So tomorrow I’m planning to mill through two pieces of aluminum 6061-T6 2x1x1/8" at the same time. In other words, the bit will be milling 1/8" thick aluminum at least two inches below the end of the collet. One of our mentors expressed concern that this might cause too much torque on the bit, potentially causing it to break. When I milled these slots the first time, I clamped the two pieces together and milled through both of sides of the top one and the top side of the bottom one at once, and then flipped the pieces over, re-zeroed the DRO, and did the other side of the piece that was on bottom. Because of a mistake I made, the slots (and more importantly the center hole for the 1/8" drop on our West Coast Drivetrain) ended up slightly offset from where I wanted them. The error was enough that I am having to redo the pieces. The issue with that method at this point is time: It’s already the end of week 3, and while we’ve made good progress with mechanism prototypes, we still don’t have a working drive base. I’m started to get really nervous about the rate we’re progressing, and right now I’m the bottleneck that is stopping electrical and then programming from working with the drive base. Because of this, I’d like to get this done ASAP, and milling through both pieces at the same time will cut the time it takes in half because I won’t have to re-zero and realign everything to do the other side of the 2x1s. As evidenced by the mistake I made the last time I tried to mill these slots (I assumed the mill would be close enough to calibrated for what I was doing; it wasn’t. The vice wasn’t indicated and was off by about .4 degrees, which screwed everything up), I’m far from an expert on milling, so I thought I’d reach out to the Chief Delphi community for some advice.
My question is two-fold: 1. Is milling through both pieces of 2x1 aluminum at the same time a really bad idea that I should avoid at all costs? 2. Assuming this isn’t a terrible idea, what can I do to minimize the chance of the bit breaking? The obvious first step is to use lots of cutting fluid; I’m more wondering stuff like what speed should I be running it at? Should I be using a 2-flute or 4-flute bit? etc.
Our mill is a PM-932M with power downfeed. Our bits are made of HSS, and we have 2-flute and 4-flute bits.
Sorry for the kind of long post. Let me know if you have any questions or need any other info.