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Daruma++ bolts

DARUMA bolts are used with Honjo fenders to mount the fender to the bicycle frame. Mark Vande Kamp is building a rack for his bike and the rack needs to mount to the same point as the fenders. A goal is to make the rack remove with just a couple of bolts. I made these replacement Daruma bolts which have an extra threaded portion for holding the rack. There is a good photo of a normal Daruma bolt here (linked from Jitensha's page on Honjo fenders): http://www.jitensha.com/eng/images/lngshrtdrmascrws.jpg It is a pretty good simple lathe project, so I thought it would be a good thing to document. It has facing, turning and drilling and uses both the 3-jaw and 4-jaw chuck. The bolt is made of 303 (free machining) stainless steel. This was my first experience using it, it machines pretty nicely.
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Now we are drilling a hole that will have the 5mm internal threads.  The drill bit is mounted in a drill chuck that sits in the tailstock.  The bit is a special center bit which is stout so that it doesn't wander off course.  This just makes a shallow starter hole.
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Now we are drilling a hole that will have the 5mm internal threads. The drill bit is mounted in a drill chuck that sits in the tailstock. The bit is a special center bit which is stout so that it doesn't wander off course. This just makes a shallow starter hole.

lathemetalworkingbicycle

  • This is the first bolt that I made, shown as a preview of what we are making in this series.<br />
<br />
At the bottom it has a M5 male thread which goes into the frame.  There is a cross-hole that the fender stay goes into.  The stay is secured with a special washer that isn't shown here.  At the other end there is a M5 female hole that the rack mounts to.  This is what makes it different from a normal Daruma bolt.
  • The first job is turning down the OD of the stainless steel to 7.7mm (the diameter of the original Daruma bolts).  This diameter is important because the bolt fits into a recess on a special washer.
  • More turning.  The 303 stainless makes pretty small curls (especially compared to aluminum where I get curls that are yards long).
  • I'm using a Sharpie to mark the location of the step for the external threads.  This isn't a precision measured length, so the wide sharpie mark is okay.
  • Cutting the stepdown for the external threads.
  • All of the turning operations are complete.
  • I'm threading the 5mm external threads with a die.  Note that I'm not doing this under power!  The lathe chuck just makes a very nice round vise.
  • It is threaded, time to cut it off of the stainless rod.<br />
<br />
The tubing block there is one that I made on my milling machine.  It can hold 3/8" or 1/4" tubing depending on the orientation.
  • After it came off.  You can see that it isn't a very clean cut, we'll fix that on the lathe.
  • Facing the cut on the lathe.
  • It is much cleaner after the facing operation.
  • Now we are drilling a hole that will have the 5mm internal threads.  The drill bit is mounted in a drill chuck that sits in the tailstock.  The bit is a special center bit which is stout so that it doesn't wander off course.  This just makes a shallow starter hole.
  • In this shot you can see the tailstock and drill chuck.
  • Drilling the final diameter (4.2mm).
  • Tapping.  Again, this is not under power, just done by hand.
  • We only have one operation left, making the cross hole that the fender stay goes into.  To do this I mounted the bolt sideways in a 4-jaw chuck.  The 4-jaw chuck lets me position the bolt anywhere relative to the drill bit because I can move each of the jaws independently.  It is centered so that the center of the hole will be about 4mm above the step.
  • Drilling with the center bit and 4-jaw chuck.
  • Untitled photo
  • Drilling to a final dimension
  • Here are the first and second bolts side by side.
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