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Loctite and brass

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kelvin2164

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I have a 32mm dia brass disc, 1mm thick and need to drill accurate holes at 24PCD. The plan was to glue it to the end of an aluminium bar and drill it in the rotary table.
I used 7471 primer and 680 loctiite and allowed to set for 2 days. The first touch of the drill and it broke away. Tried several times. Same result. The loctite sticks to the aluminium, but has no bond at all to the brass.
What am I doing wrong.
 

RichD

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Don't have an answer for the locktite issue, but have you considered making a counterbore in the aluminum to hold the brass disc for you? Be sure to leave a center hole in the aluminum for popping out the disc when finished.

Rich
 

Blogwitch

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Kelvin,

It is for little awkward jobs like this I tend to use mechanical means to hold a part.
A pot chuck or soft jaws in the chuck you will be using. Easy to do if you have or can make either. In fact I won't buy a self centring chuck unless soft jaws are available for it.

There is a reason for going down that route.
Certain non ferrous materials can be very hard to bond together because there are so many different mixes in each type of alloy, one of those components could be the reason you are not getting a strong bond on the 'brass' side. So unless you know EXACTLY what materials you are using, then contacting Loctite for a solution, you are in fact stabbing about in the dark hoping that it will work.
99% of the time, Loctite will give a very good bond, but in your case, I think you may have that odd 1% that is causing your failure.

For real quickie jobs, which have very little maching forces involved (such as drilling small holes), I have used that very high strength black coloured double sided tape that is used for permanently sticking trim (number plates, mirrors etc) onto the outside of vehicles, that seems to stick to almost anything.

I know these are only alternatives to your solution, but you may have to go down one of these routes in the long run.

John
 

bazmak

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Have you tried using a longer piece of brass and use the rotary table to drill first.Then part off in the lathe
 

abby

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Brass does not like Loctite , even grit blasted surfaces part company, ordinary super glue sometimes gives enough hold for light work .
Other options are wax/resin chucks but my preference for holding thin brass parts for machining is to soft solder them on to a suitable block or bar.
 

Tin Falcon

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Look up shellac chuck. Clock makers have used them for over a hundred years.
Also known as wax chucks.
Just a mod of you original idea. You Want machine some concentric grooves in the aluminum . basic concept melt shellac for a hot glue. Machine part. Apply heat to release.dissolve residue with alcohol.
Tin
 

WOB

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Brass does not like Loctite
This is an incorrect and gross over generalization. The anaerobic thread lockers like 242 , 270, etc. love brass and will react rapidly. 680 is a methacrylate ester which is a different chemical. See http://www.henkel.com.au/aue/content_data/327273_UPGRADE680EN.pdf

Loctite makes hundreds of different adhesives of many different chemical compositions. You have to be selective if you want good performance.


WOB
 

Herbiev

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I find a hot melt glue does the job.
 

doc1955

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Loctite 680 is not a adhesive it is a retaining anti airobic. It has a high shear strength but not so good on a tinsel strength. You are trying to use it for something it was not intended to do. Switch to a Loctite super glue or one of their adhesives and you will have much better luck.
 

AlbertdeWitte

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Good day

I do that a lot with normal super glue, after machining I use a small hammer to tap it loose and then I soak it in acetone, it removes all super glue in 5min...;)
 

kelvin2164

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Wow! Thanks guys. Lots of info there.
I eventually did it using super glue. I also needed to turn a spigot, silver soldered to the disc. I did this very carefully and when finished, lifted it off with a screw driver. It came away very easily and certainly wouldnt have stood up to much machining pressure. Again, no visible bond to the brass. The hot glue sounds good, but not too sure about getting even thickness. At least Loctite has a thin, parallel bond. Maybe shellac (if I can find any these days)
I need more Loctite expertise.
 

petertha

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This video might be helpful. He is makes CA/superglue holding fixtures with grooves in them (~ 3:00 min mark). This same technique is repeated for other brass parts in other videos. He mentions light cuts & not allowing the parts to heat up excessively from machining.
https://youtu.be/qOHSTxxAjFs
 

kelvin2164

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Nice video. Makes me feel so inadequate.
I dont get the grooves though. I understand it requires the abscence of air for super glue to harden (that's why the bottles are only half full) and he is providing air filled grooves? What is happening here?
 

petertha

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Wondered the same myself & only going to take a guess. I've also experienced the not-fully-cured state on CA-d parts & noticed usually the common factor is non permeable materials. I can get them to work better with kicker (accelerator or primer) but that doesn't lend itself to careful positioning.

This link/excerpt kind of supports the theory I've heard. The thread locking 'locktite' kind of glue cures in absence of air whereas krazy / normal CA / superglue requires humidity which is sufficiently provided by only a bit of air. No air = no humidty = incomplete or lack of CA cure. May say the 2 glues are the exact same thing & maybe even use them interchangeably, but doesn't look to be the case.

I can see where a large surface area joint of 2 impermeable materials like metal to metal may not cure properly with CA because the metal can not give up any air from itself. Equally large joints of say wood-wood or wood-metal don't experience this because the wood itself is porous, meaning containing air & provides what's required. Plus wood fibers are probably assisting CA cure as a function of shape/surface area (the smoking hot baking soda trick). Small metal-metal CA joints might be getting by & achieving full cure from relatively larger periphery air exposure?

So what I think the mandrel grooves are accomplishing is giving enough air supply from the gap valleys to serve the adjoining CA joints either side on the flattened mountain tops so to speak. Basically introducing artificial porosity to impermeable materials.

The kickers are another kind of mystery. They are intended to accelerate cure, but maybe in these metal-metal cases they provide the joint something equivalent to moisture to complete the bond in absence of air?

CA link
http://www.ipmsstockholm.org/magazine/2004/10/stuff_eng_tech_ca_glue.htm

A common source of confusion is mixing up CA glue with Locktite thread locking glue. The main reason for this seems to be historical. The Loctite brand that initially produced the thread locking glue became for many users synonymous with that type of glue. Nowadays, Loctite has an entire variety of glue products in its range, CA glue among them. The main difference between the two types is in the medium activating the bonding reaction. In the thread locking glue, polymerisation starts in the absence of oxygene (air), while CA bonds with the aid of humidity.
 

Cogsy

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When I used to sell the Loctite range in the bearing industry, there were at least 7 or 8 different CA-type glues in the Loctite range. The 2 most common were 406 and 401. Identical bottles with identical looking adhesives but 1 was for porous surfaces and 1 for non-porous. For my own, non-critical gluing, both seemed to work equally well. The rest of the range became more specialised with different viscosities, wicking, etc, and specialised for materials, glass, ceramic, etc. I know from experience that the Loctite rear-vision-mirror adhesive will bond a rear view mirror to the windscreen that well that pulling hard on the mirror will remove a chunk of glass from the windscreen rather than breaking the glue bond!
 

abby

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Thank you for your observation WOB , I imagine that I am pretty typical of model makers , I have the standard thread lock as stocked by my local auto-spares shop and have found it's failure rate , for the subject of this thread (no pun intended) , unacceptable .
I am aware that Loctite make a wide range of products , one or more may well be suitable for the bonding of brass parts however contact with suppliers of these products have never recommended anything as particularly effective .
As a model engineer I want to spend my time making models not trying out various Loctite products until I find one that works.
Brass is probably the most widely used material for the model engineer and as many users will have found out it is very difficult to get even paint to stick without etch primers etc.
Like most model engineers I want a quick , simple , reliable and inexpensive solution to my work holding problems , something that is very easy to obtain , preferably that I have in stock
soft solder ticks all the boxes for me.
 

kelvin2164

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Well I'm glad I'm not alone in the forest of Loctite products that I dont understamd.
The video that Petertha linked to showed the operator using considerable maching pressure on his CA bonded brass. If I could achieve that I would be very happy.
Tried again tonight. Another less than satisfying result.
Aaaaaaargh !!!!!
 

goldstar31

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It's appalling simple! It could be almost child's play. Look into the mouth of a modern child with orthodontic work or call it a brace.
Today, well, most don't use silver solder olr a little turret spot welder to do stainless work- as my wife did. Our daughter simply glues her wire etc to teeth and this has to stand being immersed in assorted ingestions- until the job is complete.

Me, well, I'm not quite accident proof and I stuck my finger in the doctor's waiting room door just before our month's holiday. I used one of 5 tubes of CNA which cost the princely sum of a humble quid( £1) to hold the the torn flesh better than stiches or whatever. Our dear old friend of 95 was next door and had stumbled and 'torn her arm badly'. The local Spanish had arrested the bleeding but with better stuff( nice color) on the dear old dragon! I busted my nose on the tailgate on on the little High and Dry and I patched myself up- a bit cross eyed, but OK.
Last night, my wife had an argument with a wheelchair and there was blood dripping on the airport floor. Patched with glue- at midnight. in true vampire style.

OK, the surgeons are even doing internal surgery with the stuff. Presumably, my daughter is doing teeth and her husband the internal plumbing heart surgery with much the same sort of stuff that I mended the garden gate- and my nose and finger.

This Loctite thing about brass was an urban legend- long before most of you were born. It's like me- we've lasted well.

Oh, and my wife has just reminded me. Centuries ago, I stuck a diamond back in one of her rings. Another success story!
 

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