Difference in thread depth/width?

[Joe Schlaberdowski]

Here's a quick question. Recently removed the three threaded studs/rods holding the left foot peg and rear brake support. Reason: was removing the primary chain case cover. The bottom inch and a half long stud of the three was partially stripped and also gunked up with some sort of lock-tite or equivalent. So rather than just taking the nuts and washers off, took out the studs as well. I ran a die over the stripped outer threads and also a tap through the nut to even out the threads. I even did that to one of the other studs and nut. I noticed that after that the nuts for those two fit rather loosely, whereas the third stud and nut combination was tight - as it should be. Now this measured out with the "tooth" checker to see the number of teeth per inch and the outer side was 24 and the inner side was 18. All that for this question for machinists: was there a difference between tooth depth and width between what was produced in England in 1974 and what is now SAE here in the states? I don't want to "clean" threads up to find I've just made things loose or sloppy. It wouldn't matter, but I still have to replace the stud that was partially stripped. It has to go back in the threaded opening of the footpeg support base. By the way, it's not a show stopper and am more curious than worried.

 

[joe czech]

my 2-cents, FWIW -- old brits lists those studs as 5/16 x 18 x 24 (part number 063383). if two are loose, it could be from running a thread cutting tap (and die) vs. thread reforming die in the holes or over the studs. i'm not a machinist, but my understanding is a thread cutting tap or die may remove additional material, thus making the fit a bit looser, whereas thread reforming taps and dies do not remove any additional material - they only clean and reform the existing threads. I almost never use a thread cutting tap or die to clean up existing threads. over the years I invested in a set of reforming taps (and dies). again, i'm not a machinist.

side note - hey joe - understand you're originally from Pittsburgh? what part? I grew up in the Allentown area in the 50's-early 60's....

 

[L.A.B.]

was there a difference between tooth depth and width between what was produced in England in 1974 and what is now SAE here in the states?

At that time the UK and US would have been using the same Unified thread standard introduced in 1949.


https://www.ring-plug-thread-gages.com/ti-N-vs-UN.htm

"The “UN” thread form was developed after World War II by representatives of Great Britain, Canada, and the United States of America, to prevent recurrence of the wartime difficulties in supplying fasteners and tools in both British Standard Whitworth and US Standard configurations when and where needed. In 1949, after years of committee meetings between Canada, England and United States of America the American National Standard Series was replaced with the Unified Inch Standard Series. In the end there were three base reasons identified for the change. The first reason was to provide interchangeability with Canada and United Kingdom. The second reason was to allow for interchangeability in the growing global marketplace. The third reason was to correct certain thread production difficulties. The jointly-developed thread form was named the Unified Thread Form. the Unified Thread is also referred to in the B1.1-2003 as Unified Inch Screw Thread. This Unified Inch Screw Thread both superseded the previous British, Canadian and American national standards, and later served as a prototype multi-national thread form standard that was eventually metricified to become the ISO Metric Screw Thread (the M-series)."



https://en.wikipedia.org/wiki/United_States_Standard_thread

"United States Standard thread (USS thread), also known as Sellers Standard thread, Franklin Institute thread and American Standard thread, is a standard for inch based threaded fasteners and washers.

The USS standard is no longer supported. It, together with the SAE fastener standard, was incorporated into the Unified Thread Standard. However, the term, USS, continues to be used occasionally today to describe inch based threaded fasteners with a coarse thread pitch and inch based washers that are a little bit larger than the corresponding SAE washer. The Unified Thread Standard uses the term UNC (Unified Coarse) to describe a fastener that previously would have been designated USS and the Unified Thread Standard uses the term UNF (Unified Fine) to describe a fastener that would have previously been designated SAE."

 

[motorson]

I think LAB did the best job explaining the differences in threads. I would point out that the purpose for the coarse thread on one end and fine thread on the other of those studs is because, coarse threads hold better in Aluminium than fine threads do. Fine threads, on the other hand, are stronger than coarse threads in steel and especially hardened or grade 8 steel. I have grade 8 steel lock nuts holding my foot pegs on.

 

[Joe Schlaberdowski]

my 2-cents, FWIW -- old brits lists those studs as 5/16 x 18 x 24 (part number 063383). if two are loose, it could be from running a thread cutting tap (and die) vs. thread reforming die in the holes or over the studs. i'm not a machinist, but my understanding is a thread cutting tap or die may remove additional material, thus making the fit a bit looser, whereas thread reforming taps and dies do not remove any additional material - they only clean and reform the existing threads. I almost never use a thread cutting tap or die to clean up existing threads. over the years I invested in a set of reforming taps (and dies). again, i'm not a machinist.

side note - hey joe - understand you're originally from Pittsburgh? what part? I grew up in the Allentown area in the 50's-early 60's....

Your reply answers the question. Thanks! I'd only ask if there is a quality brand of reforming dies (and taps?)?

I grew up in a small town east of Pittsburgh 29 miles called Delmont. On old US 22 and state route 66. But my grandparents lived on the South Side (of Pittsburgh) and we lived there, too, for a few years. In the 70s and just into the 80s I drove a tractor trailer and hauled steel. Can't tell you how many times I went through Allentown.

 

[Joe Schlaberdowski]

I think LAB did the best job explaining the differences in threads. I would point out that the purpose for the coarse thread on one end and fine thread on the other of those studs is because, coarse threads hold better in Aluminium than fine threads do. Fine threads, on the other hand, are stronger than coarse threads in steel and especially hardened or grade 8 steel. I have grade 8 steel lock nuts holding my foot pegs on.

I figured that was the case for the aluminum side vs steel. I think I'll get three threaded studs and the nuts as well from Old Brits. Joe Czech mentioned they have them listed.

 

[joe czech]

...I'd only ask if there is a quality brand of reforming dies (and taps?)?

hey joe - this a typical set I bought on fleabay - over the years, bought individual sets - fractional, fine, coarse, metric, fine coarse, etc.. since I procured individual sets over the years, it didn't break the bank. decent quality, and because they are not thread cutting, they're not real expensive - https://www.ebay.com/itm/Lang-NF-SA...716614&hash=item1efb7bb488:g:TBQAAOSw4d9c7wm8 . I also have one for spark plugs. handy little gadgets - I find myself using them for thread clean-up on just about everything. some folks make them out of old nuts and bolts - easy enough to do - I just chose to buy sets

 

[dynodave]

Clean up and chasing the threads is fine for trial assembly, but:

1. I like to use good/new studs since they are "to size" and with some type of anti rust plating/coating.
2. I install the studs with some low grade anti seize. I abhor coarse bolt mod as eating up the aluminum and making the brake lever/foot peg more difficult to hold/align & install.
3. I always install a norton spec plain washer under the brake cable bracket to stop the crushing deformation, from the counterbore, that will always happen.
4. In this case I use 3 fine thread stainless nuts as OK for function and cosmetics. + lock washers and 12 ft/lb

 

[maylar]

I only use a stud for the bottom (with brake cable support). The other 2 are chromed bolts. And like Dave, I use a washer to prevent deforming the bracket.

 

[joe czech]

Clean up and chasing the threads is fine for trial assembly, but:

1. I like to use good/new studs since they are "to size" and with some type of anti rust plating/coating.
2. I install the studs with some low grade anti seize. I abhor coarse bolt mod as eating up the aluminum and making the brake lever/foot peg more difficult to hold/align & install.
3. I always install a norton spec plain washer under the brake cable bracket to stop the crushing deformation, from the counterbore, that will always happen.
4. In this case I use 3 fine thread stainless nuts as OK for function and cosmetics. + lock washers and 12 ft/lb

dynodave - item #3 - didn't you find the stud used for the brake cable bracket was a bit too short to add a washer, preventing deformation of the bracket? I tried that, but found the nut too thick for proper thread engagement. my bracket was severely deformed from the previous owners. my solution was to make the bracket to fit the counterbore of the foot peg assembly and trim out the edge of the counterbore. the bracket acts like a washer for the nut without any deformation - (work in progress photo)

 

[Joe Schlaberdowski]

dynodave - item #3 - didn't you find the stud used for the brake cable bracket was a bit too short to add a washer, preventing deformation of the bracket? I tried that, but found the nut too thick for proper thread engagement. my bracket was severely deformed from the previous owners. my solution was to make the bracket to fit the counterbore of the foot peg assembly and trim out the edge of the counterbore. the bracket acts like a washer for the nut without any deformation - (work in progress photo)

I think that the shortness of that bottom threaded stud was what caused one of the previous owners to partially strip the threads. I also noticed the washer that was on that stud over the bracket was ever so slightly larger in thickness and diameter (really mean slightly) than the other two and that the other two seemed to fit perfectly in a very slight depression in the foot peg bracket. Is that slight depression what you are referring to as the "counterbore"? I thought perhaps I could use a length of 1045 rod (or 1015 mild steel if that's tough enough) and just thread that myself, making it safely longer than the original.

 

[maylar]

Or... use a 5/16-18 bolt.

 

[olympus]

I grew up in the Allentown area in the 50's-early 60's....

Its probably a great place ...but I'll always remember Billy Joel singing about it

 

[Joe Schlaberdowski]

Or... use a 5/16-18 bolt.

Having only slight knowledge of the effects of sliding pressure when tightening a steel 18 thread in aluminum, I thought it best to first insert the threaded rod under no pressure other than tightening it on it's own fully into the threaded aluminum. Then let the 24 thread steel on steel pull things up tight. But not knowing how coarse 18 thread steel effects hardened aluminum thread when pulling up tight, especially if using anti seize compound, I may be way overly cautious.

 

[maylar]

Don't overthink it. I've been securing the footrests with bolts for a few decades now. Looks prettier than a rusty old stud and plated nut.

 

[Joe Schlaberdowski]

Ok here's my excuse for overthinking the process. 1) too much coffee. 2) I think I was going down that path because the British engineers/designers at the Norton works went there. 18 count holds best in aluminum. Ok. But the lower the thread count per inch, the higher the side forces on the aluminum threads when tightening. To make that obvious, think of one thread (or even less) turn per inch. The angle would be so steep, the side pressure against that thread to achieve the required tightness along the bolt axis would be enormous. And so would the frictional force against turning such a bolt. Well, that's just exagerating to make a point. But it still must be true even to the smaller degree for 18 tpi. And that might be a factor in aluminum. So maybe they did it out of a convenience for the assembly process! and maybe they didn't want the extra side pressure necessary to tighten -- which would lead to extra friction in the tightening or undoing process in the aluminum. And maybe that could be a negative down the road.

Here's the real deal, if you've assembled and disassembled there with 18 count in aluminum on the same bike for years, it was probably done for assembly convenience. Maybe I should start drinking Ovalteen in the morning instead of coffee. But, then, how in the hell could I get out the door?

 

[maylar]

LOL Joe. From a practical point of view, there are 3 fasteners for the footrests. With standard split lock washers and hand tightening with a 3/8 ratchet they don't go anywhere. And I've stepped on them with my full weight.

In truth, the lower stud on my primary side is still there. I'm able to get a shim washer under the bracket and a flat & lock on top and still get enough thread engagement with the nut to make me happy. It's out of sight, so ugly doesn't matter.

 

[rvich]

I'm thinking that there is a lot of overthinking but I'm trying not to think about it!

 

[L.A.B.]

Ok here's my excuse for overthinking the process. 1) too much coffee. 2) I think I was going down that path because the British engineers/designers at the Norton works went there. 18 count holds best in aluminum. Ok. But the lower the thread count per inch, the higher the side forces on the aluminum threads when tightening. To make that obvious, think of one thread (or even less) turn per inch. The angle would be so steep, the side pressure against that thread to achieve the required tightness along the bolt axis would be enormous. And so would the frictional force against turning such a bolt. Well, that's just exagerating to make a point. But it still must be true even to the smaller degree for 18 tpi. And that might be a factor in aluminum. So maybe they did it out of a convenience for the assembly process! and maybe they didn't want the extra side pressure necessary to tighten -- which would lead to extra friction in the tightening or undoing process in the aluminum. And maybe that could be a negative down the road.

I think you could have stopped at: "18 count holds best in aluminum."

 

[Bob Z.]

I think you could have stopped at: "18 count holds best in aluminum."

And the several times over the years that I've dropped the bike on the left side, the foot peg snapped off and the foot peg nut dinged the primary cover. The 3 footrest fixing studs did not budge.