent to things like what color their frame is - they want to ride the living crap out of it and crash it and never wash it, etc. You do what I can only call bicycle art, it's gorgeous and unique and I would cry if I crashed a Groovy! I make pretty basic tools that are going to get abused, and I think our respective outlooks and customer bases reflect that. 

There is *always* a "good enough" in any operation - you could spend the rest of your life, for example, trying to get your frame aligned to the last 1/100th of a millimeter or getting the perfect radius on a fillet - but everyone will draw the line *somewhere* and say "Hey, it works great and looks great, putting more work into this won't make it better anymore". 

And yes, of course, most of us try to make every bike a little better. For me that means learning more about how to perfect the geometry, fit, and handling (and keep up with constantly changing suspension, seatpost, and wheel tech) and honestly has less to do with making things pretty - though if I can accomplish that too, it's a bonus. 

So I guess I'll just say it again - if you are building for yourself, build to please yourself. If that means taking a little less time to polish a fillet so you can ride ride the darn thing, great. If it's the opposite, also great. Do what makes you happy. If you're building for others, obviously build to make things safe and functional and then decide what market you're going for (and what will make you happy to send out) and build accordingly. There's nothing wrong with building hammers, and there's nothing wrong with making art.

-Walt


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## Eric Malcolm (Dec 18, 2011)

If you building for yourself, build to please yourself.

To add, you should be your own greatest critic. There is nothing wrong with the originators approach and question, either way will suffice and be totally adequate.

Eric


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## G-reg (Jan 12, 2004)

If you're giving Anvil money, and you should, the Post Punk will cover just about any current "std."


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