2 rail sweep not keeping shape

[tracys]

I am trying to create a 2 rail sweep. The shape is distorted when it is created. I am trying to copy the top of this profile from the side with the rabbet to the edge of the bullnose. All of my previews show much more curve to the profile. The overall material is 2" thick, the top half of it is 1 11/16. The rabbets will be done with the piece turned over. I think my problem is in the dimensions when the the 2 rail sweep asks for the exact dimensions of the width and height. Not sure if anyone has any ideas?

[tracys]

Ok on a 2 rail sweep the cross section legs need to be at the same plane, not offset like I was trying to do. By adding a line down on the rabbet side to match the height on the bullnose side looks like it will work.

[harold_weber]

Presumably we are talking about Aspire. If yes then correct, the right and left ends of the cross section need to be at the same Z height.

I may be wrong but I believe there is a SECOND ISSUE. Don't think it will handle the right hand side of your cross section unless you modify it as shown here.

As an example, try doing the two-rail sweep in the open hexagon and see what you get. To put it in mathematical terms, if we say the cross-section is a plot of Z versus Y there needs to be only one value of Z for any value of Y.

[tracys]

Harold,

You are right on the side of the profile. It won't undercut, which is ok I can cut that from the other side when I cut in all the rabbets.

So far my test pieces are working out very nice, although I need to find a 1/2" round nose that has a 2" + cutting length. So far I've used a .03" step over which is giving a very nice finish, but I think I can increase it a bit to speed things up.

[harold_weber]

http://www.mcmaster.com/#ball-end-mills/=71m8qn