Go Back  Bike Forums > Bike Forums > Framebuilders
Reload this Page >

Unicrown fork mitring jig

Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

Unicrown fork mitring jig

Old 06-26-21, 06:50 AM
Senior Member
Thread Starter
Join Date: Dec 2019
Posts: 605
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 212 Post(s)
Liked 123 Times in 101 Posts
Unicrown fork mitring jig

Having found the last time that these are very tricky to do by hand (at least for me) I thought I'd have a go at making a jig to hold things steady for mitring with a hole saw. Actually worked out better than I was expecting.

Simple construction out of 3/4" 16-gauge square tube, but plenty stiff enough not to move. The blue thing holding the hole-saw was unbolted from my inexpensive Metz tubing notcher (which I actually rarely use normally preferring to hand-mitre). The jig was made deliberately to place the hole-saw a little bit low so it could be put into the exact right place with shims. It's bolted to a 3mm plate welded in there with the holes a little oversized to allow fine adjustment of the angle.

Having bolted the fork ends in securely I TIG-brazed the ends of the fork not only to each other but also to the cross piece (which is bolted in so it can move around a bit), at the end of the cut:

Horrible gap on the ends of those forks but this actually worked to my advantage as that ugly bridge tack stayed in place the whole time:

Great success! Hole-saw spun nice and smoothly (with a cordless drill driving it) and nothing shook around or bent or did anything bad.

After a very little cleanup here is my fit:

Certainly good enough for the girls I go out with. Not 100% perfect as the hole-saw is 28mm, not 28.6mm. I'll clean it up a little bit more but I'm going to be TIG welding this and I can fill much bigger gaps than that (don't ask me how I know this
guy153 is offline  
Likes For guy153:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.