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Lathe tool sharpening jig cut in Oak using thin router bit


#1

Did a quick project mainly to test precision cuts with thin cheapo router bits (<=1/8") in hardwood (Oak) as I saw many posts on other sites about CNC bits breaking when cutting hard stock. Also wanted to sharpen a nice set of vintage Craftsman lathe tools I picked up for next to nothing.

Cheapo (most probably crap - do not recommend) router bits off Amazon for < $15: Cannot use all of them as router can only use 1/2 or 1/4 shank.

Project Pics: Only used the Maslow for difficult to cut pieces.

  • The ‘Adjustment knobs’ (top left) are 1" OD with 1/4 bore (for scale).
  • The ‘Teardrop shape’ cut into two identical pieces (top middle) was used to accommodate lathe tools that ranged in width from 1.25" to 3/8" and keep them level.
  • The ‘Angle adjustment base’ (top right) accommodates sharpening angle between 0-45 degrees.

  • Sorry for blurry pic. This piece is only 1" wide. Maslow did an amazing job in cutting it.


Jig assembled showing teardrop cutout fitting small diameter lathe tool. Lathe tool shown already ‘fingernail’ sharpened.


Other side of jig showing angle adjustment.


‘Fingernail’ sharpening using jig on Shopsmith. The box clamp shown under the grinding wheel was made using straight cuts on Table saw and bores using Forstner drill bits as it was too time consuming to cut on the Maslow.


‘Standard’ radius sharpening using alternate V-groove reference point on jig.

Wood stock:
Used 3/8" thick, 4 year seasoned Oak, which was very dry (1.5M reading on FloorDot moisture meter which is below 4% moisture content), and therefor very hard. Used 3/8" stock because 1/8" bit had max depth 1/2".

Router Bit:
1/8" 4 flute bit at max 20 IPM and 1/8 max depth per pass.

CAD/CAM:
Fusion360 for both.
Use Fusion360 ‘Feed Optimization’ with defaults and unchecking ‘Only Inner Corners’ to reduce speed on sharp cutting angle changes. Also used ‘Smoothing’ to reduce unnecessary Gcode coordinates.

Gcode:
Bores: 10 IPM XY feedrate with very low Z rate (<10 IPM).
Contours: 10-15-20 IPM determined by Fusion360

Results:
The only problem, with Maslow cutting the jig pieces, was that the stock depth was not cut all the way through. This was probably caused by uneven work surface backing board due to my over enthusiasm in construction and lack of attention to detail. At max there was 1/16" left in undercut. This seemed very little but trying to cut these pieces out smoothly, after the fact, was difficult as the oak was very hard. A knife blade was not sufficient and so I resorted to Dremel 1/16" spiral cut bit. This was heavy handed and caused many cutting errors as I could not manually control it, when it caught the wood grain, and veered off course. Finally resorted to a very fine 1/16 straight burr tool, that I could control, and gave good results.

Requested Input
The vintage lathe tools I picked up were incorrectly sharpened in many ways and I cannot determine the compound angles they should be sharpened at. If anyone knows this please let me know.