# machining press fit vs loctite



## dansawyer (Aug 6, 2019)

I am building a 'gear box' to drive an astorphotography camera mount. The shafts will be 6 mm steel set in ball bearings set in 3/8 aluminum plate. The large gears will be made of 1/4 aluminum discs with the gear teeth 2mm gt2 belt inside out. The small gears will be 2gt pulleys. 
The forces will be small and the rotations very low, less then one rpm on all parts.
My question is: Is it reasonable to machine a close tolerance on the parts and then assemble them with loctite? If so which variant would be best?


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## Rick Berk (Aug 6, 2019)

Loctite 607, Bearing Retainer would be my suggestion. (good stuff).


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## Karl_T (Aug 6, 2019)

double check before you machine, many loctite products need a loose fit to bond correctly


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## Flyinfool (Aug 6, 2019)

As Karl said, most Loctite products list the recommended clearances in the specification sheets.


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## ezduzit (Aug 6, 2019)

What's wrong with just machining it correctly to begin with?


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## benmychree (Aug 6, 2019)

ezduzit said:


> What's wrong with just machining it correctly to begin with?


Ease of assembly would be one point in its favor.


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## ezduzit (Aug 6, 2019)

benmychree said:


> Ease of assembly would be one point in its favor.



Not really. What could be simpler than just pressing the 2 parts together?

The other method still requires creating a proper fit, cleaning, applying the locking compound, cleaning again, and then waiting for it to dry.


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## benmychree (Aug 6, 2019)

ezduzit said:


> Not really. What could be simpler than just pressing the 2 parts together?
> 
> The other method still requires creating a proper fit, cleaning, applying the locking compound, cleaning again, and then waiting for it to dry.


Pressing two parts together is one thing, pressing together multiple components of an assembly could be much more complicated.


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## ezduzit (Aug 6, 2019)

benmychree said:


> Pressing two parts together is one thing, pressing together multiple components of an assembly could be much more complicated.



All the more reason to keep it simple. As soon as you press one item on you can immediately press on the next one without waiting for compound to dry or attempting to hold each in place.

Compound has a purpose: if you do not have the skill to create a press fit, if you're trying to salvage some worn-out/damaged parts, if you made a machining mistake, etc. Otherwise it's actually more work and less reliable.


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## Karl_T (Aug 6, 2019)

I am a proponent of the loctite compounds. Way easy to machine - no tight tolerance work  AND just heat it up to take it back apart.

on small diameters getting the correct press fit to hold any sort of rotating load is difficult.  

this one is my favorite





						LOCTITE 638
					

LOCTITE 638 is a high strength, fast curing, general purpose retaining compound.




					www.henkel-adhesives.com


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## jdedmon91 (Aug 6, 2019)

Depending on the application. Like when I’m making something that I absolutely don’t want to move, like a speed handle that I’ve made. I want to press fits, but for things for that just need to stay together I use bearing mount locktite. It is easier to machine a slip fit then lock them together however like I said for something that won’t move press fit is the only way 


Sent from my iPhone using Tapatalk


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## Mitch Alsup (Aug 6, 2019)

dansawyer said:


> My question is: Is it reasonable to machine a close tolerance on the parts and then assemble them with loctite? If so which variant would be best?



I recently did a similar job (for a telescope) where I used a 0.247 drill into 6061 which results in a thumb press fit of a 1/8-1/4 ball bearing retained only by tension around the bearing yet can be pushed out with a allen wrench from the other side. This is what we generally call "machined right the first time".

Alternately there are ways to put a slit near the bearing and use a screw to apply tension across (and around) to hold the bearing in place.

On the other hand: 6mm is pretty small for a shaft--for example the drive shaft in my C11 (circa 1989) is at least 3/8" solid steel with a bronze gear pressed on and hobbed on the shaft to fit the driven gear. Since stiffness increases quartically with diameter a 10mm shaft is (10/6)**4 = 7.7× stiffer.


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## Tozguy (Aug 7, 2019)

dansawyer said:


> The forces will be small and the rotations very low, less then one rpm on all parts.





dansawyer said:


> My question is: Is it reasonable to machine a close tolerance on the parts and then assemble them with loctite? If so which variant would be best?


 
I would say that a Loctite product is an option in this case but there are many different ones for specific clearances and metals. Choose the one best suited to  your needs then check formats and availability. You will get some valid recommendations from us but it is worth doing some research for yourself. The link that Karl provided is worth exploring.


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## ch2co (Aug 8, 2019)

Just wondering what type of astrophotography camera mount assembly?  A tracking mount? What kind of camera? Any and all details welcome. (Please)

And to just keep in line with the subject, I would go with the Loctite method.


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## dansawyer (Sep 7, 2019)

ch2co said:


> Just wondering what type of astrophotography camera mount assembly?  A tracking mount? What kind of camera? Any and all details welcome. (Please)
> 
> And to just keep in line with the subject, I would go with the Loctite method.



A reply to ch2co, sorry for the delay; I missed the question. Thank you for asking. The objective is Deep Sky Objects. The first attempts will be with a 90 mm F4 macro lens. The device will be an Arduino controlled stepping motor with 3 reduction gears There is a picture of the bearing box in the thread 'my first jig'. I will forward gear pictures in a couple of weeks


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## dansawyer (Sep 7, 2019)

Thank everyone for the inputs. There is a second part to this project for the shaft to hold the camera. The shaft is about 12 inches long and .628 inch in diameter. The bearing id is .635. Based on the above recommendations I will machine the shaft to a slip fit and use bearing mount Loctite. This is still in progress.


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