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Which bit for a smooth helical ramp?

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Forum topic by CanisLupus posted 04-07-2019 04:41 AM 231 views 0 times favorited 1 reply Add to Favorites Watch
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CanisLupus

6 posts in 957 days


04-07-2019 04:41 AM

I have a 180 degree arc with a 4” inner radius and a 6” outer radius. In plan view, it looks like a semi-circle with a thickness of 2”. In profile, the ending elevation is 1” lower than the starting elevation. The cross section of the ramp would be a horizontal line. This is my helical ramp.

I can model this in my CAD software. My question is about the physical milling process. What type of bit should be used for milling the ramp? I want to have a smooth ramp with minimal sanding / finishing work.

Another option would be to create a jig to hold the work piece in a position so the slope of the ramp is parallel to the table and mill with an end mill bit. Remove the piece from the jig and mill any remaining features. This should work for a single slope without too much difficulty. Variable slopes would pose a challenge.

VCarve Pro 9.5
CNC Shark HD4


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Ger21

1087 posts in 3613 days


#1 posted 04-07-2019 12:26 PM

A helical ramp is not flat, so you can’t just mount it in a jig.

Use a 3D finishing toolpath, with the largest ballnose bit that will work. The smaller the stepover, the smoother it will be.

-- Gerry, http://www.thecncwoodworker.com/index.html http://www.jointcam.com

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