Radiused knurling

[Roger HartParticipant @rogerhart88496]

[Roger HartParticipant @rogerhart88496]

I’m making some ‘telegraph’ pattern binding posts for a spark coil.  Old style terminals had a straight knurl on the terminal head that was radiused for good looks and ease of use.  How is this done?  Do I use a normal flat-straight knurl and round with a form tool or are there radiused knurls available – about 3mm radius say.

 

My current knurl kit does not have enough ‘bite’ to leave sufficient knurl depth for the post-knurl form tool idea to be viable.

[john swift 1Participant @johnswift1]

Hi Roger ,

 

I would knurl after the post is machined to shape

 

when made in large quantity I expect shaped wheels would have been used

 

but if your post is like my picture a straight wheel would work ( with more square corners)

 

I expect more  experienced fourm members will point us in the right direction

 

 

  John

Edited By john swift 1 on 13/10/2010 13:07:37

[john swift 1Participant @johnswift1]

Hi Roger ,

 

after a quick web search I think I’ve found what your looking for at

 http://www.frets.com/homeshoptech/projects/ropeknurl/ropeknurl.html

 

see picture of diy knurl tool

 

  John

Edited By john swift 1 on 13/10/2010 14:59:58

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

(1) You do this by mounting an ordinary straight knurling tool on a radius arm and

      swinging it around in just the same way as a sperical turning tool works .

 

(2) Shaped knurls are available but they are a bit of a rarity .

 

(3) In olden times curved knurled terminal screws were either made on a rose

      engine  (part of the gear of an ornamental turning lathe such as a Holtzapfel)

      or they were little lost wax castings .

 

(4) Dead easy by CNC but of that another day .

[Roger HartParticipant @rogerhart88496]

Thanks to John and Michael.  In the end I bought a clamp type knurling tool and modified the toolpost to a 1/2 inch round.  Mounted in my spherical attachment (MEW design).  Rounded the sides of my terminal screws then knurled.  Results are pretty good tho not exhibition quality – but this was a one-off.

 

If I wanted a really good job on a tighter radiusI might try John’s technique – but for average terminals I reckon the first technique can be persuaded to work OK.

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