Any suggested gear cutting sets?

[nautilus29]

I've been looking into getting a gear cutting set. Is there a particular sized set that I should invest in first?

 

[Brian Hutchings]

A gear cutting set comprises 8 cutters to accommodate the different tooth numbers but they will only cut one tooth size, so you need to narrow down the size of tooth you need to cut such as e.g. 1 mod in metric or 3/8" Circular Pitch or 20 DP (Diametral Pitch ).
Brian

 

[nautilus29]

Thanks Brian. Is there a tooth size you find you use the most?

 

[Brian Hutchings]

Nautilus29, a 3" traction engine used 0.4CP, 5/8"CP and 1/2"CP and a 1.5" traction engine that I am currently building is 16DP.
A lot depends on what is being built and what scale, also how close to scale it needs to be.
Some of the more obscure gears I have cut have been cut with a single point fly cutter, the actual cutters are very easy to make.
Hope that helps.
Brian

 

[nautilus29]

Yep that helps, I was hoping there was a somewhat standard size people use for model engines. Looks like I'll just have to buy or make some as needed.

 

[Donrecardo]

Sods law says what ever size you by on the off chance it will be what you need one day allways turns out to be wrong. As cutter sets are not cheap , I now only buy them when I know from the drawing what size I need

 

[methuselah1]

Where are you based, and what do you want to do? 20dp is a nice size if you like 1" scale traction engines or run a myford lathe, 18dp isn't as common, ditto for 16dp; my lathe uses 14dp, so I've got a set of those.

Usually, if it's simply a ratio you need, a massage of gear centres, or straight multiples or divisors of the specified dp will work with the cutters you have got.

I make gears quite often compared to most, and I make little IC engines too, so my requirements are catered for by the following dp sets...

14
16
20
32
36
40
48

All with 14.5° pa, as I restore pre-war machinery from time to time.

It really depends on what you want to do. Depending on your kit, it may prove cheaper to buy or make annular hobs (after J.A.Radford) instead of sets of 2 5/8" dia cutters. Last time I looked, I could have a custom hob made to my specs (Dathan Tool and Gauge, UK, no connection) for less than the price of three conventional cutters.

 

[awake]

Where are you located, and from where would you like to buy? Depending on the answers, you might find that modular gear cutters are considerably less expensive. Even here in the mostly-not-metric USA, I can buy modular gear cutter sets more cheaply. I find that module 1 gears will suit a large array of projects - keep in mind that you can make your gears with more or fewer teeth to suit your spacing needs. That is, instead of 24 and 48 tooth gears in a 32DP size, you might be able to use, say 19 and 38 tooth gears in a module 1 and come out with a similar spacing. (NO, I have not done the math, so these may not be even close to the right conversion - but hopefully illustrates the idea.)

 

[nautilus29]

I live in the US. I like the idea of going metric, it's what I first learned when I got into machining, and like you said since the world uses metric usually you can find tooling cheaper.

 

[coulsea]

if you look at an engine like the upshur with a 3 - 3.5 inch flywheel a mod 0.5 will look good. on a bigger engine with 6 - 8 inch flywheel 1 mod is good.
if you just want gears to drive a cam shaft you only need two cutters not the whole set of 8 and I have often forgotten to change the cutter between gears so if you only had 1 no one will know. you just need to adjust the center spacing.

 

[ninefinger]

The metric module cutters are significantly cheaper than the DP cutters of similar tooth size, so much so that I'm converting the drawings for the radial engine I'm building. This is mostly due to being available from China ( as opposed to being from say US / Germany / Poland / Taiwan etc. ). 0.5 mod is close to the 48 DP called for in my case so with a little math I can relocate the shafts to accommodate the relatively small variance in pitch diameter.
Ebay, Aliexpress or the currently popular Banggood.com have those cutters for ~$15 US a piece or sometimes you can find all 8 for ~$100. But as mentioned, many projects only need a few gears so buying as needed is probably the way to go as you may only need 2 or 3 of the set to make all the required gears. You can also "stretch" the range of the cutters for less critical projects as they are already an approximation and are only really correct at the smallest listed tooth count typically .

FYI - be careful when choosing cutters by their number designation (i.e. #1 thru #8), the metric sets have the numbering reversed from the DP sets - so a #1 module will cut 12-13 tooth gears while a #1 DP cutter will cut 135 tooth plus gears through to racks, though some Chinese sets mess this up too so careful ordering is required - check the claimed tooth range versus the cutter #.

Are you cutting manually or using CNC?

 

[mc_n_g]

As mentioned above the diametrical pitch (DP) is one factor.
The second factor is the pressure angle (PA) as referenced above.
Many modern sets are 20 degree PA rather than 14.5 degree.
Just pay attention you match the DP and the PA
There are many sites with gear formulas available through you favorite search engine.
Basic Gear Terminology and Calculation | KHK Gears
https://www.engineersedge.com/gear_formula.htm
Making Multi-Point Gear Cutters Is an great site with great photography to make your own cutters. I did a variation of this method.

 

[Peter Murphy]

I live in the US. I like the idea of going metric, it's what I first learned when I got into machining, and like you said since the world uses metric usually you can find tooling cheaper.

Don't say that too loud in the US lol somebody might hear you.
Here in Australia we tend to bounce between the two a little, due to a lot of old English & American machinery still in use here, but we are mostly metric especially new machinery

 

[Brian Hutchings]

My apprenticeship involved both metric and Imperial but nearly all of my modelling is of machines built to Imperial standards so that is what I use. Metric can be useful when ordering metal when you need a bit extra e.g. 8mm instead of 5/16" gives you a few thou to play with.
My machines are Imperial except for a Senior horizontal mill but it has DRO on X & Y (but not on Z).
Brian

 

[awake]

My machines and measuring tools are all imperial (not counting the digital calipers and DRO that can do either), but some of my tooling and nearly all of my own designs are a mix.

Metric bearings are so much cheaper than imperial bearings that it doesn't make sense to me to design for the latter, even if everything else in the design is based on inches. After all, when it comes down to it, I'm going to be cutting the bearing seat to as precise a size as I can, and it doesn't matter a bit whether that size is 1.250" for an imperial bearing, or 1.260" (=32mm, close enough) for a metric one; either way, for a home machinist like me, I'm going to squeak in that last .0001-2" for the fit I need. My CAD software doesn't care what unit I'm using, and it is happy to convert either to the other - put in a 32mm bearing, and get the 1.260" measurement shown to suit my inch-based lathe and mill. (Of course, 1.260" is rounded to 3 digits, but I can just as easily have it show 1.2598 or 1.25984 or 1.259843 or ... not that I generally get closer than +/- .0005, though I can get down to +/- .0001" if I really try ... and if I don't mind possibly scrapping two or three parts before I get there!)

If I'm doing 3d printing, I usually design entirely in mm, just because that's how the printer is set up, and a lot of the screws and nuts that I use with 3d prints are metric. But "designing in metric" may include converting some inch-based measurements to mm if I need to accommodate something inch-based in the design.

Meanwhile, I bought a set of 8 module 1 cutters and later another set of 8 module .8 from AliExpress or EBay or some such; each set cost around $50, but that was last year; maybe the prices have gone up. Neither set is best quality, of course, but they have proven more than good enough for what I am doing.

Honestly, for a machinist, who cares? I don't design or machine in fractions, I design and machine in decimals. It doesn't really matter to me whether those are decimals of an inch or of a mm.

 

[Richard Hed]

My machines and measuring tools are all imperial (not counting the digital calipers and DRO that can do either), but some of my tooling and nearly all of my own designs are a mix.

Metric bearings are so much cheaper than imperial bearings that it doesn't make sense to me to design for the latter, even if everything else in the design is based on inches. After all, when it comes down to it, I'm going to be cutting the bearing seat to as precise a size as I can, and it doesn't matter a bit whether that size is 1.250" for an imperial bearing, or 1.260" (=32mm, close enough) for a metric one; either way, for a home machinist like me, I'm going to squeak in that last .0001-2" for the fit I need. My CAD software doesn't care what unit I'm using, and it is happy to convert either to the other - put in a 32mm bearing, and get the 1.260" measurement shown to suit my inch-based lathe and mill. (Of course, 1.260" is rounded to 3 digits, but I can just as easily have it show 1.2598 or 1.25984 or 1.259843 or ... not that I generally get closer than +/- .0005, though I can get down to +/- .0001" if I really try ... and if I don't mind possibly scrapping two or three parts before I get there!)

If I'm doing 3d printing, I usually design entirely in mm, just because that's how the printer is set up, and a lot of the screws and nuts that I use with 3d prints are metric. But "designing in metric" may include converting some inch-based measurements to mm if I need to accommodate something inch-based in the design.

Meanwhile, I bought a set of 8 module 1 cutters and later another set of 8 module .8 from AliExpress or EBay or some such; each set cost around $50, but that was last year; maybe the prices have gone up. Neither set is best quality, of course, but they have proven more than good enough for what I am doing.

Honestly, for a machinist, who cares? I don't design or machine in fractions, I design and machine in decimals. It doesn't really matter to me whether those are decimals of an inch or of a mm.

I thimpfk, but am not sure, that at one time, calipers were made that used "fractional" instead of decimal. I thimpfk they went up to 1/128th" but am not sure. I have to convert a lot of drawings from fractional to decimal when I redraw them. Some times it's a terrible PAIN to do it.

 

[somniosus]

I've been looking into getting a gear cutting set. Is there a particular sized set that I should invest in first?

Hi Nautilus: I have been a lurker on HMEM for years and recently got into gear cutting. I self taught and avoided a lot of the complexity, someday I hope to have a fuller understanding but was able to cut useable gears in brass and aluminum with a little prep work and without advanced math. This is how I did it:
I just wanted to learn the technique so found some inexpensive involute 8 cutter sets of m1 module pressure angle 20 gears made in China on Amazon for around 140 dollars and a cutter head that would hold them on half price at a machine shop supply for 95 dollars CDN. The cutter set is actual quite good quality. I already owned a dividing head from Busy Bee I had gotten on a sale for around 200 bucks. I did some searching and found some very simple formulas for converting module to DP as I mostly work in inches not metric. I kind of reverse engineered from the module I had to what I wanted in terms of tooth number and got size of blank from that.

DP= 25.4 /module

in my case with a module 1 metric set this gives you DP of 25.4
I wanted to cut a 45 tooth gear and needed to figure out the blank diameter

this is n+ 2/dp

so 47/25.4 =1.850 inch outside diameter of work

My dividing head does 90 divisions per 360 so for 45 teeth 2 turns of the wheel

for depth of cut divide 2.157/dp =2.157/25.4= .085

to select cutter number from your set of 8-look at the tooth cut range for each cutter- turns out the Chinese number there is opposite to western so for this module 1 set:



Chinese teeth number Western
8 135-infinity 1
7 55-134 2
6 35-54 3
5 26-34 4
4 21-25 5
3 17-20 6
2 14-16 7
1 12-13 8

I used the no 6 cutter for a 45 tooth gear.
Using a similar approach I cut some 15 tooth gears and made a reduction gear system for elevation for a cannon model .
Hope this simplistic system helps. If you have some flexibility in your design these inexpensive cutters can work, if your gears need to meet a spec on a drawing and have to meet an absolute value interns of blanks OD etc then you are back to Machinerys handbook and a lot more complexity than this approach.
best regards Somniosus

 

[gilbycoath]

Does anyone know when needing to duplicate an existing gear how to figure out whether it is 14.5 or 20 degree pressure angel ??
Ron

 

[awake]

The only way I know to do it is to look at it closely (under magnification) in comparison with an example of each. Assuming the gear is standard (no stub teeth or such), the OD and number of teeth of the gear will let you figure out the pitch or module. With that in hand, I would use a CAD program to generate two full-size drawings of the gear, one using 20° PA and one using 14.5° PA. Lay the gear on the drawings, look through magnification, and see which matches.

 

[werowance]

i dont have much to add here but on metric in the USA. im fine with either however drills in the US in metric are hard to find and expensive. or at least thats the way it is in my neck of the woods.

on the gear cutters. i have ben able to get by with metric mod 1 and mod .75 sets on the engines i have made so far. but as everyone has said to be exact then each gear your plans call for will technically need the proper cutter for the size, angle and number of teeth. but dont let that scare you to awefull much. you can fudge a little on them and get by for fun use. just not in factory production i guess. i only have experience in home fun use side.