Thank you Tim, and all who responded. I haven’t snapped heads installing them; rather, they snapped in service. Still, I think Tim is on to something. I’ll try the new ones on one or two cars - ensuri

In the distant past, I tried Kadee’s 2-56 Delrin screws to mount couplers. Many of the heads snapped off in normal use and I quit using them. Slot or Phillips head - same results The 2-56 screws Kadee

I agree with William - Walmart 3x reading glasses for $5 or so. Work great.