Gear cutter help

[Generatorgus]

I've just realized I have a wee bit of a problem with my Lil' Henry build.
When picking the timing gears from a bunch that were given to me by a friend, I miscounted teeth on the pinion gear, and now have a 16T and 30T combination, not real good for an engine.

I didn't notice this rather blatant error until I was setting the timing. I couldn't figure out why it kept changing.
That said I need a 15 tooth, 32 PD, with a 14 ½ deg pressure angle.
I can buy one but I'd rather make one. I took a stab at making a single fly cutter type, but after two tries (two days of pain) the thing has me licked. Making cutting tools is not my best skill. The cutters were just not right and made metal dust rather than chips and have decided that I if buy a few cutters that will handle the size range of the engines I build I can add making gears to my repitiore.


I've been searching info on involute cutters and figure that is what I'll try next. I wouldn't mind learning to make miter gears either, it sounds a bit dicey, but nothing ventured...
I just can't quite figure out what I need. I've gleaned that they make sets of 8 that cut a series of tooth counts, but can't find the right info on Modules, and (as usual)reasonably priced. Please lead the way.

Also not sure if I should stay with the 14½ or switch to 20 deg. pressure angle. Making two gears wouldn't bother me a bit, I think.
I see from my old Boston Gear cat. that the diametral pitch is the same for both angles, so the choice won't affect the center lines I have already drilled in the engine base.

When I figured those centers I used the DP for the 15 and 30 and added a a few thou just for luck. The 16 tooth gear fit but was a tad tight but worked itself out. I'm hoping the centers will work for the 15 tooth or I'll have to make a new base, which is also the reason I'm not going to use the 20:40 set I have.

As always, thanks for any help.
GUS

 

[Philjoe5]

Gus,
Making your own gears is not too difficult. When I started making my first IC engine I decided to make the gears first. I reasoned that if I couldn't make those, the other steps wouldn't be achieveable.

The engine I'm making uses Module 1 gears with 20 deg PA, metric version equivalent to a pitch of 25.4. I bought the set of 8 cutters for about $150 IIRC. You only need 2 cutters for the set you want:
A cutter #7 will cut 15 teeth
A cutter #4 will cut 30 teeth

They cost about $40 each from:

http://www.travers.com/

The distance between gears is critical as you noted but you can cheat a bit with some engine designs and put the timing gear on a slight eccentric to compensate or adjust the gear lash. If you have space you can also insert an idler gear between the two and put it on an adjustable bracket.

Ivan Law's book on gearcutting is inexpensive and worth it if you're going to make gears.

Some folks claim it's hard to make gears with a rotary table. I was one of those until I realized I had a workholding issue with my chuck. I've made good gears using either a rotab or a dividing head. Once you make a set, it's like eating potato chips, you can't stop

Good luck

Cheers,
Phil

Added as afterthought: Module 0.8 gears are equivalent to a pitch of 31.75. Are you reasonably sure that the dp of your gears is 32? Gears taken out of an import product may be module 0.8 gears. If they are module 0.8 you can get a set of 8 cutters from CTCTools for around $135 last I checked

 

[Lakc]

If you already have a 16t and 30 tooth meshing, its going to get worse with the proper 15t, which will be smaller. Was the center distance calculated for the smaller pair?

 

[Philjoe5]

Center distance, CD for the 15 - 30 combo should be 0.703",
while for the 16 - 30 combo it should be 0.719"

Using the formula CD = (N1 + N2)/2P

N1 = teeth gear 1
N2 = teeth gear 2
P = 32, diametrical pitch

Does that help, Gus?

Phil

 

[atwatterkent]

I bought my involute gear cutters from Travers to make the recommended 30 & 60 tooth gears. Reasonably priced and I can make as many as I need.

 

[Swifty]

I purchased a set of mod1 cutters from CTC and I'm very happy with them, they should last longer than me. Cutting gears is a challenge the first time, but if you take it slow it will all work out and you will wonder why you were worried. The same applies to bevel / mitre gears, if you haven't already, read my article about cutting them, I tried to explain in plain language how to cut them.

Phil, you mentioned about using an idler gear, just bear in mind that this will reverse the direction of the driven gear.

Paul.

 

[Generatorgus]

Boy did I just get a great idea, what if I just file one of the teeth off of the 16 tooth gear......JUST KIDDING!!!

Hmmm, just gave that thought a little bit of consideration. Being the driver gear and considering there is not much stress involved here, it might work at least for a little while. Well I did say a little bit.

OK then, serious now.

Phil, I'm guessing that the info about modules is in Ivan Law's book. Thanks for the info.
The distance between centers I got from the PDs in from my old Boston cat. and yes I used .703 plus a few, guess that's why the 16 tooth turned at all.
If the centers are too far apart I can always plug the hole and move it over at tad, or use an eccentric as you suggested, I didn't think of that.
I don't want to use the 20-40 combo I have because they are too big for my crank base frame.

I have a real old book on gear cutting, 1928 I think, not much help at all.
I did get a little from Machineries Handbook, but that's something like reading a IBC building codes book, you can fall asleep before you find what your looking for.

Swifty thanks, I'll search out your article, I know I saw it mentioned in another post a while back. I checked out the CTC site, the prices can't be American dollars, but if they are it's a no brainer.
I'll check Travers also, but first I'll poke around a bit on Ebay.

Phil, your comment about the RT vs dividing head was something I was also wondering about. The few grooves I was able to make in my sample cuts were not real evenly spaced, I used my RT, which also came with indexing plates. That's why I dug them out the other day as I mentioned on your build.
I put the unevenness off as caused by the cutting tool I made. My RT has some sort of vernier behind the dial, but I think it's there for decoration more than being a serious vernier scale, but I can see how you can lose a couple of minutes on the degree scale.

Thanks guys
GUS

Forgot to add that I got the 14 1/2 deg gear ID from the Boston cat which has full scale gear tooth profiles.

Also, why doesn't the keyboard have a degree symbol or am I missing something??

Another addendum: http://www.ebay.com/itm/FULL-SET-MO...961?pt=LH_DefaultDomain_0&hash=item19e70c9171
Nice price and free shipping, but 3 to 7 weeks delivery?? Two weeks I could handle, but 3 to 7, cheese, I'd probably lose interest and start building something else, but then I would still probably want to make my own gears. I'll have to think about this for a week or two.

 

[gus]

Looks like the Gear Cutter Clan is growing. Tracy Tools website has a table show range of gear size(no of teeth) for each cutter size 1--------8. Find easier to use metric gear cutters.

No worry. Gear cutting is not that difficult.It is our "fear of the unknown". Ivan Law's book on Gear Cutting is very good. From Harold Hall's book ,I made my poor man's Dividing Head.
Bought Gear Cutters from CTCtools.

I threw away a few gears that had 1/2 tooth. Or messed up tooth when I lost count of indexing.

After a few bad gears,you will acquire the experience to cut good gears. I cut mitre gears too.
All in threw away 6 gears. The last gear was good for the Rupnow H&M Engine.

I also have a very good teacher and mentor------ Paul Swifty. I also spread gear cutting infection to a few HMEM members.

 

[Gordon]

I purchased a set of mod1 cutters from CTC and I'm very happy with them, they should last longer than me.
Paul.

I also bought them from CTC and even though they may not be the best they are plenty good enough for my occasional use. In this hobby we do not need a lot of gears and just buying them may be the best approach form an economic standpoint, but doing it yourself is very rewarding. This is a hobby not a business for most of us.

 

[Philjoe5]

Yeah, I caught the gear cutting fever from Gus. And I bought my cutter set from CTC Tools also. My records show 2 weeks delivery.

Cheers,
Phil

 

[crueby]

...

Some folks claim it's hard to make gears with a rotary table. I was one of those until I realized I had a workholding issue with my chuck. I've made good gears using either a rotab or a dividing head. Once you make a set, it's like eating potato chips, you can't stop

Glad I never heard anyone say that it was hard to do on a rotary table before I tried - thats the only way I've ever cut them (have a rot. table, dont have a dividing head), did gears for three clocks among other things. One thing that helped was working out the sequence for each size gear needed ahead of time, converting the nbr of degrees per tooth into how many full turns plus minor ticks to move the table for each cut. Started at zero, and wrote out the sequence as nbr of turns plus what tick number to stop at - usually worked out to be a sequence that repeated after several teeth. Then, I made tick marks on the list at each cut, to make sure I did not get out of sequence (did once, that goofed gear got turned into a blank for a smaller gear!). Important to make sure that you have a good arbor to mount the gears on, so it cant slip given the vibration of cutting, and maybe with a tailstock support for added stability.

 

[crueby]

Yeah, I caught the gear cutting fever from Gus. And I bought my cutter set from CTC Tools also. My records show 2 weeks delivery.

Cheers,
Phil

I also bought a set from CTC - worked fine for me (only have used them on brass gears so far, so cant speak to durability on steel).

 

[Philjoe5]

Important to make sure that you have a good arbor

I can trace a lot of my difficulties in making good gears at the start to having a gear blank on an arbor with too much runout.

Now, when I made a gear, I check TIR on the gear blank, before cutting any teeth. It has to be "0" before I proceed.

Just some of the lessons learned

Cheers,
Phil

 

[gus]

Bought a stack of gears from 20/30/40/60/80 from TokyuHands to act as direct indexing plate.
It limits my range but my requirement is tailored to above range.Fixed Indexing plates/gears is good for beginners as there is no chance of 1/2 tooth. Have plans to build conventional
Dividing Head later to improve gear tooth range. I am stilling using my DIY Harold Hall design D/Head which cost me no expense as material came from scrap bin. See fotos. Brass gear came from Japan. Aluminium gear is DIY ,cut for Webster Engine. Also cut gears for Rupnow H&M Engine. My gear cutting skill has improved lately . Q.E.D.

 

[Walltoddj]

Gus I could not find the chart you talked about I'd like a copy because I still need gears for my radial builds.

Thanks Todd

 

[Philjoe5]

Gus,
Are those module 0.8 gears or did you move up in size? They look great, but big

Cheers,
Phil

 

[Generatorgus]

Like I said, two weeks more or less I can deal with, CTC gets my business.

Swifty, I found your article. Very well explained and good pictures. You make it look pretty easy.
I will give miter gears a shot when I need them.
Skew gears also have my interest, I used a pair on my Wyvern, they don't look like they would e as simple.

GUS

This was kind of spooky. As I was typing this reply, which would have been #11 in the thread, when I posted it there are six more posts in between and it ended up being # 17.

All of them good advice.

Phil, there are four different pitch full size illustrations In my Boston cat., my gears fit perfectly.

Gus, nice looking gears.

 

[gus]

Gus,
Are those module 0.8 gears or did you move up in size? They look great, but big

Cheers,
Phil

Yes.They are Model 0.8. Close-ups can mislead. I only have Module 0.8 and 1.

 

[gus]

Gus I could not find the chart you talked about I'd like a copy because I still need gears for my radial builds.

Thanks Todd

Hi Todd,

Gus now in Otsuka,Tokyo.Could resist buying a Mitutoyo Micrometer.
Will send table soon as I get home.

There will a lot of fun cutting your own gears. There will be 1/2 tooths and tooths milled off. After at least 3---6 throwaways ,one becomes very smart,wise and accomplished,competent gear cutter.

Messed up 6 mitre gears and went to Paul Swifty crying. Paul put me back on the true path to be a mitre gear cutter. Ha ha.

 

[Walltoddj]

Hi Todd,

Gus now in Otsuka,Tokyo.Could resist buying a Mitutoyo Micrometer.
Will send table soon as I get home.

There will a lot of fun cutting your own gears. There will be 1/2 tooths and tooths milled off. After at least 3---6 throwaways ,one becomes very smart,wise and accomplished,competent gear cutter.

Messed up 6 mitre gears and went to Paul Swifty crying. Paul put me back on the true path to be a mitre gear cutter. Ha ha.

Gus thanks that would be great I'd like to make my own gears between the 4 engines I'm looking to build I'm looking at close to 40 gears, I lost count on the 270 Offy.

Thanks,
Todd