Questions about 47/37 in place of a 127/100 on a heavy 10 for metric

hsracer201 · Jul 19, 2018

To explain a bit of what is going on, I have a set of gears that I think may be a partial set of metric gears for my heavy 10. They are 26, 28, 32, 36, 40 (standard gear), 44, and 48. There is no 127/100 gear. They came with my Heavy 10.

I'd read about the 47/37 as an alternative in my research so I grabbed one of these off ebay to try because I can't find a reasonably priced 127/100.

SOUTH BEND HEAVY 1 METAL LATHE METRIC TRANSPOSING CHANGE GEAR SET 3D Printed | eBay

When I installed it last night I got this:

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I left the 56t on the gearbox alone but swapped it with the spacer. I replaced the 80t idler gear with the 47/37t and I replaced the 40t stud gear with the 48t because it is the largest. It still won't contact. In fact, it is a long ways from touching. The banjo is tilted upwards as far as it will go.

Am I missing something blatantly obvious? How does this work for some people?

Here are what the gears look like:

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They fit on the tumbler stud, but are they the correct gears? They look like the gears in this listing but I'm afraid maybe they aren't.

South bend heavy 1 Metric Transposing Gear set complete Nos | eBay

Can anyone shed some insight? Am I stuck buying a 127/100 from overseas?

I did find this for sale on lathes.co.uk but I need to know without a shadow of a doubt that my change gears are the right ones before ordering one:

https://store.lathes.co.uk/parts/boxford-south-bend-100-127t-inch-metric-conversion-gear

Thank you to anyone who can add any insight.

Erich · Jul 19, 2018

The original SB metric setup used a separate banjo. I have a single tumbler SB and the metric banjo is Y shaped and the English is straight. Long winded way of saying, you may not be able to get there from here.

hsracer201 · Jul 19, 2018

Erich said:
The original SB metric setup used a separate banjo. I have a single tumbler SB and the metric banjo is Y shaped and the English is straight. Long winded way of saying, you may not be able to get there from here.

Right. I knew the single tumber had a Y banjo, but the double tumbler does not as far as I know. I need correction if I'm wrong.

If I order the 127/100 I linked near the bottom of the post will I be set? That is my main question. I don't want to spend $300 on a gear and then find out I'm out of luck.

I found this picture on a google search. It looks like a double tumbler with a 127/100 with a straight banjo.

Click the link below for the picture.
Imgur: The magic of the Internet

JohnEvans · Jul 19, 2018

Mount another gear in the train on the banjo,any number of teeth . All it will do is reverse the direction as all it is doing is filling a space. The 47/37 compound gear is the one changing the ratio.

old_dave · Jul 19, 2018

On the "double tumbler" Heavy 10 the straight banjo does for both English and metric, at least that was the case with my Heavy 10 which was new in 1979. (I no longer have this lathe. Sold it to a friend and neighbor who really really wanted it after I got a 10EE)
David

hsracer201 · Jul 19, 2018

JohnEvans said:
Mount another gear in the train on the banjo,any number of teeth . All it will do is reverse the direction as all it is doing is filling a space. The 47/37 compound gear is the one changing the ratio.

Thank you, sir. I didn’t realize the number of teeth didn’t matter. I just scooted the 80t down and put the 47/37 in line.
Thank you.

Imgur: The magic of the Internet

hitandmiss · Jul 20, 2018

It does help if all the gears are in mesh, the 80 and 47 are not in contact.
All you need to do is use the reverse tumbler setting for forward.
The extra idler reverses the direction.

Bill

SLK001 · Jul 20, 2018

hsracer201 said:
Thank you, sir. I didn’t realize the number of teeth didn’t matter. I just scooted the 80t down and put the 47/37 in line.

It IS going to matter, since changing the ratio is not ALL that needs to be done. Your lead screw needs to turn X times for every Y turns of your spindle for EACH metric thread. A gear between the two gears will throw every calculation out of sync. You CAN do it this way, but you'll have to calculate each metric thread.

Peter. · Jul 21, 2018

SLK001 said:
It IS going to matter, since changing the ratio is not ALL that needs to be done. Your lead screw needs to turn X times for every Y turns of your spindle for EACH metric thread. A gear between the two gears will throw every calculation out of sync. You CAN do it this way, but you'll have to calculate each metric thread.

Idlers don't change the ratio, they only reverse direction. He could put in any number of idlers of any tooth count and the final ratio will not change.

Only the first and last gear, and any compound gears like the 37/47 in the pic affect the overall ratio.

hsracer201 · Jul 21, 2018

hitandmiss said:
It does help if all the gears are in mesh, the 80 and 47 are not in contact.
All you need to do is use the reverse tumbler setting for forward.
The extra idler reverses the direction.

Bill

It was just a loose mock up. It isn't being run right now.

Conrad Hoffman · Jul 21, 2018

Are those 3D printed gears? I make any new gears out of Delrin and have had no trouble. Even though it's a SB, you might enjoy my Logan threading page here- Metric Threading I seem to do more and more metric threading these days.

hsracer201 · Jul 21, 2018

Conrad Hoffman said:
Are those 3D printed gears? I make any new gears out of Delrin and have had no trouble. Even though it's a SB, you might enjoy my Logan threading page here- Metric Threading I seem to do more and more metric threading these days.

It is indeed a 3d printed gear. There is an ebay link in the original post.

There's a lot of information on your page. Thank you for that.

Conrad Hoffman · Jul 21, 2018

Ha! Can't read. Wasn't aware anybody was doing that, but it gets the price down to where everybody should have one stashed away for that upcoming metric job.

SLK001 · Jul 22, 2018

Peter. said:
Idlers don't change the ratio, they only reverse direction. He could put in any number of idlers of any tooth count and the final ratio will not change.

Only the first and last gear, and any compound gears like the 37/47 in the pic affect the overall ratio.

Looking at the photo, I see that now.

Why doesn't someone 3D print a 127/100 pair? Is it the size (I have the 127/100 set, so I know that it is rather large)?

hsracer201 · Jul 22, 2018

SLK001 said:
Looking at the photo, I see that now.

Why doesn't someone 3D print a 127/100 pair? Is it the size (I have the 127/100 set, so I know that it is rather large)?

According to the guy that printed the 47/37 gear it warps. It also takes much more material and printer time and the price grows exponentially. The error on these other gears is very small.

Zahnrad Kopf · Jul 22, 2018

hsracer201 said:
According to the guy that printed the 47/37 gear it warps. It also takes much more material and printer time and the price grows exponentially. The error on these other gears is very small.

Ever actually inspect some, professionally? I have. ( on gear inspection equipment** ) There is literally no benefit in "quality" or "accuracy" over those of Involute Form Mill manufacture, and most assuredly are lacking in comparison to well manufactured gears. I can say with the resolute certainty of someone that has quite literally done so, that the only thing they offer is cost attractiveness and convenience by purchase. There is no free ride. If they are acceptable to you, fine. But don't for one second think they are accurately done. Don't lie to yourself.

** - for evaluating just exactly how good or poor they actually are. SLA, SLS, and FDM examples were used and compared against Hobbed, Shaped, and Milled counterparts.

Cheetah · Jul 22, 2018

Zahnrad Kopf said:
Ever actually inspect some, professionally? I have. ( on gear inspection equipment** ) There is literally no benefit in "quality" or "accuracy" over those of Involute Form Mill manufacture, and most assuredly are lacking in comparison to well manufactured gears. I can say with the resolute certainty of someone that has quite literally done so, that the only thing they offer is cost attractiveness and convenience by purchase. There is no free ride. If they are acceptable to you, fine. But don't for one second think they are accurately done. Don't lie to yourself.

** - for evaluating just exactly how good or poor they actually are. SLA, SLS, and FDM examples were used and compared against Hobbed, Shaped, and Milled counterparts.

As someone who works with additive manufacturing R&D, I feel it's only fair to point out that you could not possibly have tested a cross-section that is anywhere near all inclusive of available AM technologies - which vary extremely widely in precision and quality. Yes, even within the umbrella of "SLS" or "FDM" or anything else. There's a dramatic difference between entry level industrial machines, and the best stuff available today, which is changing at such a pace that any testing you may have done last month is no longer "current."

That said, I'd be willing to bet my lunch money for the next year that your assessment is 100% spot on for parts that are available on ebay or anything similar.

Just wanted to point out that your comments sound very absolute, and the reality is anything but.

Zahnrad Kopf · Jul 22, 2018

Cheetah said:
As someone who works with additive manufacturing R&D, I feel it's only fair to point out that you could not possibly have tested a cross-section that is anywhere near all inclusive of available AM technologies - which vary extremely widely in precision and quality. Yes, even within the umbrella of "SLS" or "FDM" or anything else. There's a dramatic difference between entry level industrial machines, and the best stuff available today, which is changing at such a pace that any testing you may have done last month is no longer "current."

That said, I'd be willing to bet my lunch money for the next year that your assessment is 100% spot on for parts that are available on ebay or anything similar.

Just wanted to point out that your comments sound very absolute, and the reality is anything but.

One should not make assumptions of events one knows nothing of. I ran the AM lab of a major OEM within their Rapid Prototype Toolroom. ( in addition to utilizing standard subtractive manufacturing machinery ) Tests were done using machines from 3DSystems costing in the $0.5M range, using materials from 3DS as well as others. Samples were created by myself on our own machines, as well as farmed out to another facility. Testing was done using computer driven gear inspection machinery, using LVDT probes. So, nothing even remotely "entry level" to be considered...

And... accepting for ( and regardless of ) recent "advancements" the bottom line is that the motion control of almost universally every single machine extant these days is fundamentally similar and prone to exactly the same shortcomings with regard to comparison to Generative Gear Tooth Processes, and as such will never produce a gear of similar high level accuracies that can compete anywhere near for even mildly similar economic expenditure.

I believe I can speak to this with some slightly more insight than some, as someone that is immersed in gear design and manufacture as well as AM. YMMV.

Having said all of that, you are correct that the gear represented is very obviously very far from that level.

Conrad Hoffman · Jul 22, 2018

All that would really matter to me is the accuracy of the thread produced on a part. As long as the gear has the right number of teeth and runs smoothly, differences in "quality" might not affect the end result as much as you'd think. By "quality" I mean adherence to perfect tooth profile and dimensions. The only thing that would concern me is if it didn't run on center. FWIW, I've seen some questionable Southbend factory gears, but nobody complains about those. I suspect they vary depending on vintage.

Zahnrad Kopf · Jul 22, 2018

Conrad Hoffman said:
All that would really matter to me is the accuracy of the thread produced on a part. As long as the gear has the right number of teeth and runs smoothly, differences in "quality" might not affect the end result as much as you'd think. By "quality" I mean adherence to perfect tooth profile and dimensions. The only thing that would concern me is if it didn't run on center. FWIW, I've seen some questionable Southbend factory gears, but nobody complains about those. I suspect they vary depending on vintage.

Speaking only for myself, I am aware of how it affects threading. ( and there have been threads discussing the issue, here on the forum ) Frankly, my OCDish nature would be greatly disturbed by it. Others, likely not so much.

However, this is less about proper tooth form and dimension than it is much more about the VERY important issues of Tooth to Tooth Tolerance, Composite Tooth Tolerance, and Pitch Circle Concentricity. Specifically, how those relate to the velocity of components downstream and how they affect that thread's construction.

Now..., my original point was that OP should not deceive themselves with regard to the true accuracy of the FDM gear, and all of this that followed is almost certainly of little regard to the OP and their quest. So, as to not derail the thread further, I'm going to stop providing fodder for it.

Questions about 47/37 in place of a 127/100 on a heavy 10 for metric

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