Home-made Crayford Focuser

[Stub Mandrel]

I'll post these in a separate thread as they may be of wider interest.

I've completed all the parts for the Crayford focuser for the 66ED scope I am making. There is still some fine tuning to do to make it run smoother and correctly adjust the speed reducer and some cosmetic finishing. Also I need to make a deeper collar with a compression ring and then there's anodising...

I thought I'd copy Williams Optics idea of having a hygrometer on the 'unreduced' knob, but I went for a digital one with a thermometer as well ?

Extra points for spotting machining errors and dings  :-0

 

 

 

[Doc]

It looks lovely Neil. I for one would be interested in a build thread as it's something I should be able to manage with the kit I have.

As for the mistakes, only you know where they are, that's the beauty of making your own stuff.

[Rusted]

Superb skill and workmanship!

[Stub Mandrel]

I might draw up proper plans, I have got the basic thing modelled in TurboCAD.

[teoria_del_big_bang]

Looks very impressive.

Aluminium I am guessing ?

Steve

[Stub Mandrel]

6082T aluminium (hopefully) machines well and should take anodising OK.

[teoria_del_big_bang]

Aluminium can be notoriously difficult to machine from what I remember from my time in our machine shop, but maybe we were using cheap stuff ?

Should look really classy when anodised. Will it still be a similar colour after anodising or are you getting done in colour ?

Steve

[sloz1664]

Nice bit of design, machining and assembly going on there Neil. Being a fully indentured Toolmaker (showing my age) I can see you have spent a lot of time and effort in the manufacture of your Crayford Focuser. What colour are you Anodising it.

Steve 

[Alan White]

That looks amazing Neil
I really look forward to seeing a completed scope.
Did I say amazing, oh yes I did, twice!

[Stu]

Lovely bit of work Neil, must be so rewarding to be able to put something like that together.

[mapstar]

Nice work Neil.

Was most of this done on the mini lathe you have? 

 

[Stub Mandrel]

1 hour ago, teoria_del_big_bang said:

Aluminium can be notoriously difficult to machine from what I remember from my time in our machine shop, but maybe we were using cheap stuff ?

Should look really classy when anodised. Will it still be a similar colour after anodising or are you getting done in colour ? 

Steve

I've bought proper gold and black anodising dye. I need to practice on some other items first, but the place I got my supplies from specialise in supporting hobbyists and are happy to offer advice.

http://www.gaterosplating.co.uk/

[Stub Mandrel]

27 minutes ago, mapstar said:

Was most of this done on the mini lathe you have? 

 

Thanks, I've got an Arc Euro SC4-500 as well now, which is 'the next one up' but actually a lot bigger. I think it could have been done on the mini lathe, but it would have taken even longer! I also used my X2 mill.

[Gina]

Most of my anodising was done in black.  I did try other colours but black worked best.

[teoria_del_big_bang]

Interesting website. look forward to seeing the result.

Steve

[RT65CB-SWL]

Very nice. 

[Rusted]

Do you use a cutting fluid when turning?

I started using odour free lamp oil [UK paraffin oil] after seeing a tip online.

It has completely transformed the finish I get on aluminium.

I just keep brushing it on while I'm turning. Cheap as chips from the supermarket.

This is a 7" [180mm] cylinder for my big DIY GEM on a 2" mandrel in my old S&B 'Sable.'

Turned with a boring bar to reach along the side. There was no room for the usual tool arrangement.

 

[Stub Mandrel]

3 hours ago, Rusted said:

Do you use a cutting fluid when turning?

Only parting off aluminium, as it stops the chips jamming.

I use carbide tips for most things now, takes a lot of getting used to but the end results are good.

 

Nice lathe - is it a Colchester?

DOH! Just noticed the bit saying it' s Sm,art & brown....

Do you have a picture of the mount?

[Horwig]

WOW, that is some real machining skill there Neil, looking forwards to seeing the whole scope.

(note to self: remember to never show any more pictures of stuff I've machined?)

Huw

[Rusted]

30 minutes ago, Stub Mandrel said:

Only parting off aluminium, as it stops the chips jamming.

I use carbide tips for most things now, takes a lot of getting used to but the end results are good.

 

Nice lathe - is it a Colchester?

DOH! Just noticed the bit saying it' s Sm,art & brown....

Do you have a picture of the mount?

Sorry it wasn't my intention to hog your thread. I mostly use industrial bits in holders now.

I didn't even spell the lathe name of my old lathe correctly. Smart & Brown "Sabel."

https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=312122

https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=311774

[Stub Mandrel]

1 hour ago, Horwig said:

WOW, that is some real machining skill there Neil, looking forwards to seeing the whole scope.

(note to self: remember to never show any more pictures of stuff I've machined?)

Huw

Well I can see the defects and mistakes!

Your work (and Rusted) looks equally or more impressive to me. I have taken extra care with this, my normal standard is 'agricultural' but I do have the benefit of a well-equipped, if modest sized and very messy, workshop.

[Stub Mandrel]

52 minutes ago, Rusted said:

Sorry it wasn't my intention to hog your thread.

Not at all, I'm more interested in seeing other people's work - I know what mine looks like!

You should post a thread on that mount, it looks seriously rigid.

Oh dear, I'm beginning to think I need to follow in the footsteps of you and @Horwig and make a mount ....

[Rusted]

A mounting need NOT be complex if you accept weight as a good thing.

It is easier to build heavy [agricultural] than clever and light.

Just remember the chain hoist to get it off the bench.

The drives are a real problem unless you can afford to import Byers.

A nice project to make your own wormwheels but do build a simple cutting engine first.

Fly cutting using a large dividing/indexing wheel always appealed over tap hobbing.

It would cost a fortune for a machine tap big enough.

I'd wrap a perforated, roofing strip around a big plywood disk for the indexing.

You only need one so choose your perforated strip carefully.

No doubt Peter could offer far more expert advice than mine.

[Stub Mandrel]

Thanks, making gears is one of my favourite machining tasks.

I have a nice 6" rotary table (a bit big for my mill, but it does fit) that I got to make a 10" gear for my Jovilabe (must make that gear some time!) it will be ideal for making large precision worms.

I've made small worm and wheel pairs before by free hobbing, for a dividing head/rotary table and a tiny dividing head. I made two worm for each on, one in silver steel, which I gashed to make a cutter then hardened and tempered. I'm far from convinced of the accuracy of the resulting gears, which is why I ended up buying a 'proper' one.

I also have the parts of someone's home-brew gear hobbing machine which would be ideal, but making it work might be more work than building one from scratch.

Gears for the Jovilabe, some of them on adjusted PCDs:

 

Governor drive gears for a 1:12 steam engine:

[Rusted]

Great stuff! Very impressive work!