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Bending fork blades

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Bending fork blades

Old 03-30-06, 04:49 AM
  #1  
Jonny B
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Bending fork blades

Having looked at nearly half of the galleries on Richard Sachs' 'How Frames Are Made' page, it seems that people like to bend their own fork tubes (and rightly so). Is it possible (and reasonable) to make your own mandrel (they often seem to be made of wood, a material I'm more than familiar with)? Are there any web-based plans around? And since we're on the subject, is the bend circular or parabolic (not that it really matters I suppose)? Is there any easy way of calculating how far to bend for a certain rake?
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Old 03-30-06, 10:12 AM
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The Paterek manual has a full size template for the tooling.

A great method of construction is a "laminate".

Cut a .750" (or whatever suits the type of blade you are using - MTB, track etc.) thick chunk of hardwood in the desired curvature, and then quite simply cut 2 additional sideplates (taller of course) and glue them on the sides.

A great fork bending jig is born. You will need to drill for the blade clamp etc.

Fork blades are quite easy to bend.

Bend them individually, and make the curvature uniform in radius and location.
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Old 03-30-06, 10:18 AM
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The Paterek manual has a full size template for the tooling.

A great method of construction is a "laminate".

Cut a .750" (or whatever suits the type of blade you are using - MTB, track etc.) thick chunk of hardwood in the desired curvature, and then quite simply cut 2 additional sideplates (taller of course) and glue them on the sides.

A great fork bending jig is born. You will need to drill for the blade clamp etc.

Fork blades are quite easy to bend.

Bend them individually, and make the curvature uniform in radius and location.
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Old 03-30-06, 01:10 PM
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https://pg.photos.yahoo.com/ph/bobbes...esrs/my_photos
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Old 03-31-06, 02:20 AM
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If you look at the Nova site, they sell the jigs. Which means there is a sketch (bad but understandable) of how a go bar can be attached and other details. They also sell the radiused forms, which means you can determine what the various bend radii are. I just worked out what amount of fork offset I needed for the trail I am constructing, drew that out in a given radius, and from that I can create the form required. One detail I love in Ritchie's photos is the little metal stud that limits the bend. It should contribute a lot to repeatability.
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Old 03-31-06, 07:13 AM
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Originally Posted by Peterpan1
One detail I love in Ritchie's photos is the little metal stud that limits the bend.

and here is that little metal stud in the flesh...
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Old 03-31-06, 01:23 PM
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"don't laugh. it works"
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Old 03-31-06, 02:14 PM
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Originally Posted by chimblysweep
"don't laugh. it works"

let em hear ya in the cheap seats yo
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Old 03-31-06, 11:01 PM
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Do you just eyeball it for vertical alignment before bending.
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Old 04-01-06, 04:45 AM
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Originally Posted by Peterpan1
Do you just eyeball it for vertical alignment before bending.

of course
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Old 04-01-06, 11:33 AM
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What? No numerically controlled alignment machine!
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Old 04-01-06, 12:53 PM
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Originally Posted by Peterpan1
What? No numerically controlled alignment machine!
why limit myself?
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Old 04-01-06, 11:29 PM
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I worked for a frame builder in the late 70's / early 80's, and he used a 16" steel automobile wheel* to bend fork blades (High-end Columbus, Reynolds, Ishiwata, etc). Depending on the head angle, he'd make a rough sketch of the necessary off-set, and then spend a short time carefully bending the tubes around the middle of the rim until they were close to the sketch. His finished silver brazed, lugged frames & forks were first-rate, and tracked true.

*The rim was welded to a heavy steel plate that had a hole in which to place the end of the fork tube. The hole secured the tube while you bent it.
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