Gears cutter

[kadora]

Guys please explain me this:
I would like to start to cut my own gears so i have decided to buy
gear cutter from Ebay .
One vendor description is:

HSS Tool Steel
Precision Ground Form Relieved Cutting Teeth
Pressure Angle 20 Degr.
Bore with Keyway
Module 1
A different Cutter is required for each Gear:
Cutter #1 will cut a Gear with 12 to 13 Teeth
Cutter #2 will cut a Gear with 14 to 16 Teeth
Cutter #3 will cut a Gear with 17 to 20 Teeth

I absolutely do not understand why i can not
use cutter 1 for cutting gear with / say / 84 teeth
or why is required different cutter for each gear.
Thank you a lot

 

[rklopp]

Think about the difference in tooth shape comparing a rack and a low-tooth-count pinion of the same module or diametral pitch. The shapes are markedly different, right? Hence the need for different cutters for different numbers of teeth.

 

[SmithDoor]

If have gear of size you can use as a template for grinding a cuter
I have use this in past and works great

Dave

 

[Swifty]

Kadora, you have to realise that you are cutting the GAP in the gears, on the smaller gears the gap is "wider" at the top to give the correct tooth shape, as the gears you are cutting are getting bigger, the gap is smaller at the top. To allow for this difference, they have come up with a set of 8 cutters, which as you have seen, have been designated a range right up to cutting a straight rack.

Paul.

 

[nemoc]

Before you spend money on the cutters, might I suggest you invest in a book that shows you how to make your own cutters and teaches the basics of gears and gear cutting. I have found this book very helpful. .http://www.amazon.com/dp/0852429118/?tag=skimlinks_replacement-20

 

[kadora]

Thank you friends for your help.
First what i have to do is to get more theory so
i will buy Amazon book as nemoc advices me.

Many thanks

 

[Cogsy]

Before you buy a bunch of cutters, check out this info about making your own hob. I've made several sets of timing gears for small engines and they work just fine. It really isn't hard either.

 

[gus]

Hi Kadora,

You are in good hands as all five of us have cut our teeth on gear cutting.And been cutting our own timing gears for engines and the very difficult mitre gears too.
Cut my very first spur gear in trade school and had the wrong idea you can cut a range of gears with 10 tooth ----100 tooth with one cutter.
Every Module has 8 cutters to cover a range of tooth count.
All my gear cutting know-how came from ''Gears & Gear Cutting'' by Ivan Law.
There is a book-----------Milling--A Complete Course by Harold Hall which covered milling and also some simple dividing heads for gear cutting. Gus made some simple direct indexing dividing heads. I believe possibly all five of us had a collection of DIY gears with 1/2 tooth.Part of learning curve.

 

[gus]

Later on you may need to have a Rotary Table with dividing plates to cut a range of gear tooth count.
You could also DIY RT. Made my own. Indexing Plates follow later.

 

[gus]

Hi Kadora,

Involute Gear Cutters per Module Set of 8 cutters cost US$86 per set for Module 1.0 from CTCtools.
These are HSS. Ebay etc not good place to buy gear cutters.

Attached is a tabulation from Newmantools on Gear Cutter selection given the number of teeth on gear.

A master catalogue from KG Gears will be good reference. Cut some gears using this catalogue data.

Took me a while to get a grasp on gear cutting. Gear hobbing best done on a Gear Hobbing Machine.

I have standardised on Metric Gears. This is because I can buy metric gear cutters cheaper.

 

[Swifty]

Hobs are fine, but if you ever think about cutting bevel gears in the future, you will need single point cutters. Hobs will not work with bevel gears as they interfere with previous cuts.

Paul.

 

[Jeffrey]

May I suggest, Ivan Laws book on Gear cutting and if you really get into gears, Gear Cutting Practice by Colvin and Stanley. After you understand what makes a gear, then you will be ready to cut a gear. It's not difficult, especially when you're talking form tools and spur gears.
Good luck

 

[kadora]

Thank you guys once more for your advices.
First I need to invest money to gear cutter set and a tutorial book to be
able to cut my first gear.
Gus price for CTCtools set is really reasonable so i am going to
find how to order it.
Thank you