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Discussion Starter · #1 ·
So I'm building my first frame (TIG welded Chrome-Moly street/trials bike) And I'm wondering what would be the most cost effective and accurate way to mitre the tubes.
I do have access to small mills and lathes but would need buy any hole saws or mounting equipment, so I would like to avoid this if possible as I'm on a tight budget.
I've heard you can do it with templates but I'm concerned I won't get the accuracy. eg down/head tube mitre perfectly horizontal to down/seat/bb tube mitre.

Thanks :)
 

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Full scale drawing, bevel protractor and hand files.

I started my number #1 with the printed templates, but ended up only using them on one joint. My 38mm down tube needed to be squished to mate up to the 36mm head tube so the templates were useless. My top tube also needed a little oval at the seat tube. So that only leaves two joints to use the templates. Might as well learn how get it done without the printed template.
 

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If you are using a jig to hold HT, BB and top of ST, just cut close then slowly remove material & adjust phase of copes until it is tight. File, test fit, file, repeat...
First, get the ST to BB welded at 90 degrees. 20+ frames built all done by hand without templates and they are all as straight as new bikes in your local LBS.
Don't over think it
 

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Man you guys really guess and check every joint?

A good full size drawing (Or CAD if you've got a program) will help you get all of your miter to miter lengths. I like the Nova templates. I scribe a center line on the tube using a straight edge and line up the templates on that to keep them in phase. The templates are totally accurate enough and good patience helps too.
 

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Nemophilist
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Hey;

It SHOULD be done by hand. That's how you learn best. Fixtures and other aids only work best if you know why they are being used and what they are for. If they are used for any other reason than simply saving time, they are being used for the wrong reason. The time you spend learning to do it totally by hand with no other aids will be invaluable experience with which to proceed in the future. You won't regret it.
 

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Even the guys that do it with hole saws in mills generally have to touch it up or do the final bits of the miter by hand. You can't rely on the machine to do everything for you. Hand filing is not that hard to do after a little practice, and works very well.
 

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I only have one frame under my belt, but templates and bench grinder worked perfect for me. Never touched a file. I don't even want to think about how much time I saved using templates. Like adarn said, I was impressed by how accurate the templates are. Always more than one way to get the same results, as you can see in thread, and I don't agree with the mindset that you have to do it by hand first to understand/learn the process. I would have jumped straight to the mill . . . if had one and the money for fixturing. I have more frames in the plan, but never see myself getting to that point.
 

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Discussion Starter · #11 ·
Just need some help with one thing. With the bb/dt/st intersection do you just print out two different templates and overlap them/trace ect? Because the nova and tube coping calculators only allow two tubes to be calculated at a time
 

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All tubes connecting to the BB are at 90*, so no templates are necessary. There can be an over lap however between ST and DT, which requires a notch removed from the DT. The ST is attached to the BB whole, the DT is the tube you 'Fit' into the ST with the notch to get the right angle positioning. This where a full sized drawing helps, so you can lay your work on it and match it up.

Eric
 

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I measure the angle between the DT and the ST and print a template that has the ST going through the DT. I put the DT in place and slide the ST down and mark where it touches the DT. Cut out the template and line it up with the mark. You'll only need the part of the template where the notch will be. Start lower than the mark and work your way up until it fits. Hope that makes sense without pics.
 

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I have a template I made using CAD. Have only used it once, but it worked well. Send me the spec's on your st/dt junction (diameters of st/dt/bb shell, and included angle between st/dt) and I can generate a pdf template for you.
 

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Discussion Starter · #16 ·
I measure the angle between the DT and the ST and print a template that has the ST going through the DT. I put the DT in place and slide the ST down and mark where it touches the DT. Cut out the template and line it up with the mark. You'll only need the part of the template where the notch will be. Start lower than the mark and work your way up until it fits. Hope that makes sense without pics.
Yeah I get you, that seems like a pretty straight forward way to do it, thanks man
 

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Discussion Starter · #17 ·
I have a template I made using CAD. Have only used it once, but it worked well. Send me the spec's on your st/dt junction (diameters of st/dt/bb shell, and included angle between st/dt) and I can generate a pdf template for you.
Thanks man, that would be great, I haven't got my final designs yet but when i do i'll give you an email
 
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