Triple Gear Reaming Measurement

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jagiven
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Triple Gear Reaming Measurement

Post by jagiven » Tue Mar 19, 2019 9:32 am

What is the correct reaming measurement for the triple gear bushing? As I recall it is 0.680".

I am at work right now, and my book is at home. The machine shop at work said they would ream (Sunnen hone) my new triple gear bushing. FYI, I have new triple gear pins.

Thanks


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Re: Triple Gear Reaming Measurement

Post by HaroldRJr » Tue Mar 19, 2019 1:41 pm

I'm not the one who should be commenting about this, because I've had little experience with Model T transmissions,....engines,....yes, but NOT transmissions. However,......

From what I've learned from this forum, by far the most important dimension, or "measurement", is the CLEARANCE between the triple gear pin & bushing. And, it seems that the real danger, and a very common problem is to "NOT" have enough clearance which eventually causes the bushing to seize up on the pin, which then causes the bushing to begin turning in the gear. Also, I guess what I gather from so many problems that I've read about here on the forum, is that it seems that one of the common acceptable and recommended clearance dimension seems to be NOT ENOUGH "bushing/pin clearance", which causes the bushing to seize up on the pin. All that to say, if there is any variance from whatever the PROPER recommended clearance is, if there is any error, it had better be in the direction of a bit too much clearance! Again, there is much disagreement on this I guess, but anyway, that's one thing I've learned from just long-time constant & regular reading of this forum, FWIW,.....harold

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Re: Triple Gear Reaming Measurement

Post by DanTreace » Tue Mar 19, 2019 3:46 pm

The Ford print for the P/N 3314 1/2 , factory # T-716B triple gear bushing ( Ford 'Z' bronze), has note to 'Ream after pressing (into the triple gear) to .6785"-.6790" diameter'

Other bushing materials may need more clearance.
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Re: Triple Gear Reaming Measurement

Post by John kuehn » Tue Mar 19, 2019 4:46 pm

Several earlier postings from earlier forums about the triple gear bushing and pin clearance say it’s best left at a running fit. Several old timers posted to stay away from getting to tight a clearance.
Trying to get all the clearances ‘tight’ on triple gears usually would cause the pins to seize the bushings and cause the transmission to bind.
Seems like a running fit was achieved by feel instead of completely relying on mike readings.
I guess experience would rule in this.


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Re: Triple Gear Reaming Measurement

Post by mike37 cdn » Tue Mar 19, 2019 4:55 pm

0.681 4 OVER THE PIN SIZE


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Re: Triple Gear Reaming Measurement

Post by Dan Hatch » Tue Mar 19, 2019 5:28 pm

I size the bushing with a sizing ball. I found that this work much better than reaming or honing. This also makes the bushing swell to fit the gear better. Helps to stop spinning in the gear. I posted about this last year. Dan

P.S. You should also polish the repro pins, finish is not good enough. Dan


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Re: Triple Gear Reaming Measurement

Post by Allan » Tue Mar 19, 2019 5:52 pm

I believe Mike's .004" measurement is correct. Somewhere I read of a .002" running fit. This means .002" all round, so the actual diameter is .004" This is one time when more is better., i.e. .005" clearance is preferred over .003"

Allan from down under.

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Re: Triple Gear Reaming Measurement

Post by jagiven » Tue Mar 19, 2019 5:59 pm

Dan Hatch wrote:
Tue Mar 19, 2019 5:28 pm

P.S. You should also polish the repro pins, finish is not good enough. Dan
What do you recommend polishing with? Die grinder with a scotch pad?


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Re: Triple Gear Reaming Measurement

Post by Dan Hatch » Tue Mar 19, 2019 6:32 pm

I put them in my lathe and polish with super fine wet and dry, wetted with oil. polish before installing. Dan


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Re: Triple Gear Reaming Measurement

Post by Jerry VanOoteghem » Tue Mar 19, 2019 8:30 pm

jagiven wrote:
Tue Mar 19, 2019 5:59 pm
Dan Hatch wrote:
Tue Mar 19, 2019 5:28 pm

P.S. You should also polish the repro pins, finish is not good enough. Dan
What do you recommend polishing with? Die grinder with a scotch pad?
NO! Maybe some 600 grit emery paper.

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Re: Triple Gear Reaming Measurement

Post by jagiven » Tue Mar 19, 2019 9:27 pm

Jerry VanOoteghem wrote:
Tue Mar 19, 2019 8:30 pm
jagiven wrote:
Tue Mar 19, 2019 5:59 pm
Dan Hatch wrote:
Tue Mar 19, 2019 5:28 pm

P.S. You should also polish the repro pins, finish is not good enough. Dan
What do you recommend polishing with? Die grinder with a scotch pad?
NO! Maybe some 600 grit emery paper.
Dont have a lathe, so this will probably be hand work.

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Re: Triple Gear Reaming Measurement

Post by George Mills » Tue Mar 19, 2019 9:33 pm

Jason,

The 'size the pin and add 0.004" is the safe way to go at it if you have a Sunnen at your disposal. Folks will argue that Ford said change them at 0.005" and you are using up life, but the flip side of that is that if you do it 'right' there is long life and minimal wear.

Before you mount the pins in the flywheel, you might want to mic them in the 12-6 o'clocks plane AND the 9-3 o'clock plane. One supplier makes his dead nuts round even at the 4th decimal place, the other maker produces 'eggs' that could affect that 'at 0.004"' maxim. I can't tell you whose is whose as I think all suppliers take turns with the vendors. Both match print since it has no concentricity requirement and I have never found a house standard for Ford...the one is just a whole level of precision better in the world of perfection.

Dan Hatch,

For what it is worth, Dan Hatch, I am firmly convinced that Ford got away with the claimed super close tolerance they used for 3 reasons only and one of them was that they DID use sizing balls from some point in annual production as early as the end of the brass era. How do I know this (and why I have trouble with traction on the claim) is that I bought the technical library section on Ford that was in the former Humber Motor Car UK library and in the apparent technical exchange section between Ford and Humber there are talks about bronze pushback at various speeds and feeds and using trial and error methods until needed size is achieved. That doesn't confirm a ball sizing, but no one has ever tried explaining to me how those words can apply otherwise! I also would, at the design interference and there being bronze, there was probably also an insert tool used before the ball. Just a guess on my part...but enough to convince me that is how Ford must have done it to achieve what they did. (It's a shame Ralphie went and died on me before we were done and I'll admit that I lost interest in bringing the blind test full circle with conclusions.)


For others,

I have always suspected that super polishing is not the best way to go and there should be a bit of surface finish difference between the pin and the bush. When RDR and I did the blind test involving 100's of pin sets we had about half that were made of the right metallurgy (ergo Ford made) and none of them were better than a 32 finish....Further,for my 2 cents at the 0.004" total clearance, the reality of the situation is that finish actually is pretty much out of the equation.

For what its worth,

Here is something some may find interesting, others will go 'ehh'. This was from the work Ralphie and I were doing, never made it to publish...

APPENDIX # 1 New replacement Pins and Bushes

As an adjunct to the forensics testing done on the used NOS and used NORS pins and bushes in the blind test organized by Ralph Ricks, it was decided to buy a set of new pins and new replacement bushes and perform full QC testing on the as received in order to have a modern comparison. Only one bush and one pin were tested this way.

The vendor is ‘nameless’ however the pins were bought in 2012 and the new replacement pin is the type having grinding centers and the ‘step’ in the pin diameter with the larger flywheel end. There is no rim as on original pins. The bush is the type with a spiral oil groove with ends broken through, that does not match the original Ford drawings on groove specification.

The testing was done at one of Chi-com highest level tier #1 test centers certified to do direct testing for Ford Motor Company, TRW, Mercedes and Brembo in a standard format to the third decimal place, metric.

The results are shown as Figure #1

figure 1 pins.jpg
figure 1 pins.jpg (79.55 KiB) Viewed 2336 times

Conclusion-
• The pin inspected is as near perfect and flawless as possible to basic dimensions. The pin is manufactured to the lower limit (bush end) specified on drawings for the T-3315, factory number 715 pin on original Ford drawings, however that is not a bad thing.
• Run-out and coplanar (out-of-round) tolerances were not checked as a sample of 1. However, due to the way the grinding centers were made and the 4th decimal place (Imperial measure) absolute control ‘to size’ in planes 90 degrees apart, these pins are at least as accurate, if not more, than original pins made by Ford.
• The hardness although shown 36-40 is the lab way of bracketing hardness reporting when slice and dice photo micro-sectioning is NOT performed. Nominal is Rc 38 which needs to be compared to the original NOS and NORS forensics when completed.
• The surface finish is 32 on both the flywheel end and the bushing end. 32 is definitely correct for the press fit into the flywheel and some may question the 32 for the bush end as being too rough and further shoe shine of the surface would be required for a bush to self-hone.
o The reporter holds that 32 is probably the finish that Ford originally intended in spite of lore that micro-lapping to get ‘wrist pin’ smoothness was the way to go. The report in the forensics of NOS & NORS will explain why the author believes the 32 probable.
o The vendor has been asked to inform their supplier that shipping pins built to this precision open and loose in bags of 3, or shipped in boxes without sleeves from the maker causes small bumps and nicks, some almost microscopic however a simple care in handling, storage and shipping would allow these pins to be used with no further attention to detail once received.
• Since these are the 2 diameter pin a calculation was performed which shows the flywheel end to be EXACTLY 0.0041” bigger than the bush end and this value, when using this maker’s pins needs consideration when determining the press fit into the flywheel.
• The bush was sent out for metallurgical content and grain size analysis and will be reported on in a further supplement.


George R. Mills
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Re: Triple Gear Reaming Measurement

Post by jagiven » Wed Mar 20, 2019 9:14 am

Thanks George! I mic'd them last night. Two were almost identical at both 12 and 3. One pin measured about 0.00035" difference between 12 & 3.

Largest measurement recorded;
0.66715
0.6770
0.6777

Decided to have the shop open them up to 0.681"


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Re: Triple Gear Reaming Measurement

Post by Adam » Wed Mar 20, 2019 9:48 am

George, I like your research. The .002” running fit referered to in the Ford Service Manual does refer to a bushing bore that is .002” larger than the diameter of the pin. Ford published engine rebuilding manuals shortly after T production that have clear definitions of fit tolerances and exactly what they mean.


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Re: Triple Gear Reaming Measurement

Post by Scott_Conger » Wed Mar 20, 2019 3:11 pm

George

lots of good stuff in your research. I will second the vote on surface finish. Any study at all of mechanical/lubricated components relating to bearing surface finish on plain bearings will support your conclusion. Oil films do not like polished surfaces, and when running, with proper clearances, the metals are not touching other other than at start up and shut down. That said, 32Ra finish can be made a number of ways, and anyone that has used a Taly Surf to measure finish will be surprised the first few times, just how different parts can look and still measure the same finish, if certain defects and deviations happen to be missed during measurement. Bottom line, a turned surface at 32Ra can sometimes be problematic, whereas a ground or honed finish at 32Ra will be very consistent part after part.
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Re: Triple Gear Reaming Measurement

Post by George Mills » Thu Mar 21, 2019 10:07 am

Thanks for the comments. There was a lot of work that went into the blind test at the time. Ralphie was a treasure, this whole subject was professionally analyzed from any direction and Ralphie was absolute in keeping the test “blind” to the point that he got sick before we did final summary, and passed away without ever revealing the key code as to where all the used pins and bushes came from duty wise. I never finished the project after he passed, frankly lost interest emotionally as Ralphie n I were as close as brothers! if anyone wants some of the bits and pieces pick a subject and let me know, I’ll email that section

Adam, you are absolutely correct that Ford found a way to make the running clearance 0.002 as per the prints...yet point of fact, anyone who has tried since with even modern ideas and production practices has transmissions that have a bad habit of swallowing themselves in the first 200 miles. Sort of like modern FoMoCo Gear research used on the T1000 to supposedly take away howl and also survive a hundred miles a day, everyday...those modern process gears lasted all of a couple of months!

Scott...good point on surface finish
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Re: Triple Gear Reaming Measurement

Post by Les Schubert » Thu Mar 21, 2019 10:44 am

Lots of interesting stuff posted and I believe it is all pretty accurate.
I will now put forth a slightly different perspective;
I almost never change the triple gear bushings.
New triple gear pins, YES absolutely!!
I have found that the original Ford bushings experience very little wear and the new bushings we can buy are not as good a material.
I have followed this approach for several transmissions with good success.
Further to this, I always replace the three main shaft bushings, but almost never the low and reverse bushings.
Lastly, I always get the flywheel dynamically balanced.
All the best


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Re: Triple Gear Reaming Measurement

Post by Les Schubert » Thu Mar 21, 2019 10:46 am

Lastly, I have considered making some oversized triple gear pins and then get them case hardened and polished

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Re: Triple Gear Reaming Measurement

Post by RajoRacer » Thu Mar 21, 2019 11:15 am

I mostly agree with you Les as I have also rebuilt dozens of transmissions but it seems the thrust surface of the triple gear bushing "goes away" well before the bore does that I've have determined - I also install new pins.

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Re: Triple Gear Reaming Measurement

Post by JWalters » Thu Mar 21, 2019 11:37 am

RajoRacer wrote:
Thu Mar 21, 2019 11:15 am
I mostly agree with you Les as I have also rebuilt dozens of transmissions but it seems the thrust surface of the triple gear bushing "goes away" well before the bore does that I've have determined - I also install new pins.
The bushings can be pressed out and a shim added to make up for thrust wear.

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Re: Triple Gear Reaming Measurement

Post by RajoRacer » Thu Mar 21, 2019 12:20 pm

Yes, you could if the bore was within serviceable limits.


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Re: Triple Gear Reaming Measurement

Post by rgould1910 » Thu Mar 21, 2019 1:35 pm

One man's approach. Press out the original bushings from the triple gears just enough to get a copper wire wrapped under that flange and press back in, with a bit of Loctite. The pressure of the flange against the wire will crush it some and keep it in place, even without the Loctite. The wire will cause the flange to stick out. By pressing the bushing out just enough to get the wire underneath, you are not disturbing the placement of the bushing inside the gear bore, which would occur if you removed the bushing entirely. If you need to take off some of the flange at that point to achieve a 6 to 10 thou clearance from the flywheel, it is simple to do on a lathe. If you use OS pins, you can usually get by with the originals just the way they are while still achieving an acceptable fit.


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Re: Triple Gear Reaming Measurement

Post by Kohnke Rebabbitting » Sat Mar 23, 2019 3:28 pm

jagiven wrote:
Tue Mar 19, 2019 9:32 am
What is the correct reaming measurement for the triple gear bushing? As I recall it is 0.680".

I am at work right now, and my book is at home. The machine shop at work said they would ream (Sunnen hone) my new triple gear bushing. FYI, I have new triple gear pins.

Thanks
The hole from a Wilson reamer is .680.

Ford pins were from .676-50, to .677.

On repro pins, you have to make sure they are the right diameter, some are not.

Herm.


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Re: Triple Gear Reaming Measurement

Post by HaroldRJr » Sat Mar 23, 2019 4:27 pm

Herm - I'm not that much of a machinist, and certainly not an engineer, but in reading this whole thread, it sounds to me like besides making certain that replacement pins are the right diameter, it sounds as if the surface finish of the replacement pins is also much more important than one might realize!


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Re: Triple Gear Reaming Measurement

Post by Kohnke Rebabbitting » Sat Mar 23, 2019 5:16 pm

HaroldRJr wrote:
Sat Mar 23, 2019 4:27 pm
Herm - I'm not that much of a machinist, and certainly not an engineer, but in reading this whole thread, it sounds to me like besides making certain that replacement pins are the right diameter, it sounds as if the surface finish of the replacement pins is also much more important than one might realize!

Yup!

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