Find an old toy worn gear drive or Crescent wrench adjusting screw to use as a pattern and cast one. You have to have some parts made from some different material to set it off. 

Quote from: rusty on August 21, 2014, 05:35:48 PM
It seems the original meaning of swarf was the grit that wore off a grindstone when sharpening cutlery. It has evolved into any metallic debris that isn't supposed to be somewhere (eg swarf in an engine). The aircraft folks use it often to describe filings from manufacture that end up somewhere bad, like in a (clogged) fuel filter. There seems to be a tendency now to use it for stray debris in general these days...

(It has the sound, to me, of a mangled Scottish word..)
Edit: Oxford says mid 16th century: either from  Old English geswearf 'filings' or from Old Norse svarf 'file dust'

It's not everyday you learn something as old as this.  Old Norse and Old English are rather similar languages.  With a little work, if you can read one you can read the other.  Nothing Scottish about it.  Scottish is actually Gaelic, a version, really of Old Irish. "Swarf" does exist in *Scots Dialect* but Scots Dialect is actually derived from Old English.

Swarf exists in Old English as "gesweorf" from the verb "sweorfan" to rub or to file.  So the word has a firm English pedigree.  By the 16th Century swarf had the meaning of "dust and grit formed by grinding metal," but in Old English (before 1150) it meant filings.

Shown at the bottom left of the picture in reply #501 is the cylindrical part of the worm gear set and the wheel type gear (I don't know their proper names). 
I found the cylinder part at an old surplus store and attempted to cut the wheel gear by hand and failed miserably since I couldn't match the pitch nor tooth spacing (again I don't know the correct terminology).  Plus the wheel gear must have a concave shape to the teeth compatible with the cylindrical worm gear which can not be achieved with jeweler's saws and files.

I had considered the worm from a crescent wrench but can't match one to a round wheel gear.  I even realized that a bolt with regular coarse thread could be used as the worm portion,
but how to match it up with a wheel gear that has to be concave across the grooves?

It becomes readily evident that I don't know much about gears and couldn't even order a set from a professional company since I just don't understand the language of the business --
like pitch, pressure angle,CD, PA, PD, HD, HP and etc., etc., etc.

This is beginning to sound completely incoherent, so it's time for a break (or is it a brake).      Thank goodness the weekend is here.  It is Friday . . .  isn't it??

Ralph

Maybe some help.
http://www.girdersandgears.com/modelpower.html

https://www.youtube.com/watch?v=H4PpKuZZT6E

https://sdp-si.com/eStore/CoverPg/Gears.htm

Consider the gear system in a "high speed" chalk box.

>Worm gears are easy - they are just threaded pieces........

The worm isn't the hard part, the other gear is. The teeth on the matching gear are not just deeper in the middle than the edges, they are also angled to match the diagonal angle you get because the thread on the worm is a spiral. When you combine the two, you get a rather complex inverted helix....

You can drive a normal gear with a worm, but to do it, the worm has to meet it at an angle other than 90 degrees...

The other issue with worms is they work differently than normal gears. Normal (cog) gears have very little friction, the teeth push each other mostly, you can generally assume they have none at all when designing things. Worms on the other hand, slide across each other sideways, you can not ignore the friction. The reason this matters is, when selecting the sizes and ratios for the worm and spur, you have to take into account the relative wear rates of the materials the two parts are made of, and that often plays a part in selecting the sizes used for a certain gear ratio. This is why there are so many different things to specify when you want to buy a worm gear.

> Plus the wheel gear must have a concave shape to the teeth compatible with the cylindrical worm gear which can not be achieved with jeweler's saws and files.

The shape will match the outside edge of a grinding wheel (think dremil) the same diameter as the outer diameter of the worm measured at the pitch angle , when cutting at the pitch angle of the thread on the worm
(The pitch angle is the angle between 90 degrees and a line parallel to the thread on the worm)
Note that this diameter is slightly *bigger* than the regular outside diameter of the worm.

Time to go to the flea and buy some small plastic throwaway toys with battery powered motors, they almost always have a worm and spur on the little motors....(plastic)

pps: Sintered bronze might be easier to make teeth in...

Thanks, Les.  Those sites are very interesting, informative and helpful - easy to follow.  I've bookmarked 'em.
The Youtube page demonstrates why a layman would have difficulty building those items.  Damn!  That is really something.

I do have a chalk box somewhere in my stuff pile.  I'll dig it out.

Whoa, rusty.  Yea, that's what I meant - I think?  Little did I know - "a complex inverted helix", pitch angle and concave shape and what not.
You are right.  It is time to search and scavenge the Flea Market.  I will know what I need when I see it. 
It's just that verbalizing it is much more difficult than visualizing.

Ralph

Might be of interest:

http://www.instructables.com/id/Cast-Aluminium-Gears/

Just found this today at auction, thought this was an excellent representation of the worm gear.

Thanks, Oily.  That is an interesting process.  I've done some similar to build special parts. 
But Didn't know about the repair clay / process.

Yes, John K; that is exactly what I'm looking to accomplish.  Good picture, thanks. 
Went to the Flea Market yesterday and found all sorts of stuff I wanted but not the gears.
Will try again today.

Ralph

Another day at the Flea Market and found all kinds of stuff except the Worm & Gear I needed for the road grader.

It was a very hot day, so I went to the pavilion midway for refreshment.  A band was performing in the area where I sat,
and a guitar player paused to replace a broken string.  I found that interesting as he quickly replaced the string and proceeded to tune his guitar.

And EUREKA!!!  As he turned the thumb screws, I saw Exactly what I'd been looking for --
a guitar tuner with a gear and worm screw all in one compact, sturdy unit just the right size and form for my application.








The guy advised that I could get one at, of course, the local music store, and I ran right down there only to find it closed on Sunday.
First thing Monday morning I was there again and found that they indeed carry guitar tuners  --  only in packages of six and they cost a million dollars.

Next music store = same tune.
But at the third one the tech showed me a box full of used / replaced tuners, and said that sometimes the thumb screw breaks off,
and musicians replace all six to have a matched set.  He offered to give me a pair - one right hand and one left hand. 
I tipped him generously for two sets, and hurried home to see how they might fit the grader.

They will work just fine, are in good scale with the grader and should not be difficult to adapt.

Thanks, everyone for all your ideas and efforts to help.  With assistance like yours, this project is destined to succeed.
I'll post pictures as it continues to develop.

Ralph

We are proud to be of assistance, Ralph.

Hi Ralph,  I knew that sooner or later you would find the answer,  and the answer came when the man up above decided that you should take a break from the heat.

who would ever think of a "git-box tuner ?"    you have sharp eyes to spot the guy using it.

I had been keeping my eyes open, but never spotted anything like that.

and now we will wait for the next operation on the grader, good luck,  Frank

Thanks, Papaw.  I do get motivation, inspiration and valuable assistance from members of the forum.

Isn't it really something, Frank?  I spent two eagle-eyed days out in the hot sun, walked 100 miles looking for something,
and when I stopped looking so exhaustively -- it found me. 

Those guitar tuners are working out very well.  The hand wheel hub fit the gear shaft perfectly,
and they are in perfect scale with the miniature grader.
I can see now by studying them thoroughly that they are indeed complex devices as rusty stated:










Now I'll figure out how to mount them on the grader frame so that they can operate as blade raising and lowering mechanisms.

Ralph

The hand wheel and gear assemblies mounted nicely on the frame rails.
Next, I'll build and install the blade, blade assembly and turn table and figure out how to hook  it all up to result in a functional machine.

Ralph