help needed to identify a screw (retainer?)

[MartinVi]

Hello All,

I'm an owner of Bresser Exos 2 goto mount. Like many others, I've also experienced problems with significant backlash and free-play on this mount, I decided to tighten things up a bit and basically destroyed a screw in process.. I was not expecting them to be made of soft aluminum, I tore the threads off clean. Attached are two images - 1st is the location of the said screw - basically it retains worm gear and its bearing in place. There was also a nut sitting on top of it. Second image is of the screw (retainer collar?) itself. The diameter is roughly 14mm.. I'm looking for any info that would help me identify it and order a replacement - if there's a DIN number or the proper English name for it, any help will be appreciated.

[Peter Drew]

I think I would call this a sleeve nut.  It would be intended to adjust end float on the worm shaft, not backlash.       🙂

[Rusted]

It's not exactly your off-the-shelf item either. You'll probably have to find a dealer and ask for an original, replacement spare part. In aluminium!

Failing that: Screwed sleeves or thread [size] adapters are widely used. Large male thread on exterior. Smaller female thread inside.

Do an online search for M14 screwed sleeve. Assuming your part is actually M14. Presently unknown.
You may have to modify an M14 part by drilling it out to size. Or having somebody do that for you in a lathe.
Model engineer? Local tech college or school with a metal machine shop? The latter should have a thread pitch checking tool too.
If you can find an M14 bolt or M14 threaded part you can hold your mashed up fitting against the thread to confirm the pitch is the same.

 

[RichM63]

Threaded insert for metal, no idea what size.

Just bang it into Gargle n Cough you'll find many choices.

[symmetal]

Not sure if it's suitable but Accu.co.uk do a range of threaded inserts and the M10 one in the link, and shown below, has an outside diameter of 14mm with a pitch of 1.5mm which is M14 fine pitch. M14 coarse pitch is 2.0mm. It's self tapping so should clean up your damaged threads and it's stainless steel. The M10 inside thread should clear the shaft on the worm by the looks of it. They aren't cheap though at £8.40 for a single item.

Alan

[PhilB61]

If you can find a replacement, I'm not sure it will necessarily solve your problems as it looks like the casting into which it threads is equally mangled. Maybe take the whole worm block off and take to a small engineering workshop and see if they can undertake a repair. 

[MartinVi]

On 18/03/2024 at 20:58, Peter Drew said:

I think I would call this a sleeve nut.  It would be intended to adjust end float on the worm shaft, not backlash.       🙂

As I wrote, it is not just backlash, that I was trying to fix. The whole worm gear was dancing around causing free play in RA axes even when gears wouldn't move

On 18/03/2024 at 23:22, Rusted said:

It's not exactly your off-the-shelf item either. You'll probably have to find a dealer and ask for an original, replacement spare part. In aluminium!

You're probably right, dealer and manufacturer have not responded to my queries. I can only assume they order whole blocks to be made in China and don't have spares lying around

On 19/03/2024 at 11:08, PhilB61 said:

If you can find a replacement, I'm not sure it will necessarily solve your problems as it looks like the casting into which it threads is equally mangled. Maybe take the whole worm block off and take to a small engineering workshop and see if they can undertake a repair. 

Sounds good but I'm out in the sticks and have no connections to such workshops

On 18/03/2024 at 23:29, RichM63 said:

Threaded insert for metal, no idea what size.

Just bang it into Gargle n Cough you'll find many choices.

That is what I was about to do, but before I take any risks of messing up threads even more I decided to try a much gentle method - I'm not gonna share pictures, because I'm a bit embarrassed of the craftsmanship, but basically I discovered that using some well lubed spacers (perhaps later on I will replace them with a bearing) I can wedge the worm gear on its drive gear side so that on the other side where this retainer sleeve nut used to be, I only needed to find a way to hold the bearing in its place. Since this side wouldn't need to carry any load anymore I then manufactured a small aluminum tube that I hot-glued into its position to make sure bearing doesn't go anywhere. By exercising the mount/gears, so far its holding up nicely but I haven't had a chance to test for real as it is cloudy. I do suspect that friction between spacers and in general their imperfect shape will cause some issues, but we will see. In long term I'm looking to upgrade away from it anyway, so In short term let's just call it a learning exercise

Thanks to all your inputs

[RichM63]

I hope it works out OK, best of luck. I would have still gone with an insert, that cast aluminium is very soft.

[fozzybear]

Have you tried to contact Bresser in Germany direct? As looks like you might tightened the locking nut and that has then stripped the insert and the casting on the worm gear assembly? the locking nut is to be released and the insert +/- to remove the end float on the worm and then the locking nut nipped up. 

[MartinVi]

On 23/03/2024 at 00:01, fozzybear said:

Have you tried to contact Bresser in Germany direct? As looks like you might tightened the locking nut and that has then stripped the insert and the casting on the worm gear assembly? the locking nut is to be released and the insert +/- to remove the end float on the worm and then the locking nut nipped up. 

 

Yes, sent them an email on March 18th, all I got was an auto reply saying that a ticket has been created and thats it.

[Seme]

Hi Have you tried Telescope House they maybe able to help.

 

[Naughty Neal]

I wouldn't be surprised if it isn't a generic size used and  the same as  Syywatcher use on Skytee2 or EQ5.