# Over the top ball turning attachement



## YYCHM (Dec 22, 2018)

My lathe only has 2 1/4" clearance between the cross slide and the center of the chuck, so a horizontal swivel base approach is not practical as far as I can tell.   I drew up some plans for an over the top ball turner (same idea as https://littlemachineshop.com/products/product_view.php?ProductID=1970&category= ) and am now wondering what orientation the tool needs to be.  I assume 90 deg clockwise (from normal) such that the cutting edge intercepts the oncoming metal as it turns into the tool at the top of the swing (am I making any sense here?).  This affects how high the support arms need to be when using a standard carbide insert tool.  Also affects where the tool holder hole needs to be positioned on the swing arm.  Am I on track here?

Also, forgive me father but I am about to sin and go to MSM to source the materials I need.

Base - 1/2" X 2" X 6"
Supports - 1" X 1" X 5" (will suffice for both)
Swing - 1" X 3" X 3 1/2"

Anyone want to suggest an appropriate steel for this project?


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## kevin.decelles (Dec 22, 2018)

What part of the city do you live in?


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## YYCHM (Dec 22, 2018)

kevin.decelles said:


> What part of the city do you live in?
> 
> 
> Sent from my iPhone using Tapatalk



NE - Falconridge


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## kevin.decelles (Dec 23, 2018)

I have some stock that may help you out, no idea what kind of metal it is though 

Send me a pm if interested



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## YYCHM (Dec 23, 2018)

I'm interested.   MSM quote for cold rolled for this project came to $75.  Yikes!!!!

PM inbound.


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## TheLocalDrunk (Dec 23, 2018)

Joe pie did it without the tool. 





Also so a mod using the cross slide mount. Could that be an option too? 
Like this.


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## Dabbler (Dec 24, 2018)

YYCHobbyMachinist said:


> I'm interested. MSM quote for cold rolled for this project came to $75. Yikes!!!!



Yikes indeed!

I jut picked 200 lbs of metal tubing out of a recycling bin - with the shop owner's consent, of course.


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## YYCHM (Jan 4, 2019)

A BIG BIG THANK YOU to member kevin.decelles.  Kevin donated bar stock for my ball turning project.  He even delivered it to my end of the city!!!!

I'm off to the races with this project now.

Stage 1 - The swing.






Lobbing off a 3" piece of 1" X 4" flat stock with my trusty PHS.  Cut time was approx. 20 min.

I have discovered that the saw likes to walk all over the basement floor LOL.  Looks like some sort of base is in order.







Milling the PHS cut square.






Next, I need to mill this piece into a horse shoe.  A lot of metal to remove, 4.5 cubic inches worth.

I'm open to suggestions other wise it's going to be a LOT of back and forth with my mini mill, that piece is 1" thick.

Cut the two vertical lines with my PHS and mill the bottom horizontal line, might be an idea, I guess?


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## Dabbler (Jan 4, 2019)

You use your PHS to cut out as much as you can, even resorting to (horrors) using a hand hack saw to get out most of the extra material.  Saves $$$ on milling cutters/inserts.


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## PeterT (Jan 4, 2019)

If you dont need square inside corners, drill them as so & saw the lines. Or even so, hand file the fillets square


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## RobinHood (Jan 5, 2019)

As PeterT mentions: drill the corners (i would even leave them round if at all possible to prevent stress risers). Make the holes big enough for the PHS saw blade and after cutting the bottom line, cut down both sides and voila. Leaves you a nice chunck of steel for future projects...


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## PeterT (Jan 5, 2019)

Depending on that big hole size & your blade, you might be able to come in from either side of the hole & connect to the corner holes. Basically roughing out material so your end mill is reserved for cleaning up & finishing the opening to final dimension.


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## YYCHM (Jan 5, 2019)

oooops…...

I was attempting to square up one end of a 1" X 4" X 7" piece like this






The end mill grabbed and stalled.  The down feed on this mill is terrible.






Pulled the head over a good 4 degrees or more.

Now I have to re-tram it.

Won't attempt this sort of thing again.


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## Janger (Jan 5, 2019)

PeterT said:


> Depending on that big hole size & your blade, you might be able to come in from either side of the hole & connect to the corner holes. Basically roughing out material so your end mill is reserved for cleaning up & finishing the opening to final dimension.


Chain drill along the bottom...
And get a vise that opens wider. I know money money money....


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## YYCHM (Jan 5, 2019)

Janger said:


> Chain drill along the bottom...
> And get a vise that opens wider. I know money money money....



I'm not following the "get a vise that opens wider" part?


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## Janger (Jan 5, 2019)

Ah. If you had a larger vise you could grip it like this and mill off the edge much easier and with more rigidity.

You could also just use your clamp down kit I see in the background and clamp the material to the table. Put a spacer in to avoid hitting the table.

For chain drilling drill a series of holes not touching in a line. Then redrill every second hole with a larger drill bit just big enough to remove the web of material left between holes. Eg drill 1/4” holes 5/16 apart and then drill every second hole with 9/32”.

@johnnielsen taught me this one... thanks John


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## YYCHM (Jan 5, 2019)

I got it now.  Keep the milled surface as close to the table as possible.

That piece of steel in you image looks just like the piece I have?  1" X 4"  with a hole in the same location.  Where did this stuff come from?


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## Janger (Jan 5, 2019)

From Kevin! Thanks Kevin...


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## YYCHM (Jan 5, 2019)

Janger said:


> From Kevin! Thanks Kevin...



And that's where I got my piece from to.  If I recollect correctly he said they came from some sort of louver that gets periodically replaced?   I can't picture 1" thick louvers on anything.


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## RobinHood (Jan 5, 2019)

Janger said:


> You could also just use your clamp down kit I see in the background and clamp the material to the table. Put a spacer in to avoid hitting the table.


X2

Also use a smaller diameter milling cutter (ie. 3/8” to 1/2” max) and employ step-over passes. That reduces the amount of power / rigidity required from the mill and works safer (albeit slower) for questionable set-ups (like stuff that sticks out a long way from its hold down).
Looks like you are trying to use about a 1”, two flute cutter. These require some serious power and rigidity. I rarely use anything bigger than a 3/4” endmill on my Bridgeport size milling machine in steel.


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## RobinHood (Jan 5, 2019)

YYCHobbyMachinist said:


> Keep the milled surface as close to the table as possible.


Yes. That allows the mill head to also be way further down the column => more rigidity.


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## PeterT (Jan 5, 2019)

Setup wise, a useful accessory is a slotted angle plate. It gets mounted firmly to the table. Then the work gets clamped to a face. The added surface area + clamping force = increased security of drift & also rigidity. The cast iron imports can be reasonably accurate but they are heavy so beware shipping. Also the slot spacing needs to be checked vs your T-slots.   

Another option is clamping stock to the table flat side down with some kind of offset riser or sacrificial board. MDF works reasonably well unless you need to a couple thou. Now you would mill 2 parallel sides say in X direction, dropping the end mill in whatever depth increments it can take. Then then take a very light finishing pass of only say 0.005". Put new clamps across & mill the 2 Y direction same way. This method gives you automatic squareness & possibly sets you up for the internal relief.

In both cases, tall + thick + steel + smaller machine is a tough combination so there are pros & cons to each. The more you can cut away with a saw the better. Also roughing end mills work well, nut just for hogging material on big boy machines. They put less stress on smaller mills. But they are not for finishing. That's why I like to have a rougher in same diamter as conventional end mill, saves on setup & calculations with just one tool change.


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## PeterT (Jan 5, 2019)

flat side down method


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## YYCHM (Jan 5, 2019)

RobinHood said:


> X2
> 
> Also use a smaller diameter milling cutter (ie. 3/8” to 1/2” max) and employ step-over passes. That reduces the amount of power / rigidity required from the mill and works safer (albeit slower) for questionable set-ups (like stuff that sticks out a long way from its hold down).
> Looks like you are trying to use about a 1”, two flute cutter. These require some serious power and rigidity. I rarely use anything bigger than a 3/4” endmill on my Bridgeport size milling machine in steel.




Now this is an interesting comment.  A book I have states to use the biggest end mill available to do the job?

I was using a 1" 4 flute end mill.


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## RobinHood (Jan 5, 2019)

YYCHobbyMachinist said:


> A book I have states to use the biggest end mill available to do the job?


I do agree with what your book states. It probably also assumes that you are able to clamp the work securely in a rigid manner and have the spindle power to turn the endmill at the proper feed and speed for optimum material removal and surface finish. If any one of these variables are not 100% (as often is the case in a hobby environment), it is time to come up with an alternate plan: take lighter cuts, use a smaller cutter to reduce the “grabbing”, and you thus have make it up by doing more passes.

A single finishing pass with an end mill / shell mill / fly cutter of slightly larger diameter than the work width does give the best results and would be preferred, but not every one has acces to “Abom79” sized machines...


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## YYCHM (Jan 6, 2019)

I promised myself that I would complete at least one part of this project today, so I made one of the support legs.






I started with this thinking I would just hog material out of it on the mill.  That got stale real fast.






So I drilled a 7/8" hole in the sucker figuring I would cut to the hole with my PHS.






The piece was too small to mount on my PHS so I ended up doing the cuts the hard way.






40 minutes later I had this piece liberated.






It took the better part of the day, but I finally ended up with one support leg.

If I had been on the ball I would have used the hole to implement a fillet.  Ohhh well, live and learn.


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## YYCHM (Jan 7, 2019)

After much head scratching and dreading the thought of more manual hacksawing I devised a method of getting my PHS back into this game.






Where there is a will there is a way.

I have also discovered why this PHS won't cut straight along the vertical.  The front blade attachment bracket is bent causing the blade to cant over.  I'll have to do something about that before attempting to gut the swing.


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## Tom Kitta (Jan 7, 2019)

I just completed this style of attachment - 




I made two spots for a handle.

It attaches next to my tool post. I need to re-do the base as the attachment forces too much sickout of the part to be made into a ball. Also the base has to be rather tight link with the round post - too much wobble is no good. 

Rounding steel stock is easy - making balls is not that easy - you need to play with radious setting. You can polish the round part with sand paper making it shiny. Don't expect total round balls - there is as on the video part where some shaft goes in. There is a bit of learning curve. In order not to hit the tool post I run late backwards and make ball in reverse. Remember that you only move your ball maker in 90 deg arc - you will kill your insert if you go to the other side by accident.

Well after some fixing it should be better. So far made one round rod and one ball attachment.


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## YYCHM (Jan 8, 2019)

Tom Kitta said:


> I just completed this style of attachment



How high is yours from bottom of the base to tool edge?


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## Tom Kitta (Jan 8, 2019)

Not sure - I would guess more than 5 inches - it is a large lathe with CA tool post - 16" swing. I have the base located behind the tool post right on the cross slide thus it is low to start with.


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## YYCHM (Jan 8, 2019)

Tom Kitta said:


> Not sure - I would guess more than 5 inches - it is a large lathe with CA tool post - 16" swing. I have the base located behind the tool post right on the cross slide thus it is low to start with.



Do you think it can be done only 2 1/4" high?


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## Tom Kitta (Jan 9, 2019)

The top part - where the insert goes has to be able to be set at the proper tool height - i.e. it has to touch the centre - just like any tool you put in your tool post. 

For some inserts it can be a touch higher for some a touch lower but generally in the ballpark of the centre. 

Thus, for larger lathe the tool has to be taller and for smaller lathe it can be rather short. 

The L shaped attachment can stick from the base as long as it is sturdy - I doubt people will take very heavy cuts with a ball turner & my super limited experience with it so far points to it as not something that is a very precise ball maker so any flex in the L is a non-issue. My L is made of 1/2" by 1" mild steel, the large round part is made of hard alloy steel (as this is the only large round stuff I have).


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## PeterT (Jan 9, 2019)

Like Tom says the cutting edge has to be on spindle center line. regardless. But the base + swivel + 'L' holder must collectively accommodate the ball diameter itself, so that might limit the maximum diameter you can cut depending on how you make it.


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## YYCHM (Jan 13, 2019)

Got my PHS issue fixed or so I think.






I concocted this blade tensioner from a 5/8" bolt on my mill.











Makes a pretty square cut in both planes now.  Not perfect but much better.






This is what was liberated squaring up the bad cut that the original blade tensioner caused.  It was pretty bad.

Tomorrow I'll attempt to gut the swing using the saw.


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## RobinHood (Jan 13, 2019)

YYCHobbyMachinist said:


> I concocted this blade tensioner from a 5/8" bolt on my mill.


This is worlds better than what you started out with (i believe it was welded before). It shows in your much better cuts. Good job.


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## kevin.decelles (Jan 14, 2019)

Here is how my blade attaches















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## Tom Kitta (Jan 14, 2019)

I decided to upgrade my a bit unstable attachment with a set of two bearings - one is for the thrust and the other for usual rotational forces. Both are total overkill but 40mm bearings is what I had on hand. The thrust bearing is from MT4 live centre so it can definitely take some beating. Maybe I post some pics. 

I am going to use 3/8-16 screw from the top to apply the pressure to the thrust bearing - I hope it will be enough to make this whole thing stable. 

I try first without re-doing the base plate but I probably will have to - Its not a great feeling when a chunk of say 1.5" thick metal sticks out on a 0.5" thread around 20cm from the chuck and goes around 800rpm. I guess I would either have to take very tiny cuts or use some kind of thick sleeve for the 0.5" thread or use some kind of support.


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## YYCHM (Jan 14, 2019)

kevin.decelles said:


> Here is how my blade attaches
> 
> 
> 
> ...



Yup.... same arrangement as mine.  Thanks for posting.


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## kevin.decelles (Jan 14, 2019)

I'm curious about the 5/8 bolt. Mine is nowhere near that size . Can u post a pic of the entire piece you mAde?


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## YYCHM (Jan 14, 2019)

kevin.decelles said:


> I'm curious about the 5/8 bolt. Mine is nowhere near that size . Can u post a pic of the entire piece you mAde?


















Here you go.  I chose 5/8" because I wanted lots of meat to thread the blade screw into.  Probably over kill.

Without the top notch I found that it canted, so the notch was added to bring the nut bearing surface to the center of the arm slot (if that makes sense).

I'm really impressed with how square it cuts now.


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## YYCHM (Jan 14, 2019)

Had the day off today so I took the opportunity to gut the swing.






So I now I have the base, two supports and the swing roughed out.

Never in my wildest dreams did I imagine a 1" thick piece of steel would be such a challenge to work with.


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## kevin.decelles (Jan 14, 2019)

Thx for the tension nut pics, nice solution . 




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## YYCHM (Jan 14, 2019)

kevin.decelles said:


> Thx for the tension nut pics, nice solution .



Looking at the image now, it needs one more tweak.  The flat the blade contacts needs to have a step milled to the center of the web + 1/2 blade thickness.  Got ahead of myself in my enthusiasm to try it out.


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## YYCHM (Jan 17, 2019)

More progress today.  Mainly drilling and tapping mounting holes.






The tool point ended up within 1mm (high) of the chuck center.  I can correct that with a little milling.

Should have given more thought to the swing pivot.  Drilled holes and standard cap screws don't have a very tight tolerance.  There is a wee bit of slop there.

Mounting the sucker to the cross slide is the next challenge.  Cross slide only has provision for 2 M6 screws.


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## PeterT (Jan 17, 2019)

When you figure out final centering, it might be better to err on the high side as you can always grind back the tool steel but hard to add on. having said that I think some of the cheapo carbide brazed shank tools stand proud of the square shank section. You could even use like a 60-deg threading point, but better to stick with HSS which you can shape yourself

You can also get round section HSS bits if that helps. It probably would provide more contact area & tool rigidity in your tool holder vs the edges of the square. OTOH its light cutting anyway & maybe more work grinding a flat on the side of the round for your your set screws & trying to get a consistent cutting profile. 

What I found is you want a smooth swivel action but no play or it shows up in the finish. Are those cap screws acting as combination axles & tensioners?

If you already know this then disregard, but its helpful to know the distance from the edge of the U ends to the center of your axles. You then add this to the radius when you set the cutting tool tip position so it will turn a ball of a specific diameter.


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## YYCHM (Jan 17, 2019)

PeterT said:


> If you already know this then disregard, but its helpful to know the distance from the edge of the U ends to the center of your axles. You then add this to the radius when you set the cutting tool tip position so it will turn a ball of a specific diameter.



Boy.... you lost me!  I thought the ball diameter was controlled by the distance between the tool point and the swing pivot point?

I mounted an indexable carbide insert tool but could switch to HSS if needed. 

The cap screws are intended to act as axles.  I don't follow the tensioners question?


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## PeterT (Jan 17, 2019)

_I thought the ball diameter was controlled by the distance between the tool point and the swing pivot point?_
It is, but its typically not easy to measure from the center of your pivot axles to the tip of the cutter. Maybe this markup helps explain. There are other ways of doing this but you have similar flats at the end of your U frame.


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## PeterT (Jan 17, 2019)

_The cap screws are intended to act as axles. I don't follow the tensioners question?_
I guess I'm wondering if the frame is too free floating (with play)  or loosens up over time, you anticipate cranking in the bolts a bit to compensate?


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## YYCHM (Jan 17, 2019)

OK.  I see what you mean now about measuring the tool tip to swing axis dilemma.

As far as the swing axle goes, I was hoping for better tolerance.  Had no intention of cranking the bolts to compensate.  Do you think a brass screw tensioning the axle in the perpendicular would remove the slop?


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## Johnwa (Jan 18, 2019)

Glad you got your PHS working for you.

May I suggest a shoulder bolt for the axles in your ball turner.  They look like this
https://www.amazon.ca/Aj-Antunes-Ro...&qid=1547841232&sr=8-3&keywords=Shoulder+bolt

The shoulder portion is a precision cylinder, length and diameter wise.  You can get them from local bolt suppliers.


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## YYCHM (Jan 18, 2019)

Johnwa said:


> May I suggest a shoulder bolt for the axles in your ball turner.
> The shoulder portion is a precision cylinder, length and diameter wise.  You can get them from local bolt suppliers.



Man....  I wish I had known such a thing exists!  I have already drilled and tapped the swing and support legs.  May be too late for this iteration.

I checked Fastenal's offerings.  They spec cylinder dia, len and thread len but no thread dia and TPI?  How are you supposed to work with that info?


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## Johnwa (Jan 19, 2019)

I think the thread specs are dependent on the shoulder diameter. For example I think all ½” S bolts have 3/8x16 threads.


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## YYCHM (Jan 19, 2019)

Johnwa said:


> I think the thread specs are dependent on the shoulder diameter. For example I think all ½” S bolts have 3/8x16 threads.



Upon revisiting Fastenal I discovered that if you select the details of each offering the thread dia and TPI are provided.

This may very well be the way to go.  I could bore out the current drilled holes to the next size and obtain a much better fit.


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## YYCHM (Jan 21, 2019)

Getting there.... slowly but surely.











Tool is 1mm too high (as predicted) and I managed to screw up locating the support leg holes by 1/16"... Grrrrr

Need to revisit the axle bolts next, as Johnwa suggested.  

Also, maybe a couple of holes and roll pins to keep the supports in alignment with the baseplate?


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## YYCHM (Jan 22, 2019)

Today I upgraded the axles to cylinder cap screws per Johnwa's suggestion.  Drilled the 3/8" support pivot holes 1/32 less than 1/2" and bored the holes out to match the 1/2" axles with a nice tight fit.  Much better.

Tried her out with a 1" piece of aluminum round stock I had kicking around.






I'm a little confused (nothing new) now.  Why am I getting 1/2 a ball?






A second go with a smaller dia yielded this....  Getting closer.  I'm wondering if the tool moved on me the first go?

In retrospect I should have mounted the tool hold down screws on the bottom of the swing.   Guess I could flip the swing over and run the lathe in reverse.






Couldn't resist....  I parted off that knob I had turned and mounted it on the end of the swing handle.


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## YYCHM (Jan 24, 2019)

Decided to try a different stock mounting approach today.






Mounted a piece of aluminum round stock on a bolt and chucked that up.






Almost got a ball, but the finish ended up poor.  Too much deflection by the bolt.  This arrangement could really use some tailstock support.  Hmmmm another project?  A narrow/thin tail stock dead center perhaps?


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## kevin.decelles (Jan 24, 2019)

What did you bore the holes to final diameter on? (Lathe or mill)


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## YYCHM (Jan 24, 2019)

kevin.decelles said:


> What did you bore the holes to final diameter on? (Lathe or mill)



If you are talking about the axle bolts I used my mill.

And THANKS AGAIN for the raw materials to make this!!!!!!


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## RobinHood (Jan 24, 2019)

YYCHobbyMachinist said:


> Almost got a ball, but the finish ended up poor. Too much deflection by the bolt.


Good job on getting this far with your ball turner.

You may want to try a “shear tool” cutting geometry on your cutter for a better finish. You can grind one from a HSS blank. Because of the much lower tool pressure a shear tool creates, you can better get away with the amount of stick-out you have.


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## PeterT (Jan 24, 2019)

Ball turning is one of those 'seems simple but actually more than meets the eye' type deals. I suspect your true swivel radius (tool tip to bolt axle center lines) may be a bit larger than your target ball diameter because there are remnants of a cylinder. But if your tool tip is not centered on the spindle axis looking at it in top view (the in-out dimension across the bed) and/or not centered on the spindle axis looking at it from front view (the vertical tool height setting in your case) that will impart what results in egg shape. So your final shape could be a blend of these discrepancies & hard to distinguish which is the main culprit. Not that we are trying to make perfect bearing balls, I'm just talking about cause & effect. That's why I was saying if you had a means to measure the tool tip off the C end flats & deduct some fixed dimension, that would be a more precise way of setting radius & that eliminates one of them. Centering is a bit easier to spot visually.

Another complication is we set do our best to set these variables but we have to advance the cutting in progressive steps. Which means the pivot center is moving & so we have to know when to stop. Too short or too long also affects shape.

Maybe this sketch helps. We want to make a 1" dia ball inscribed in the imaginary 1" stock. But I have exaggerated the radius to something larger & (tried) to show it advancing right to left. You can see the shape is something like what you have. And this assumes exact X & Y tool centering, just messed up the radius a bit.

What I have found useful is
- nail the tool radius with certainty because everything depends on that
- measure your stock diameter with micrometer. Make contact with your tool & zero your dial position. Now you just advance the leadscrew by half the amount & this is more precise way of establishing center vs eyeballing a cut


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## Dabbler (Jan 25, 2019)

You will end up with a far superior product if your stick out is minimal.  If you must stick due to limitations of your lathe/ball turner, consider getting a 2" diameter stock and threading it for your balls, and your deflection will be minimal.


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## John Conroy (Jan 25, 2019)

As Dabbler suggested, somthing like this to mount your ball blank on adds stiffness and resist deflection while providing tool clearance between the chuck and the ball. This one has 3/8" threads on the ID and I use a short stud to mount the ball blank.


You might also consider putting a bend in your handle so your hand stays further from the chuck (toward the tailstock) when the tool is swung behind the center line of the ball. Using a center in the tailstock is not really practical if you want the balls fully finished on the tailstock facing surface.


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## YYCHM (Jan 30, 2019)

Interesting..... Interesting...… Interesting.....   Looks like tool geometry is a big part of my issues.






I decided to try and turn a 2" ball, just to see if it could be done.  Here you have a 2" long piece of 2" dia aluminum mounted on a 1/2" bolt shank.  Note the nice finish across the top.  I did that with the swing in the vertical running the saddle power feed.  Can't get much better than that!  Now, note the crappy finish on the right side of ball.  Hmmmm…. what the heck is different doing that part other than not using the power feed?






The swath while turning the ball portion looks like this, no matter which side of the ball I worked on and the finish was crap.






When I got close to turning the left side of the ball to the center line, I decide to advance the tool only last time to the center line and cut back from center to outside.  I had for the most part been advancing outside to center.

WELLLL the tool grabbed way more of the ball than I expected and started carving a rather deep slice off the outside of the ball.  I figure I had pooched it for sure.  That cut kept advancing rather smoothly though producing a much much better finish.  It was pretty obvious the tool was now cutting on one side of the carbide insert rather than the point.






The swarth in this case looked like this.

So, now I need to find the right tool geometry.


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## Brian H (Jan 30, 2019)

YYCHobbyMachinist said:


> oooops…...
> 
> I was attempting to square up one end of a 1" X 4" X 7" piece like this
> 
> ...



About the down feed....I have virtually the same mill and have cursed the down feed also. If you ever come up with a solution I'd love to hear it. Mine has about .045" of backlash that I cannot get rid of. Great project BTW. It's on my to-do list.


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## YYCHM (Feb 2, 2019)

Brian H said:


> About the down feed....I have virtually the same mill and have cursed the down feed also. If you ever come up with a solution I'd love to hear it. Mine has about .045" of backlash that I cannot get rid of. Great project BTW. It's on my to-do list.



Haven't found a solution as of yet, but I'm still looking.  Mine seems to build up a bunch of backlash (mm's worth) and then dumps it all at once.  Very Very frustrating.


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## YYCHM (Feb 2, 2019)

So.... in my quest to find the proper ball turning tool (I tried every tool shape I have on hand) I have ended up turning an Acorn LOL.






While in the process of this experimentation I upgraded to a 4-jaw chuck.  Setting that puppy up was a real learning experience.  Going to be while before I'm proficient with that exercise.

Today I'll be picking up a 3/8" HSS tool blank and will attempt to grind an appropriate tool profile.  Any suggestions other than a "shear tool" profile?


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## YYCHM (Feb 2, 2019)

Does the tool in this ball turning attachment make any sense to anyone?

https://littlemachineshop.com/products/product_view.php?ProductID=1970&category=

What basic shape is it? 

A "shear tool" makes less and less sense to me for this application as I grind the HSS tool blank to shape.


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## RobinHood (Feb 2, 2019)

YYCHobbyMachinist said:


> What basic shape is it?


From what I can see, the basic shape should be like this:




The nose radius is exaggerated in the top view. Make it razor sharp and it should cut just fine.

On second thought, the shear tool geometry I suggested earlier will probably be less effective since it only cuts on one flank by design. You may also run into clearance issues with it.


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## TheLocalDrunk (Feb 2, 2019)

This thread is making me want to try now. I commend your persistence on this. 
Cheers!


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## Bofobo (Feb 3, 2019)

I want to relay an experience about turning a ball, it was in  shop and he was turning a ball with cnc, now as he began to get close to a spherical shape the tool path set at a constant depth of cut had an acorn shape that under more power ended “violently” as it tried to follow the circle pattern as it ran onto more material than it could move, in your machine (having owned one myself) the extra pressure flexes the assembly and the extra heat likely ruins the cutter, now, i suggest try making smaller cuts, each progressive tool advancement should be minute untill a near sphere is reached, and dont forget cutting oil, its messy and can smoke a bit sometimes but it makes for much better times had on the mini lathe


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## YYCHM (Feb 3, 2019)

RobinHood said:


> From what I can see, the basic shape should be like this:
> View attachment 4275
> The nose radius is exaggerated in the top view. Make it razor sharp and it should cut just fine.
> 
> On second thought, the shear tool geometry I suggested earlier will probably be less effective since it only cuts on one flank by design. You may also run into clearance issues with it.



This makes more sense to me.  I ground a sheer tool and that was a big fail.  Will save it for future experimentation.

Will grind the other end per your image and give that a try.  I think the rounder the nose radius the better actually.

Bofobo:  I have been making many many light cuts.. adnosium.  A better finish occurs when a more substantial cut is achieved.






The Acorn shape is due to me reworking one side over and over again.


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## YYCHM (Feb 7, 2019)

So, I ground this tool from scratch.  Was the first time I have attempted such a thing.  Took a few hours or more to achieve a shape that I thought might work.  Lots of breaks to allow both the tool and grinder to cool down.






End result turned out pretty good for a novice IMHO.






Finish on my aluminum ball is much much better now, however I appear to have turned a bit of an egg LOL.
My 2" ball has been reduced to approx. 1.8" after all of my experimentation.

The tool proved sharp enough as it sliced off the ridge on the acorn in a single pass no problem.  Needs to have the sides relieved more as it didn't appear to cut all that well as the tool approached the horizontal on the ball stem. The other thing I noticed is the aluminum appears to gall(?) and stick to cutting edge.  Would cutting fluid alleviate that?


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## PeterT (Feb 7, 2019)

Hard to say, but on regular aluminum like 6061 the smear finish is usually indicative of things like rubbing (not quite right tip geometry, not close enough to center, insufficient rake angle...). Or an extended contact edge. Cutting fluid will help but its not a cure all for finish. It helps with aluminum sticking to tool tip which in that mode can degrade finish.  A shot of WD40 will tell you that right away. I would have expected the better finish to be on the largest diameter of the ball where the speed is highest. You can actually get nice finishes with even a smallish (1/32" rad nose) tools in aluminum. especially in your application where you might be passing over the same shape without increasing feed like finishing pass. Its getting there. Tool geometry is an art in itself. But you have to have rigidity in the system. If the mandrel is bendy or the ball turner has excess slop in the hinge action, or the swing action is not aligned....it will show up in the work,


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## Bofobo (Feb 7, 2019)

I would think aluminum cutting fluid better than wd-40, in the shop we used silver diamond shaped inserts for aluminum that always left a beautiful finish. Had some time back there just yesterday 


fixing up a dual fork seal, by removing a shoulder....
Use some emery cloth to finish the surface and hit the buffing wheel


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## YYCHM (Feb 14, 2019)

Not one to give up readily I decided to try turning another 2" aluminum ball.

This time I turned a mandrel hoping to get around the excessive hang out dilemma.






The threaded stub is 3/8-16 NC.






This arrangement gave me no end of grief.  So I went back to using a 3/8" bolt and the steady rest.






This worked better.  The 3/8" bolt stub proved not to be a good choice.  1/2" was better.






I got this far.  Now all that I had to do was setup such that the ball was as close to the chuck as possible and finish the right side.  That didn't happen.  When I positioned the ball close to the chuck the run out made it impossible to turn.  Truing the bolt shaft in the chuck caused the ball to wobble badly.  Truing the ball caused the bolt shaft to be excessively eccentric.  I gave up at this point.

Ends up.....






The root problem was that the threaded hole in the 2" X 2" round stock had been drilled on center but at an angle off axis.  Either drilled badly or the tap did something unexpected.  I kind of knew this from the get go but thought the flaw could be turned out of the equation.  NOT.

In any event the stepped mandrel didn't work out very well.  It wouldn't allow the swing to come down low enough and the chuck jaws didn't appear to have enough holding power for the amount of stick out.

Live and Lean.

Back to the drawing board.


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## Janger (Feb 14, 2019)

10/10 on effort and perseverance. You'll get it and then we can get a tutorial?


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## YYCHM (Feb 21, 2019)

I repurposed that wobbly wonky ball I had turned into a flag pole cap.






Couldn't figure out a way of salvaging it.


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