Broken dial repair.

[Retired]

Hi,

It seems forever since I last added a thread but with the onset of milder weather I’m always very busy doing jobs around the bungalow although this has not stopped me enjoying tinkering around and I’m pleased to add the story of the radio dial I’ve just successfully repaired.

I was contacted with an enquiry asking if I could possibly make a “bright” for a radio dial and I must confess that at first I was rather reluctant to take on another job but after thinking about it and wanting to help if at all possible I relented; after all if you need a job doing ask a busy person. I thought the bright being nothing more than a polished brass disc would be a push over of a job in my Myford lathe but I was quickly to be proved wrong.

I asked for the dial to be sent to me so that I could take accurate measurements and as usual my bad luck kicked in. The number of simple projects that I take on then turn into a nightmare should have warned me by now and here was another that decided to bite me.

The plastic dial had been posted in a Jiffy bag; the dial mounting protruded making it longer than the depth of our letterbox and the post man was going to deliver come what may. Bron said “a parcel has arrived for you but the postman appeared to have difficulty delivering it” and by the time she reached the front door the parcel was sitting on the carpet. When I opened it the dial had been destroyed.

Once I agree to do something I will never go back on my word and here I was now committed to making a bright and the job had already gone down the tubes. I contacted the owner and explained what had happened but still wanting to help I offered him two choices; I could still make the bright then return all the bits to him for him to repair or at his risk I was prepared to attempt repairs upon his behalf.

Yes I now had a much bigger job that was to take my life over for a couple of days and at this point I thought I had taken on an impossible task. I was still busy around the bungalow but this dial kept popping into my thoughts; I have never ever had any success at gluing plastic other than using solvent weld on plumbing jobs; epoxy and superglue were considered but rejected considering the amount of damage to the dial as surely if the dial was glued the first time the dial was once again removed from the set the joint would break so I was really up against it again.

I was awake in the middle of the night thinking about the repair and having decided the job was hopeless thought anything I do to the dial cannot make it worse. I then thought about re-designing the dial mounting completely after all this would be hidden once the dial was in place?

I must have spent hours thinking about various designs and it kept me awake in bed for a couple of nights. The mounting was not only for the dial but also incorporated the double pointer to complicate matters. The original design of the dial was that it had a short mounting with a spring clip that in turn attached to a ¼” dia plastic spindle this being nothing more than a common spindle extension as used on items like pots. The pointer was located on the ¼” dia section and it was this that really caused the trouble; the end of the extension also had a spring clip.

Having both woodturning and engineering lathes I wondered which would be best to use to spin the dial to true the damage; where it was broken the edges were very jagged and the dial being so old was extremely fragile. I was very worried about two aspects of the turning; chucking the dial and the problem of whether it would hold up to the cutting action of the tool? I could make a “jam” chuck out of wood easily enough and do the work in the wood lathe but then what tool would I use knowing a single catch would shatter the dial so in the end rejected this and turned my attention to the Myford lathe.

By this time the dial had taken over my thoughts and my life and I was going to do my utmost to bring about a satisfactory repair so turned this into a project and gave it my full undivided attention; I would only have one chance with this as any mistake would abruptly end the job once and for all so a great deal of care and attention were called for. It was no longer a dial to me but a challenge and I was well up for it.

My rare Myford MF36” lathe has suffered many decades of abuse by previous owners (vandals) the three jaw chuck shows hammer marks and one of the jaws is a sloppy fit; I found that the jaws fouled the lathe bed before opening enough to admit the dial and as I don’t have alternative jaws for this chuck I removed it and mounted the independent four jaw knowing this would hold the dial. To set work up in a four jaw I use a DTI (dial test indicator) but given how fragile this dial was I dare not play around adjusting the jaws as a single nip too tightly would crush and shatter the dial; the dial already had a number of stress cracks showing.

I used the circular rings on the face of the chuck to lightly position the dial as near as possible on center and I was on eggs as I nipped the dial up; had I nipped it enough and would a tweak extra crush the dial or was it too loose and would it become detached due to the action of the cutter? I secured a very sharp lathe tool in the tool post and double checked everything then double checked again before putting the lathe in motion. It was a long painstaking job taking cuts of five thou (0.005”) each time to bring the jagged break down to something approaching a flat surface; it was in fact slightly rounded because the dial had little strength to withstand the tooling and was flexing all the time as the cut was engaged. Each cut was intermittent causing vibration and at last with fierce concentration I had reduced the surface as much as I dared. Next job was to use a centre bit and run a hole through followed by a ¼” drill bit; I expected the drill bit to grab so fed it in very slowly.

Boy what a relief it was to remove the dial from the lathe and bring it up into the workshop out of the way. Next job was to make the newly designed mounting. I could now add measurements to my sketch; I knew the maximum length from the outer face of the dial to the end of the mount was exactly 1.5” but as the dial is dished I had to wait until the hole was drilled to ascertain the length of the new mounting which I could now obtain with the help of my digital vernier caliper.

At last I was on familiar ground knowing any mistake now would only end up with a bit of wasted material and my time so I could relax and enjoy tinkering around. My intention was to turn a brass mounting to attach the dial to using a specially designed threaded bright then add a plastic extension as this was yet another problem; the dial bright would require chassis electrical isolation and got about half way in making this when I remembered I might have a bit of round Tufnol bar stock left over from another job? Sure enough after a quick search I had the Tufnol in my hand and now I could re-design the mount making it one piece.

I enjoy turning Tufnol as it turns like butter but can be turned to very fine tolerances; with the three jaw fitted the job progressed much more quickly from here as I’m used to lathe work and each stage of making the new mounting had been carefully thought through before starting. With the turning completed it was a simple matter to drill and ream at 1/4" for the spindle mounting at one end and drill and tap at 6mm to accept the new bright. When doing turning in the lathe it is always important to do as much work as possible before removing the work as remounting in the lathe can result in loss of concentricity.

To complete the newly designed Tufnol mounting I used an hacksaw and ran a slot down where he mounting fits onto the spindle then added the spring clip. I had turned a reduced diameter to accept the thickness of the dial plus the thickness of the new pointer and using the hacksaw again two parallel flats were firstly cut then filed using needle files these would be the drive for the dial and pointer.

Next job was to make the bright which kicked this job off in the first instance; a short length of round brass bar stock was chucked in the three jaw allowing enough to protrude to cover the thickness of the bright with the length of the screw to be cut and a bit extra as I did not want to run into the chuck with the lathe tool. I had decided to knurl the outer edge to aid grip for tightening the bright up to the dial so attached the knurling tool and added a good deep diamond pattern knurl. I was unsure as to the best method of producing the front curve but settled on roughing out by eye using the compound slide and lathe tool and then used one of my engineers scrapers in similar manner to using a tool in wood turning and this peeled brass away very efficiently indeed; this was followed by abrasive paper and Solvol Autosol to bring up a nice shine; I didn’t go over the top to produce a mirror shine but left tiny scratches that made the bright look more aged. The back of the bright was reduced to 6mm to accept the thread and to tidy the knurl I cut a shallow land at each side then used abrasive paper to remove sharpness. The new bright was then cut away using the hack saw.

To ensure the screw thread was true I used the 6mm die in the lathe and added the thread. I was very pleased as I looked at the new bright thinking it a job well done.

In the workshop I used the new Tufnol mounting as a pattern and cut out the rectangular slot in the centre of the dial with a fret saw fitted with a very fine piercing saw blade then fettled the cut with a needle file taking a lot of care to get this just right then again using the fret saw the new double pointer was cut from brass sheet; with the pointer cut out it had the mounting hole cut then was fettled with the needle file.

At last I could now assemble all the bits to ensure everything fitted as they should and I was over the moon at achieving such success; the bright although non-original looked good and I liked the design with the knurling added.

This story goes to prove just how the most simple job can quickly get out of hand; my bad luck can hang around in the background until next time when no doubt it will put in an appearance.

The parts were packed very carefully into a carton adding plenty of bubble wrap then I had the pleasure of a three mile round walk to post it first class with my compliments to a most delighted owner.

I hope this story has been of interest; it certainly entertained me.

Kind regards, Col.

[ms660]

Hello Col.......absolutely hats off...great job.

Lawrence.

[MichaelR]

Up to usual standard Col.....superb.

Are you related to the Huddersfield guy that invented the timepiece for establishing Longitude during the Sail ship era

Mike

[Retired]

Hi,

Many thanks for your kind comments Lawrence. This repair would not have been possible had I not owned the lathes. Although the dial is from a radio I feel rather cheeky because as with many of my threads the main theme is one of mechanical engineering but it pleases me to add my stories in the hope of encouraging others to try something new when things break.

Many thanks also to you Mike for the kind comments; I'm pleased you liked the story. Regarding me being related to the guy who invented the timepiece I cannot really say because I took a chainsaw to my family tree many years ago.

Kind regards, col.

[valvekits]

Another very interesting story Col.
I was reminded that it was my failure to be able to center a four jaw chuck that ultimately decided I would spend a lifetime in electronics!

Eddie

[MichaelR]

Originally Posted by Retired

Hi,

Many thanks for your kind comments Lawrence. This repair would not have been possible had I not owned the lathes. Although the dial is from a radio I feel rather cheeky because as with many of my threads the main theme is one of mechanical engineering but it pleases me to add my stories in the hope of encouraging others to try something new when things break.


Kind regards, col.

Actually your mechanical skills are very relevant to the "boatanchor radio's" that a few of us spend alot of time nurturing.Part and parcel of the performance is quite often due to the stability offered by the mechanical design of the radio. The quality of the tuning mechanisms is quite often achieved by precision gearing and much effort was put into the deign for overcoming backlash etc.

Even if you were unable to make a spare for one of my radio's , knowing that there is the expertise to help me come up with a solution myself is a great comfort.

Mike

[Retired]

Hi,

Thank you Eddie; yes a four jaw can be a pain at times in trying to get the work to run true but for accuracy it can't be beaten. My quick approach is to roughly centre the work by eye then place a piece of white paper on the lathe bed below the tool; turning the chuck by hand and watching the distance between the tool and the work I find it reasonably easy to adjust each jaw until the tool touches the work all the way around; the paper helps to show the gap. For great accuracy I use the dial test indicator (DTI). I went into mechanical engineering because I'm hopelessly colour blind.

Many thanks Mike for pointing out the relevance of mechanical skills in radio work. I think most restorers/repairers would try to obtain a suitable replacement part wherever possible before attempting spending a lot of time repairing the original.

All the old skills are yet still around as I have friends with well equipped workshops and are skilled in both wood and metal turning. Whilst the introduction of CNC (computer numerical controlled) speeded up mass production and allowed semi skilled operators to run machines it did little in encouraging the basic use of such machines and I believe it is here where the skills are being lost. Where I worked before retirement we had a number of operators working on centre lathes producing one off and specials whilst the army of robots and CNC machines spit out components 24 hours per day.

I enjoy tackling projects that appear beyond repair as these give me the biggest challenges and help to keep my head and hands working together; I don't mind helping anyone out as long as I can fit their request between my other more pressing jobs; I've gratefully received help from forum members and friends in the past so think it only right that I respond in kind whenever I can.

I find the hardest part of any project is in making a start on it but once I do make the start then I'm locked into it and like a dog with a bone as I just don't have enough sense to quit however difficult it becomes; if I don't have the necessary skills I will have the skills by the time the project is completed. If ever you need a special part Mike and as you live within reasonable distance you can always ask and if I can fit it in I'll be happy to help out.

Kind regards, Col.

[valvekits]

Just one question Col.
Did you have a plan B for if the dial broke in the lathe?
I'm sure you must have thought long and hard about this, if you didn't have a plan B what would you have done next, because I know you don't like being beat.

Eddie

[murphyv310]

Hi.
What an amazing story Col, your work is done to very a high precision and beautifully executed, I wish I had your skills and expertise.
Right now I am looking for a big pile of projects for you!

[Phil G4SPZ]

Nice work Col, and a good write-up too. In a way I'm glad it's not just me who gets more than my fair share of 'ten-minute jobs' that end up taking several days and sleepless nights. But we all keep at it, don't we? Great stuff, well done.

Phil

[Retired]

Hi,

Thanks Eddie; very good question; yes I did have a plan "B" and also a plan "C". Plan "B" would have seen me in Sheffield visiting Gary at Direct Plastics;

http://www.directplastics.co.uk/

I would have asked if they stocked or could get hold of a slice of clear round plastic rod or a piece of thick sheet taking the measurement along with me.

Plan "C" was to say Oh dear I appear to have broken it!!

Many thanks Trevor; you could always stabilize your shed foundations and install a lovely Colchester lathe and then get stuck in as even a bit of practice on a lathe will lead to producing accurate items as you gain the skills assuming the lathe doesn't pull you in first as they are dangerous machines for a novice to play with. I've been using lathes for almost fifty years and am still learning new techniques; its amazing what can be done on a lathe.

I'm trying to keep my head down Trevor as I already have lots of projects waiting for me to get around to doing them; I've just taken on an interesting restoration job for a friend on his vintage wooden clock case and also there is a Murphy TV cabinet veneering job lurking somewhere in the background that I've agreed to do for another friend; perhaps some day I'll get around to working on my Ekco TV chassis as it seems ages ago that I restored its cabinet.

Thank you for the kind words Phil; I'm pleased to hear I'm not the only one to suffer from the effects of a "Ten minute job". I'm sure you will agree that phrases like "Can you just" or "What do you think" make your toes curl too? I do enjoy taking on a "woody" basket case but find there is a limit to the new techniques I can learn; at first I made just about every mistake possible but with plenty of time and practice I now know that I can turn out a decent job.

What I like to do now is to take on different challenges such as this dial; the dial and even the radio it belongs to are not worth a great deal in money terms but the enjoyment and frustration I got out of repairing it was priceless. Where else could I get so much pleasure and interest as I did playing around with my toys and using offcuts of material. As long as I've got a project on the go that is driving me mad then I'm happy.

Kind regards, Col.

[Herald1360]

Originally Posted by Retired

I'm sure you will agree that phrases like "Can you just" or "What do you think" make your toes curl too?

Sooooo true! Especially at 4pm on a Friday afternoon

I've not got a lathe or mill or the like, but I do enjoy your write-ups (writes-up?) whenever they appear.

[Retired]

Hi,

Many thanks Herald1360; I'm pleased you enjoy my write-ups.

I've dropped myself in for yet another simple job; a very good friend asked if I could restore a wooden clock case for him and of course I agreed before even looking at it. As I loaded the empty case into the car I noticed bits of missing veneer but on the whole I didn't think it looked too bad.

On the bench however the story was totally different; I tried scraping to remove the original finish but I've never encountered a finish as hard as this before; the freshly sharpened scraper either slid along the surface or tended to dig in so this was abandoned. I then tried various abrasive papers but they also hardly touched this finish then I tried 100 grit garnet abrasive paper and this was much more effective but slow.

It took well over an hour to remove the finish down to bare veneer on one side of the case and by this time I had aching arms. On my next session I was working away and noticed the job felt "different" when I cleared the dust away I found the veneer was loose in a couple of places so to cut a long story short I then struggled spending all yesterday afternoon using a hot iron and wet rag to remove completely the veneer from one side; the top front panel and two top side panels. The case now looks ready for throwing into a skip.

The walnut veneer felt more like plastic than wood and if it was hide glue used it must be the toughest hide glue on the planet; the finish was harder than glass because I can easily scratch glass.

What a delightful project this is turning out to be; rather than regard it as a repair/restoration I now regard it as a project and something I can really get interested in; once I've sorted out the veneer then I'll French polish the case.

I don't want to go off topic and won't add pictures but this is just to demonstrate how a simple job can quickly get out of hand; just as the dial did. I've now got many happy hours ahead of me working on this project.

Kind regards, Col.