bark_eater 

I have a bike with loose headset cups. The head tube appears to be slightly ovalized and has been opened up with abrasive in a prior attempt to glue the cups in. The cups fit in and out by hand and if I rotate the ones I have they will cam in with their own tolerances. SWAG but my maximum gap at .15mm. I am faceing the head tubes so that the faces are parallel. I am still waiting on the new head set, which will be aluminum with replaceable cartridge bearings.
I'm trying to decide on which adhesive to use to glue them in. Any suggestions?

rosefarts

Loctite 680

HillRider

If you are sure you can get replacement bearing cartridges in the future so the cups never have to be removed, then you could either epoxy them in or use one of the strong Loctite Bearing Retaining compounds like Grade 609 or Grade 620.

wsteve464

You might find some good info in this thread.

https://www.bikeforums.net/framebuil...-headtube.html

bark_eater 

Reading the Manufactures literature Loctite 638 looks good. I hadn't focused on the way this stuff expands when it cures.
I started that post on the frame building forum to get a feeling about the worst case scenario of taking a torch to the bike. Got lots of glue suggestions. Not sure if I'll get fill it with silver suggestions here....

bark_eater 

Retaining Compound Design Guide

Hoping to hear some success story's before smundering goop.

shelbyfv

You got more good info in your other thread than you'll get here. There isn't much more to add to what they said.

bark_eater 

Yea... but...... opinions on glues have been a little slim on details, IE, "use epoxy" There's 2000 flavors of epoxy.

Trakhak

Just buy some LocTite 603 and fix the frame. I've fixed a couple of bikes (one of them mine) with ovalized head tubes using this stuff. Worked perfectly, never failed.

Juan el Boricua

May I suggest using JB Weld ( 2 part epoxy; the "runny" one), and a thin coat of grease/oil/Spam cooking oil on the cups (as release agent)? I've used it to repair two crankcases (lots of vibration; constant exposure to heat and oil) and one headtube with your described situation. All three subjects were sold, with an informed consent to their new owners, after several years of ownership without oil leaks(on the first two subjects), and without binding or looseness on the latter. Mind you, this was more of a cruiser/weekend commuter bike and, although I did a refurbishing of the headset, including greasing the cups as so they would not "fuse", I had no need to use a cup removal tool on them; just gentle tapping with a plastic mallet eased the cups out. It worked for me, might do it for you. Good luck with your endeavor.

dsaul

As I said in the other thread, Loctite 609 is made for this purpose and I have used it with success on one of my own bikes. https://www.amazon.com/Loctite-13551...s%2C151&sr=8-2

bark_eater 

It looks like Loctite 609 gap filling maxes out at .005" or .127mm. I'm getting a gap of approximately .15 mm. The used Headsets I have are both slightly ovalized, so I'll recheck the tolerances when the new one. I'm leaning towards Loctite because it expands in the joint, locking the part in with more than just stiction.
Loctite 638 and 648 have a significantly greater shear strength than 609, but that is based on both surfaces being abraded, so if I leave the headset smooth, I will have a better chance of removing the headset in one piece. I think Id rater just buy a couple sets of replacement cartridge bearings though. Using an aluminum head set, I will also be able to use thermal shock to loosen up the parts, more so than if I used a steel head set.

I'm not sure about the idea of pot casting the headset in with JB weld. Using a mold release to reduce the stiction of the bond increases the chances of the cups breaking lose and turning in what is now a slip fit. I dont think JB weld has that great of an abrasion resistance so small movements will be come large movements as the glue wears. If you get the get the head set out in one piece it seems like you'd have to re-cast the whole glue joint to put it back securely.

HillRider

True but that's overthinking it. Any of the two-part epoxies you can get at a hardware or home store will work. Just mix it in the recommended proportions and have the surfaces clean and free of dirt, grease and oil. JB Weld is a metal powder filled epoxy and works well.

WizardOfBoz

I think the "abraded surface" issue for loctite 638 may be a bit of overkill. I don't see that requirement on the Tech Data Sheet, here. All the Loctite products mentioned are similar and are designed for a much higher duty cycle than a bike headset. Stuff like gears and bearings in power-driven gearboxes. I'd probably just go with 638 and be done with it. If it fails, its pretty easy to remove (compared to epoxy), too.

If you really want a a permanent, removable solution, you could have the headset skim-bored or reamed to remove 0.05mm, and install the bearing with a 0.02mm shim. That's overkill, though, and this app seems to me to be tailor-made for 638.

I think that 648 is more for hotter applications. Not needed for your headset.

Fissile

Not a lot of details from OP. What kind of headset are you working on? Threaded or thread-less? 1" or 1 1/8? If this is a one inch threaded headset (yes, some 1 inch headset use cartridge bearings) is it ISO or JIS? Although these headsets are nominally "1 inch" there are some differences. The headset cup OD for JIS measures 30mm while the cup OD for ISO is 30.2. Most JIS cups can be installed by hand into headtube that's been made for ISO and should not be used for a bike frame headtube sized for ISO headsets.

bark_eater 

1" ISO. Toaster plugged in. Head tube is ovalized, and previously reamed out with sandpaper to glue cups in, which failed. Maximum gap is atleast .15, but I will check against the new headset when it arrives.

The brochure I linked to describes roughing the surfaces and I think there's a graph in there showing the difference that it makes in joint strength.

PS. Found the reference.

"Surface Finish FACTOR 4 Retaining compounds benefit from a certain degree of surface roughness 1.6 to 3.2 μm Ra. Smoother surfaces will lower adhesive performance and rougher surfaces have the risk of misalignment when assembled. Note that the f4 factor only applies to axial loads and not torque. Use 1.0 for torque calculation."

"Surface Finish: One component of joint strength is dependent on a mechanical interlock with the roughness of the metal surfaces. A surface roughness of 1.6 to 3.2 μmRa, equivalent to a steel surface abraded with emery cloth, is recommended. A smoother finish will reduce mechanical interlock and correspondingly reduce the maximum achievable strength of the bonded joint."

Another point for the "638" is it less effected by surface oil contaminates.

WizardOfBoz

So, I'd make the point that the major force on the cup is axial, and that the shoulders resting on the bottom of the head tube support that force. The retaining compound only affects centration and rotation. There will be some force of that nature but not as much as the axial force. So I think any of the products would work.
I did look up a Henckels URL that offered a comparison. This seemed to indicate that 638 handled a wider gap, and was stronger than 609. If you want to rough the id up with emery, and wipe off the dust and oil with isopropanol, I don't think you'll have much problem.

https://www.henkel-adhesives.com/us/...ctite_609.html