HT oven build WIP

I finally got to work on my oven some more. Here's some pics of the progress. I do have a question though. The last pic shows my TC placement. It's about an inch off the back wall. Is this ok? If not and I move it, should I replace the brick or just plug the hole with some .125 stainless rod? I know I should have asked first but I was impatient. Thanks.

Matt


So, I finally got my oven running, just need to tie up some loose ends. Its kinda Frankenstein but It works great and heats up fast. I have a manual for the PID but it's written in engineer language. Anyone know if I can program different settings in it? Say 1 for 440c, 2 for 1095..... I noticed the element seems to have some hot spots and it's due to not being evenly spaced. Will this cause any problems? I'm sure I will make adjustments as I use it and figure out what works and what doesn't. Know if I can figure the PID out we will be on to something. Thanks for all the advice!

 
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If it's not too close to the elements there (in terms of electrical safety), it'll be fine. Thermocouple location is a balance between putting it where it sees what the workpiece sees and not obstructing the working volume.

If you move it, you can leave a hole. Maybe plug the inner end with a smear of furnace cement or similar. As long as it can't move, air is a pretty good insulator. Don't use the rod: it'll give you a hotspot on the outside.

Couple of thoughts:

Before you autotune the controller, give it a run up to the highest temperature you are likely to use. This will get an Oxide layer on the thermocouple and ensure the tuning run is done with the thermocouple in the same condition as it will be used in anger.

If you have a separate means of tempering, tune at Austenitizing temperature. However, if you are going to use it for tempering, tune at tempering temperature, rather than Austenitizing temperature. Final approach will be slightly slower, but overshoot will be less, when tuned this way.

Before you fully commit to the door catch, have a think about whether it will meet your future needs. I used an overcentre catch like yours on my first oven. It works fine, but is not conducive to treating multiple blades; mine was a definite 2-handed job to close.

To meet the need for something that can be quickly and easily opened and closed with one gloved, non-dominant hand, whilst providing some compression on the doorseal, I came up with something that works but lacks elegance. A bit of thought could probably come up with something that looks good and works well.

 
This will be the first one I have built or used so I'm sure that things will get "upgraded" along the way. I bought the 6" long TC and I think I am going to shorten it or just not stick it in all the way. I think i will move the TC to the top/middle and see how it works. Since I am going to harden and temper with this oven, I should calibrate the controller at my tempering temperature. It will vary depending on what steel I am using so should I just pick a temp in the middle?
 
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