I was first reached out to by a recruiter. The entire process only took 2 weeks from that point forward, it could have easily been a week but I was busy that next week for an onsite interview. Needless to say, it's impressively quick.
I don't remember applying but the email was sent to my university address. The 30 minute call was purely behavioral: you'll talk to a recruiter. Be ready to tell him/her a bit about yourself, weaknesses, strengths, situations like disagreements with your boss/team, a time when you messed up, motivated others, etc.
A couple of days later, I received an email inviting me for an onsite interview. Since there isn't much information about McMaster-Carr online and hence the interview, it's in your best interest to ask questions as they come up to your recruiter. Mine was extremely nice and open to questions. The Glassdoor reviews were also pretty helpful to me. Basically, I had a good idea of how the interview was going to go before I got there, which definitely helped my comfort level once I was there. Just in case you're wondering, it's all paid for and you're treated pretty nicely.
The on-site interview: It starts with a 45 minute-1 hour "tour" of the warehouse. Something to know: McMaster-Carr has 5 branches and all of their corporate offices are attached the warehouse. HQ is in Chicago, everything I can tell is that that's where you want to be. I placed "tour" in quotes because it is a walking interview. You'll be walked around to the different departments and asked questions about their operations, mainly "Why do you think we do x task in this way?" or "How would you do this?"
After the walking interview, there will be 5 back-to-back 1 on 1 interviews. One of those will be over lunch. These interviews are all behavioral and are meant to pick your brain. The overarching question is, "Can we trust this person to solve problems with a sense of efficiency?" They determine this by asking about experiences from your resume and then going further in depth. There isn't a formula for the questions they ask so there's no point in me writing them down because they were mostly specific to my experiences. The one case question is listed below. In general, I found the interviews to be conversational and fun. Hopefully you do too.
I received my offer the next day and as a kid out of college, very few offers can beat it.