How long does it take to make a trigger lock T-bar? 2 evenings.
Some prep first. We need to rough fit the safety connector to give us a rough point to index everything from. We can fine tune later. With the safety selector in it's rear most position (and no trigger lock T-bar installed - we don't have one yet!), stone or file down the front of the connector (red arrow) until trigger(s) pin fits in the notch of the connector.
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This may also be necessary when you adjust a worn top-lever from left of center to center. When taking up the slack, the bolt alignment block will be slightly more to the rear with the bolt in the locked postion. This will push back the safety connector by that much, and so you may need to re-index it by removing a little of material from the front.
I took tight measurements from the trigger assembly to lay-out my trigger lock T-bar on a piece of 1/8 flat bar. The key measurement, taken from my 3d printed version, is the the top of the slot to the lower edge of the T. Getting this right will set your connector's notch against the trigger pin with the safety in the rear-most position.
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I used a center punch under a magnifying glass to get good dimples. The safety connector rod's tab is about 40 thous. thick. So I used a 1mm centering bit to start the 2 holes, then drilled them through with a No. 56 wire gauge bit (0.0465). This left a sliver of material between the holes. Using the centering bit, I was have to clear out most of this, coming at it from both sides. Next, I used a couple drill bits (I have these
https://www.amazon.com/dp/B07NDHMM4W to broach the hole open. This broke the remaining material in the slot, good enough so that with the tip of a pointed needle file and my centering bit I could clear it out enough for the tab fit down in. This wasn't my original plan. I laid out two templates. One to try and bubba it, and a second as backup for which I would order a 3/64" end mill to do it right. It's not very pretty, but I don't think I need the tiny end mills now!
I had the template on an overside piece of steel so I could handle it easier while laying it out and while refining the slot. So now, I put a piece of masking tape over my template so it wouldn't rub off, and cut off the extra half. I needed to remove ~0.037 from he back to get it to start sliding under the hooks on the trigger assembly, so most of my time was spent filing this down. Takes time and patience to remove that much material and keep everything even.
Next, use a hacksaw to cut out the rough shape of the T-bar, leaving the layout lines. A square file is used to get the inside corners of the T to 0.135 wide, then the rest of the vertical part is filed down until it's even with the sharp inside corners. Once the long edge of the T slides between the triggers easily, I started working on the Upper part of the T. Each side of the notch on the assemble was a different width (~0.008 difference). I worked the thickness of those until they slid into the notches, but not so easily that there was play in the triggers when in the safe postion. Don't overdo it! Next, I evened up the forward surface of the at that contacts the trigger nubs when the safety is in the rear position. Only remove material until the slot starts to come up under the trigger pin. Then, remove material from the back with the selector in the forward most position until you start to see the trigger nubs. Last, I beveled the underside rear edge of the T to match the surface of the trigger nubs, causing the triggers to rise when pulled with the safety in the forward most position. A light polish with fine paper backed by a file to clean up my marks...and Bingo!
Photos below show safety in safe and forward positions. Verify with a stout rap with a rubber mallet on the frame that the gun indeed does not fire when the selector is in the safe position. You can simulate a drop-test with a wooden dowel on the recoil bearing surface under the upper tang and mallet.
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All is well now and we are in business.
For my next trick - make the trip spring and pin.