Horse drawn Galion road grader circa. 1913?

[gbritnell]

The next step was at the milling machine. I had made a cutter from drill rod. I laid out the drawing to approximate the needed radius for the involute curve of the teeth and ground a high speed lathe tool to that radius. (.085 dia.) I had the required dimensions for the plunge and step-over so using a piece of .375 drill rod I formed the cutter shape on the end. The cutter was then fluted. After cutting I cleaned up all the edges with a magnifier then hardened and polished it.
I put the cutter in the spindle and set the height with a 123 block and adjustable parallel using a magnifier.
The rod was put in the dividing head and set true.
The surface of the gear was colored with a marker so I could see when I touched it with the cutter.
The Y axis was then moved to the full depth of the tooth (.039)

[crueby]

 

[gbritnell]

When making miter gears with a standard involute cutter 3 passes are generally needed but being as these gears are so small and they are brass I decided to skip the first through pass.
The first pass makes a parallel slot with pie shaped teeth. Not good for meshing. At this point what's needed is to trim the sides of the pie shaped teeth so they are parallel with a radial line from the center. This requires rotating the blank and then offsetting the spindle the appropriate amount.

For those interested here's the math involved in setting up the dividing head to make the gear.
The gear has 14 teeth. 360 degrees divided by 14 = 25.714 degrees per pass. When using the dividing head that will require using an index plate with 49 holes and making 2 complete revolutions plus 42 more holes in the plate. I have a basic Brown and Sharpe #0 dividing head (Vertex) Making the first pass isn't the problem it's how to make the parallel cuts.
On a 40:1 dividing head each revolution is 9 degrees so if you take 49 holes (the plate I'm using) and divide 9 degrees by 49 holes each hole will have a spacing of .18367 degrees.
Each tooth is 25.714 degrees so now you divide that by 4 which will make the side of the teeth parallel to the center line axis. (6.4285 degrees) Now how to get that number with the setup I'm using.
Each hole in the 49 hole plate is .18367 degrees and I need 6.4285 degrees so 6.4285/.18367= 35 holes. (I just happened to be lucky with this configuration. Usually you have to fudge the number)
From -0- on the dividing head I counted 35 holes in each direction. One direction for one side of the teeth and the other direction for the other side.
With the cutter touched off, the index crank in the proper hole and my spindle set for the proper offset (.008) I made 14 passes.
The dividing head was then rotated in the opposite direction to the starting hole and the indicator set to the other side of center and the remaining 14 passes were made.

[gbritnell]

This is what the finished gears look like. You have to realize that these gears are really small so just being off by .001 or .002 make a huge difference. These aren't going to be precision gears but just a means to change rotary motion on a shaft to 90 degrees. The last picture is for you Zee!!!
gbritnell

[zeeprogrammer]

The last picture is for you Zee!!!

I saw the picture before I saw your comment.
I can't describe my amazement.
Just look at that! Someone (I mean George) HAND-made those gears.
Wow.   

If they fell on the floor, people would think it was swarf and sweep it up.

[Don1966]

Those look like the gears i made on my Eastern and Anderson engine very small. Those are parallel depth gears George? In my gear calculation spreadsheets they calculate the offset and rotary table for you but that was a great explanation of the process loved it........


 
Don

[gbritnell]

Hi Don,
Yes they are parallel depth gears. I have all your spread sheets in a file headed 'GEARING'. The Helical one is great! Thanks for all your work on them and going way back some years ago for making the spreadsheet to calculate the offset miter gears for my differential.
gbritnell

[Admiral_dk]

I have always been amazed by the quality of your work and your engines George and this build looks to be just as big a challenge for you and with similar results 

Per

[gbritnell]

This is the first assembly using some of the miter gears that I showed. This part bolt to the back of the frame and by cranking the handle, transmits the rotary motion through the gears to the lead screw. Mounted on the lead screw is a traveler that will have a link going to one of the axle yokes. This will offset the rear of the machine relative to the axle assembly.
The bracket was machined from solid as was the crank handle. For the handle I first drilled the center hole then cut the central ribs. The part was then cut from the parent stock with a slitting saw. A threaded bushing was made and soldered into the center hole. The ball was turned with the shank then pressed into the hole in the handle.

[cnr6400]

 

[Don1966]

Awesome!!!!.......




   
Don

[Dan Rowe]

You have to realize that these gears are really small so just being off by .001 or .002 make a huge difference.

George, as the offset is only 0.008" for each side pass how did you find the exact center of the blank to set the indicator at zero? I am not sure any of my methods are accurate enough for this small of a gear.

Dan

[gbritnell]

Hi Dan,
Actually I do it by eye. Well partly by eye. I know the center of my dividing head so I set up a gauge block, in my case a 1-2-3 block with an adjustable parallel on top to get the required height for the dividing head center. As close as I can measure the tip of the cutter (.015) I bring the spindle down and using a fairly strong magnifying glass I line up the bottom edge of the cutter with the top of the parallel and set a -0-. I then do it again without looking at the indicator and see if I get the same reading. If not I do it a third time and split the difference of the readings. I then move the spindle down .0075 which gives me my center. When it comes time to offset and trim the teeth I rotate the dividing head (which I already know the angle) and offset the cutter using the dial indicator and make the cut. Like I said I'm sure it's within .001-.002.
With a proper involute cutter it's assumed that the cutting teeth are centered on the cutter so it's just a matter of touching of the flat surface of the cutter and dividing by two.
gbritnell

[gbritnell]

Making progress but all these tiny parts are very time consuming.
I finished the top for the draw bar gear box. A piece was cut to the overall dimensions and the mounting holes were put in but rather than drill the clearance diameter they were drilled and tapped for 0-80 screws to mount it to the fixture plate. After machining the holes would then be enlarged to the clearance size . The part was mounted on the fixture plate and that was bolted to the rotary table. The center was picked up the ribs and raised area over the worm gear were machined. The part was removed and the tops of the ribs files to the triangular shape. The center boss was then turned and soldered in place. The whole part was then filed and sanded smooth.

[gbritnell]

Next up are the two gear boxes that are used to cant the axles and wheels. These gear boxes were first roughed out to the overall sizes and the holes put in. Three of the holes are for attaching the cover plate and the other two are for mounting the gear box to the axle. The squared up part was first drilled for the worm gear. The hole was drilled then using the same size drill but with a squared off end I flattened the bottom of the hole. The part was then turned 90 degrees and the bore for the gear was roughed and bored to size. The shaft diameter is .104 so this hole was also drilled on center. The gear box has a cover plate so using the boring head a counter bore was cut .03 deep. I then cut material away from the outside prior to mounting on the rotary table for the circular shape.
The cover plate was next. I cut a piece of brass to the overall dimensions and clamped it in the mill vise standing up so that when the pieces were machined they could then be cut free with a slitting saw. The reason for this set-up is because of the raised boss that fits into the gear box. I located the center of the stock and put the clearance holes for the screws in. I then mounted my boring bar with the bar set with the cutting edge toward center. Running the spindle backwards I then cut the boss onto the stock.
The worm gear will be permanently trapped in the gear box once finished. I turned up a flanged piece of brass with a .104 center hole. This was parted off and the flange was filed and fitted to the gear box. Once I had a good fit of the part I put the worm in place put the cap piece over it then soldered it in place. I have and access hole under the cover plate to tighten the gear to the shaft. This way I can remove the shaft for further machining.
To get the main gear into the box with the worm already in place I filed the high points off of 4 teeth on the back side. This will allow the center shaft to be soldered to the gear and the whole thing put into the box.
The pictures show the front and rear of the gear box along with the cap piece and the gears.
The next picture shows the main gear and worm in place.
The last pictures show the finished gear box with the spur gear in place.
gbritnell