Metal lathe Accessories ball turner on a 16" lathe

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Eyerelief

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For Christmas, my wonderful bride gave me the MLA-13 ball turning / boring attachment kit. Don't know if I will ever use the boring attachment, but liked the ball turner design. Thought I would share my build experience for anyone interested.
The kit comes well documented and Andrew is very supportive, responding to email questions within 24 hours (only question I had was what type of lubricant to apply to the bearing).

The challenge was throwing the majority of the dimensions out the window since the unit was designed for a 9-12" lathe and mine is a 16". That required some additional thinking juice so the first thing I made for this project was a juice dispenser:
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Following Andrews lead, I de-burred everything and painted it all with Rust-O implement paint (shown half painted so you can see the raw castings):
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Started turning down all the OD's and ID's per the provided drawings. I left all the material I could in hopes of reaching spindle center on my 16":
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After the above, I was pretty much on my own. Started by making an adapter plate utilizing my cross slides dove tails and compound mounting screws:
IMG_8464.jpg The screw sticking up on the far side is mounted eccentric, drawing the adapter plate up tight before tightening the dovetail clamps. The big screws are the compound mounting screws, we tighten those last. The plate is rock solid and very snug when tightened up. What is not shown in the picture is I ultimately recessed the ball turner in the plate, sinking the ball turner in about .250. This put the attachment on center line with the spindle.
The unit turned out very good. I kept very tight tolerances between the metal bearing and the turning post which resulted in very smooth pivoting. I intentionally took the depth of the bearing a little deeper so that I could add and remove shim stock to get the resistance I wanted. Currently, I have a .002 shim and two .001 shims installed and the pivot is smooth as silk with just enough resistance. As the unit wears, I can remove a shim and tighten it back up.
I finished later on Sunday than I had planned but couldn't walk away without at least trying it out once. Here is the turner mounted on the plate and a ball turned out of some scrap steel I had. No, not scrap, just yet to be used. Stuff is too expensive these days for any of it to be called scrap.
IMG_8466.jpgI was in a hurry when I did this. It's 1" diameter, turned at 700 rpm using an HSS cutter that I quickly ground. Finish on the ball was great, no chatter and great looking, smooth chips coming off.
A few seconds with some 400 sand paper (all I had) and some Flitz and here it is.
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I still have to figure out how to properly set it up to hit specific dimensions, but I like the design. I missed something as I was trying to figure proper height. When properly set up, the ball turning attachment sits .110 lower than the boring bar on my set up. I don't plan on using the boring bar set up but provisioned for it just the same. I added a .110 spacer to the recess in the plate to accommodate for the difference. Again, this is on my set up and not a reflection on the kit. I tried to keep the two set ups in mind when machining, but I missed something somewhere, I don't know where. Only limitation I see is it looks like it maxes out at about 1" radius, 2" diameters. Overall tho, I like it.
 
Came out looking amazing!!!
 
If you took more photos, please share them... Would love to see more photos of the process to get the parts finished...
 

wachuko said:
If you took more photos, please share them... Would love to see more photos of the process to get the parts finished...
Click to expand...

Thanks Wachuko. I didn't take any more pics while making it, but here are a few of the unit including the boring bar holder. Hmmmm. I now realize I should have taken more pics. Here goes:
The boring bar is held by the two grub screws up top. Between the two grub screws are metal plugs. The grub screw provides the pressure to the plug, the plug binds the boring bar. This way, the grub screw doesn't mar the boring bar. I was fortunate enough to have a 3/4" reamer so I was able to get a great finish on the hole that holds the boring bar. This setup is tricky unless you are boring the hole "in situ" as Andrew referred. He bored the hole with the base and unit mounted up on his cross slide and used his lathe chuck to turn his cutter. By default, he is in perfect alignment with his spindle that way. I didn't get to do that so it was a milling operation for me.
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Since I was able to bore the center mounting hole on the lathe (1/2" socket head cap screw on top) I had a reference point when I moved to the mill. With the boring bar chucked in my BS-0 dividing head, I indexed off of that center bore with a coaxial indicator. Once I was over center, I rotated the BS-0 90 degrees and moved the "Y" axis 1.25" per the drawing. The "X" axis was then established by indicating off the bottom of the boring bar holder then moving 1.0625". This was the theoretical center of the casting location for the boring bar itself. It looked correct, so I went with it. I started off with a 1/2" bit and drilled through. After checking the exit hole the 1/2" bit made I realized that I was a little less than .020 off center at exit which meant either the casting was not straight or I was not in perfect alignment with the casting. I assumed my setup was off. I adjusted the BS-0 about 1 degree and used a boring head with a half inch bar to clean up the hole. Running a carbide cutter at about 1400rpm, I could hear the cutter taking material at about the half way point in the original hole. Keep in mind that this boring bar hole is 3.5" deep so by definition it is a deep hole. After checking again, I was within a couple thou as best I could tell considering its a casting without a finished edge to really reference off of. I continued to use the boring bar until I reached .740 in diameter, then finished with my 3/4" reamer.

The base is bored 1.5" in diameter 1.0625 deep. Its here I will mention that I made the alignment sleeve and ball turning bearing first. I did this so that I could bore the actual ID's to fit by feel.
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The boring bar holder is bored the same ID, .109 deep. It uses the alignment sleeve to mate the holder to base and allow rotation in the event you want to slightly angle your boring bar. I don't believe the two set screws on the side are engaged to the alignment sleeve, the boring bar is simply tightened from the large cap screw on top. Engaging the set screws will likely mar the finish of the alignment sleeve making it difficult to remove from the base.
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The ball turning attachment bearing is similar to the alignment sleeve. The bearing itself is a little shorter since it has a "cap" on the bottom, a larger ID, and two flats to accommodate the set screws on the base. I have seen a couple pics online where people have turned a groove in the OD to accommodate the set screws, dont do that, just two flats 90 degrees from each other. The ID is important. This ID provides the bearing surface that the ball turner rotates on. Once you make the bearing, you will turn the ball turning piece to a very close fit. A little resistance here is good. Any end play is very bad and will likely result in chatter at the cutter.
IMG_8487.jpgYou can see the flats in this photo as well as the end cap. The ball turning piece is countersunk where the end cap is installed. Inside this countersunk hole is where I added the shims to give me the "feel" I want during operation. The bearing has a good finish on it as well as the cap, but it has a little way oil on it so it looks distorted. The slot with the 1/4" HSS insert was easy, my vise has a rotating base. For the slot, I did not use a 1/4" end mill, instead I used a 3/16" and crept up on the dimension so the insert fits inside nicely. I also milled the slot .265 deep instead of .250 so that I could move the set screws away from the edge a little. Not necessary, but they seemed really close to me.
Lastly, the tensioner for the adapter plate. Its simply some 1" round stock turned with a 60 degree taper to match the cross slide. I milled a hex in the bottom to fit a 7/16" open end wrench then drilled it .110 off center. This way, when I install the adapter plate, I can turn this tensioner to bind the opposite side tightly before tightening up the clamps. In the pictures, the screw is too long. I am using a 2" screw that I will shorten, but I wanted the bearing surface of the unthreaded portion of the shank in my half inch plate to reduce galling. Need to cut the excess threads off.IMG_8489.jpg
Of all of the operation, the only real tricky part for me was lining up the boring bar holder, which was funny because I don't intend to use the boring bar but wanted it finished correctly just the same. Now I can use it if I want to. With a little patience and plenty of thinking juice, it worked out just fine. If you decide to get this kit and have any questions, don't hesitate to ask. Andrew is the man tho, he is a great source if you find anything I have told you thus far as "dicey" or improper.
 
Thank you!!
 
Nice job! It looks great!

I just received a set of drawings for the MLA-13 from Andy - I wanted to see the details before deciding to buy the castings. The drawing package is really nice.

Something I am not clear on - what retains the ball turning part into the base? It looks like there is nothing to prevent the steel bearing from lifting out of the base. Or is this just not a problem because cutting forces will always be downward?

Also, what is the purpose of the curved slot on the ball turning part? I don't have a rotary table and would leave out the curved slot if it isn't really needed.
 
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The two set screws in the side anchor the ball turning attachment. Two flats only, don’t turn a groove around the OD. You can see the flats in the 4th picture.
I think your going to want the curved slot. It works with the straight slot to set the radius. If you leave it out the set up might not be rigid enough.
For the ball turner, keep your tolerances tight. I held about .001 on those parts. If the gaps get to large the end play will certainly cause chatter and a poor finish.
 
Thanks Eyerelief. I understand now. The set screws anchor the steel bushing and the steel disk on the bottom is captivated under the bushing. I was thinking of machining just a hole at the center of the currved slot, but I see now that the curved slot is necessary for cutter positioning.

I'm going to order the castings today.... and another adventure begins...
 
You are correct. The ball turner will have material in the casting that is to be machined down to the ID of your bushing (or if you turn the attachment first like he suggest, you will bore the bushing to match the OD of the attachment). This is the most important dimension to hit. Matching these two will insure smooth operation and a great finish. On the bottom you can see material attached in the center with a SHCS. That captivates the bushing to the ball turner. The second most critical dimension to hit. This is where I intentionally lengthened the bushing. By making the bushing .005 longer, I add shim stock between the casting and the end cap. As the mating surfaces between the end cap and the bushing wear, I can remove shims to keep the end play to a minimum. Currently I have one .002 shim and two .001 shims installed. I think you see where I'm going.

I followed Andy's order for doing things with the exception of making the bearings and sleeves first. You will be providing the material for the bushings, bearings and shims. I bought a foot of material so that I could remake if I missed a dimension. You only get one casting of each....

Good luck, don't hesitate to ask any questions. For me, some of the instructions started out kind of confusing (or didn't work for me since I did not have a 9" SB lathe) but in hind sight I now understand exactly what he is saying.
 
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