Facing a head tube on the mill

Without a lathe, it’s difficult to get the newly cut-to-length head tube faced to load in the fixture.  If it’s not very close, it’ll sit in the fixture crooked and could mess with alignment later on.  First starting out, I used the Park saw guide and hacksaw to get it somewhat of a straight cut (it never is though) and then used a machinist square and 10″ file to get it closer to faced.  That works, but it’s not very accurate and I never ended up getting it just right.
Then, I got an abrasive chop saw and that works pretty well but…it’s still not perfect. It’s definitely better than the hacksaw method.  I’d love a nice cold saw for this and other cutting but whoa, they are freakin costly (cheapest i found is $800?!). Maybe a used one will pop up some day. The other thing I tried was using the head tube reamer/facer on just the head tube.  It works if you (1) have the right spacer for the inner diameter of the head tube (instead of the cutting tool used for reaming out the inside to the correct diameter of the headset cup), and (2) have some way of holding the head tube very solid while facing with the tool.  It like to spin with the cutting tool otherwise.  But why shorten the life of your head tube facer? I needed another way.

So i have read it can be done on the mill, albeit clunkily, so I tried it for the next frame I’m starting (another singlespeed cross frame for a friend in Minnesota).  I got these new vise jaws that are very versatile and are perfect for this task.  I may cut the in half so to be able to clamp tapered or swaged chainstays but it’s hard to do that without…well..a cold saw.  A hacksaw would ruin their perfection.

With the head tube cut with the park saw guide, I then leveled with the digital angle finder.  I loaded up a 3/4″ end mill and set it to cut off 1mm of each end of the head tube. Lots of cutting oil, slow feed rate, and a fast cutting speed it did what needed to be done.  It’s not the cleanest finish (see photo) but it is as close as I’ll get to perfectly square head tube facing without a lathe.

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