Horse drawn Galion road grader circa. 1913?

[Don1966]

Nice looking Hobb George and gears which I know you love to make. Really looking forward to more updates on this project since I grew up on a farm and saw these in action.


 
Don

[Craig DeShong]

Beautiful work George.

[gbritnell]

This part is probably the most complex in terms of setups, fixturing and machining. This is the housing that holds the worm gear that runs the blade up and down. It's mounted onto a combination of plate brackets and some bent angle iron.
I started with a block of brass that was machined to the overall dimensions H 1.677 W 1.292 D .597. As with any complex machined part you really have to plan the cutting steps so you don't end up with no where to hold for the final cutting. Due to the shape of the part I drilled the worm cavity so that it would accept plugs that would have the shaft diameter reamed into them. I drilled though first then opened up the hole with first a drill then a drill of the same diameter that had the end ground like an end mill to created a flat bottom in the hole.
The next step was to rough out the worm wheel cavity. It was first drilled through then roughed out with a .375 end mill to depth. The cavity was then bored to the final diameter.

[gbritnell]

Several step cuts were made and using my radius step of routine I cut the radius over the large diameter hole for the worm cavity. The part was then rotated in the mill vise and several step cuts were made to create the shape of the lower area of the part. The radius on the end of the .25 diameter mounting lug was also stepped off.
The part was then filed and sanded smooth.

[gbritnell]

The boss on the back of the housing has 3 supporting ribs. I contemplated how to add them to the part. One way was to machine the piece then solder the 3 ribs to the cylindrical boss but that would have been extremely fiddly and the chance for misalignment was too great so the plan was to mill them right out of the stock.
The part was turned over and the ribs first roughed leaving enough stock to provide fillets at the rib/housing joint.

[gbritnell]

The ribs then needed to have an angle milled onto them and the one direction was no problem because I could clamp the part in the mill vise at 30 degrees but the other direction didn't have anywhere to clamp so I set the pieces up in my Sherline vise and clamped it into my mill vise for the cutting.
A piece of .25 bar was turned and drilled to fit between the ribs and into the counterbore in the housing. It was then soldered in place.
For this soldering job I had purchased some Stay Bright solder. It has a higher melting temperature (450 degrees) than regular 50/50 solder and is stronger.

[gbritnell]

Before proceeding I need to make another fixture. This one will hold the part to a plate mounted on my rotary table. It will locate by the bored hole and the part will be secured from possibly turning while cutting with a stop boss mounted on the fixture plate. I don't need any oopses at this point. With this setup I will machine the circular outside shape and machine the 4 lugs that hole the cover.
I'll keep you informed.

[crueby]

Great sequence for a complex part!  Watching along with great interest, as usual...   

[Kim]

That's a lot of work in those parts, George.  Beautiful!
Kim

[gbritnell]

The gear boxes are finished. The outside diameter was milled leaving the bolt bosses. The part was removed and the radii filed on the bolt bosses. Next up were the covers. I chucked a round piece of brass in the chuck on the rotary table and basically cut the same shape as the outside of the gear boxes. The hard part was cutting the finished cover from the parent stock. The first one I did I put the bar back in the lathe and used a parting tool. I had a little bit of an issue with the part cupping somewhat around the edges (fixable) so the second cover was cut from the bar with a large .032 slitting saw. The cover is only .047 thick so it's kind of fragile. The raised triangular shape on the outside of the cover is a boss for an oil hole. When I get my mill table cleared for another tool I'll drill them at an angle matching the top of the boss.
When the gear boxes were made I had to drill out the cavity for the worm gear. This left a large diameter on one side of the box. To fill it I had to make a patch piece which matched the radius of the outside of the box. Into this plug went another piece which has an elongated rectangular shape. It had to be filed to match the radius of the first piece. I think I have about 3 hours just making the tiny plugs and soldering them in place.

[fumopuc]

Hi George, the parts are looking great.

[gbritnell]

I have never cut a worm gear before, well except if you count the one that was originally published many years ago by using a tap held against a circular disc.
I started out by developing some dimensions that would fit within the confines of the gear box. To cut the worm I had to use an available pitch that my lathe would cut.  After some calculating I settled on 16 TPI for the worm. The worm would have a 14.5 degree tooth profile like a spur gear. I ground up a lathe bit and approximated the tip width of the tool erring on the side of too sharp. This would at least give me enough depth for clearance.
I'm assuming the gear boxes on the grader, one one each side of the operator that raise and lower the blade, would be moved forward for down and backward for up. This would necessitate a left hand set of gears and a right hand set.
I cut the worms first and used my thread wires to measure the depth or width as the case may be. The thread wire set is calculated for 60 degree threads so I had to find a set that would fit into the 14.5 degree tooth form. This is where Autocad comes in so handy.
Next up I turned a couple of discs for the wheel. (I think that's the proper reference, worm and wheel) I also made a mandrel to hold them for cutting the teeth.
The worm is a screw and therefore has lead to it. Taking the circumference of the pitch diameter of the worm and the lead for 16 TPI I calculated the lead angle. I came out to 5.262 degrees. When doing all the figuring to get a tooth count on the wheel that would match the pitch for the 16 TPI I came up with 50.2655 D.P. For a diameter that would fit into the gear box the tooth count came out to 54.
To cut the wheels I set the dividing head at the proper angle and using a blank bar I indicated it to get the exact angle. The next task would be to set the cutter exactly on the center of the face of the wheel. To do this I put a layout line on the blank disc and mounted it on the arbor. Then using my height gauge I set the blank perfectly horizontal by lining up the scribed line. The scribed line also carried around to the edge of the gear. By eye I set the cutter as close to the line as possible, using a magnifying glass. I moved the cutter in until it just touched the disc then adjusted the Z and X positions until the witness mark was as close to center as possible.
I cut about 10 teeth  then moved the cutter out of the way so I could get a measurement over the worm and wheel. Here again the CAD drawing makes this a snap. I had to adjust my Y depth about .006 to get a proper overall reading. Once I was satisfied with the depth I set the Y -0- and cut all the teeth.
To cut the second wheel I had to change the angle of the dividing head to the other side of -0- and do all the same procedures as the first wheel.

[Admiral_dk]

The gears look amazing for a first try 

The third picture, first looked wrong to me, like you had the cut exactly 90 degrees to the gear (result of the angle the photo is taken from), but the next picture reassured me that all is good as one can clearly see the angle the teeth are cut to match the worm - phew, nothing wrong with my mental "setup" from your description.

Thank you for writing you build log here George   

[gbritnell]

It's been awhile. You all know that sometimes life gets in the way.
If this project was just machining it would progress at a much faster pace but it's going to be about 80% fabrication. Such is the case with the gear box mounts. They are made up of 3 pieces, 4 actually if you count the piece of angle material across the bottom. First there is a bracket, a flat plate with 4 bosses going through it. After assembly the bosses need to be machined to match the angle of the frame rails so that the gear boxes axis will be parallel with the centerline of the machine. Mounted to these plates is a flat curved piece of stock (.025 thick) and a piece of bent angle stock. Not being able to bend angle stock necessitates machining it from solid. There is a left and right hand. This required yet another fixture plate and setting up the rotary table. It seems I jump from the vise to the rotary table almost daily.
Mounted to the angle stock is another plate (.032 thick) that follows the curve of the angle stock. I machined and filed the upper part the annealed the middle section and bent it around a piece of stock with the same radius as the angle material. It was then temporarily bolted to the angle material and clamped so that the other mounting hole could be drilled. This whole affair is then mounted to the frame with rivets but while in the construction period I am using 0-80 bolts with round heads to replicate the rivets.
From the gear boxes is a .156 diameter shaft that ultimately will lift the blade assembly up and down. The shafts are supported by cast brackets on the full sized machine so I had to replicate them. The stock was roughed to the overall dimensions then another fixture was made to mount them for machining, yet again on the rotary table. These 2 innocent  looking brackets have almost 8 hours of machining on them, holes, angles, rib steps and through shapes. Once one side was done the fixture had to be reset so that parts could be flipped and the other side done.
The pictures show where I'm at. It doesn't look like a lot of progress to the naked eye but at this point I have many hours invested.
gbritnell

[crueby]

Stunning work, as usual, on a very complex set of shapes. Watching along here!