I've been playing around lately with attempts at fire bluing. I made some slide blanks for Lyman 48's and thought I would try my hand at fire bluing them. After a few semi-successful attempts, I tried this which works repeatedly. I machined a trough in a piece of aluminum bar stock. Aluminum is a good heat conductor and I heated the block with a propane torch
It took a while for the block to heat up, but eventually the slide blank became straw colored, then purple began to appear
The purple gave way to blue
Just as the last bit of purple disappeared, I used tongs to pull the slide blank off and drop it into some 10W-30 oil
Once the block was heated, it didn't take very long to do additional slide blanks. In fact, with the subsequent ones, it was actually easier to get a more uniform color change during the process.
Here is a picture of 5 consecutively fire-blued slide blanks. They are more uniform and actually better looking than the picture shows. There is still a bit of oil film on the blanks and the camera caught them at different angles. In person, I would say that the second from the right, is the most representative of the lot.
I've got some other things like skeleton grip caps and plan to make other holders and try this again.
I hope that someone here might find this useful. Thanks to those that are contributing to my request for information on checkering tutorials.