Hi my friends, welcome to our new video Today we are working on a fuel tank cap of a Porsche 944 This is the cap of my friend Reidiekl The cap has a problem. Now it is unlocked, no problem the inner and outer part are coupled But if I lock it, the parts are still coupled Thus it is impossible to lock this cap With the actual fuel prices this is not good For separting the upper cover, heat it up Use a strong screw driver to lift it off After dismounting the cap, you can pull out the lock cylinder Now you can see the function. Here are grooves for the lock bolt When the cover is locked and the cap can be screwed in or out When the lock bolt is in the lock cylinder we have freewheel and you cannot open the cap anymore Here you see the problem, the lock bolt is broken Turning the cylinder we find also the rest The spring is rather strong and has destroyed the bolt The quality of this plastic part isn’t good This we’ll make this bolt out of brass For the futher dismantling remove the securing clamp Here you see the lock itself My friend Stinni proposed that I should explain how to adapt a lock cylinder to another key Here you see one of the tumblers, which have to be adapted to the key, so that everything is plane when the key is inside Insert the tumblers carefully Here you see the function. When the key is inside all tumblers are flat, if the key is outside the tumblers lock the cylinder My friend Reidiekl, the owner of the cap, has also delivered the raw material It’s a piece of square brass and we’ll make the bolt of it The piece have been cutted with saw, thus we go first on the lathe to shape it Now the surface is absolutly flat The square brass has 10 mm x 10 mm. Because we need now 8 mm x 8.9 mm we are going on the milling maschine First we check the parallelity … 51 … … 53 … The parallelity is inside of 0.03 mm, rather good for such a mill The brass has just very small scratches, we have the zero position Precisely 9.00 mm, perfect! Repeat the procedure with the other side We have now the correct rectangular profile, now we have to cut a piece of 15.8 mm We finished with the shell end mill, now we need a sawing blade Perfect horizontal Thus the sawing blade is vertical Cutting pieces of 15.8 mm using this hell maschine Next we’ll make the hatch in the piece The hatch has a depth of 2.6 mm. We’ll start from this edge I’ll try now to adjust the coordinate system Using a precision pin I measure 0.40 mm for the gap The origin of the coordinate system is now adjusted to the edge of the brass piece Remove the pin Install a cutter in the collet and fasten it From the edge 3.4 mm should remain plus the radius of the cutter gives 5.9 mm 1 mm, 2 mm, 3 mm … a last check I adjusted the cutter on a depth of 2.6 mm. Now I cut 6.9 mm along the end … 1.5 … … 3.5 … … 6.5 … … 6.8 … and 6.9 mm Now we have the hatch in the full depth, here is 1 mm of material left Now we cut in this direction The hatch is completed At the plastic part the edge is absolute rectangular Milling this shape is impossible, but the key bolt has also an radius, thus I use the thinnest cutter Use a file to smooth it a little The hole comes next. Here it is in the middle, and here are 0.7 mm I adjusted the mill in the direction to the mid Now I’ll show you how to calculate the coordinates and how to position the drill I use such a feeler gauge 0.42 mm, 0.40 mm The 0.40 mm just fit in the gap while the 0.42 mm don’t enter The pin has 5 mm and the drill has 5.2 mm We have 5 mm for the pin, 0.4 for the gap, 0.7 mm for the wall and 2.6 for the drill 2.5 from the pin, the 0.4 and 0.7 count fully, and 2.6 for the drill Together we have 6.2 mm We’ll move the 6.2 mm Now the position is correct We use a small center drill Just touch a little and then do a final check I remove the center drill and we’ll change to a drill chuck now Thus I remove the collet chuck Shake the atoms a little to loosen the cone and I mount the drill chuck Fasten it The hole needs a diameter of 5.2 mm I adjusted the depth control stop to 13 mm The diameter of the hole is perfect, but the end of the hole has a conical shape For the cylindrical shape we grind a drill With this drill the hole will get a flat bottom I adjust again the depth control stop This are just 2.45 mm First we go the 0.45 mm 0.3 … 0.4 … and 0.45 Calibrate the scale to zero and then we go 15 mm Now the bottom of the hole is flat The bolt has a slope here The slope is needed for the overturn slipping and it has 10° Mount the vice under the same angle For the slope we may use a thicker cutter and of course the fitting collet I cut now 0.3 mm along the edge At the side of the hole the bolt is round We’ll try to make the radius with a form cutter Here it is less, thus I move the cutter more down than left In order to keep the overview during mass production, every bolt gets a production number We’ll try the bolt in the cap Insert the spring in the bolt and insert the bolt in the lock cylinder an secure it with the clamp The bolt is now out and the cap is coupled I insert the key and I try to turn it But here is a problem, we cannot turn the key to the end The hatch is a little too short, I’ll use now a thick cutter to make it round here The original part doesn’t has this rounding, but maybe it broke because of this We’ll use a 8 mm cutter for milling the rounding Now you see the function, the cap is coupled. If I turn the key the bolt is in and the cap turns freely Here you see the function in the cap The cap is coupled, you may open and close the tank If you turn the key, the cap turns freely and the tank is locked If the cap is coupled, the bolt is in the groove Turning further, the bolt has to be lifted out of the groove For this function we have the slope in the bolt But the friction and cutting forces are different for plastic and brass Due to this I made the slope deeper and additionaly I’ll make this corner round In this direction it slips easily out of the groove and in other it blocks We’ll try the overturn function The cap is coupled but you can turn it over If all is finished, press the red cover on the cap Now the cap will go back to my friend Reidiekl Next time we’ll make something bigger than this small piece. Bye, Bye!