3D milling with no roughing pass

I was wondering if this would be a bad idea:

Take for example my slingshot design, my CAM software always generates the finishing pass from the handle up to the fork. Let’s say I use 10% stepover with a 3mm ballnose.
So what if I rough only the first centimeter of the handle. This way it can easily start off the finishing pass from there and reach 100% plunge depth, After a few parallel passes, it will reach the unroughed material, but since the stepover is so small (0.3mm) it should have no problem finishing all the way.

Am I missing something here?

Try it out as a test piece… I’d recommend a tapered ball nose as they take the stress much better.

I do it with foam a lot, but I would guess you would break any 1/8" bit with wood. You may be able to get away with a 1/4 in bit if your wood is anchored very well, but you’ll most likely burn out the bit.

Yeah I do it with foam too.

I do a lot of double sided machining. This is my typical practice when 3d milling soft and hardwoods.

I used both 1/4" and 1/8" tapered bits to router the profile of my part (i use double sided tape with dowels as alignment holes) and then run a “finishing pass” at full depth but with the stepover between 8-15% of my bit diameter. It saves SOO much time when 3d milling because you are able to run the parts at a much faster feedrate and not 10+ passes. As of late i have been cutting full depth 3/4" cherry at 120ipm with a 1/4" ballnose and its working great! good surface finish, no more ridiculous 5 hour run times (you could go deeper but i only have bits that have a cutting depth of .75"). Just take extra care when setting up your toolpath since you are cutting at full depth. Make sure to simulate a few times so you are sure it is doing what you want, where you want it to. I have crashed a few times and its not a fun sound at full depth of hard or softwood. Once you have your toolpath tested tho, you can leave the machine area to go work on other tasks.

This method also gives you more incentive to run multiple iterations of a design. Instead of waiting 2-3 hours for part to finish just to realize something needs to change, it now takes 20-60mins. Our time is valuable and finite so I like being able to run multiple 3d jobs after work instead of just 1.

Hope my experience with this method can affirm your idea is practical. Ciao!