DIY remote filter wheel

[fwm891]

It took a while to put all of the little grooves on the inside to disperse any stray light, they are only just visible in the picture.

Jason.

Jason - nice job. Doing those inside faces - just run a thread up the inside, much faster than individual grooves....

[JAS]

That's not an idea I'd thought of. I've seen modifications involving putting a handwheel on the end of the leadscrew. I guess that might help in this situation. Given that I don't want to have to make the handwheel up before I attempt to cut my first thread I may well just make up a crank to go in the back of the spindle.

Or I'll ask on one of the model engineering forums. Now there would be a plan

James

I have a hand wheel on my lead screw, I am not sure it would turn everything tho. I also have a crank handle as part of an indexing attachment I made, I think I will try that.

I would be interested to hear what the guy's on the model engineering forums have to say.

Jason.

Sent from my LT15i using Tapatalk 2

[JAS]

Jason - nice job. Doing those inside faces - just run a thread up the inside, much faster than individual grooves....

I have always stayed away from threading on the lathe, that is about to change!!!!!

It will allow me to do a lot more in the future.

Jason.

Sent from my LT15i using Tapatalk 2

[JamesF]

I would be interested to hear what the guy's on the model engineering forums have to say.

Turning the lathe by hand does seem to be the favoured option.

James

[JAS]

I have finished the OAG adaptor tonight. I parted it off, added the relief to the back and then milled out a space for the prism to pass through on the lathe.

It all fits together, I now need to order the correct size gear for my lathe so I can try to cut the M42 thread for the camera side.

I also have to start writing the sketch for the Arduino and see how the magnets and hall effect sensor preform.

Jason.

[JAS]

Turning the lathe by hand does seem to be the favoured option.

James

Looks like I will be taking the crank handle off of my indexing jig then .

Jason.

[Lonestar70]

Hi Jason,

You are making a super job of that filterwheel, must have a go at one myself soon.

That is a very interesting looking divider attachment you have there, is it your own design?

If you have a spindle handle for your lathe then that is the thing to use for this sort of threading.

Don't even think of trying to run the lathe in reverse, with the tool at the back... you will almost certainly unscrew your chuck.

If you make an undercut about 1 thread wide, and the same depth as the thread + about 5 thou = (0.127mm) at the shoulder this will allow you to run the thread cleanly up to the shoulder.

Make a 60 degree threading tool on the end of a piece of a 1/16" or 3/32" wide parting tool, this will save a good bit of grinding.

The M42 thread you need is 0.75mm pitch, so you will need a 21 tooth change gear.

Once you have the gear train set up... the tool fitted (make sure that it is at 90 deg to the work and at centre height) and you are ready to begin threading... engage the leadscrew nut and leave it engaged until you have finished the thread completely.

Lock your compound slide (tighten one of the gib screws if you don't have a separate lock bolt).

a/ Take shallow cuts ( a few thou at a time... this is put on using the cross slide handwheel) and wind the spindle until the tool reaches the undercut... you should see a shallow thread forming.

b/ at this point retract the tool, using the cross slide handwheel so that it is clear of the thread... wind the spindle in the backward direction until you are back to the start position...

c/ put on a bit more cut,using the cross slide handwheel and repeat steps a thru c until you have reached the required depth...You can check this using an M42 t-ring or some such.

The thread depth will only be around 15 thou so keep an eye on your cross slide dial (this is why it is handy to be able to zero it).

Hope this is of some help.

Look forward to seeing how you get on.

Best regards.

[JAS]

Hi Jason,

You are making a super job of that filterwheel, must have a go at one myself soon.

That is a very interesting looking divider attachment you have there, is it your own design?

If you have a spindle handle for your lathe then that is the thing to use for this sort of threading.

Don't even think of trying to run the lathe in reverse, with the tool at the back... you will almost certainly unscrew your chuck.

If you make an undercut about 1 thread wide, and the same depth as the thread + about 5 thou = (0.127mm) at the shoulder this will allow you to run the thread cleanly up to the shoulder.

Make a 60 degree threading tool on the end of a piece of a 1/16" or 3/32" wide parting tool, this will save a good bit of grinding.

The M42 thread you need is 0.75mm pitch, so you will need a 21 tooth change gear.

Once you have the gear train set up... the tool fitted (make sure that it is at 90 deg to the work and at centre height) and you are ready to begin threading... engage the leadscrew nut and leave it engaged until you have finished the thread completely.

Lock your compound slide (tighten one of the gib screws if you don't have a separate lock bolt).

a/ Take shallow cuts ( a few thou at a time... this is put on using the cross slide handwheel) and wind the spindle until the tool reaches the undercut... you should see a shallow thread forming.

b/ at this point retract the tool, using the cross slide handwheel so that it is clear of the thread... wind the spindle in the backward direction until you are back to the start position...

c/ put on a bit more cut,using the cross slide handwheel and repeat steps a thru c until you have reached the required depth...You can check this using an M42 t-ring or some such.

The thread depth will only be around 15 thou so keep an eye on your cross slide dial (this is why it is handy to be able to zero it).

Hope this is of some help.

Look forward to seeing how you get on.

Best regards.

Thanks for the advice, I will be ordering the 21 tooth gear tomorrow, I also need another gear stud as I only have the one!

The indexing attachment is a tapered pin locked into the spindle and a sprung pin that locks into teeth I punched around the outside of a disk like a saw blade, to hold the headstock in place. It works very well, I can also use it with the My ford gears if I need to.

Jason.

Sent from my Nexus 10 using Tapatalk 2

[sloz1664]

You are making a cracking job Jason. Yes, turning the chuck by hand is a safe way of cutting the screw thread using your chuck key for added leverage.

The thread is a M42 x 0.5 and not M42 x 0.7. That's the old Pentax photographic thread.

cheers

Steve

[Lonestar70]

Hi Guys,

Steve... The old pentax thread was M42 x 1mm pitch (same as Zeiss and Praktica)

for astro fittings M42/T2 is 0.75mm pitch.

Jason... The thing that caught my eye on your dividing attachment was the size of the dividing wheel... how many divisions has it got?... I have a similar unit on my Myford which can take Myford gears, and it fits into the back of the spindle where it is locked in place with an expanding taper.

It also has a sliding rod through the spindle, which serves as an adjustable backstop... this has a separate locking mechanism.

For Screw cutting I can attach a separate hand crank.

I also meant to add that Internal threads an be done using the same technique... the only differences being that you move the tool outwards rather than inwards to increase thread depth and the tool can be made from a spare boring bar.

Keep happy.

[sloz1664]

Hi Guys,

Steve... The old pentax thread was M42 x 1mm pitch (same as Zeiss and Praktica)

for astro fittings M42/T2 is 0.75mm pitch.

Jason... The thing that caught my eye on your dividing attachment was the size of the dividing wheel... how many divisions has it got?... I have a similar unit on my Myford which can take Myford gears, and it fits into the back of the spindle where it is locked in place with an expanding taper.

It also has a sliding rod through the spindle, which serves as an adjustable backstop... this has a separate locking mechanism.

For Screw cutting I can attach a separate hand crank.

I also meant to add that Internal threads an be done using the same technique... the only differences being that you move the tool outwards rather than inwards to increase thread depth and the tool can be made from a spare boring bar.

Keep happy.

Yes your right Sandy. I knew one was 0.7mm pitch but went down instead of up. Thinking about it 0.5 pitch is too small.

Sorry to confuse you Jason.

cheers

Steve

[JAS]

I have the gear and stud on order, and I have sorted a 60 degree tool. Hopefully I will have the parts for the weekend so I can have play.

I punched the indexing wheel at work, it is 180mm diameter with 144 teeth to give 2.5 degree increments.

I like the idea of having a back stop integrated into the deviding attachment, I have been looking at making one.

Jason.

Sent from my Nexus 10 using Tapatalk 2

[JAS]

Well the 21 tooth gear and the mountng stud arrived yesterday. So I have been out in the shed trying my hand at thread cutting........

I am pleased to say that it went very well and I managed to cut the thread first time .

I test fitted it into my Cannon adaptor and it is a nice secure fit.

I can't belive just how straight forward it was. I have been avoiding thread cutting for years!

I cut a back cut and turned the lathe by hand cuting 5 thou at a time, as suggested.

I have turned a 45mm dia shoulder on the back edge, this will sit into a 45mm hole in the cover. I will then make a clamping ring to hold it all in place, this will allow me to rotate the camera to any angle I might need. I might add some indexing marks so I can repeat an exposure at a later date if I ever needed to.

Jason.

[Lonestar70]

Hi Jason,

Very well done... I told you it was easier than you thought... No stopping you now

Best Regards

[JamesF]

That looks lovely Jason. Well done. Very encouraging for my own first foray into thread-cutting any day now

James

[JamesF]

Of course, now you know you can do it those eyepiece sections you've glued in were unnecessary. You could have just threaded the holes in the plate

James

[JAS]

Thanks Sandy/ James, I am very happy with it, I was concerned about the weight of the camera being supported by such a small amount of thread but i does look like it is up to the job.

Hi Jason,

Very well done... I told you it was easier than you thought... No stopping you now

Best Regards

Yes you were right Sandy, i now have a couple more ideas in he pipe line for thread cuting!!!

If you hadn't replied to my coments abot not being able to cut metric threads, I probably wouldn't have ever tried it.

Of course, now you know you can do it those eyepiece sections you've glued in were unnecessary. You could have just threaded the holes in the plate

James

That had crossed my mind, but I would not be able to fit it on my Lathe.

Good luck with your future attempt, I sure it will all go to plan.

Jason.

[George]

Lovely job there Jason your obviously a gifted machinists, I'd love to have the skill and tools to make something like that

[Lonestar70]

Hi All,

The important thing to remember, when thread cutting METRIC threads on an IMPERIAL machine, wheather you use motor power or hand power to turn the spindle, is to not disengage the feed (half nuts on the leadscrew) until the thread is complete***. This method will always work wheather you have a threading dial fitted or not.

Threading large holes in a plate can also be done if you have enough clearance in your lathe bed to enable the workpiece to rotate when attached to a faceplate. Not difficult when the hole is in, or close to, the centre, however, multiple holes which are located around the centre (as is the case with the filterwheel) would mean quite a large off set of the plate. This now means the plate is rotating eccentrically and will require considerably more bed clearance... not very likely unless you have a very large GAP BED lathe available.

For heavier pitch threads (Metric or otherwise... Say 2mm pitch or 10 tpi or larger), where the depth of thread is greater, it would be better to use the method where the compound slide is set at half the included angle of the threadform since this will reduce the loading on the cutting tool (especially if using hand power)... this method uses the Cross slide to advance/retract the tool to the ZERO position (the outside or inside edge of the work) and uses the Compound slide to apply the cut depth... but that is for later. :evil:

*** There is a method on an imperial machine with a thread dial fitted (specific note must be made of the number on the thread dial when the leadscrew is first connected before any threading begins), but it requires a lathe where the spindle can be stopped very quickly when the motor power is turned off, usually involving a fast spindle brake,immediately after the leadscrew is disconnected, specific note is made of the overun of the thread dial which is then corrected for by turning the spindle in reverse... the carriage is then returned to the start position and the leadscrew re-engaged with exactly the same number showing however, for most home workshop lathes, which often don't have a thread dial fitted, or a spindle brake, this can not be used easily, or without running the risk of error.... For home use it's much easier and error free just to leave the leadscrew connected.

Incidentaly... the same rule applies when cutting Imperial threads on a Metric Lathe.

Keep happy... and I look forward to seeing both your respective completed filter wheels.

[JAS]

Lovely job there Jason your obviously a gifted machinists, I'd love to have the skill and tools to make something like that

Thanks George.

Threading large holes in a plate can also be done if you have enough clearance in your lathe bed to enable the workpiece to rotate when attached to a faceplate. Not difficult when the hole is in, or close to, the centre, however, multiple holes which are located around the centre (as is the case with the filterwheel) would mean quite a large off set of the plate. This now means the plate is rotating eccentrically and will require considerably more bed clearance... not very likely unless you have a very large GAP BED lathe available.

For heavier pitch threads (Metric or otherwise... Say 2mm pitch or 10 tpi or larger), where the depth of thread is greater, it would be better to use the method where the compound slide is set at half the included angle of the threadform since this will reduce the loading on the cutting tool (especially if using hand power)... this method uses the Cross slide to advance/retract the tool to the ZERO position (the outside or inside edge of the work) and uses the Compound slide to apply the cut depth... but that is for later. :evil:

Hi Sandy, as you have said I do not have enough clearance on my lathe to thread the filter holes.

I actualy cut the M42 thread with the compound slide set at 30 degrees, just as you have described. This method was advised to me by the machinist at work, I aso watched a couple of youtube videos to make sure I fully understood what he had said. I was retracting the cross slide to repositoin the saddle back to the starting point ready for the next cut and then brought it back in to zero before advancing the compound slide for the next cut.

Jason.

[JAS]

I have been writing the code for the Arduino control for the last week or so. I got a bit fed up sat at the PC when it was nice and sunny outside, so I decided to go ahead and make the spacer to go between the front and rear plates. I started by marking it all out on MDF and then proceeded to cut it all out. I cut out the inside with the router and a hole cutter. And also removed 1mm from the back to give the 14mm thickness I needed. I then screwed the rear plate on as a guide for the router to cut the outside profile. After some sanding I then applied several coats of thinned down fibreglass resin. Sanded it and sprayed it black. Getting there slowly. Jason.

[Gina]

Interesting - I never thought of using MDF for the casing. Looking very good indeed I've ordered some 30mm x 10mm ali bar to make the casing of mine. Thinking of an octagon or maybe square with rounded corners - not sure yet. A circular one would be much nicer though.

[JAS]

Thanks Gina.

If you have access to a router, it is very easy to profile aluminum from an MDF template. Just roughly cut the alloy about 2mm larger all around and then run the shank of the cutter against the template while cutting the alloy. Aluminium cuts surprisingly well, I have done this with 12mm thick!

Alternatively, once you have mocked up what you want I am sure I could come to some arrangement with my boss and punch out any shape you would like from 3mm alloy. Would just need a drawing.

Jason.

Sent from my LT15i using Tapatalk 2

[Gina]

Thanks Jason And thank you for the offer - I'll bear it in mind

[JAS]

I have been working on the code for the Arduino control over the last few days.

The Hall sensors are very sensitive, I had about 5 degrees of movement in the wheel while the hall sensor was detecting the magnet, this did not result in very accurate positioning of the wheel. Perhaps it would have been better to have gone with a linear sensor rather than an ON/OFF one.

Being to impatient to wait for another sensor, I decided to ditch it and went with a mechanical switch instead.

This proved to be a good decision, and works well. I did have to debounce the switch though, I went with a hardware solution to save hassle with delays blocking the code. I now have a working code, it just needs a few tweaks here and there to finish it off.

I decided to make a cover for the area where the electrics are going, and to cover the exposed end of the hub.

I have not done this before, I saw the method in a book years ago, and thought I would try it.

I started by shaping a block of hard wood to form the cover over.

I then cut some 1.2mm alloy and 2mm steel at work and punched 4 holes in them, the holes are used to clamp the plates to the wooden block, they will also be the holes to fix the cover to the filter wheel.

The steel plate clamps the alloy tight to the block.

I then got a large hammer and got to work.

30 minutes later it looked like this.

Another 30 minutes of sanding and it was looking good.

I then trimmed the height to size and test fitted it.

There are a couple of marks that could have been worked out with the hammer, but nothing a bit of filler wont sort out before painting.

I have the circuit working on the bread board, so I am now making up the circuit boards to fit behind the cover.

Jason.