macgyver
Stainless
- Joined
- Aug 2, 2012
- Location
- Pittsburg, KS
I have a job that I have been running for awhile on the shaper with a set of custom ground knives and I am wanting to achieve better finish and longevity. I am cutting plastic, specifically Nylatron, it starts out as round bar and I cut it into a "+" shape. I think the shape of the knife is causing some reweld issues once I have ran enough to heat up the knife and dragging. The grinder made them to my drawing and does have relief included, I am just wondering if I can do better as I need to redo the knives now. The inside corner of the part is sharp and the leg of the + is parallel. I am getting good finish on the vertical faces, but on the horizontal, it is rewelding like it is dragging. On those sharp inside corners it is app 7/16" doc. I have a single speed on the shaper and I am running the slowest feedrate on the feeder at 10 ft per min. It gives a chip that is 0.008" thick.
So, I am thinking if I can change the shape to give that inside corner a small radius like 0.030-0.040" it might help that edge durability and I am also thinking about changing the horizontal leg from being parallel to having some taper, say 3-5 degrees, thinking it may reduce or eliminate any dragging.
I ran these on my cnc router the first time and had a bit of the same issues, the vertical face would be nice but the bottom cut on the bit would not leave a nice finish.
Hopefully the pics are good enough to help explain what I am doing. The pics show the bar after the first op, they get turned around to do the other side.
Jason
So, I am thinking if I can change the shape to give that inside corner a small radius like 0.030-0.040" it might help that edge durability and I am also thinking about changing the horizontal leg from being parallel to having some taper, say 3-5 degrees, thinking it may reduce or eliminate any dragging.
I ran these on my cnc router the first time and had a bit of the same issues, the vertical face would be nice but the bottom cut on the bit would not leave a nice finish.
Hopefully the pics are good enough to help explain what I am doing. The pics show the bar after the first op, they get turned around to do the other side.
Jason