30 replies to this topic

[superlinux]

Hello. Where can I buy the tools that can cut screw threads of different telescope accessories?

I ask this question because  here in Beirut Lebanon there are lathe machine workshops. but they don't have the screw thread templates for cutting for example the screws of telescope filters and etc..

[Astrojensen]

You normally don't have specific tools for that, though they are available in a lot of different sizes, but use a lathe. A lathe can cut many, many different threads. The threads are common metric threads and use the standard 60° shape. 

 

Taps and dies for a vast number of different threads can be found on Amazon and Ebay. Examples:

 

T2: https://www.ebay.com/itm/314895935793

 

M48 filter threads tap: https://www.ebay.com/itm/256040262509

 

They're not inexpensive, but if you're desperate enough, they are available.

 

 

Clear skies!

Thomas, Denmark

[TelescopeBah]

https://www.ebay.com...media=WHATS_APP

Cheaper Chinese options

[Astrojensen]

The M28.5x0.6 thread for 1.25" filters doesn't exist as a tap or die, though. It will need to be cut on a lathe. You can get M28.5x0.5, but I'm not sure how well filters will fit.

 

 

Clear skies!

Thomas, Denmark

[Astrojensen]

https://www.ebay.com...media=WHATS_APP

Cheaper Chinese options

Those are just small, standard size taps and dies, not large ones you need for telescope adapters. 

 

 

Clear skies!

Thomas, Denmark

[Jon Isaacs]

Optical threads are very fine pitch which means they are very shallow as well.  One has to be a skilled machinist to have a chance of making acceptable optical threads.

 

Jon

[walt r]

Yes, cut the threads on a lath. I have done this many times on my Chinese mini Lath in both metric and Imperial.

 

It requires a lath with gears to set the 'feed' to match the thread pitch. The thread is cut with a single point tool either inside or outside. Any reasonably skilled machinist can do this.

Edited by walt r, 11 February 2025 - 09:10 AM.

[Jon Isaacs]

Yes, cut the threads on a lath. I have done this many times on my Chinese mini Lath in both metric and Imperial.

 

It requires a lath with gears to set the 'feed' to match the thread pitch. The thread is cut with a single point tool either inside or outside. Any reasonably skilled machinist can do this.

 

If someone does not know that a lathe is needed to cut optical threads, it is unlikely they have any skills as a machinist.  Lathes are potentially dangerous and one should take a class in basic machining before purchasing a lathe.  

 

Jon

[Astrojensen]

If someone does not know that a lathe is needed to cut optical threads, it is unlikely they have any skills as a machinist.  Lathes are potentially dangerous and one should take a class in basic machining before purchasing a lathe.  

 

Jon

This. 

 

Treat a lathe like you would a dragon. With great respect. Small ones can bite and maim, larger ones will eat you alive, if you're not careful. 

 

 

Clear skies!

Thomas, Denmark

[Jon Isaacs]

This. 

 

Treat a lathe like you would a dragon. With great respect. Small ones can bite and maim, larger ones will eat you alive, if you're not careful. 

 

 

Clear skies!

Thomas, Denmark

 

 

My father was an Oceanographer and had a rather large group that included an old school German machinist. When I was in high school, I spent a summer working in his shop.  This was the early 1960s so he had come over from the old country after the war.  He did not bear fools lightly and I qualified as a fool and got my comeuppance when necessary.  I learned the basics but I was never a skilled machinist. 

 

But that training was a big help later in life during my 30 year career as research engineer.  I worked closely with some highly skilled and very creative machinists.  My time with Eric Dufferin, the German machinist had taught me respect for the many skills of a machinist as well as the various ways parts were made by machinist.  

 

Many engineers consider themselves above the machinists making their designs but I was just the opposite.  When I needed to build something, I would consult with them as the best way to do it.  When I came back with the drawings, we would brainstorm and make changes.  As such, because of my respect for them, they had respect for me and would go out of their way to help.  And on several occasions it was their insight that solved an nasty experimental issue.  Their contribution would be acknowledged in the papers that followed. 

 

Enough rambling...

 

Jon 

[geovermont]

In these diameters and with these fine thread pitches, this really is lathe work, and precision lathe work at that. A truly skilled machinist should be able to do the work as long as they have a lathe that can cut metric threads. Perhaps the ones you've talked to are used to a different class of work. A less-than-expert machinist could well make a mess of it.

[MKV]

Taps and dies for a vast number of different threads can be found on Amazon and Ebay. Examples:

T2: https://www.ebay.com/itm/314895935793

M48 filter threads tap: https://www.ebay.com/itm/256040262509

Large taps still require a lathe or a milling machine to use properly. I can't imagine trying to tap a large diameter whole manually.. 

[geovermont]

Some years ago I had a need for some parts with threads of just this sort. At the time I did not own a lathe. I drafted the plans and brought it to the best machine shop in the area. I talked it over with one of their machinists (the head guy I think) and he took the job and turned it out in fine form. However, when I went back to take delivery, he was shaking his head and said it really gave him some difficulty getting those fine threads just so. I thought he did a beautiful job on them, but it seems it challenged him a bit. I suspect that if I was doing the same job today that I might ruin a piece or two getting it right. It's a highly, highly skilled business to be in.

Edited by geovermont, 11 February 2025 - 11:13 AM.

[Astrojensen]

Large taps still require a lathe or a milling machine to use properly. I can't imagine trying to tap a large diameter whole manually.. 

I did use the word "desperate", when talking about them.  And you would of course need a lathe to make the rest of the adapter anyway... 

 

 

Clear skies!

Thomas, Denmark

[superlinux]

Thanks for the replies. Every response is appreciated. thanks a lot. 

I searched for my question. my question is a first timer. I don't think it was discussed before. Thanks anyway.

after this I feel i would better buy a the accessory instead of doing it here in Lebanon. 

Edited by superlinux, 11 February 2025 - 11:41 AM.

[MKV]

Thanks for the replies. Every response is appreciated. thanks a lot. 

I searched for my question. my question is a first timer. I don't think it was discussed before. Thanks anyway.

after this I feel i would better buy a the accessory instead of doing it here in Lebanon. 

I am sure there are many small machine shops in Lebanon that can turn any size and pitch thread you might need for a reasonable price.

[andylsun]

Single point thread cutting on a lathe is what you are looking for. It does take practice but is achievable on hobby sized lathes. If you can find a machine shop they will probably know how to do this.

Lots of cool videos on YouTube showing how it’s done.

Good excuse for a clickspring video post
https://youtu.be/nCZ...84cS7OWsi_imiy3

Edited by andylsun, 11 February 2025 - 12:57 PM.

[MKV]

I did use the word "desperate", when talking about them.  And you would of course need a lathe to make the rest of the adapter anyway... 

If he's desperate enough, as you said, then he will get a lathe and cut the threads without a tap. :o)  But if he buys a large tap, then will need a lathe or a milling machine to hold it properly while cutting threads.

 

I drafted the plans and brought it to the best machine shop in the area. I talked it over with one of their machinists (the head guy I think) and he took the job and turned it out in fine form. However, when I went back to take delivery, he was shaking his head and said it really gave him some difficulty getting those fine threads just so.

That has to do with the technique. Some like the straight power approach, jam the tool at 90° to the work piece, and rake along. That's not necessarily the best way. I prefer the compound method, which cuts only with one side of the tool and gives me much better results. Also, for delicate threads (such as 80 or 100 TPI optomechanical threads), I use a hand crank to feed the cutter, and an abundant supply of cutting oil in most cases.

[Bob4BVM]

If someone does not know that a lathe is needed to cut optical threads, it is unlikely they have any skills as a machinist.  Lathes are potentially dangerous and one should take a class in basic machining before purchasing a lathe.  

 

Jon

I doubt that Walt R was suggesting the OP buy a lathe and develop the skills to use it, just to make some threaded parts.

He said, "Any reasonably skilled machinist can do this."

 

What he said is true, and points the OP to finding a good machinist to do the work

[Oregon-raybender]

You tube has a lot of videos on cutting threads.

Just look up cutting threads on a lathe, metric.

But it does require a high level of skills. It's best to

ask for a mentor. Fine threads used for telescope optics

is not a easy task.

 

Starry Nights

 

https://www.youtube....h?v=_lDFBGxVwFM

[Mike Lockwood]

The nice thing is that these threads are quite shallow, so one can cut them by hand cranking the lathe (no motor power, just by hand).

 

What is needed is the right cutting tool and the right gear ratio driving the leadscrew and carriage to get the right thread pitch.

[calypsob]

Andy Ermoli is a regular on here and an imager, he has experience with a beginners lathe successfully cutting threads for astro use

[don clement]

The best tool is  one you can't buy: your own skill to cut threads

[Celerondon]

Hello. Where can I buy the tools that can cut screw threads of different telescope accessories?

I ask this question because  here in Beirut Lebanon there are lathe machine workshops. but they don't have the screw thread templates for cutting for example the screws of telescope filters and etc..

What exactly do you need?  Many types of adapters and accessories are available from Amazon and different vendors in this field.  Earlier this month I bought a threaded adapter from Amazon and a focuser extension from Ron at MoonLite Telescope Accessories. Both parts worked fine for me, but your requirements may be different.  Are you making some sort of custom fitting or adapter?

 

Don

[triplemon]

Single point thread cutting on a lathe is what you are looking for. It does take practice but is achievable on hobby sized lathes. If you can find a machine shop they will probably know how to do this.

Lots of cool videos on YouTube showing how it’s done.

Good excuse for a clickspring video post
https://youtu.be/nCZ...84cS7OWsi_imiy3

Second that - large diameter threads like eyepiece adapters, filter threads are not cut with taps, but machined on a lathe with a single point tool. That tool you make yourself on a bench grinder (I'm old school, I don't use inserts).  An those threads are all metric, i.e. have metric pitches. I assume in europe one would by default have metric leadscrews. Not the usual US problem where one needs to find the infamous 127 tooth change gear to get the 10TPI leadscrew driven so it feeds at metric rates.

So this would leave set screw threads and some other bolt-on things - all small threads, like #6/8/10. For that you would want a tap or better a tap set including a bottom tap. These can be hard to find outside the US, chinese tools out for sale are usually all metric.

 

US sellers for economic taps would be ebay (yep), amazon, https://www.shars.com/. Getting those shipped to Beirut is likely another issue. Shars does ship anywhere UPS or FedEx go, though. Major industrial suppliers like https://www.mcmaster.com/ will almost certainly ship anywhere and immediately, but they are pretty expensive.

 

If that is just about a few small SAE taps - superlinux, PM me. I have a friend that travels regularly to Lebanon and might be able to help out.

Edited by triplemon, 12 February 2025 - 04:29 AM.