Topic: Rear shock tower/mounts threaded hold-down portions;threads getting worn..

[grcamna2]

I have the little Honda single cyl. 200 street bike and have adapted a cobbled-together luggage rack made from a CCA 3-piece main rear rack,then added vintage BMW factory Krauser lower hard case mounts to each side. I had a few welders add weld and gussets to it over the years.
The rack isn't pretty,but it's very strong and I have carried many different items on this daily driver commuter bike for the past 8 years
The price of Regular gasoline is up to $6 a gallon here  recently;this bike helps.

My rear factory Honda upper shock tower/mounts threaded ends(10x1.25mm by only 12mm long),which are fine threads)have been getting lots of use during my ownership of the bike;the raised,machined portion of these studs measures only 11.9mm O.D. to fit 12mm I.D. shock bushings.. I may need to replace the mounts to gain more strength.
I'm afraid if I drill and tap for a 10mm stud,it will leave these 11.9mm upper shock tower studs too thin & weak.
I need to remove the rack and reinstall it regularly,for maintenance,etc. I torque and loosen the hold-down nuts to attach the rack and this has worn the threads down to the point that they're now loose;I need to consider what to do to replace these threaded towers.
I was speaking with a person who threw an idea at me of,  "you could possibly cut the threaded portions off both towers flush,then drill and tap them to 10x1.50mm(more coarse threads,stronger?),then install a pair of 10.9 hardness bolts and red LocTite them in and then cut the heads off the bolts when you're finished"  ??  I'm not sure if that's the best option,but might work?
 Do you have any ideas for me to replace the threaded studs? or the complete upper shock mounts?

[newday777]

I bought two 10x1.25 studs at Ace hardware for $3.09/each to keep the stock cap nuts.
I have the tap but had to oder a 8.8mm drill bit for the tap size hole to finish. I had one side bust off carefully removing the nut/thread extensions that were rusted on the threads on the 76 750 I'm working on. The other side the threads are damaged so I'll cut it off also and drill and tap it for the new stud.

[Don R]

 I drilled one stud all the way through, inserted a bolt through to the inside and welded the end inside the fender.

[BenelliSEI]

I drilled one stud all the way through, inserted a bolt through to the inside and welded the end inside the fender.

I did the same on a cb550. Used a grade 8 bolt and never welded it……

[calj737]

You could simply use a lock washer and stop torquing the nut down so hard.

If you know someone who welds, they can easily weld a new bolt  in place of the stock stud. Cut the stock stud off flush at the outside, drill through the gusset, weld the bolt from the backside. Find a 10mm bolt that is only partially threaded to mimic the stock bolt (McMaster sells them). If you do the cutting and drilling, it’s literally a 5’ job for a welder as the bolt only needs 3 tacks to hold it (use stainless bolts).

[simon#42]

You could simply use a lock washer and stop torquing the nut down so hard.

If you know someone who welds, they can easily weld a new bolt  in place of the stock stud. Cut the stock stud off flush at the outside, drill through the gusset, weld the bolt from the backside. Find a 10mm bolt that is only partially threaded to mimic the stock bolt (McMaster sells them). If you do the cutting and drilling, it’s literally a 5’ job for a welder as the bolt only needs 3 tacks to hold it (use stainless bolts).

you would weld a stainless bolt to a steel frame?

[grcamna2]

I drilled one stud all the way through, inserted a bolt through to the inside and welded the end inside the fender.

I did the same on a cb550. Used a grade 8 bolt and never welded it……

Grade 8,is that sufficient?
 A man in a hdwe. store was telling me that the 'Grade' numbers on these bolts today are not as accurate as they used to be;he said a bolt w/ 8.8 on it is more of a Grade 5.
He said an equivalent to the strength of a true Grade 8 is actually labeled 10.9 

[simon#42]

I would have thought the grades were more accurate these days . Any way either of those bolts will be much stronger than the original set up

[grcamna2]

You could simply use a lock washer and stop torquing the nut down so hard.

If you know someone who welds, they can easily weld a new bolt  in place of the stock stud. Cut the stock stud off flush at the outside, drill through the gusset, weld the bolt from the backside. Find a 10mm bolt that is only partially threaded to mimic the stock bolt (McMaster sells them). If you do the cutting and drilling, it’s literally a 5’ job for a welder as the bolt only needs 3 tacks to hold it (use stainless bolts).

you would weld a stainless bolt to a steel frame?

I would choose a different option.

[calj737]

You could simply use a lock washer and stop torquing the nut down so hard.

If you know someone who welds, they can easily weld a new bolt  in place of the stock stud. Cut the stock stud off flush at the outside, drill through the gusset, weld the bolt from the backside. Find a 10mm bolt that is only partially threaded to mimic the stock bolt (McMaster sells them). If you do the cutting and drilling, it’s literally a 5’ job for a welder as the bolt only needs 3 tacks to hold it (use stainless bolts).

you would weld a stainless bolt to a steel frame?

All day long. That’s why they make 309/312 filler wire.

[calj737]

you would weld a stainless bolt to a steel frame?

I would choose a different option.
[/quote]
Only because you don’t weld do you think it’s not appropriate.

[simon#42]

You could simply use a lock washer and stop torquing the nut down so hard.

If you know someone who welds, they can easily weld a new bolt  in place of the stock stud. Cut the stock stud off flush at the outside, drill through the gusset, weld the bolt from the backside. Find a 10mm bolt that is only partially threaded to mimic the stock bolt (McMaster sells them). If you do the cutting and drilling, it’s literally a 5’ job for a welder as the bolt only needs 3 tacks to hold it (use stainless bolts).

you would weld a stainless bolt to a steel frame?

All day long. That’s why they make 309/312 filler wire.

Not something I have ever done , I guess it won’t rust but are there any other advantages to doing it this way .

[RAFster122s]

I drilled one stud all the way through, inserted a bolt through to the inside and welded the end inside the fender.

I did the same on a cb550. Used a grade 8 bolt and never welded it……

Grade 8,is that sufficient?
 A man in a hdwe. store was telling me that the 'Grade' numbers on these bolts today are not as accurate as they used to be;he said a bolt w/ 8.8 on it is more of a Grade 5.
He said an equivalent to the strength of a true Grade 8 is actually labeled 10.9 

I think he maybe a little confused and is trying to equate a metric bolt that uses metric units of measurements and international standards that use those abd different units of measure for calculating the fastener strength or different scale or different granularity in their units being measured. The fasteners are using the same formulas for calculating the strength but the units of measure are introducing apples and oranges for comparison

The 10.9 is closest to a grade 8 and yes the grade 5 is closest to a grade 8.8 in metric.

Chinese fasteners can have poor quality or quality control and therefore sometimes they are super unreliable causing you not to trust them.
You can get good built in China that have high quality but the rigor employed to obtain that quality is costly and this the price is high.

The Chinese don't do anything unless they can find profit and they are very good at squeezing out the profit and sometimes * have heard of them making changes after initial product to lower grade of materials or similar things to scrape out more profit and after the product initial is deemed to be good quality and a good buy the orders really start hitting with volume and the output product has issues because of those changes and the increased production volume putting out lesser quality and they are shipping stuff not meeting initial quality. Then there are kmock offs of the original and the forgeries are no where near the quality. That happens on products they can mic after success of the initial product.

China isn't a friend of America, never has been. The more you can do to not buy Chinese products or bring manufacturing back to America or other countries whom are not wanting to see America's destruction and their domination the better in my opinion.

David

[calj737]

you would weld a stainless bolt to a steel frame?

All day long. That’s why they make 309/312 filler wire.
[/quote]
Not something I have ever done , I guess it won’t rust but are there any other advantages to doing it this way .
[/quote]
Aside from corrosion resistance, not a lot. They (stainless bolts) weld up stronger than mild steel bolts. Stainless welds in general are very strong, even when autogenously welded. But corrosion is a factor in thread life hence the recommendation.

[simon#42]

Interesting , I have always shied away from welding dissimilar metals unless there is no choice .

[calj737]

Interesting , I have always shied away from welding dissimilar metals unless there is no choice .

In most situations, I'd agree. But in this scenario, there's no adverse effect to it. You certaibnly could use mild steel bolts in lieu of stainless, but for the reasons above, I'd opt for stainless and lock washers.

Case in point: the past two weekends I spent helping my eldest build a smoker/grill from a compressor tank. Most of the welding was carbon-carbon. But, there are a few valves for gas feed, drainage, and thermostat bungs that are 304 stainless. To weld them in place to carbon, I TIG'ed them with 312. No choice about the parent metals so to have the resource and capability to do it was ideal. I have also welded stainless ehaust hangars to carbon frames for CognitoMoto. Or TIG brazed CroMo to carbon with SilBr because the application didn't require a full pen weld. (I even did this same technique on my eldest's smoker door to air seal the flange to the lid.)

So it all boils down to the application and variables of the metals being welded. GTAW allows tremendous flexibility and assurance if you know what you can do with it. Like welding 6061, 5052 or mystery cast on AC. Different wires work better than others. Frequency effects temper and distortion more than amperage. Balance has an impact too. But when I weld ally, I use 250Hz predominantly and have my machine set to max amps and use a pedal to modulate heat. And nothing warps as a result. Get in, get out and don't effect the temper.

[grcamna2]

you would weld a stainless bolt to a steel frame?

I would choose a different option.

Only because you don’t weld do you think it’s not appropriate.
[/quote]

That's true.

[grcamna2]

I drilled one stud all the way through, inserted a bolt through to the inside and welded the end inside the fender.

Don,this option is the most appealing to me so far.
The large,smooth section of the shock mount is 12mm,the threads are 10mm.
The threads are bent back on this left side shock mount;the right side threads have even more wear and are loose from 8 years of removing and torquing to remove the rack,seat,tank numerous times.
I'm considering cutting the shock stud off flush from the surface of it's pad/mount,then drilling a hole all the way through and sourcing two 12mmx95mm w/ 11.9mm O.D.(to fit my 12mm I.D. shock bushings)hardened bolts which have countersunk heads to fit the oversize width rear tire into my plastic inner fender and have it welded on the back side. I have been looking for them;countersunk heads are not easy to find.
Doing this will allow me to get threads on the end which are larger diameter and longer to better tighten-down my luggage rack forward mounts.

Edit:I called Grainger and we spoke and they'll sell me a minimum quantity of 25(I only want 2)of this type of bolts;this is very close to what i want,considering a 12mm shock bushing will fit over the top of it.
I prefer a fine(1.25mm)thread,which they didn't have. I'll keep searching.

[calj737]

I drilled one stud all the way through, inserted a bolt through to the inside and welded the end inside the fender.

Don,this option is the most appealing to me so far.

Its the same thing I suggested with the difference being buying (2) bolts from McMaster or BoltDepot.com or Allensfasteners.com and using stainless.

[Don R]

 I found a chrome moly tube that fit snugly over the shock stem and a little long, then made a drill bushing that fit into the tube to keep the hole straight. It could have been tighter but worked well enough.

[grcamna2]

I just recd. these today 12x1.75x100mm.

[calj737]

Because the shock tower flange is two layers of stamped, thin metal, that countersunk head will be a bit of an issue.in order for it to sit flush, you’ll need to countersink that backside, but it’s too thin to accommodate that. You’d be better off getting either a standard flange head hex bolt, or a pan head and use a flat washer. The washer or flange head will help distribute the shear stress on the bolt head across a greater area.

And if you do happen to exchange which bolt types you use, get partially threaded. There will be a straight unthreaded portion of the shank from the head for 50-75% of the length (you can find different options online)which will provide a better mounting area for your luggage. Fully threaded just increases the likelihood of damaging the threads if you use different width mounted bags. That makes tightening the thinner mounted stuff harder if the threads get buggered.

Food for thought.

[grcamna2]

I can see what you mean;there's not enough material left on the back side to keep it's strength,if I countersink to the taper required for that bolt head to be recessed. 
I'll need to use a flat/flange head,then notch the plastic inner fender in those two spots.

[Terry in Australia]

Years ago I bought a CB750 that a previous owner had actually cut part of the threaded portion of the top shock mounts off, and there wasn’t enough”meat” left to install a decent pair of OEM shocks and install the standard dome nuts.

I cut the remaining threaded portion off, drilled and tapped them for 12 x1.25mm (standard thread for CB750 top shock mounts) and was horrified at how hard the original mounting posts were, I had to buy a special tungsten drill bit to drill the holes! I then just threaded them and installed some 12 x 1.25mm bolts into them and called them it good.

[grcamna2]

Years ago I bought a CB750 that a previous owner had actually cut part of the threaded portion of the top shock mounts off, and there wasn’t enough”meat” left to install a decent pair of OEM shocks and install the standard dome nuts.

I cut the remaining threaded portion off, drilled and tapped them for 12 x1.25mm (standard thread for CB750 top shock mounts) and was horrified at how hard the original mounting posts were, I had to buy a special tungsten drill bit to drill the holes! I then just threaded them and installed some 12 x 1.25mm bolts into them and called them it good.

Terry,to clarify,you said you "cut the remaining threaded portion off,drilled and tapped them for 12 x 1.25..." ?
I don't understand:if you cut the remaining threaded portion off,what part did you drill and tap ?
I would imagine the remaining shock mounts O.D. were much larger than 12mm ??

Did you install 12mm bolts all the way through the shock mounts after drilling all the way through them ?