I've always been frustrated by the depth stop (or lack of) on the Stanley 71. I've read everything I can find about the front mouth foot depth indicator and still can't understand how I'd successfully use it in practice.

Some time ago I made a depth collar for the blade from a circle of metal cut from an old socket. Filed the inside to 3/8 square and drilled and tapped for a locking screw. This stops against the top of the blade mounting post.
Since it's directly on the blade and working against a solid mount it doesn't have any adjustment slop like a collar on the depth adjusting screw, plus the fixing screw is against the side of the blade - not against threads.

For small depths I don't use the depth adjusting flanged nut. I just install the blade, set (and tighten) it down against a flat surface and then use the hardware or a gauge block to set the depth stop. Easy enough to work down in small increments to the stop.
setting depth.jpg depth_set.jpg

Recently I was leafing through a woodworking catalogue and read about the spring loaded blade holder on the Veritas router. I clipped a small length from a larger spring and put it round the screw on my 71. It works just as on the Veritas, the blade holding thumb screw can be slackened off without the blade trying to fall out the bottom.
spring_noblade.jpg spring_holding_blade.jpg spring_tightened.jpg

The only thing to watch out for in construction is that the depth stop should sit flat on both shoulders of the holding post when sliding down the blade. Easy enough, the only critical bit that has to be square to the blade slot is the area marked in the pic. I slightly angled up the tapped hole for ease of use and the side towards the adjusting screw has to be thinned for clearance.

For the spring less is better, surprisingly few coils will hold the blade, too many and it's difficult to put on the adjusting nut if you want both screw adjustment and depth stop.

If I didn't have a router plane and was buying now I'd probably get the Veritas, but the 71 can use any of the Veritas blades (I have the Veritas 1/2" two piece easily sharpened blade). With the addition of the depth stop and spring the 71 seems not to lack anything useful compared to the modern planes.

PS Much the same depth stop for a modern 271 copy. Since this one (Made by Soba) is a 1/4 inch square blade the only work required is a drill and tap on a 1/4 drive socket.

depthstop271.jpg depthstop271_2.jpg