# Gear cutting from scratch

Discussion in 'General Engine Discussion' started by Moper361, Oct 27, 2017.

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1. Oct 27, 2017

### Moper361

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Hi All hope it's a good day for you all

I am in the throws of working out bits and pieces for small engine I plan to build ,I have come to the area of timing gears .I am not following any build plans for this project but have worked out I require the shaft centres to be approx 55 mm apart this is crank centre line and cam centreline this is for sufficient Conroy clearance ,and require 2 to 1 ratio .

I have never done gear cutting before ,I do have a universal indexing head on my mill with a direct plate with 24 holes and I do have dividing plates for it that I think I can work with .

My problem is I have absolutaly no idea on how to work out what cutters I require etc ,I would like information on what to buy to carry out this task what pitch and what number cutters that would be usable to cut gears for this task .
I am also a dunce when it comes to maths I was a practical kid not an academic 😞.I would like to purchase some cutters and an arbor online whilst I am away at work so as when I return I can practice the concept of cutting gears and get some experience .

I will read as much as I can on the subject whilst I am away and try my best to get some ideas on the calculations etc but a bit of help at the start on equipment for this task would be greatly appreciated until I am upto speed .

Regards Nat

2. Oct 27, 2017

### Moper361

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Is this remotely correct ?

I have been racking my brain all day on working out involuted gear cutters with what I can find online

This is what I have come up with on my calculations please correct me if I an not correct

If I was to make a 40 tooth gear using following cutter
M 0.8 32 DP #2 cutter my outside diameter would be 1.312

If I was to make another gear using
M 0.8 32 DP # 3 cutter my outside diameter would be 2.562

From here how do I work out the diameter pitch so I can see centre lines we tweet the two shafts
I am looking for 45 to 50 mm between centers

Also how do you determine the depth if the cutter is not marked ?

If I'm totally wrong in my understanding of cutters please correct me

Any help appreciated

3. Oct 27, 2017

### ShopShoe

#### Senior Member

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You can find all the information you need in Machinery's Handbook. There is an older version online that will have the gear information, but I don't have the link to it.

I've only cut gears in plastic and it worked out well. For that purpose, I made my own cutters. There are others on here who are more expert than me. I can recommend practicing on plastic just to get the hang of the indexing and cutting. (Or machinable wax?)

There is a book by Ivan Law that many cite in their posts here and elsewhere:

If you like videos, Keith Rucker on YouTube works through the process several times, for instance:

I hope this is helpful. I'm sure others with more experience will chime in with advice on purchasing cutters.

--ShopShoe

4. Oct 27, 2017

### Barnbikes

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What size gears do most people make?

Cut some SST ones today out of .250 material on the laser today.

5. Oct 28, 2017

### lohring

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If you want to machine several gears with the same tooth size, this is a great method. Only one easy to make cutter is needed.

Lohring Miller

6. Oct 28, 2017

### Wizard69

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I can't say im real strong on gear calculations but i do know one thing your center to center distances need to be precise. Saying that it is 45-50 mm is not useful. Your calculations should be to at least 3 decimal places {probably more} rounding off at the end.

7. Oct 29, 2017

### quickcut

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Hope fully I have this right. If you choose 48mm as a centre distance and at a ratio of two to one would mean that the one gear would need a PCD of 64mm and one 32 mm. ( radius would be 32mm and 16mm to make up the centre distance of 48mm ) . Using module 1, the required no. of teeth is 32 teeth and 64 teeth respectively. Module 2 would be 16 and 32 teeth . Module.8 ,as you mentioned, would be 80 teeth and 40 teeth . The choice of module would be determined by a host of requirements , transmitted power ,speed, type of material being a few.

Hope this helps

8. Oct 30, 2017

### ozzie34231

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9. Oct 30, 2017

### bazmak

#### BAZMAK

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I went thru the same excercise as you 12months ago.With advice from the forum and buying Brian Laws book it gets very easy very quickly

10. Oct 31, 2017

### Moper361

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I think im getting a handle on it and all advice given on here has been helpfull thank you to all that have taken time to advise .

Ive just taken a plunge and ordered a set of
M.5 ,m.1 , m1.25 , M1.5 all 22mm bore and no 1 to 8 cutters

This will give me a start
I have 1 question for those who have experience with russian and chinese cutters will the 22mm bore chinese cutters fit a 7/8 arbor , as i have been searching for a 19 mm straight shank 22mm arbor but all that seems to keep comming up on ebay is 3/4 straight shank 7/8 arbor i ca t seem to find metric specific straight shank arbors

11. Oct 31, 2017

### bazmak

#### BAZMAK

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I use R8 on the mill and bought a 50mm face mill with RCT mainly because the
the spigot was 22mm dia and i made a couple of collars for fitting the invalute cutters also 22mm.2 tools for the price of 1

12. Oct 31, 2017

### Hopper

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+1 on get yourself a copy of Ivan Law's book Gearcutting. It's one of the Workshop Practice series and costs about \$14 delivered to your door. It has everything in it you need to know.
There are also online calculators that you can use to find out the centre distance of various size pairs of gears in various modules. I dont have a link to one but have used them in the past. Law's book also has charts and calulations for centre distance vs module vs number of teeth etc.

bazmak likes this.
13. Nov 1, 2017

### john_reese

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If at all possible you should make the cam- crank center distance such that gears of a standard pitch will work. If your center distance does not allow use of a standard pitch Ivan Law's book contains info that lets you make a cutter for any pitch.

14. Nov 1, 2017

### bazmak

#### BAZMAK

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As pointed out many times and as i found out Ivan Laws book
is worth its weight in gold.Simple to understand and cheap at \$17
Makes the learning curve so much easier

15. Nov 2, 2017

### Hopper

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Under \$14 delivered to your door if you get it from Book Depository!

(No connection other than happy customer.)

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