Gear Cutters

[Brian Rupnow]

I am considering purchasing a set of gear cutters for use when building model engines, etcetera. I know that members on this forum have them---I think Tel and Chuck do. What size would you knowledgeable people recommend? I feel kind of dumb, as I'm not even 100% sure what these things are called. I just did a search for "gear cutters" on littlemachineshop. com and nothing came up. ---Brian

 

[steamer]

If your talking about timing gears and such...you may only need two instead of all 8.

But if you talking the full range from the smallest pinion to a rack you will need the full set.

I probably wouldn't bother with a rack cutter....#1 cutter IIRC....as I've NEVER had to cut a rack.

You need to decide on DP or Module and pressure angle. I believe 20 degree PA is more popular, as it will transmit more power for a given gear width than a 14 1/2. The reaction forces are slightly higher.

DP of 32 to 48 seem to fly around the forum on a regular basis.


Dave

 

[Mosey]

Isn't it more fun to Hob your gears, and forget those infernal cutters? Isn't there a thread somewhere nearby about doing that?

 

[steamer]

Isn't it more fun to Hob your gears, and forget those infernal cutters? Isn't there a thread somewhere nearby about doing that?

YUP....but that wasn't the question.... ;D

There's a few here who make their own involute cutters....

What ever gets it done for you is the right way I suppose.....I look forward to input from Tel....

Dave

 

[kcmillin]

I have a full set of 48DP gears. Sometimes I wish I had a smaller DP set, but this is pretty much the smallest that is readily available. a 12 tooth gear is about .291" in diameter. I have also made 12 tooth 45 degree bevel gears with the same cutter and they ended up just under 1/2" in diameter.

I got mine from Travers
http://www.travers.com/skulist.asp?...evel3+id+30188&AttribSel=Pitch+Diameter='48"'

When I bought 2 cutters from them, they sent me a 20% off coupon which I promptly used to purchase the other 6. I cant say if this is still their practice, but it is something to think about.

I have only made a handful of gears, but I do not regret my decision to buy a full set. It really keeps my options open when designing, or thinking about future projects. Something I know you will appreciate.

I have seen Chuck Fellows make helical gears using these involute cutters. It can really opens up a lot of doors that were once closed.

Kel

 

[Brian Rupnow]

I'm reading all the answers, and appreciating the input. I will probably buy a complete set so I'm soliciting input BEFORE rushing out to spend a considerable chunk of money on the wrong thing.

 

[steamer]

No worries Brian....Horses for courses....

I think I do enough different work...small to medium size, that it seems I never have the right cutter for the job at hand...wrong DP, PA, wrong number.....NONE THAT SIZE!

It never fails with me.....

I have 2 or 3 for 16 DP for lathe change gears on my Logan...

Dave

 

[portlandron]

I have the following 32 pitch cutters and they have handled all the gears I needed for the four engines I have built.

#1 cuts 135 teeth - rack
#2 55 - 134 teeth
#3 35 - 54
#4 26 - 34
#5 21 - 25
#6 17 - 20
#7 14 - 16

I can't ever remember using the the #1 or 2 so if you want to save some money
just get # 3 through #7.

 

[tel]

My cutter collection is a bit of a mish-mash, 20dp, 26 dp, 40dp and module 1.

The 20 dp's are fpr Myford change wheels, likewise the Mod 1's are for the 9x20 change wheels, the 26 dps are some I got cheap somewhere. I find for out size of engines that the 40 dp's are very good - small enough to be tidy without having to strain the eyes.

The 'other' big advantage with them is they, as they fall exactly in the middle between 32dp and 48 dp, you can always arrange to make a set of gears to a given ratio with the same overall dimensions as the 32's or 48's.

 

[Mainer]

Personally, I would wait until I needed a specific gear cutter before buying it. I don't believe you'll save any money buying a set, and there is little point in trying to guess what you'll need ahead of time buying a bunch of expensive cutters you may never use because you never have occasion to need that number cutter, or that diametral pitch, or that pressure angle. Once you get a set of plans and decide you want to build THAT engine, you'll have plenty of time to order what you need before you need it.

 

[Brian Rupnow]

I know this is asking a lot, but can anyone post a picture of their particular gear "size/type" along with a coin about the size of a Canadian or American dime so that I can see the tooth profile?---Please

 

[lee9966]

Travers does still send the 20% off coupon, I just got some conical end mills from them yesterday. Coincidentally these are for making gear cutters. I will post a link to the method I am trying once I get to the shop, although I know a different method is not what you are asking for.

Lee

 

[cfellows]

As with Tel, I have a mishmash collection. I have a complete set of 40 DP which I bought only because I got a really good deal on it. However, I rarely use them. I have all but 2 of the 24 DP and use these almost exclusively for model building. They seem to yield the best sizes for what I do. Since I'm not fond of gear cutting, I try to design my engines so the gears have the fewest teeth possible. Therefore, I use the #8 and #5 a lot, for 12 teeth and 24 teeth respectively.

I also have begun collecting 32DP cutters as I can find them. Think I have 3 so far.

If I were to have one, complete set, I would go for either 32 or 24 DP.

Chuck

 

[tel]

I don't have a pic handy with a coin in it, but here are a group of 40dp - the large ones (50t) are 1.300" outside diameter.

 

[Mosey]

another of my dumb questions...what are the pros and cons of hobbing gears vs "cutting" with cutters?

 

[steamer]

OK ....question...hobbing as in like a automatic gear hobbing machine?...or like Chuck makes it?

Dave

 

[gbritnell]

Hi Mosey,
I have cut gears with home made hobs. The difference between using them and and involute cutter is the hob will cut a close representation of the involute curve. It all depends on the diameter of the gear (number of teeth). The more teeth the smoother the curve is. With an involute cutter the curve is correct.
When I was building my V-twin I posted some pictures and information showing the cutting of the gears with the hob. Another fellow posted some additional information showing how the steps could be faceted rather than smooth.
For our work the hob works just fine.
gbritnell

 

[Maryak]

Pros

Hobs can be made in the home shop from drill rod, (silver steel).

You only need one hob for all teeth at a given PA and DP/Mod.

Cons

In the home shop the cutting action of a home made hob produces a series of small flats rather than the correct involute curve. These are easily removed using fine lapping paste and a "Running In" process.

This is IMHO still probably more accurate than a hand ground fly cutter.

It is also possible to make your own cutters using a button tool which relies on the fact that most of the involute is very close to a circle.

For everything you need to know about gears and gear cutters I strongly recommend a book "Gears and Gear Cutting" by Ivan Law, available from My Hobby Store ISBN 0 85242 911 8.

Best Regards
Bob

 

[Brian Rupnow]

As with Tel, I have a mishmash collection. I have a complete set of 40 DP which I bought only because I got a really good deal on it. However, I rarely use them. I have all but 2 of the 24 DP and use these almost exclusively for model building. They seem to yield the best sizes for what I do. Since I'm not fond of gear cutting, I try to design my engines so the gears have the fewest teeth possible. Therefore, I use the #8 and #5 a lot, for 12 teeth and 24 teeth respectively.

I also have begun collecting 32DP cutters as I can find them. Think I have 3 so far.

If I were to have one, complete set, I would go for either 32 or 24 DP.

Chuck

Chuck---I have the utmost respect and admiration for your abilities as a model machinist. Now that I have started out by sucking up as much as possible---If you have an almost complete set of 24 dp gears, why are you starting to collect 32dp gears? Are they better, and if so why,--- if not, then why are you collecting them? I know, probably a dumb question, but I truly am starting out from zero knowledge base. Could you post a picture of the two types of gear side by side so I can see the difference. I just checked the Travers catalogue that somebody posted a link to, and it looks like I may have to pay about $400.00 or a bit more for a set of 8 cutters. This is one of those situations where if I order the wrong thing I may have to commit honourable Hari-Kari.---Brian

 

[Catminer]

Brian;
Check out gear cutters on e-bay,I just purchased a full set of 24 Dp from a manufacturer in Hong Kong. I think the price was 160.00 C and I have made two gearsets for my 1/3 Fairbanks Morse with them, worked very well. Two sets just because I was having fun.

Peter