Assorts' Exclusive World's 1st Direct Fitting Ball Turning Attachment for 7 x 14 / 7x16 Mini Lathe -Turns Concave & Convex Balls (*See Working Video on The Link)

The description says this can be used to turn convex or concave. Works fine for convex but it is impossible to make concave curves at the end of a piece of stock because the cutting tip protrudes the tool holder by only a few thou. so after one or two passes the tool holder hits the work being cut. This is probably a limitation only if one is trying to make a concave indentation on the end of a piece of stock. Should be OK for making curved relief or concave cuts along the side of the stock. I made a new tool post to accept 1/4" lathe bits which can be extended beyond the tool holder to get around this problem.

sehr gut

I watched a few Youtube videos before purchasing this product and it seemed to bolt on to some lathes without any modification. However, on my new Vevor 7 X 16 lathe it was way too short to reach the chuck centerline. It needed a .485 thick spacer to raise the cutter to material centerline. Actually I just got a piece of .500 aluminum and fabricated the spacer. This left it .015 high but it works great for the moment. The bolt holes were no problem they all lined up perfectly and the stock screws were correct although on the very short side. It was only the height that needed adjustment. So FYI : The height of the cutter from the base on the one I received was 2.225 in / 56.5mm. You may want to check this dimension on your particular lathe to determine if you will need a spacer. I am very happy with this product. If it is mounted and used properly it is rigid based on the design, the bearing provides a very smooth turning action, there is no chatter at least on aluminum and it produces perfect chips if speeds and feeds are correct. I believe it is the best design out there. However, I have spent time improving the rigidity of my lathe. There is plenty of room for improvement on these Chinese lathes

Whomever made this piece of tooling must have skipped the bulk of their schooling. They laid out the tool in such a manner that the cutting bit does not align with the actual centre of the yoke resulting in a substantial misalignment of the cutter bit as it swings in the yoke. Completely useless since nearly 1/4” or 5mm of useful space has been lost which prevents the tool from being properly centred on the work. The work in the photos is only 23 and a bit mm in diameter. QUALITY CONTROL during manufacture and testing of these would have gone a long way since the tool would otherwise have rated 5 stars.

The replacement for the first tool (received without a cutter bit) was complete. After I insured all screws were tight, I attached it to my lathe using a quick-change tool holder. First thing I tried was to simply turn a rounded end on a piece of Delrin plastic. It took a bit to get used to the process, but I turned a very nice half round onto the end of the plastic. I then chucked up a short length of 1/2" aluminum rod. I insured the rod end was far enough out of the chuck that the tool would not impact the chuck jaws in use. I undercut a length of the shaft from about 1/2" from the end of the rod back about an inch and turned that down to roughly 1/4 diameter. Then I set the tool horizontal to the work, touched off at the dead center of the rod. I moved the cross feed out far enough that the cutter was clear of the work. I then started the lathe and moved the bit in until it made contact with the right hand end of the work. I swung the handle left and right and knocked the edges off the work. I advanced the tool and swung the handle between the center of the end of the rod and back as far as it would go - that is, until it struck the undercut section of the rod. I continued advancing a little at a time until I was cutting the entire surface of the nicely-forming ball on the end of the shaft ! Once I had tool cutting during the entirety of the swing I stopped cutting and polished the ball and shaft with 400 grit sandpaper. The result a smooth, shiny ball about 3/8" diameter. I hadn't measured anything exactly in this test, just wanted to see if it worked. IT DOES!! Feed slowly and use enough speed to prevent chatter. I think this will work for all the small projects I may want balls for. I will try drilling and tapping the next one with 1/4-20 thread so I can screw it onto a "handle" - this is still test, try, learn mode. But think it will get lots of practical use in the future.