Steam Tractor 3/4" (Rudy K)

[Don1966]

Well Kim all I can say is looks like your gearing up.........
Cool buddy enjoy it.....

Don

[Kim]

Thanks Don!
Kim

[fumopuc]

Hi geared man, looks great.

[Kim]

Thanks Achim!

Another weekend working on the gears 

For my next gear, I decided to move to the large bull gears.  They are 48 DP, 120 tooth gears, with a PCD of 2.5” (20 degree PA).  Using Don’s Handy Dandy Gear Spreadsheet, I calculated the size of the button I needed, and went to work.

Not a lot of pics of this, since it’s just turning. This one was 0.855” in diameter!  Much larger than the last.  So when I went to cut the relief on it, I decided to do it a different way. Since I’m doing single button, I will be using each side of the button. So I cut a relief on each side, about where I’ll be doing the work. After some figuring, I came up with about where I wanted to cut the reliefs. And here's the button, after the first side was cut:


For the second side, I turned it in the collet, just eyeballing it.  I figure its close enough.  And here are the two relief angles cut:


Then I went through the heat treating process.  I also made a larger hole in the other side of my button tool holder for these larger buttons.  This side has a 3/16” pin.


My latest button tool assembled:


Now to the lathe with a fresh gear cutter blank in place.  As I was setting up for the cuts, I hit my first snag of the day.  The button is so big, I can’t move it in the required infeed distance without hitting the mandrel.


To work around this, I decided to take off the end of the button, since that part really isn’t needed for the cut. Off to the grinder to take off a little more than a quarter inch of the end of the button. This worked great!


Or, it WOULD have, if I hadn’t made my NEXT stupid move.  I messed up on the infeed  calculations and ended up going in WAY too far. For one thing, I have to double the infeed, since my DRO reads out in diameter, not radius. But the real problem was I messed up when I subtracted off the part of the button I’d ground off.  It was just bad math. As simple as that. 

So, I poped another blank on, did my math right, and out came a much better tooth form!


I went through the process of cutting the teeth, reliving them, then heat treating.  Oh yeah!  And I remembered to stamp this one BEFORE heat treating it! (pretty impressive, right?)


Now, with the gear cutter complete, its off to make the gear blanks.  These are going to be 1/8” thick brass, just bit over 2.5” in diameter.  So, I’m making them from 1/8”x3” brass bar stock.  First I cut some chunks of brass:


Then I drilled & reamed center holes for the 2 blanks.


And fit them both up on the1/4” gear mandrel, and turned them to round on the lathe, like so:

My last move for the day was to get the mandrel and blanks setup on the mill to cut the teeth (an extraordinarily lengthy process for me  )


And here’s the list of stops that I have to make on the RT to cut the all the teeth!


Tomorrow, I’ll cut those gears!
Kim

[Bertie_Bassett]

looking good there

thats a lot of cuts to be making, hope you dont get distracted and make a slip up.

at least they are nice whole numbers so any mistakes should be easy to spot before the tooth is cut

[b.lindsey]

Very nice write up Kim. Looking forward to seeing the finished gears. 

Bill

[fumopuc]

Hi Kim,  120 cuts for 120 teeth, thats a lot. First I have been at bit irritated by the amonunt, but after checking the imperial
dimension of the 48 pitch with a pitch center diameter of 63,5 mm and the pictures with the brass disks in Front of the 4" RT it seems to be logical again

[Kim]

Thanks Bertie, Bill, and Achim!

Yes, I was a little worried about maintaining focus for 120 cuts. But it worked out OK in the end 

Achim, I’m glad you were checking up on me!  I’m new to this gear cutting, as is quite evident the many twists and turns in my lengthy tale here 

First cut – so far so good…


But a few cuts in, and I’m not so sure.  The teeth are not looking right.  I’m no expert, but they looked way too skinny to me!


So, I got my carefully calibrated 16 tooth 48 DP gear that I made first, and gave it a test.  Yup, those teeth are terrible!


After fretting a bit, I went back over my calculations for making the gear cutter.  I re-measured everything and sure enough, I was off in my numbers. At least what I wrote down.  Not sure how I got those numbers. Anyway, I re-measured multiple times, with different devices, and they all came out the same.  So I re-did my calculations, and it was clear that I hadn’t gone in far enough for the infeed.  Which would explain why the teeth are turning out so skinny – the gear cutter is too wide.

Rather than start all over again with another cutter, I thought I’d try to anneal my current one, and see if I could correct it.  So, that is what I set out to do.  To anneal, I used the same magnet trick, but WITOUT the bucket of water underneath.


Then I put it back on the mandrel in the lathe, lined up the tool again, and gave it another shot.


After that, I hardened it (note that I remembered to place the water back UNDER the magnet for the heat treating ).


Set it back up in the mill, and cut a few new teeth, on what had by then become, my test gear.  You can see that the upper 10 teeth took anemic and skinny.  The lower 10 teeth look much better!


So, I made 2 more blanks. This time, I did the bulk of the rounding on the mill – this was MUCH nicer than the interrupted cut on the lathe!


After turning them to sized on the lathe, I put the blanks back on the mill, lined up everything ever-so-carefully, and went at it again.  Here I am at the half way mark:


Here it is all done.  This took me longer than watching a feature length Disney movie, and it was almost as interesting!


After a little cleanup, here are the bull gears, and the two 16 tooth pinions:


Not fast, but very satisfying!

I’ve got an 80 tooth, a 66 tooth and a few other gears to go!
Kim

[b.lindsey]

Sorry about the miscalculation Kim but those final gears sure look great to me. That must be very satisfying  and rightly so!!

Bill

[10KPete]

It may be the camera angle, Kim, but those gear teeth look more like saw teeth in that they seem to be 'tilted' in one direction.
As if the cutter wasn't on center line.

This is an interesting adventure and I'm following right along!   

 

Pete

[Kim]

Thanks Bill!  Yes, very satisfying

It may be the camera angle, Kim, but those gear teeth look more like saw teeth in that they seem to be 'tilted' in one direction.
As if the cutter wasn't on center line.

Yes, you're right there, Pete.  It's a little inconsistent around the gear.  The camera angle causes some of the angled look, but not all of it.  Some of the teeth are spot on, and some of them are off a bit. I think there are multiple factors here - one is a small amount of asymmetry in the gear cutting tool - I'm getting better at these, but the large button was very hard to line up accurately. Also, there is some run-out with my RT.  The closest I could get it was about +/- 3 thou, and that causes some of the 'saw-tooth' shape too. I'll see how it works together as I move forward. It isn't perfect, but it's better than any gear I've ever made before .  And each one will get better still.  If it causes me problems, I'll do it again and call this one practice.

Thank you for the comments and the input!  If there are other things that are contributing to this, I'd love to hear that too!

Kim

[10KPete]

You're way ahead of me, Kim. I've never made a gear from scratch so it's very educational watching you, and others, learn this process. Neat stuff....

Pete

[mal webber]

Hi Kim, just catching up with your build, very interesting on the way you went about your gears making your own cutters as Pete said very educational.

Mal.

[Don1966]

Kim for being your first gears you have achieve good results even with the mishap. Mishaps happen when we are learning. They will get much better as you progress in your venture. You have taken the time to read and prepare yourself. The key here my friend is trying and succeeding no matter how many tries, this is what you have done. If you don't, you would always be on the sideline watching others progress. You will enjoy making your own now that you have tried. Bravo my friend for your accomplishment.......

Don

[Jasonb]

Kim, I wonder if the cutter is a bit blunt or getting bluntand bending the tooth above it into the previously cut space, edge looks a bit dull in this pic. This would be more likely to give inconsistant teeth than setup or cutter geometry