Metric Threading on a 24" Hendey Gearhead Lathe – Part 2

[Frank_Dorion]

I’m posting this as a new item because it’s essentially a different question from the inquiry I just made about the metric transposing plate.

John Oder was kind enough to post a nice legible version of the plate in question. With that information in hand, my friend and I got out the new metric transposing gears he had made and began to set up for cutting a metric thread on his Hendey 24” gearhead with a 2 TPI leadscrew. Big problem! When the 127 tooth gear (Gear C) is mounted on the banjo, it interferes with the gear box housing before the adjacent gear (Gear E) is even close to meshing with Gear F. [See attached diagram] We fooled with the banjo for a while looking for a way to make this gear combination work, but were forced to conclude that there is no way to complete the gear train because the 127 tooth gear is just too large to allow Gear E and Gear F to mesh.

So, we threw in the towel for the moment and I was on my way out the door when I remembered that the metric transposing gears on my Monarch 10EE are a smaller pitch than the rest of the gear train so a 127 tooth gear can be squeezed into a relatively small space. Is that what’s going on with the Hendey? Are my friend's transposing gears the wrong DP? Anybody have a set of metric transposing gears for a big gearhead Hendey that can tell us what pitch those gears are, or at least whether or not the transposing gears are a smaller pitch than the rest of the gear train? Any help would be much appreciated. Thanks.
Frank

 

[johnoder]

Largest combination of stud and gear "C" shown in this chart is 36 stud and 102 sector.

You would need to select a pitch that would enable the two largest ON THE METRIC CHART to fit in the same space. These two are 75 teeth and 127 teeth

Example:

If the DP is currently 10, the 102 and 36T gears use up 13.8"

Dropping down to 16 DP, the 75 and 127 would use up 12.625"

If you don't plan on cutting coarse metric pitches, you can concentrate on smaller stud gears

Like 127T and 55T at 14DP use up 13"

Little pitches on big lathes need better material. Think about 60-45-12 Ductile iron or ASTM A514 steel plate

 

[Frank_Dorion]

John,

Thanks once more for your help. Looks like my buddy will be turning the teeth off his new metric transposing gears so he can have them cut again in a smaller DP. Or maybe starting all over with tougher material - the current set was made up from Durabar.

It would be nice to hear from someone who has an actual set of Hendey metric transposing gears for one of the big gearheads with a 2TPI lead screw. Always nice to know how the factory did it.

Frank

 

[kitno455]

Frank, if gear 'E' was larger too, could you make everything mesh? I bet we can find a way to do that, and keep using the 127 tooth gear.

Here's the 'other' thread: http://www.practicalmachinist.com/v...ic-threading-24-hendey-gearhead-lathe-316875/

allan

 

[Frank_Dorion]

Allan,

Thanks for your suggestion. Gear E is a 68 tooth gear. To make it larger and preserve the same tooth count, it seems you would have to go to a much coarser DP to close the current big gap between Gear E and Gear F. In that case E and F would have different DPs and would no longer mesh. If you attempt to make E larger by increasing the tooth count from 68 to some higher number, the relationship between the transposing gears (D and C) and the rest of the gear train gets messed up. Did you have another approach in mind for getting Gear E to mesh with Gear F?

Frank

 

[kitno455]

There are lots of ways to make metric threads. Some are approximations, others are exact. You could likely compound the 127 with a number of other gears, and still make perfect threads. The chart will just need to be updated. What are the tooth counts on gears C, D, and E? I can work something up from there.

allan

 

[Frank_Dorion]

Allan,

Thanks for your reply. Stud Gear D is the variable transposing gear, and for the Hendey, the choices are tooth counts of 35, 45, 55, 70, and 75. Gear C is the 127T gear. Gear E is the Hendy standard for this lathe - 86T.

Frank

 

[kitno455]

Frank, I'm confused- in an earlier post, you said E was 68, now it is 86? I'm looking for how many teeth these three gears have when you are cutting imperial threads. I see 'D' has lots of choices, but I don't know what C and E are.

What little info I can find looks like the stud gear 'D' is normally 48 for the threads listed on the gearbox plate?

allan

 

[johnoder]

Both stud and sector (C) are normally 48T on 24" (thread index plate in twenties catalog)

Stud and sector (C) in '40 manual for 2 TPI are 36 and 72T

I'll have to suppose the earlier 24" was 4 TPI screw
(ON EDIT, add photo of earlier 24" showing off its 4TPI screw - thanks to Miles)

If the scan can be read above in Post #2, you can see the 36/72 line is the one without all the fractional threads.

Frank, I'm confused- in an earlier post, you said E was 68, now it is 86? I'm looking for how many teeth these three gears have when you are cutting imperial threads. I see 'D' has lots of choices, but I don't know what C and E are.

What little info I can find looks like the stud gear 'D' is normally 48 for the threads listed on the gearbox plate?

allan

 

[Frank_Dorion]

Allan,

Sorry to make the situation more complicated with a typo - Gear E is 68T, not 86T. When cutting normal threads per the gearbox index, Gear E is 68 teeth and gear C is 72 teeth for the 2TPI lead screw on the lathe in question. The diagram above that I used to illustrate the relative positions of the various gears is for a lathe with a 4TPI lead screw (it's the only one I had that was large enough to be legible).

Frank

 

[kitno455]

No problem Frank- When cutting imperial threads, is gear D still 48 teeth normally?

On edit- also, what metric pitches is your friend interested in?

allan

 

[johnoder]

Stud (D) and sector (C) in '40 manual for 2 TPI are 36 and 72T

 

[kitno455]

Assuming that this lathe cuts 1-56 TPI threads, and the gears from stud down are: 36 driving 72 compounded with 68, the answer seems to be to change the compound to a 127 on the outside, and a 136 on the inside. This jives with one of the metric diagrams shown earlier. The only questions then are what stud gears, and what gearbox settings. I've worked something up:

A 35 tooth stud gear will make the leadscrew act like 14 mmpt, and cut the following, exact metric pitches, with the listed gearbox settings:

gearbox mmpt
56 0.5
40 0.7
28 1.0
16 1.75
14 2.0
8 3.5
7 4.0
4 7.0
3.5 8.0
2 14.0
1.75 16.0

A 45 tooth stud gear will make the leadscrew act like 18 mmpt, and cut the following, exact metric pitches, with the listed gearbox settings:

gearbox mmpt
48 0.8
40 0.9
36 1.0
24 1.5
18 2.0
12 3.0
9 4.0
8 4.5
6 6.0
4.5 8.0
4 9.0
3 12.0
2.25 16.0
2 18.0
1.5 24.0

A 55 tooth stud gear will make the leadscrew act like 12 mmpt, and cut the following, exact metric pitches, with the listed gearbox settings:

gearbox mmpt
44 1.0
11 4.0
8 5.5
4 11.0
2.75 16.0
2 22.0

The 70 and 75 are of no use with this larger compound in place, they turn the gearbox more than double its normal speed. There are a number of other useful stud gears here, including 30 teeth. If you see a metric pitch that you need not listed, let me know, and I'll figure out what stud gear will cut it.

Oh, I should also mention that another possible option would be to put a second shaft on the banjo, and put an idler between the 68 tooth gear and the gearbox input gear. Not sure you have room for that, and it would make the leadscrew spin backwards from normal, however.

If you think the 136 is too big to fit, 102 is also an option. That will use the 70 and the 75. Let me know if you think that is more likely, and I'll work up another list.

allan

 

[kitno455]

Frank- I decided to run some additional numbers with a 127/102 compound instead. I was concerned about the lack of half-mm pitches in the original list. The 102 tooth inner gear on the compound seems to help, and let you use the 70 and 75 (assuming you already made those)

A 35 tooth stud gear will make the leadscrew act like 10.5 mmpt, and cut the following, exact metric pitches, with the listed gearbox settings:
28 0.75
14 1.50
12 1.75
7 3.00
6 3.50
3.5 6.00
3 7.00
1.75 12.00
1.5 14.00
1 21.00

A 36 tooth stud gear will make the leadscrew act like 10.8 mmpt, and cut the following, exact (and probably pointlessly fine) metric pitches, with the listed gearbox settings:
48 0.45
36 0.60
24 0.90

A 45 tooth stud gear will make the leadscrew act like 13.5 mmpt, and cut the following, exact metric pitches, with the listed gearbox settings:
36 0.75
18 1.50
9 3.00
6 4.50
4.5 6.00
3 9.00
2.25 12.00
1.5 18.00
1.125 24.00

A 55 tooth stud gear will make the leadscrew act like 16.5 mmpt, and cut the following, exact metric pitches, with the listed gearbox settings:
44 0.75
11 3.00
6 5.50
3 11.00
2.75 12.00
1.5 22.00

A 70 tooth stud gear will make the leadscrew act like 21 mmpt, and cut the following, exact metric pitches, with the listed gearbox settings:
56 0.75
28 1.50
24 1.75
14 3.00
12 3.50
7 6.00
6 7.00
3.5 12.00
3 14.00
2 21.00
1.75 24.00

A 75 tooth stud gear will make the leadscrew act like 22.5 mmpt, and cut the following, exact metric pitches, with the listed gearbox settings:
36 1.25
18 2.50
10 4.50
9 5.00
5 9.00
4.5 10.00
3 15.00
2.5 18.00
2.25 20.00

Again, there are other ways to do this, and other stud gears that will work. Let me know if you need something you don't see here.

allan

 

[Frank_Dorion]

Allan,

Thank you very much for the obvious effort you put into calculating alternative gear combinations for the Hendy metric transposing gears. We will have to check to see if the 68T gear at E can be replaced by either the 136T or the 102T gear you suggested in your calculations. If either or both will fit, you have given us a viable alternative to the original metric transposing setup. Your generous help is very much appreciated.

To close out the thread, I would like to mention that I spoke to Hendeyman last night and he was kind enough to look up the DP of Hendy’s original metric transposing gears (Thanks, Hendeyman!). Turns out Hendey used smaller 12 DP gears to get the big 127 tooth gear to fit into the gear box. So, recutting our existing transposing gears to 12 DP is another alternative.

Frank

 

[johnoder]

A few scans from "later twenties" catalog - showing 36/72 normal index and metric index referring to 136 tooth

 

[Frank_Dorion]

John,

Thanks for metric plate photos - they could be handy - and thanks for your help above.

Frank