Request for two small steel rod-esque lathed part!

[HankMcSpank]

I don't have access to a mill, but really need the following parts made...

Part 1.

A 9mm diameter mild steel rod, about 50mm in length. Milled into the centre at each end, a 5mm circular 'recess'/pocket 2.5mm deep at one end of the rod, & a 5mm circular 'recess'/pocket 1.8mm deep at the other end of the rod. Ideally, on the outside edge perimeter of the 5mm pocket, I would like the smallest hole 'do-able' drilled at say circa 45 degrees through the rod body to pop up at the main rod edge (it's to thread enamelled copper wire through...more on this below!)

Part 2.
A 9mm diameter mild steel rod, 30mm in length. Milled into the centre at one end, a 5mm circular pocket 1.6mm deep ...at the other end of the rod, no pocket, but about 1cm of M8 thread. Once again, ideally, on the outer perimeter of the 5mm pocket, I would like the smallest hole 'do-able' at say circa 45 degrees through the rod body to pop up at the main rod edge


Just for a bit of background..this is to wind small coils.

Part 1 will go into a 'holding/turning' heath robinson chuck - a 5mm diameter magnet will be inserted into the small pocket/recess. Part 2 will be threaded onto an M8 rod, but then used to push up against the other end of the magnet - the idea is to rotate the magnet by a motor while feeding copper wire onto it - essentially making a coil. These parts hold the magnet in place & provide a pseudo bobbin 'edge' for the wire boundary as it traverses left to right. Therefore The above 'recessed' circular pockets need to be razor sharp from an angular perspective - ie a 90 degree corner (I'm using wire that is very thin ...0.1mm diameter & don't want any wire to be able to go into the recess). I could post out the small cylindrical magnet that I'll be using to ensure there's a nice tight fit for it into the recessed pockets.

This is not for a commercial venture...just a little hobby project I've started out on!

Could some kind soul quote me? (or if they don't fancy quoting, at least give me a flavour of what would be a ballpark price (I have some acrylic rod that in theory I could try * mill thos pocket into...but I'd really like this to be steel as the magnets will adhere to them (since the recesses are quite shallow, I need all the help I can get at holding the magnet steady!)

here's a very rough and ready sketch ...

[HankMcSpank]

Hall effect pickup coil?

Could the holes simply be drilled/bored on a lathe?

9mm is an odd size...is that to be the guide for the OD of the coil winding?

No nothing as clever as a hall effect... just something I'm toying with in my spare time, but I've had little success getting decent coils ...& I need six of them for each of the pickup I want to knock up. It's got to the point where I've exhausted all other options (sewing machine thread bobbins, etc!)

Re drilling the holes....I need the far endof those end pocket/recesses to be nice & flat flat (the magnet end has a completely flat face & I want it to mate up to those recess perfectly - else when they're turning they'll wobble)...I'd also need the magnet to be a nice tight fit diamter wise( same reason...anti wobble!)...so unless I got lucky with the drill diameter, then I'm not sure it'd be precise enough.

The 9mm is derived from the maximum distance permittable between guitar stings (ie it's about 9.2mm from the centre of one string to the next string). Therefore the coils ought to be 9mm wide (max) - these two parts I'm asking for will hold in the edges of the coil as the copper wire is being wound onto the magnet from side to side.

Back of an envelope (literally), bad drawing here...

[John S]

I make a few bobbins for the rewind industry from time to time and they also have to make non cored coils, not as small as this but similar principle.

What about getting a bar turning part down to 4mm longer than your coil and threaded it M4

The can be any size within reason but the part next to the thread turned down to 9mm as I gather that's just a visual guide on the coil being full ?
This will allow you to wind onto a thin plastic or paper former which can then be removed after.
The ends can have a card washer fitted with a small hole in to locate the wire at the start and then be disposed of after winding. This does away with the tiny drill hole at an angle. not sure why you need two start holes as the end of the wire is going to be on the OD.

Length of coil is controlled by a 9mm diameter 'washer' threaded M4 and held in place by a lock nut to adjust length of coil.

Or am I missing something ?

[HankMcSpank]

Firstly thanks for the comments.

My needs are only to wind copper wire directly onto an Alnico magnet (let's call this magnet the 'core', as essentially that's what it will be - the core of a coil ...essentially a solenoid)....I have no other coil winding requirements (paper /plastic formers etc)

These parts are towards a hobby DIY projectette for a guitar ...therefore I'm constrained to the dimensions of the guitar. So One limiting factor is the core length (ie the magnet you see in my second scribble above), which will be about 8mm max (of 5mm diameter Alnico magnet). This is a very small bit of metal to be turning 150 turns of copper wire onto! Therefore I need all the help I can get at keeping it rigid between those two parts. To help centralize it (since it'll be turning at about 200RPM) & stabilize/rigidize it while turning, I figured I'd need....

1. The parts I'm requesting to be made of steel (bearing in mind I want these parts to 'hold' a magnet...being steel will help them 'click' into & hod in place)

2. The 5mm diameter pocket/recesses at the end of the parts, to be a nice tight fit.

The tiny 'start' holes (I'm thinking 0.5mm!) I mentioned are a 'nice to have', but I can appreciate that it might be a task to get them drilled so small & at an angle. The angle isn't important, but what is important, is that I can thread the wire through the part out of the way - so as I start to wind the coil, the wire isn't a pain to get to start 'biting' (for want of a better word) around the core quickly...to get the coil off to a nice neat start on it's first layer. I need a 'start' hole at both ends, because I anticpate, some coils will be wound starting at the left moving right & other coils wound starting at the right moving left.

The 9mm diameter 'dimension' you picked up on, is both a visual representation (that said, I'm knocking up a PIC based coil winding program which will count the coil turns anyway), but more importantly, to make sure the edges of the coil are nice & perpendicular to the magnet core.

It's all a bit hard to explain in writing,

But in short..the way I'm proposing making the coils perhaps the only way I think it'll be possible to get decent results on a core so small (& I'm sure my mates will probably ask me to make them one too...so I may need to make a good few coils!)

[BillTodd]

Does Part2 turn with the magnet ? - I'd worry about the run-out of the M8 thread coupling. If it doesn't I suggest you make it turn with the other end, else the coil will drag.

Drilling a 0.5mm hole more than a few mm deep might prove interesting. Presumably you only need the hole to be 0.Xmm near the coil end, so most of the length of the hole could be larger. Actually, a slot might be of more use than a hole (saves that 'threading the needle' problem)

The magnet hole doesn't need to be flat bottomed it just needs a definite stop - have you considered having a set screw at the bottom of the hole, so the depth could be adjusted? (you could probably rely on the grub screw to attract the magnet and make the rest of the piece from Al or plastic)

[edit]

Thinking some more...

Hold the magnet in a brass collet with a smaller collet on the other end as an end stop (that way you'd get a concentric positive drive on the magnet)

[HankMcSpank]

Does Part2 turn with the magnet ? - I'd worry about the run-out of the M8 thread coupling. If it doesn't I suggest you make it turn with the other end, else the coil will drag.

Yes part 2 will be turning in sympathy with part 1 (which has the motor). I have to admit this is the most troubling bit. Essentially this will be a similar setup to what you see on a lathe tailstock...excepot it';s a right heath robinson cheapsjaket's version. A bit more meat...

Part 2 will connect to a length of m8 threaded rod (I will connect it via one of these ... http://www.tinyurl.com/ny63ds ) One other option is to have part 2 with a tapped M8 hole - & the M8 threaded rod screwed directly into it...I'm not sure what the best option would be?

ok, so now part 2 is affixed to a a length of M8 rod. Along this M8 rod will be some roller skate bearings (yes, you heard me right), these in turn will be held by some SK16 mounts ( http://tinyurl.com/nw8tlp
the outer diameter of the skate bearing is 16mm...the inner dimension is 8mm, so these are ideal). ok, so there you have it...part 2 is now mounterd horizontally into some M8 threaded rod, which turns within some skate bearings held steady by the Sk16 mounts - I told you it was a heath robinson!

Part 2 will then be pressed up agaist the magnet. If everything align (if!!!), then the magnet should turn easily & be held stable & 'true'.

Drilling a 0.5mm hole more than a few mm deep might prove interesting. Presumably you only need the hole to be 0.Xmm near the coil end, so most of the length of the hole could be larger. Actually, a slot might be of more use than a hole (saves that 'threading the needle' problem)

That's a great point ...you are right, it would only be the last bit that would need to be 0.5mm....the rest of the hole could be larger. The slot is another good option, but I'm not sure what the optimum wire size is yet (to determine the slot). I do know from the few times I've tried to wind these coils that the 'loose' threaded end, ideally needs to exit the edge (ie part 1 'small hole') at the actual perimeter of the magnet core ....else it interferes with the coil 'neatness' (& I'd like this to look neat, since it's going on my guitar!)

Some great points though....thanks!

Since posting, I'm now seriously considering using the fact I need these parts as an excuse to buy a hobby desktop lathe ...her indoors won't be happy, but hey "McSpank-ess, shut it!"

[HankMcSpank]

Hello Hank,

How big a hurry are you in!! . . . . . . . . If no rush IE: next week will do then i will "try" to make you this part, TRY being the word. probably take be a few go,s being so small.
Dont want anything for doing it just cover the postage thats all.
Will need you to send me the magnets for test fit.
Q: how are you going to wind these coils. . . .IE do they fasten to winding machine or some device you made?

IF you want it doing send me a PM with ya details and well av a natter.
Cheers
Dean.

Wow Dean...thanks! Certainly the internet working at its finest!

I'll PM you, but keep this thread running as there are some good points being made (I'm not really an engineering type...just a part time kludger - my area is more electronics), re your question...

Hello Hank,

Q: how are you going to wind these coils. . . .IE do they fasten to winding machine or some device you made?

you'll not believe this but here goes anyway (& no laughing at the back!)...

I have a reasonably powerful 48V DC fan ...in the middle of this fan I hot glued (yes, you heard right!) a 13mm drill chuck. It took a bit of effort, but I eventually I got the chuck centred pretty much perfectly in the middle of the fan (hot glue is excellent for this as you can keep reheating it until you get it right - also there's not a lot of load going top be placed on this setup, so no worries about it falling off) . Ok, so now I have a turning mechanism capable of holding 'rod'. The problem was that at 48V it turned *way* too fast, so I knocked up a PWM DC motor speed controller. I can now start the fan from static up to any speed I care to nominate. So in short, part 1 will be held in place by 13mm drill chuck jaws.

Not realted to my needs, but just for some background info, to get really slick I made an encoder wheel (a circle with 192 black on white stripes radiating out from the centre)....this is attached to a CD and stuck to the fan blades. I then knocked up an electronic circuit to count the black stipes as they pass an optical pickup. This give me two things...

1. The RPM.

2. the distance travelled - this bit allows me to 'synchronize' a stepper motor to move back & forward as the main motor turns - this stepper has a bit of plastic M8 threaded rod inserted over the stepper shaft. I then feed the copper wire over this plastic M8 threaded plastic onto the rod held by the drill chuck & it traverses left to right in perfect syncronism. To get an idea of this last bit, look here - [http://www.tinyurl.com/m4mmfl (from about 27 secons, in - that's not my video, but I've got a similar setup except the wire I'm using is hair thin!)

Convoluted, but like I say, there's not a whole lot of budget...& you can't exactly buy such coil winding machines at the local MachinMart! Therfore I've had to get creative!

I'll try & get a photo posted up tonight.

[John S]

Firstly thanks for the comments.


I need a 'start' hole at both ends, because I anticpate, some coils will be wound starting at the left moving right & other coils wound starting at the right moving left.

No just one hole, left to right, right to left can be obtained by reversing the bobbin direction.


.

[HankMcSpank]

:clap: MR Creative.

Will you have to sync the stepper and the motor so they turn together at the same speed?

Yes, but this bit has been sorted...ie no matter what speed the main motor turns at, the stepper adjust its traversal speed accordingly.

A bit nerdy but here we go...

If the copper wire width is 0.2mm in diameter, then I know for every turn of the main motor, the stepper motor has to rotate the plastic M8 threaded rod on its shaft sufficiently to move the wire exactly 0.2mm to the left (or right). M8 threaded rod has a 1.25mm pitch, therefore all I need is a simple PIC program to count/map 'black stripe incoming pulses' from the main motor, to stepper pulses out.

For example, the program is typically doing this "For every 10 black stripes received , send a pulse to the stepper" ...it took a while to sort, but it works perfectly. You might think this is a lot of work for a simple guitar part, but I wanted to learn about steppers anyway (I was about to build my own CNC mill) & I also wanted to learn about PIC proramming - I'm the type that needs an end goal to motivate myself enough to do it!


I hope i'm not clouding the issue here...wrt the parts I need, this stepper traversal bit isn't a factor!

[HankMcSpank]

No just one hole, left to right, right to left can be obtained by reversing the bobbin direction.


.

i'm not sure I'm following?

I can't change the parts around from side to side as they have different 'pocket' depths milled into their end bits (this is becuase I need different amounts of magnet core to protrude outside the copper coil at each end). Also each part is held in a different manner ... ie part 1 is held by a drill chuck, whereas part 2 is threaded onto some M8 rod. Therefore if I need to start the coil winding at a different end, then they both need the 'start' holes drilled.

But as Bill helpfully mentioned...the 0.5mm hole wouldn't need to go the whole way, just the last say 0.3mm if drillling from the main rod perimeter down towards the part 1 end surface.