Guillotine Tool Angles

I was making a Mark Apery style guilotine tool and was having some issues with the device.
I was spending way too much effort trying to get the tenon forged down

These three videos are what I was basing my tool on.

Blacksmithing - Getting Started: Simple guillotine tool for isolating tenon material. CBA Level I.

The Guillotine tool or Smithing Magician. - blacksmithing tools

The Guillotine tool or Smithing Magician. - blacksmithing tools

I initially made my butcher dies at a 45degree angle and was frustrated by the results and how many heats it took to refine
I decided to try a 70 degree angle and found the results much easier to deal with and I was curious why.

I wanted to look at the exact numbers.
Lets say to make the math easy I will always fuller down the same amount an arbitrary unit of 1.
If we use the right angle calculator
we find the following
45 degree b=1 c=1.41
60 degree b=1.73 c=2
70 degree b-2.75 c=2.92

Since B is the margin of error I will need to swing a hammer into fo roughing out the tennon with my hand hammer I end up with 2.75 times as much space with a 70 degree angle as a 45 and a 60 degree angle is not enough difference from a 45 degree angle to mess with.

I then made another set of dies by drilling a hole. cutting it wit a bandsaw and softening the corners.
In this photo I need to add a small radius on the leading edge to prevent a stress riser.

I was pleased with how the tennon looked and this was at 3 heats.
1st with the butcher dies
2nd hand hammering to rough out.
3rd rounding dies.