Which Adhesive?

[Sub MandrelParticipant @submandrel]

[Sub MandrelParticipant @submandrel]

This weekend I made the camshaft for my small 4-stroke engine (aside from hardening it). I also cut the 38 tooth timing gear which is a push fit on a 0.375" register, it is just under 1/8" thick and made of brass. Rather than using a key, I'd like to hold it in place with an engineering adhesive. It will be hot and oily and subject to reasonable loads.

I am guessing that Loctite 420 (or an equivalent) would be best as it needs to be strong and penetrate a quite close-fitting joint.

Am I right, or is there a better choice? Should I add a small pin, half in the register and half in the gear?

Neil

[Jeff DaymanParticipant @jeffdayman43397]

638 cylindrical component compound would be best for cams to shafts, as Loctite recommend it for gears and bearings fit to shafts. Link Below.

**LINK**

I buy and use 609 for this kind of job in Canada, 638 is probably the UK number for the same stuff.

JD

[Michael GilliganParticipant @michaelgilligan61133]

 

Neil,

 

I agree wholeheartedly with Jeff.

 

638 is remarkable stuff, and Loctite's data excellent.

 

 

 

I would just mention a couple of points:

 

Strictly speaking, these "gap filling resins" are not particularly strong adhesives … and that's what determines the best joint design. In your application, a light knurl, or spline, would be ideal … it centres the components,but leaves space for some resin.

 

Copper is a chemical accelerator for these resins, so your Brass to Steel joint will cure quite rapidly.

 

MichaelG.

Edited By Michael Gilligan on 21/04/2013 22:41:53

[Roderick JenkinsParticipant @roderickjenkins93242]

Neil,

I used a "high strength retainer" (I think it was a different brand to Loctite) 20 odd years ago to glue the cam gear to the cam shaft on my Matador and that was fine (the cams themselves are pinned to the gear which has several holes so the timing can be adjusted).

On a slightly different tack, it has been suggested that Loctite type adhesives dont work well on fabricated i.c. engine crankshafts because of the percussive nature of the stroke (compared to steam engines). Has any body any experience of this phenomenon?

cheers,

Rod

[David LittlewoodParticipant @davidlittlewood51847]

Michael is quite right; these retainers are not strictly speaking adhesives. They have rather poor peel strength (at least they did when I tested them); they work by polymerising in the absence of oxygen to form a plastic similar to perspex, which forms a firm interference joint inside the shaft/hole gap. Even a couple of mm is enough to give a fierce grip in a small diameter hole.

One thing to check though is the temperature. As you will appreciate from the above description, the interference fit depends on the polymer formed on curing. This will melt above a certain temperature, and you shoud check the manufacturer's specification for details of this.

David

[Michael GilliganParticipant @michaelgilligan61133]

**LINK**

MichaelG.

[nigel jones 5Participant @nigeljones5]

and clean the joints with alcohol/ethanol before application – no fingers!

[Jeff DaymanParticipant @jeffdayman43397]

Quite right fizzy, cleanliness with any Loctite or other adhesive or sealer product is very important. FYI Some Loctite grades require primer – best to check, and if they do require it, it is a very good idea to use it if you want the full rated strength in the bonded joint.

Thanks also to MichaelG for the Permabond pages, a great resource for good adhesive joint design.

JD

[Sub MandrelParticipant @submandrel]

I never thouight of looking at retainer instead of adhesive. I think the very thin 'bearing grade' us what I need hear, I seem to have excelled myself in getting a good fit for once!

Just checked in the workshop to see what I have got, but its loctite 243, which certainlyu won't be up to the job!

Permabond guide downloaded and added to the archve!

Thanks all,

Neil

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