# Boring Head Ball Turner



## Baithog (Aug 3, 2014)

A while back I posted about my T-nut project. This is the next task on my way to making a tool grinder.  The mill is a CNC converted Seig X2. The mill was run semi-auto using the Mach3 MDI interface. 

The ‘Milling – A Complete Course’ book that inspired me has a chapter on making a boring head. I already have a boring head, but I do need a ball turner for my eventual tool grinder project. The book used pieces of square stock, but round stock in small quantities is much easier and cheaper to find. I took apart my 2-inch Chinese boring head and shamelessly copied the design. 


  The material for the body and the tool carrier is 12L14 steel round stock, 2 pieces 2 inches long.


  First step is to face one end of each in the lathe so that the ends are perpendicular to the sides. The hole in the center is there to make sure I didn’t have a tit in the center after the facing.





  The first problem is how to index the part so that all subsequent cuts are in the same plane, even if removed for measurements and such. The original plan was to clamp it in the vise, and mill a tab across the part the width of the table slots and about 0.100 high. That way I could use the table slots to index the part. I clamped the parts faced side down in the vice with substantial torque on the vice handle. I put a shapie mark, crossing the part and the vice jaw so I'd know if the part rotated in the vice. Cuts were very light to keep the torque on the part down.



Cutting the dovetails is next. I cut the male side into the tool carrier first. The original intent was to use my newly made T-nuts and commercial clamp bars to mount the stock directly to the table.  After much fiddling, I came to the conclusion that it was not going to work. The little 3 slot table and tiny Y-axis travel would have made it necessary to turn the part 180 degrees to cut the second side. It might have been OK to turn the part, but the cuts are more likely to end up parallel if it is clamped and not moved. So I ended up mounting the part in the vice. The index tab worked great for holding the part.

I indexed the X and Y DRO’s to the center of the part. That makes it easy to keep the dovetail centered. The hole that was originally drilled during facing was handy as the zero point.

The wide end of the male dovetail is approximately 1 inch across. The exact size can be plus or minus quite a bit.

I cleaned out all of the excess metal that I could with a 3/8 end mill before switching to the dovetail cutter. A 3/4, 60deg. cutter is just big enough. Cuts were light... 0.020 @ 3ips. Both the cutter and I survived the process. A bigger mill could be more aggressive.






More to follow.


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## mattthemuppet2 (Aug 6, 2014)

Lovably work! Don't forget to leave space for a brass or bronze gig between the dovetails though. That'll maker it easier to adjust out any play and to lock it down for cuts.


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## Baithog (Aug 10, 2014)

*Re: Boring Head Ball Turner - next Part*

This has taken longer than I expected. The tortoise bringing the required taps was even slower than usual.

  The next task is to make the dovetail adjustable and lockable. The common dovetail slide that we encounter is cut loose, and adjusted with a gib. The gib allows a tight fit that still slides under load. That is the kind of arrangement we need for machine ways. A boring bar does not need to slide under load. It is adjusted while unloaded and locked in position before cutting. A simpler arrangement will work for something like our boring head. The dovetail is cut so that it is close but free. The adjustability is provided by cutting a slot parallel to the dovetail. It is cut close enough to the dovetail that a small amount of metal is left at the base. The metal left at the base will act as a hinge. Hinges need to be thick enough to be stable and thin enough to flex with pressure from adjusting screws. The hinges I’ve seen are 0.060 to about 0.090 inches. Bigger dovetails need bigger hinges. I suppose a picture is better than my flawed description for someone that hasn’t seen this arrangement.




  There are 3 screws to adjust/lock the slide. The outboard ones are set so that the dovetail just slides. The center one is the lock screw. For this dovetail, I used 6mm screws and 0.150 bearings between the screw and the dovetail. The tap drill is run deep enough to leave a depression for the ball to sit in. A bottom tap will most likely be needed to finish tapping the holes.
  The slot was cut with a 0.060X2.25X0.625 slitting saw. I had a request for video on a different thread, so I gave it a shot with the slot. I have a lot of learning to do with this smart phone recorder. I nearly ruined the part by playing with the phone rather than paying attention to the mill controller. ‘G1 Y020’ is a lot more exciting than ‘G1 Y.020’.

[video=youtube;-BNocuYpaMg]https://www.youtube.com/watch?v=-BNocuYpaMg&amp;feature=youtu.be[/video]

  Drilling the holes for the adjust/lock screws.



[FONT=&amp]And tapping for the 6mm screws.



[/FONT]  Next is the adjusting screw. That will have to wait on tortoise delivery as my 1 inch round stock seems to have evaporated.


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## ray hampton (Aug 10, 2014)

one photo stated that you drill a hole to remove the tit but I saw the word tilt and was confused until my brain caught up with my eyes, NICE WORK by the way


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## chuckorlando (Aug 10, 2014)

Looks nice. I could be speaking from ignorance but thats how we learn. Most triangle ways I have seen are two dove tales with a gib. The triangles lock it in. How will this style hold? I would think it would want to rotate on the tip and pull the flat side out.


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## Baithog (Aug 10, 2014)

chuckorlando said:


> Looks nice. I could be speaking from ignorance but thats how we learn. Most triangle ways I have seen are two dove tales with a gib. The triangles lock it in. How will this style hold? I would think it would want to rotate on the tip and pull the flat side out.



My original plan was to do the standard gib arrangement. I discovered this method when I took my Chinese made boring bar apart. I shamelessly copied their design, which is probably copied or derived from somewhere else. The center screw pushes against the split side of the slot and forces it to rotate on the hinge. The split portion forces the male (pin) against the other side of the slot, as well as down. It works well in this kind of service. Many thousands of Chinese boring bars of this design are in use. It would not work for a dovetail slide under load. The contact area from the hinged side is small.


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## Baithog (Aug 24, 2014)

The tortoise has arrived with my steel, so time to get a few more tasks in motion. I will tap the body for the screw first, so that it can be used to test the screw when it is single point cut. I find it very easy to cut threads on the lathe that are either to fat or rattling loose. My preferred method is kinda cheating and only works with standard thread sizes. I cut the screw until I’m just a hair too big, and then run a die over the screw to finish it up.  Why single point at all if a die will be used? It is really easy to get the die started crooked… just a little is killer on a long thread. I’ve ended up with screws that look like a snake when starting from the round.

The first photo is the setup for drilling. I couldn’t us the vise because it made the part sit too high to clear the tap drill. I suppose that I could have cut an inch off the drill, but this situation is why I made T-nuts and bought blocks and such. The problems of clamping round parts to a flat table were readily apparent. I needed a V-block, which I didn’t have (along with thousands of dollars of other tooling). Suffering a terrible bout of impatience, I cut a V shaped slot in a piece of hardwood.  



If this project had been properly drawn and modeled, the screw hole would have been drilled and tapped before the dovetail was cut. Then I could have used two clamps. The 1-2-3 block is clamped to the table to stop the part from rotating under load. The real trick is to get the part clamped so that the dovetail is parallel to the screw. Against all odds, it came out OK.



Drilling the tap hole for the 7/16-20 adjusting screw proceeded without mishap. Not so the boring that followed. The hole needs to be bored out to about 0.750 for screw head clearance. The need for that will soon be apparent. There was a lot of vibration on the first pass with the boring head. The wood fibers had compressed. I tightened down the main clamp nut. There was a mild popping sound when I turned the nut signaling that the wood had split. The part turned and slid off to one side. Still resisting the need to order a proper V-block, I drafted the middle slot of my miniscule table. That was not an option when drilling. I have so far escaped making extra holes in the table.



Boring preceded OK. The imported junk brazed carbide bar complained, but still scraped and sorta cut the hole.



The next task is to cut slots in the tool carrier half. The will engage the adjusting screw. The shop was nearly 100 today, so I forgot to shoot pictures of the process. It’s hard to keep from dripping on the machinery with the heat and humidity. Sweat rusts machinery at a surprising rate.  The photo below shows the head ready for assembly. The commercial version of the boring head is below it.


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## zmotorsports (Aug 25, 2014)

Very nice job.

Mike.


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## Rbeckett (Aug 25, 2014)

I think I am a little lost.  The last comment was about cutting slots but I did not see any and you either have not bored the hole in the tool holder yet or it is turned and facing away in the photo.  Could you un-lose me please?  Otherwise it is very beautiful work with a lot of attention to the small details that will result in an excellent high quality tool when you finish it completely.  Thanks a bunch for the step by step and "how to" so far, even a novice like me can follow your well thought out directions!!!!  Keep up the great work!!!!

Bob


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## Baithog (Aug 25, 2014)

Sorry that the picture and my explanation didn't come out well. Lets try this - 



The screw on the left has a slot cut into the head - see arrow.
The hunk of metal on the right will eventually become the tool carrier. The arrow points to a pair of slots cut into the bottom of the dovetail. The slot in the screw head engages the land between the two slots on the tool carrier. As the screw is advanced into the base (which is to the left out of the picture) it moves the tool carrier along with it.

I don't seem to be doing all that well with my descriptions. Things may be clearer when the machining is done and the tool assembled.

Beyond getting some practice presenting a project, I wanted to show that you can do cool things with a HF mini mill... small footprint, backlash, floppy head, and all. A good machinist always trumps a fancy machine. And the only way to get good at machining is to try stuff. No, I'm not a machinist. I characterize myself as a metal butcher that hopes to be a half-assed machinist someday.


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## Baithog (Sep 20, 2014)

Back from vacation, so lets finish this.

The shaft for the head is straight forward lathe work. The first problem to solve is how to attach the shaft to the head. It has to turn both directions under load, so a plain screw in will not work. After casting about for a while I decided that keyways weren’t the solution, nor was a lock nut that would increase the overhang even more. So I embarked on a solution that would use a pin to keep the shaft from rotating in the head. The hole was bored first. The shaft body was turned to 5/8 to fit my boring bar holder. One end was single point threaded to 5/8-18 NF. The other end of the shaft was then turned to fit the head. I turned the shaft just a wee tad big, then let it cool before final fit. The shaft was just barely too big to push into the head. I put the shaft in the freezer rather than trying to take off the few tenths, and risk making the fit too sloppy. The next morning I heated the head on a hot plate to 300F. With head on a stout piece of hardwood and the shaft straight from the freezer, I set the shaft to the hole and whacked it with a hammer. It went in almost all the way, so I whacked it with the 3 pound hammer. I doubt that I’ll ever have to cross drill the head for a pin any time soon. Now if you have a well stocked shop with a 5/8 chucking reamer and a stout hydraulic press, you can forgo the hammer.




Next up is the tool carrier. One hole was drilled on center and another near the edge of the adjuster side. The intended cutter was 3/8 round HSS, so the holes were naturally 0.375”. The hole depth is well short of breaking through the dovetail. With the two cutter positions and the screw adjuster should make balls from really tiny to nearly 2”. Flats were milled parallel to the dovetail to ease fabricating the grub screw holes that will lock the cutter.




Nearly done now. Only one more part to fabricate. The turner needs a lever to rotate the head in operation. The 0.625” shaft is too small to directly attach a handle. Placing the handle on a carrier presents the same rotational problem as mounting the head to the shaft. The solution at the outboard end of the shaft makes use of locking nuts, one of which is the lever carrier. The carrier was made from a left over piece of head stock. The 2” round was faced, center drilled and tapped for 5/8-18 NF. The resulting round nut was chucked into my rotary table and six flats milled on it. The lever itself is a 6” rod, threaded ¼-28 NF at both ends. The hole in the carrier was not actually drilled until after the turner was assembled so that the lever wouldn’t end up at some strange angle.




To assemble the ball turner – A thrust washer was placed on the shaft, then the shaft was inserted into an AXA boring bar holder. The clamp screws are adjusted so that the shaft just turns freely. A thrust washer on the threaded end is followed by a 5/8-16 nut to take up end play. The threaded carrier is then run onto the shaft to lock the nut. The carrier is then marked on the ‘up’ flat, removed, drilled and tapped for the lever, then reinstalled and locked to the adjustment nut. This provides lock for the lever in one direction. To lock the other direction, a final 5/8-16 nut is installed and locked to the carrier.




The ball at the end of the lever was turned with this turner.
The cutter design is still under development, but this first guess works. I hope to make round knobs instead of oval ones with a bit more practice setting up the turner.


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