How can I remove this rear flange? (carbon tube refractor, metal flange)

[pipnina]

Update:

Spoken to the guys at work, seems like cutting the male M117x1 thread into the existing flange and parting off the end is going to be possible! We're going to take a closer look at it tomorrow and possibly have our go at machining it. Failing that, they've said I might be able to bring in some 5" aluminium bar to machine a flange new. Looking at prices that could run me £80 if it came to it, but I'm still hopeful the original will fit!

Fingers crossed!

[Carl Au]

Good luck with it, fingers crossed 🤞 

[AMcD]

On 15/10/2022 at 17:09, pipnina said:

I was looking at either the feathertouch R&P 3" (M109 x 1mm thread), or the TS 3" R&P (M117 x 1mm thread).

I am having a similar issue with my TS Optics 152 Individual achromat.  The rear cell is a flange attachment that needs an adapter if a TS 3" R&P is to be fitted to the scope:

TS have said they may be able to make me an adapter if I send them drawings, using their custom adapter service:

Teleskop-Express: TS-Optics custom-made Adapter

[pipnina]

15 minutes ago, AMcD said:

I am having a similar issue with my TS Optics 152 Individual achromat.  The rear cell is a flange attachment that needs an adapter if a TS 3" R&P is to be fitted to the scope:

 

TS have said they may be able to make me an adapter if I send them drawings, using their custom adapter service:

Teleskop-Express: TS-Optics custom-made Adapter

I sent them an email last week and they never responded, so I presumed they either didn't speak english or were disgusted at my german haha.

Good luck with the service if you go that route! Let us know how it goes!

[Rusted]

T-S adapters are very expensive and may take several attempts to get it right.
I needed a 160mm D-ERF adapter to fit on the cell of my 6" iStar objective.
I falsely assumed that any machinist would know what fitting a certain diameter meant.
So I [naturally] expected a sliding fit for the [standard] D-ERF glass. How else could it possibly fit in there?
They made it an interference fit by exactly matching the diameter of the [standard] Baader D-ERF.
So it had to go back in the post with all the inevitable delays going both ways.
 

[Budgie1]

4 hours ago, Rusted said:

T-S adapters are very expensive and may take several attempts to get it right.
I needed a 160mm D-ERF adapter to fit on the cell of my 6" iStar objective.
I falsely assumed that any machinist would know what fitting a certain diameter meant.
So I [naturally] expected a sliding fit for the [standard] D-ERF glass. How else could it possibly fit in there?
They made it an interference fit by exactly matching the diameter of the [standard] Baader D-ERF.
So it had to go back in the post with all the inevitable delays going both ways.
 

To be far to Machinists (I used to be one), they can only go on the quality of the drawings or sizes they're given. If you ask for an ID of 160mm then that's what you'll get, normally with a standard tolerance of around +/-0.02mm if one isn't specified. 

If you want a sliding fit then you need to specify this by saying ID of 160.05mm +0.02 / -0.00, then they know they can go 0.02mm larger than 160.05mm, but no smaller.

Of course, if you did specified this and they got it wrong, then it's down to them to remake the item to the correct specifications.  

[Rusted]

1 hour ago, Budgie1 said:

To be fair to Machinists (I used to be one), they can only go on the quality of the drawings or sizes they're given. If you ask for an ID of 160mm then that's what you'll get, normally with a standard tolerance of around +/-0.02mm if one isn't specified. 

If you want a sliding fit then you need to specify this by saying ID of 160.05mm +0.02 / -0.00, then they know they can go 0.02mm larger than 160.05mm, but no smaller.

Of course, if you did specified this and they got it wrong, then it's down to them to remake the item to the correct specifications.  

 

I specified that the adapter be suitable for the Baader 160mm D-ERF.
No dimensions should have been required by an associate machining parts for an astro sales company.
I too have been a machinist for decades and have owned a vintage machine room lathe for similar decades.
I didn't have large enough bar stock to make my own adapter.

Edited October 26, 2022 by Rusted

[pipnina]

3 hours ago, Rusted said:

 

I specified that the adapter be suitable for the Baader 160mm D-ERF.
No dimensions should have been required by an associate machining parts for an astro sales company.
I too have been a machinist for decades and have owned a vintage machine room lathe for similar decades.
I didn't have large enough bar stock to make my own adapter.

I agree your information should have been enough from a customer point of view. But the only problem is the machinist doesn't have access to the part you're mating the adapter to, so they can only go by the drawing. I'd probably look up a fits table, find a tight-ish clearance fit, and slap those tolerances onto your drawing. 

[Rusted]

The replacement adapter was fine.
High standard of machining and protective detail for the optics and objective cell.
Large nylon thumb-wheels for location. All good.

[pipnina]

Update: Worked with two guys in work today on machining the existing flange. Machinist reckoned only 13~mm of depth could be achieved before we went through, so it was going to be a bit close!

Thankfully there was enough depth and now the m117 tilt adapter is threaded onto the rear flange, and looks pretty tidy doing so!

And after all the kerfuffle about cutting the flange off... I chipped the carbon out with fox wedges, screwdrivers etc, only to discover that it WAS threaded onto the carbon fiber all along! It was just stuck better than I could grip it to twist. Thankfully the outside of the carbon tube is soft enough that the flange can re-start a new thread for itself, so it is basically already re-attached without the need for glue or resin!

Om the downside, there is a LOT of carbon fiber dust to clean off of the objective lens and the inside of the tube... I think tomorrow I will be spending some time with the vacuum and dabbing the inside and the objective with damp cloth to remove it before I use some lens cleaner and microfiber to clean the lens cell properly.

All seems to be going to plan! I get paid and can buy the focuser on Monday, so I hope to recommission the scope very soon!