Ridge When Milling Multiple Passes

rex21

rex21

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Ok guys, I am trying to get my mini mill adjusted as perfectly as I can. I made a column stiffener today and trammed the column. Adjusted the Column in the Y(nod?) direction while cutting a piece of aluminum til I had no step between the passes. Looked absolutely beautiful.

Switched to a piece of delrin just to see if I got the same results and I did not. I have a step that will catch a nail between passes.

Both materials I was using a .005" depth of cut.

Any ideas why the change? Am I worried about nothing?
 
Could it be that the delrin expanded a bit due to heat? Or maybe if you had it in a vice, it bowed a bit? If the aluminum came out OK, I would not worry about it too much. Maybe try a different setup on the delrin.
 
Both of those things came to mind. Just has me wondering if I have something wrong or if it's just because it's delrin and it moves more than the aluminum. I tried multiple feeds thinking it was heat related and it did not make a difference.
 
One other thing that comes to mind is using razor sharp tools on the delrin. Try a good wood router bit or better yet a bit designed for plastic. I use those a lot in my mill when cutting plastic or wood.
 
Razor sharp(agree) and clamping pressure affects Delrin type materials and overlap of next pass
 
Delrin will bend with too much pressure in the vise. Try the Delrin again with less clamping pressure and I'll bet most of the ridge goes away. Overlap the passes a little more than usual also. As for the tram, if the aluminum has no ridge, you have it correct.

"Billy G"
 
I think you guys are probably right about being clamped too tight. Will have to give it a try later tonight. On my last pass I did use a brand new 2 flute and the ridge was still there. I was overlapping about .100".ImageUploadedByTapatalk1442444173.440233.jpg
 
when clamping Delrin and other slipper stuff the old paper /emery cloth in vise jaws will help with out excessive pressure
 
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