CNC Clock Build W.I.P.

[J-G]

Hi Don - just noticed your EDIT re WIP-7B so a new version is attached. It's apparently too late to do an edit of my original post.

Yes - 4 or 6 segment would be easier --- IF you are doing the work purely by 'Hand' or even a manual milling machine or scroll-saw, Using CNC frees up all the constraints of accurately moving a work-piece 72° - rather than 90° or 60°. Even a 7 side (51.42857...°) becomes feasible and of course for clock making 7 can be important (days of week). Mind you, I've seldom shied away from those sort of difficulties - back in 2007 well before I thought about CNC, I built a skeleton clock in Brass with a seven spoke 'Day Wheel'.

It's not so much about the 'Reuleaux' polygon (curved side and constant diameter) but a [Pentagon] to match the dial.

 

[J-G]

4th Oct
I can’t explain why it has taken me so long to appreciate that using the surface of the work as [Z = 0] is by far the easiest option. Up to now I’ve been using a stepped block with 10, 11, 12 ----> to 20mm to set the cutter position and that has meant that when setting the parameters in CamBam I’ve had to work out the target depth allowing for the clearance above the surface - see Fig-35 in WIP-7B.

A chance remark by an experienced CamBam user (on another Forum) and the issues I was having with the depth of the centre joint on the [Frame B] component made me re-think the whole methodology. This meant that I had to re-visit CanBam to modify the [Surface] and [Target Depth] parameters for all the MOPs but that’s a small price to pay for the greater convenience afforded.

I was having some problems with skimming the surface because the blanks came directly off the bandsaw - well I did run one face on the Linisher but to all intents and purposes the top surface was ‘sawn’ so therefore had undulations so wasn’t ‘flat’ nor particularly parallel to the bottom surface - well, within less than a millimetre but not close enough to provide an accurate datum. I created a [Skim Surface] MOP taking two cuts of 0.2mm so if the surface didn’t clean up I could adjust Z0 by 0.2 to 0.4 and run it again. Once the surface is ‘clean’ the next tool can be [Zeroed] to that and whatever the depth of cut needs to be will be accurate to that surface simply by using ‘Stock Surface’ = 0 and ‘Target Depth’ = whatever figure is needed - - - - Result!

Whilst I was waiting for the Denford to complete its work cutting out the [Frame B] component I got on with work on the Lathe and since the Pendulum Rods had arrived I decided to start on the components for the Bob adjustment. This consists of a small brass section which will be epoxied into the end of the Carbon Fibre tube - I did think about putting an M4 thread directly into the tube but the suppliers warned against trying to cut threads as they thought that the fibre would just crumble. Only time will tell whether I need to also use a cross-drilled hole and pin to secure this section to the Carbon Fibre tube. This small section just has an M4 thread which will have a 130mm long brass rod with 50mm of M6 thread screwed into it.

When assembled, this ‘rod’ will pass through the Pendulum Bob and into the [Adjusting Nut] in the centre.

Regrettably, my phone camera won’t show the component adequately so I’ve resorted to showing the assembly as a drawing (Fig-48). I've rotated it 90° to reduce the white space on the forum.

Looking at which part to make next I decided to carry on with the Pendulum - in fact the [Bob] which although I originally designed as a conventional disc, I’ve now decided to make as a Reuleaux Pentagon. I still haven’t decided whether it should have the point Up or Down!

I have a ‘lump’ of Walnut which was given to me some while ago with the caveat that it came from a sack of ‘firewood’. There is enough to make three - you will have noticed, I’m sure, that I’m making 4 of everything with the hope that I might end up with at least two clocks. This is essentially a ‘learning CNC’ exercise so there are bound to be mistakes made but hopefully by the time I’ve made 4, I should have sorted any issues. This ‘lump’ was accompanied by another three, two of which really are firewood but I can get the fourth Bob out of the last ‘lump’. Fig-49 shows the 'Lump' with a template attached to determine the location of the centre hole.

Today I've cut the outline roughly to size and drilled/reamed a 6mm hole in the centre as a datum. This will become the clamping hole, positioning the blank at X0/Y0, but the first thing that needs to be done is to get the thickness down to close to finished size. Ultimately the surface will be curved and therefore machined on the lathe but I also need to drill a ¼” hole from top to bottom (125mm) and for that I need the blank to be flat and parallel so that I can hold it in an independent four jaw chuck on the lathe so that there is a fighting chance that the hole will be central and straight – It is much better to turn the work rather than the drill and I will start with a stub drill moving on to a ‘Jobbers’ series and finally a long series . If necessary I also have a 12" long drill if the long series doesn’t quite cut the mustard. This will be an ‘interesting’ operation!!

 

[J-G]

6th Oct
Machining the Pendulum Bobs has indeed been interesting - and I haven’t even looked at drilling the through hole! I originally intended to use a 6mm cutter for the outline but then realized that the only 6mm cutter I have is only capable of cutting up to 15mm deep and I need at least 25mm. Fortunately I do already have a 63mm long router bit but it is ½” Ø so I had to re-jig the G-Code accordingly.

The first P-Bob blank I left as it came off the saw which meant that the ½” cutter was taking a full width cut for about 50% of its travel but by the time that it was 24mm deep there were issues with parts outside the pentagon breaking free and causing some surface damage. Not that it mattered too much since it was a ‘roughing’ cut and the finishing cut of 0.3mm would clean that up but it made me decide to trim the other three blanks to within 5mm of the finished size before mounting them. Once I’d done that it was just a matter of letting the Denford take its time and a travel distance in excess of 20m @ 200mm/min does take some time.

While that was being done I did the lathe work on the Pendulum adjusting nuts so the next job will be cutting the ridges in the sides of those. I haven’t cut Brass on the CNC machine before so I first made a ‘dummy’ out of Maple just to check that the G-Code did what I expected. You’ll notice in Fig-50 that I’ve crossed out the original design dimension of 30mm and penciled in 28mm. The brass I had on the shelf was only 1-1/8" diameter so I took the pragmatic approach and re-designed the part rather than order new.

Fig-50

The brass billet is there because I did a physical test to make sure the Denford could handle the forces needed to cut brass but I forgot to turn it around so that you could see the test cut. In fact it proved that I needed to reduce my estimated feed and speed. Rather than cut a ‘Profile’ I had decided to use a ‘Drill’ Canned Cycle MOP so that I could easily control the amount of material being removed with each pass which I’d assessed to be 0.4mm. It would also give me a cleaner edge to the indentations though to some extent these will be smoothed out when I do the final polishing - Brass deserves to be polished! - Fig-51 is a drawing of the four cuts that I need to take and Fig-52 shows the Denford part way through one of the cycles.

Fig-51 . . . . . . . . . . . . . . . . . . . . . . . . .Fig-52

7th Oct
To give you a clearer idea about how these parts go together Fig-53 shows the Pendulum Rod (Carbon Fiber Tube) with the connecting piece as well as the Adjusting Screw and Nut.

Fig-53

Eventually they will all be inside the Pendulum Bob of course but since I haven’t yet drilled that hole, this just shows you where they will fit - assuming I can drill a straight hole through the Bob.

I said that drilling the hole would be ‘interesting’ well it certainly was! The first thing that brought me concern was the fact that the Bob Blanks do not have a ‘flat’ side which I can use as a datum so positioning them in a four-jaw independent chuck needs to be done with some care. The ‘points’ can be used to check that it is held centrally the one at the top must lie on the lathe centre-line and the next two must be equidistant from the centre-line.

To check this I used pointers in the lathe tool-posts and the first one took me about 10 minutes to get to a satisfactory position. In Fig-54 you can see the two pointers, one connecting to the top point and the other locating the side point. To check that the Bob was centred, I could flip it over 180° and the pointers should still connect to both points.

Fig-54

It is also necessary to make sure that the Bob is centred when rotated 90°. To do this, all I needed to do was set it upright and bring a centre drill up in the tail-stock. The centring is not hypercritical so holding a steel rule with the centre-drill and making sure the two sides are equal. Fig-55 shows this. I could have done this by checking the cross-slide dial reading for each side as well.

Fig-55

Once I was happy that the Bob Blank was centred I could start the lathe and drill a centre hole followed by the various length drills, finishing with the 12" long ¼”. This was necessary because although the long series drill did break through, it is only 6mm diameter and the hole needs to be a clearance for the 6mm Ø adjusting screw. Although the blank is not a solid round, the fact that it is centred means that there is no danger of it being ‘out of balance’ but even so there is no need for high speed. In Fig-56 you can see the long series drill but the blank is a blur.

Fig-56

Now I have to make a small jig to locate the Pendulum Bobs so that I can position them so that I can cut the centre slot accurately in line with the side that is already done - but that’s for another day!

 

[donwatson]

Thanks again JG

 

[J-G]

I've now edited my last post to add an image that I referred to but didn't insert and add annotations for the Fig. Numbers.

The new image is Fig-53 which shows the Pendulum Bob with the Adjusting Screw/Nut and the bottom of the Carbon Fiber Tube which is the Pendulum Rod. I would appreciate opinions as to the orientation of the Bob - whether the point should be UP or DOWN?

 

[Yojevol]

1 for UP

 

[J-G]

Can anyone suggest why this thread - and the one by jonzjob - has lost the reads & replies information?

This also inhibits the thread rising up the order when a new reply is posted.

 

[MikeK]

Can anyone suggest why this thread - and the one by jonzjob - has lost the reads & replies information?

This also inhibits the thread rising up the order when a new reply is posted.

I moved both threads from the General Woodworking forum to the Projects forum. If you, and everyone who is watching this thread, have Notifications enabled, you would have received a notice stating why the threads were moved. The notification icon is the little bell in the upper right corner of the screen to the right of your user name.

The threads you see, with no reads or view counts, are temporary redirects to the threads in the Project forum. The redirect will expire soon, and you will not see it in the General Woodworking forum. Until the redirect expires, every time you click on the thread in the General Woodworking forum, you are automatically taken to the thread in the Projects forum.

 

[Yojevol]

I moved both threads from the General Woodworking forum to the Projects forum. If you, and everyone who is watching this thread, have Notifications enabled, you would have received a notice stating why the threads were moved. The notification icon is the little bell in the upper right corner of the screen to the right of your user name.

The threads you see, with no reads or view counts, are temporary redirects to the threads in the Project forum. The redirect will expire soon, and you will not see it in the General Woodworking forum. Until the redirect expires, every time you click on the thread in the General Woodworking forum, you are automatically taken to the thread in the Projects forum.

Thanks for your explanation MikeK and also for your notification to me about my comment on Jonzjob's clock. However i think my comment is still relevant and it should have been migrated along with Jonzjob's thread. I will be grateful if you will reinstate it in its 'correct' location.
Brian

 

[donwatson]

1 for point down

 

[J-G]

I moved both threads from the General Woodworking forum to the Projects forum. If you, and everyone who is watching this thread, have Notifications enabled, you would have received a notice stating why the threads were moved. The notification icon is the little bell in the upper right corner of the screen to the right of your user name.

The threads you see, with no reads or view counts, are temporary redirects to the threads in the Project forum. The redirect will expire soon, and you will not see it in the General Woodworking forum. Until the redirect expires, every time you click on the thread in the General Woodworking forum, you are automatically taken to the thread in the Projects forum.

Thanks for the explanation Mike --- I did notice the [Redirect] and did click on it but it had no effect. I hadn't noticed the alert on the [Bell] though. I didn't know there was a [Projects] forum and had some difficulty finding it and I still haven't found jonzjob's post but I'll look again after posting this.

 

[J-G]

1 for UP

1 for point down

That's interesting - and aligns with my thoughts - since I'm making four of these I've done two of each

I'm sure there will be a difference explained by 'Physics' but lack the knowledge to quantify what it might be so the only criterion I have is aesthetic - ie. how does it 'look' - and I still can't decide which I prefer.

 

[Yojevol]

That's interesting - and aligns with my thoughts - since I'm making four of these I've done two of each

I'm sure there will be a difference explained by 'Physics' but lack the knowledge to quantify what it might be so the only criterion I have is aesthetic - ie. how does it 'look' - and I still can't decide which I prefer.

That's a pity. I thought you be democratic and go sideways. However you have found another way to sit on the fence

 

[okeydokey]

Hi another vote for down looks aesthetically better

 

[AES]

Again, thanks to MikeK for moving this thread (and no, I didn't see any "notification" but it IS possible I missed it).

And as already said, thanks to J-G for an excellent WIP & pics (I DO understand your initial use of .pdf format and have done the same myself for a couple of long posts, but I must say since the "takeover" of UKW, the new software makes the job of a "sensibly" formatted document with pix in the "right" places is MUCH easier than it was before).

LOVELY clock Sir.

 

[J-G]

...but I must say since the "takeover" of UKW, the new software makes the job of a "sensibly" formatted document with pix in the "right" places is MUCH easier than it was before.

I'll agree there AES - it still needs some lateral thinking on occasion though, - for instance 'white space' is ignored so where I wanted to put the Figure Number under Fig-52 it defeated me until I put some dots between the two anotations and made them white. Even then (I've just checked) if the display isn't wide enough then it moves the image down! I (we?) have to accept that this is a text forum not a Graphic Layout program

LOVELY clock Sir.

Thanks

 

[AES]

I'll agree there AES - it still needs some lateral thinking on occasion though, - for instance 'white space' is ignored so where I wanted to put the Figure Number under Fig-52 it defeated me until I put some dots between the two anotations and made them white. Even then (I've just checked) if the display isn't wide enough then it moves the image down! I (we?) have to accept that this is a text forum not a Graphic Layout program

Yup - we were obviously "brought up in the same school" when it comes to creating "readable reports" (!), and I must say, that using the relatively restricted laptop screen makes the job a bit more difficult too - BUT this new software is certainly streets ahead of the old UKW software. What I haven't tied yet is writing a whole "report" in MS Word, placing the pix (and their titles) exactly where I want them (that's also a bit of a fiddle with Word but I learnt those tricks years ago) then doing a simple cut & paste direct into the Forum. I shall find out soon though, as a long WIP that I started off in .pdf over a year ago now, now needs to be updated and extended, and I shall, try just that. i.e. no more .pdf. So "We'll see", but yeah, clearly a text-based system, that "just manages - more or less" to handle graphics too).

Cheers

 

[J-G]

...What I haven't tied yet is writing a whole "report" in MS Word, placing the pix (and their titles) exactly where I want them (that's also a bit of a fiddle with Word but I learnt those tricks years ago) then doing a simple cut & paste direct into the Forum.

Good luck with that!!

MSWord not only has its own idea of what you might want it also changes any imported graphic to its own format which may or may not be acceptable to the forum software.

 

[AES]

Yeah, I know J-G, but at least I can - usually! - make it do what I want (BTW, I deliberately STUCK with Word '97 - THAT works for me!).

But as said, "we'll see".

 

[J-G]

There's nothing wrong with older versions of software AES - unless it's Microsoft's of course I do have a copy of Office 2002 from which I use Excel but for writing (not that I do much of that) I use WordPerfect - in my opinion a vastly superior word-processor.

Anyway, enough of that discussion, I have another two pages of the W.I.P. - PDF 12 attached.
========================================================================

9th Oct
The second side of the Pendulum Bob Adjuster Nut slot has now been machined along with the recess for a brass plate which is there to prevent wear caused by the brass nut rubbing against the Bob. On reflection, I suspect that this is overkill since the only time that any adjustment will be made, after initial set up, is when (if) the clock is moved to a different location - either Latitude or Altitude - and the Centre of Mass of the Pendulum needs to be changed due to the change in the value of gravity. The brass plates have also been cut to size and drilled for the Adjusting Screw to pass through. Ultimately they will be epoxied in place. Fig-57 is the [Bob Assembly] with the adjusting Screw and Nut in place. The Pendulum Rod is not yet attached as I still want some freedom.

Fig-57
​

I now need to make a fixture to position the Bob ready to have the face ‘Domed’. This will need to be a billet of Ash or Beech fixed to a Lathe face-plate, turned with a suitable size ‘boss’ in the centre and then that held in the Denford so that the precise size of a plug to fit the Adjusting Slot can be machined. Both sides of the Bob can be done using the same fixture as it will be supported by the tail-stock and a live centre. Before I do this, I can get on with making the [Frame Brace] as I’ve selected the material from a very nice piece of white Ash that is left over from a Presentation Case project. The blanks have been sized, had clamping holes drilled and the first one has been ‘CNCed’ - Fig-58 shows it on the Denford table alongside the piece of card I use under each component to try to minimize damage to the ‘Sacrificial’ table – It took me some time to make that with the 67 threaded inserts so I would sooner cut into the card than the table!

Fig-58

Fig-59

Fig-60

After I’d removed the waste part from the Brace, I realized that I could have also machined the other face to size by surface skimming on the Denford as I had done the first face. To do that would need the other side to be counter-bored to accommodate the clamping screw heads, just as the first side had been. It would also allow me to cut the other side of the tenon which fits into the [Frame A] part as well so the other three blanks were re-mounted on the milling machine to do just that. The result can be seen in Fig-59/60. In Fig-60 the face has had a clean up on the Linisher so that face will be down on the table for the first cuts which will enable me to clean up the face in Fig-59. After the shape has been cut out (kept in place by the ‘Holding Tabs’) the blank can be turned over - using different clamping holes - so that I can skim the ‘cleaned’ surface to size and cut the other side of the joint. I’ll finish the first Brace to size on the linisher and mill the joint. Nothing about this component is really ‘critical’ and the only reason I’m doing it on the Denford is due to the shape.

I’ve also worked out what Walnut I need for the rest of the Frame and Dial so I’m going to a couple of local(ish) wood-yards later this week to select a 2.1m board of 6" x 1½” which I’ll have to ‘slice and dice’ into 50 pieces.

From Fig-61, you’ll see that there will be some spare. I’ve had quotes from both but I want to see exactly what each are really offering. One is at £55 and the other is £80 for Grade A or £65 for Grade B. The fact that I paid nearly £70 for a 600mm long 4"Sq. piece about 6 months ago makes me think that the Grade A will be my best bet.

11th Oct
Waiting for the Denford to complete the work on the Frame Brace, I started looking at my options for Holding/Driving the Pendulum Bob to finish the face. I have a small (4"Ø) faceplate which will be plenty big enough but holding it on the Denford table with a sacrificial plate attached would be challenging since it is 28mm thick. I can get clamps on the bare plate so I could make space for the clamps by using a triangular block. A piece of scrap floor-board is perfectly good as the drive peg. First though I had to make a locating peg so that the face-plate could be clamped accurately and an oddment of Ash fitted that bill perfectly. It was a five minute job to first draw the position of the locating peg (on the CNC Table) and in accurate register with the oblong driving peg for the Bob and then create G-Code to do the work.

Fig-62
​

That would both position and drive the Bob but it would also need to be supported by the tail-stock since even a good tight fit would be insufficient to stop it wanting to creep off. Fig-62 has both drive and Tail-stock support on the lathe bed and Fig-63 is the Bob mounted on the spindle, supported by the tail-stock and with a tool-rest which I used to hand turn the face to the domed shape you can see in Fig-64.

Fig-63

Fig-64

It will have to be sanded to a fine finish and for that the tail-stock support will need to be removed but as I will be applying pressure towards the head-stock, that will stop any possibility of it wanting to come off the peg.

​

As predicted, I didn’t have a problem sanding the faces so, because I skimmed the face by hand, I started with 80 grit then went through from 180g to 400g before using Sanding Sealer which was cut back with 600g and finished with MC Wax. I’ve only taken one of the four as far as the wax and even that is only one side so the driving fixture will be retained - it will always go back to the same place on the lathe spindle so I don’t have an issue about de-mounting.

Fig-65​

Fig-65 is the first Bob with one face ‘finished’ mounted on its Adjusting Screw and Nut. I say ‘finished’ but in reality I’ll need to give it another coat of MC Wax and eventually it will be buffed just as the rest of the Walnut Frame and Dial will be.

Now I can return to the second stage of the Frame Brace which I put aside to make the drive fixture for the Bob so I'll report on the problems that I encounter doing that in the next installment.