The gas tank is leaking when filled up. Not Good! I had this problem a couple of years ago and fixed it. Looks like the problem has returned… No choice but to drop the tank and fix it again!
It is fairly straightforward to drop the tank using a floor jack to support it. Except that the top of the jack is only about six inches wide and the tank wobbles on it. And wants to fall off. Especially when there is some gas sloshing around in the tank. This job would be easier if the jack were wide enough to support it.
Well, what would it take to make the jack wider? Pulling up the rubber pad on the jack reveals a bolt securing the standard 6″ square plate to the lifting arms. It should be possible to replace it with something wider.
Searching around the shop turned up a frame from a previous project that didn’t work for that project and was tossed into the “materials for future projects” pile. Well, this is a future project!
Cut off the unneeded bits and weld in a center section of 2″ x 2″ square tubing (also from the “materials for future projects” pile). Drill a hole in the middle of the center section for a bolt. Now we just need a proper size bolt.
Which is where the project came to a screeching halt. Detailed measurements showed that the jack uses M24x1.5 threads. This is basically a one inch diameter metric size – which I don’t have and isn’t readily available.
No problem! I have a lathe and can create a custom part with the needed threads.
This is where things went sideways…
I had upgraded the lathe with a Quick Change Tool Post – QCTP. A QCTP is one of the most valuable upgrades you can make to a lathe. It allows you to change the cutting tool you are using in seconds instead of minutes and without setting up the cutting tool each time you use it – a major productivity gain!
The first task was to make a test piece to make sure that the threads would work. To do this I needed to first turn down a piece of steel rod to the needed size and then cut the metric threads.
When I ordered the QCTP I had to choose the size – AXA or BXA. The BXA size is the largest that would fit my lathe. Bigger is more rigid and more rigid enables deeper cuts, more accuracy, and better surface finish, so BXA it is!
I’ve been having problems setting up the cutting tools – they ride just a little bit too high. Turns out that the tool holders for the QCTP are hitting the cross slide on the lathe. Yup, I should have gone with AXA.
Well, the lathe isn’t the only machine tool in the shop! Do a bit more shop tetris and expose the milling machine. Mount the 2″ facing mill on it. Flip the QCTP tool holder over so that the bottom is up. Adjust the mill to take a 1/8″ cut off the bottom of the tool holder and fire it up.
This is a small milling machine and the tool holders are hefty blocks of steel. I wasn’t sure if the mill had enough power to take a full 1/8″ cut in a single pass. And I was curious to see what kind of surface finish it would leave.
To my pleased surprise the milling machine chewed through the tool holder with enthusiasm and no signs of strain. While throwing hot razor sharp chips everywhere.
The first tool holder came off the milling machine with great surface finish. Take it over to the lathe and it slides smoothly onto the QCTP and locks solidly in place. This is encouraging!
Take it off the lathe and install one of the cutting tools. Put it back on the lathe and try taking a facing cut across a steel rod. This is a bit of an acid test – if the cutting tool is adjusted properly it will leave a smooth face across the end of the rod. If it isn’t adjusted perfectly it will leave a little nub sticking out of the center of the rod.
After several test cuts to get it dialed in I got a perfect cut across the end of the rod. And there was moderate rejoicing!
Repeat the process for the other four tool holders, including loading and setting various cutting tools. Finally, the lathe was working properly!
Time to make a test piece to see if it would screw into the jack. With everything set up properly turn a chunk of 1-1/4″ steel rod down to 24mm.
It has been many hears since I actually cut threads on a lathe. I had already checked and knew that the lathe could cut 1.5mm threads. With some configuration changes…
Dig out the manual for the lathe and see what is required to actually cut 1.5mm threads. Hmm, the back gears need to be changed. Go digging through all of the accessories that came with the lathe. OK, found a pile of gears. Looks like I need a 76 tooth gear and a 42 tooth gear. After cleaning the gears and studying them closely I found one stamped with 76 and another stamped with 42. Holding them up to the existing back gears installed on the lathe I could see that they wouldn’t fit. Why am I not surprised?…
Go back to the manual and study it closely. Hmm, it looks like one of the pivot arms has two adjustments. Cleaning it up reveals a socket head cap screw and a bolt. Well, maybe this almost makes sense…
Loosen the bolts and then work the old gears off of their shafts. Slide on the new gears and then use the various adjustments to fit them to the main drive gear. Strange, everything is fitting together! Add some grease to the gears, power up the lathe, and engage it. Everything works! This is really making me nervous.
Set the gearbox to B6 (which the manual says will cut a 1.5mm pitch thread), shift the lathe to thread cutting mode, and start making test cuts. Alignment is critical – you have to engage the feed rod at exactly the same place every time to cut a clean thread. Or you can run it forward to cut the thread, stop at the end of the threaded area, back out the cutter a bit, run the lathe backward, run the cutter back in to the starting point plus the depth for the next cut, and repeat until you have cut full depth threads.
All this took a bit of practice. I screwed a number of things up. I also managed to break a couple of threading inserts. But I ultimately succeeded in cutting threads that looked good.
But were they the right size? Dig out a 1.5mm thread gauge and measure the newly cut threads. A perfect fit! While really encouraging, this wasn’t definitive. Take the test piece over to the floor jack and try to screw it in. It fit perfectly! And there was much rejoicing!
At this point I had everything needed to make the actual part.
To be continued…