Gear forms

[don-tucker]

I need to cut gears in .6 MOD and .55 MOD so I have been trying to find info on the form to make the cutters,can someone help please.
Don

 

[gbritnell]

Purchase the book called Gears and gear cutting by Ivan Law. For the home shop machinist this is one of the best books available.
Short of that do a search on this forum and you'll find many instances of gear cutting that was done by the members.
gbritnell

 

[kvom]

I understood the modulus system to be teeth per mm, so .6 would be really tiny. Do you mean .6 teeth per cm?

 

[MuellerNick]

I understood the modulus system to be teeth per mm,

m = d/z = p/pi

with:
m: modul
d: pitch diameter in mm
z: number of teeth
p: pitch in mm
pi: 3.14

Nick

 

[don-tucker]

I understood the modulus system to be teeth per mm, so .6 would be really tiny. Do you mean .6 teeth per cm?

It is for a clock so it will be tiny,def .6
Thanks lads,what I really really want is a drawing of the tooth form.
Don

 

[MuellerNick]

Thanks lads,what I really really want is a drawing of the tooth form.

Depends on the number of teeth -> gearotic

Gears in clocks are often not evolutes.


Nick

 

[don-tucker]

Is it possible that someone on here could let me have a drawing of the shape I need to make a flycutter for cutting a .6 mod gear for the clock I am making,the clock uses the same form for all the gears.I have been trying for a while to get this info but no luck.
Don

 

[Jasonb]

As said you will need more than one cutter to suit the number of teeth, a small sproket does not have the same profile tooth as a large wheel even though they are all the same MOD so a picture or drawing will be of little use. This is why commercial cutters need eight cutters per pitch.

http://www.rdgtools.co.uk/acatalog/05_MODUL_E_GEAR_CUTTERS.html

Get Laws book as this shows how to make the button cutters to cut the actual gear cutter and gives the formula for working out the sizes. Take a look back through Ramon's "Table engine tale" to see it being done.

J

 

[Cogsy]

I don't know if it's going to be good enough for your needs, but I followed the directions on this link to make a 'hob' for cutting module 0.8 gears, and the author made module 0.5 gears with this method. Just follow the steps on the various pages.

Mine turned out good enough for a model engine, but I'm not sure about a clock.

At the very least, it has a heap of good info on gears.

 

[Mainer]

I think clock gears are typically a cycloidal tooth form, not involute.

Also, the tooth shape is not as critical because in a clock speeds are slow and parts are a "rattling good fit" to minimize friction.

 

[don-tucker]

This is where the confusion arises,The guy who designed the clock,says it can be built with just two cutters .6 mod for the main wheels which have 100 t,96,and 50 t,and the pinnions use a .55 mod cutter.
maybe he is not being very fussy and it would still work,
Don

 

[Cogsy]

You could fill books with how much I DON'T know about gears, but mixing mod's in mating gears seems plain wrong to me...

 

[don-tucker]

Maybe the fact that not a lot of power is being transmitted it is not that critical,as long as the ratio is right.
Don

 

[MuellerNick]

Clock gears really are not made to envolutes or cycloides. They have a different shape (but please don't ask me how it is called. Basically, it is quite crude. Ask a watchmaker about the shapes.
Keeping this in mind, hack a cutter that resembles a tooth and mill all gears with it, no matter how many teeth. You just have to adjust cutting depth, so the gears mesh (at a given distance of the axles).

One cutter does it all.


Nick

 

[SmithDoor]

If you are replacing a gear just use the old gear as your template. If you making both gears and is great that 24 teeth use the Excel work sheet found at http://www.homemodelenginemachinist.com/downloads/ this is the old type gear form not INVOLUTE gears.

Dave

I need to cut gears in .6 MOD and .55 MOD so I have been trying to find info on the form to make the cutters,can someone help please.
Don

 

[don-tucker]

Thats what I wanted to hear Nick ,thanks ,I just wanted to get somewhere near.
Don

 

[LongRat]

Geardxf is a nice, simple program that will allow you to extract the tooth form (and therefore cutter form) for any spur gear. Check it out: http://www.forestmoon.com/Software/GearDXF/

 

[chipenter]

I hope this will give you something to work on .

View attachment gear cutters.pdf

 

[don-tucker]

Thank you all very much
Don

 

[SmithDoor]

I try out the software works great use the old one on the list. I even try 4 tooth gear

Dave

Geardxf is a nice, simple program that will allow you to extract the tooth form (and therefore cutter form) for any spur gear. Check it out: http://www.forestmoon.com/Software/GearDXF/