pinion gears

[kwoodhands]

I'm working on a tractor with plans from Rudy K. The boiler has tested good and now I'm making the gears.
So far all the gears I made except for the pinion gears that mesh with 120 tooth bull gears. I have made them but the gears do not look correct and do not mesh well. I ordered a ser of 48 DP 16 tooth pinion gears from Amazon just before this post. $12.00 for a set of 4, very reasonable. The pinions I made look like their are too many teeth and too fine.
I would like to know what I did wrong. The pitch is .333, I figured the blank to be .373. I used a # 7 cutter. The tooth depth is .045.
I made two sets from Acetal and one from brass. They all look wrong to me. A picture on the Amazon website shows the pinions and they look correct. All the other gears turned out fine. Two 120 tooth bull gears 66 tooth , 32 tooth and 80 tooth all mesh well.
I still have to make the steering worm .

 

[Jasonb]

The problem with cutting small tooth counts with involute cutters is that they can't undercut the base of the teeth like a proper hob can so your gears won't look right or mesh well.

 

[ninefinger]

without pictures its hard to say, but Amazon could be one source of your troubles. At the price mentioned the cutters are likely from China. Metric cutters (Module) are numbered opposite of DP so a #7 DP cutter is like a #2 Module and vice versa. If you were provided a "#7DP" but in reality its a #7 Module (equivalent to #2DP) that may explain it. Does the profile of the cutter have a pronounced curve, or does it look like it makes almost straight teeth? Pictures would help - both of the cutter and the resultant gear.

 

[kwoodhands]

without pictures its hard to say, but Amazon could be one source of your troubles. At the price mentioned the cutters are likely from China. Metric cutters (Module) are numbered opposite of DP so a #7 DP cutter is like a #2 Module and vice versa. If you were provided a "#7DP" but in reality its a #7 Module (equivalent to #2DP) that may explain it. Does the profile of the cutter have a pronounced curve, or does it look like it makes almost straight teeth? Pictures would help - both of the cutter and the resultant gear.

The cutters are made in China. The teeth look straight, no curve .
I had no problems with the other gears. I have four cutters, #2 , #4 ,#6 and 7. The gears all look and mesh well , except the pinions.
It appears that there are a lot more than16 teeth. I don't have a camera , the phone I had took good pictures but I tossed it in the trash when one morning it overheated in my pocket.
I have single pointed screws , 3/8 / 48 and that fine thread is similar to what I produced with the #7 cutter.
I think that the number of teeth is the problem. There are too many teeth to count in a small gear , I'll try to count the teeth when I get back in the shop.
I think I will try to cut another gear with a 16DP # 7 , Only to see if the cutter can produce 16 teeth. I have that set made in Ukraine that I bought from a lady selling her husbands tools.
This almost a full set, # 8 is missing but their are two #2 cutters. All look brand new , I don't think they were ever used.
I haven't used them yet.
In any case I have a set of 4 pinions coming.
I am sure I turned the blank to the correct size. I added 2+16 for the teeth and divided by the DP which is 48. The blanks are .375 diameter. Used same formula for the other gears and they came out very good.

 

[ninefinger]

So if the tooth form of the cutter looks straight sided, its likely made for a larger number of teeth gear. here's an example I have where you can't rely on the # of the cutter, and need to look carefully at it and figure out that they made a marking mistake. It shows #7, but also shows its for 55-134 teeth (Z55-134) even though its a DP cutter. You can see it has a relatively straight tooth profile. The #2 cutter is the one that needs to be used in this case (Z14-16). the last picture shows it tooth profile is far more curved (relieved) and should result in more material being left on the gear.

As noted before these cutters are marked improperly for DP, but would be marked the way its done for Module (metric gears).

 

[kchmn]

I'm working on a tractor with plans from Rudy K. The boiler has tested good and now I'm making the gears.
So far all the gears I made except for the pinion gears that mesh with 120 tooth bull gears. I have made them but the gears do not look correct and do not mesh well. I ordered a ser of 48 DP 16 tooth pinion gears from Amazon just before this post. $12.00 for a set of 4, very reasonable. The pinions I made look like their are too many teeth and too fine.
I would like to know what I did wrong. The pitch is .333, I figured the blank to be .373. I used a # 7 cutter. The tooth depth is .045.
I made two sets from Acetal and one from brass. They all look wrong to me. A picture on the Amazon website shows the pinions and they look correct. All the other gears turned out fine. Two 120 tooth bull gears 66 tooth , 32 tooth and 80 tooth all mesh well.
I still have to make the steering worm .

I an working on my version of the same traction engine, For gears on mine I went with 24DP 60 tooth for the bull gears and 8 teeth for the pinions, worked out great, and cheaper than the time to cut my own.

 

[kwoodhands]

So if the tooth form of the cutter looks straight sided, its likely made for a larger number of teeth gear. here's an example I have where you can't rely on the # of the cutter, and need to look carefully at it and figure out that they made a marking mistake. It shows #7, but also shows its for 55-134 teeth (Z55-134) even though its a DP cutter. You can see it has a relatively straight tooth profile. The #2 cutter is the one that needs to be used in this case (Z14-16). the last picture shows it tooth profile is far more curved (relieved) and should result in more material being left on the gear.

As noted before these cutters are marked improperly for DP, but would be marked the way its done for Module (metric gears).
View attachment 143195

Thanks, I am sure you are correct. I will try the # 2 cutter Monday morning. Come to think of it , I do not recall seeing DP on the cutters, might say module. I'll run out to the shop this morning to check on this.
mike

 

[kwoodhands]

I just got back from daughter's house and went out to the shop.
I counted the number of teeth in several size gears. All were the wrong count. 120 tooth was about 100 teeth. the pinion gears were too fine to count, tomorrow I'll cut new ones with the #2 cutter . You are correct, the numbers are for metric.
I should be okay now, thanks .
mike

 

[DrMike]

I don't understand what's happening here.

Even if the gear cutters are metric (module) instead of Imperial (diametral pitch), if you made a 120 tooth gear, then you cut 120 spaces into the circumference and it should have 120 teeth. Granted they would be the wrong shape, but there would be 120 misshapen teeth, not "about 100."

I also don't understand how you tried to make a gear with 16 teeth and ended up with more teeth than you can count. Again, you should have ended up with 16 badly formed teeth, not more.

Can you give a description of the process of how you cut these gears?

 

[kwoodhands]

I don't understand what's happening here.

Even if the gear cutters are metric (module) instead of Imperial (diametral pitch), if you made a 120 tooth gear, then you cut 120 spaces into the circumference and it should have 120 teeth. Granted they would be the wrong shape, but there would be 120 misshapen teeth, not "about 100."

I also don't understand how you tried to make a gear with 16 teeth and ended up with more teeth than you can count. Again, you should have ended up with 16 badly formed teeth, not more.

Can you give a description of the process of how you cut these gears?

I cut the blank first. Number of teeth +2 divided by DP
120+2=122
48= 2.541 I used the cutter marked #2 the #2 cutter would be correct if they were DP. I counted the teeth in the bull gear , about 100 teeth instead of 120.
Next I will use the #7 cutter that should produce 120 teeth if my cutters are metric, module.
The pinion gears are supposed to have 16 teeth, there are so many and so fine I could not count them. There are many more than 16 teeth in the pinions I cut. I will cut new pinions using # 2 cutter tomorrow. The idler gear is supposed to have 80 teeth and the crankshaft gear 60 or 66 , not in the shop now and forgot the number. In any case I used #2 cutter and will cut new gear using #7 cutter. All gears have tooth depth .045. I tried making the pinion gear a little bit deeper in case I did not hit .045 exactly. No change . I checked the depth two ways. Handwheel on the mill locked at.045.
I have rod mounted along the underside of the mill with a stop block. I used feeler gauges to get to .045 between the block and the mill table. Both showed the same.045.

Nine fingers clued me in his post. I downloaded the Evolvent Gear Cutter Size Chart.
You can see this in his post.
I did not count the teeth in the crankshaft or idler gear yet as I was in a hurry. Went to daughters home for Christmas breakfast and gift exchange.
I am sure that both of these gears are the wrong count too.
In any case I'll find out tomorrow and post the results.
mike

 

[Jasonb]

If you are wanting a 120T gear and doing the calculations based on 120T then you MUST find a way to index 120 divisions. Likewise the 16T gear must be done by Making 16 equal divisions around the blank.

The cutter number will only affect the profile of the teeth not how many it will cut as that is determined by your indexing the correct number of divisions

Anything else and you are just wasting your time as you will either get the cuts too close together and too many teen or too far apart and not enough teeth. At the very least properly count your bull gear teeth as "about 100" is never going to give a known number of teeth either using all of them or working out what divisions are possible from a given gear. For example every 5th gap on your 80T gear will give 16 divisions. And with the right design of index pin that locates in the valley and also on the crest of a tooth the 60T could be used to index 120 divisions but you would nee dto make an arbor to hold the gears and the indexing pin.

 

[Drawfiler]

You make no mention of how you are controlling the number of teeth on each gear, are you using a dividing head?
I am with Jasonb, the problem is not with the blank size or cutter, you will get some form of gear with the wrong number cutter but/the right dp, to get so many teeth on the .375” blank that you cant count them is eithe a division problem or the blank is turning during milling by either the mandrel slipping in the dividing units chuck or;on the mandrel itself.
post some photos of the setup and then we can help.

 

[kwoodhands]

You make no mention of how you are controlling the number of teeth on each gear, are you using a dividing head?
I am with Jasonb, the problem is not with the blank size or cutter, you will get some form of gear with the wrong number cutter but/the right dp, to get so many teeth on the .375” blank that you cant count them is eithe a division problem or the blank is turning during milling by either the mandrel slipping in the dividing units chuck or;on the mandrel itself.
post some photos of the setup and then we can help.

I am using a rotary table. The locking pin is set on the #16 circle. One full turn and 14 holes. The mandrel is not slipping or the blank is not moving.
Each gear except for the pinions looks correct , but until I actually counted the teeth I found that the number of teeth was incorrect. 100 tooth count was close, did not try to get exact number of teeth because I could see that the gear was not even close to 120 teeth. I marked the gap between teeth, counted 10 and marked again. Repeated this and counted each mark til I got to 90. There was less than ten teeth left on the last count. This is how I came up with " about" 100 teeth.
As soon as I get in the shop I will cut new gears using the info Ninefingers shows. Apparently the gears cutters are marked for modules instead of inches.
I will use #2 cutter for 16 tooth gear instead of the #7 I had used. My cutters are marked dp, but I will find out if they are marked wrong .
This is the first time cutting gears , I have learned a lot. Hopefully the problem lies with the wrong markings for dp and should show module instead.
mike

 

[DrMike]

Before sorting out whether your cutters are Imperial or metric, the issue you have to solve first is indexing the blank. You are clearly not indexing the blank properly to produce the correct number of divisions. If you were, you'd have the correct number of teeth.

Please find and refer to the manual for your particular rotary table to determine the correct procedure for indexing. I'm assuming from your description that it has division plates that you are using for indexing.

I'm also going to suggest that before you cut another gear blank, you run through the procedure but use a Sharpie to mark the blank where you would be cutting. If you end up with the correct number of marks, then your indexing procedure is correct and you can proceed to cut (with the marks as a rough guide). If not, wipe the marks off with acetone, re-read the directions and try again until you have it.

 

[Jasonb]

You don't say what the gear ratio is on your rotary table but usual is 90:1 so if using a 16hole plate you want 5 full turns and 10 holes. to get about 100T when trying to cut 16T you must either have a very high ration or not be turning the handle enough.

If you are using teh 16hole plate I suspect you are onlu moving 14 hole sat a time if it is a 90:1 as that is 3.5degree spacing so would give close to 100 teeth

Once again I will say the number of teh cutter does not affect the number of teeth cut. you need to sort out the correct indexing

Your

 

[Drawfiler]

I also agree the problem is with the dividing system, you may not have the book for the rotary table so start by finding the ratio, the simplest way is to just count the turns of the handle for one turn of the table.
I have seen tables 90:1, 60:1 so get this sorted, do the calculation fore wasting another blank.
the cutters in the set will probably be ok, even the nastiest Oriental ones will do for our purposes, stick with the dp ones you have and try again.
Petet

 

[kwoodhands]

You don't say what the gear ratio is on your rotary table but usual is 90:1 so if using a 16hole plate you want 5 full turns and 10 holes. to get about 100T when trying to cut 16T you must either have a very high ration or not be turning the handle enough.

If you are using teh 16hole plate I suspect you are onlu moving 14 hole sat a time if it is a 90:1 as that is 3.5degree spacing so would give close to 100 teeth

Once again I will say the number of teh cutter does not affect the number of teeth cut. you need to sort out the correct indexing

Your

Your exactly right. I went thru the whole process this morning. Checked blank size ,correct plate etc. Then I saw what I did wrong. I used the wrong amount of turns. I used 1 complete turn and 14 holes, this is a mistake. I then used 5 complete turns and 10 holes. Now the pinions are perfect. 16 teeth and easy to count.
I will remake the gears tomorrow, only did the pinions today .
Only in the shop 15 minutes when wife told me of a death in the family Christmas morning. My son-in-laws dad passed, was expected . He was in poor health for several months.
Kind of made a sad Christmas .
Thanks for all the help, I feel dumb that I made a mistake like that. Also the cutters are marked correctly, I got a lot of experience making gears the wrong way. Now I will get more experience cutting gears the correct way.
mike

 

[Jasonb]

Now the number of teeth have been sorted you may well have been using teh right cutter with the correct number. Due to cutting the teeth far too close together one cut will have overlapped the next so most of the (curved) part of the tooths flank will have been milled away making the small teeth look the wrong profile.

does the cutter have the tooth range engraved on it or just the number? Are all cutters from the same source? if so they are likely to be numbered correctly if the other correctly divided gears turned out OK

 

[kwoodhands]

Now the number of teeth have been sorted you may well have been using teh right cutter with the correct number. Due to cutting the teeth far too close together one cut will have overlapped the next so most of the (curved) part of the tooths flank will have been milled away making the small teeth look the wrong profile.

does the cutter have the tooth range engraved on it or just the number? Are all cutters from the same source? if so they are likely to be numbered correctly if the other correctly divided gears turned out OK

All the cutters are from same source. They are correctly engraved with the # of teeth and the cutter #. the tooth range is engraved on the cutters with the DP also.
I did use the correct cutter for the number of teeth but I used the wrong amount of turns and holes on the rotary table.
Now that I understand what I did wrong I will cut the gears correctly. The pinions I cut this morning are perfect, I'll recut the rest today.
Thanks to all that helped me, and Merry Christmas to all
mike

 

[mcostello]

A lot of times We learn more from Our mistakes than any other way.