I need some help with designing this thing

[lister]

To mods: If you think this thread does not fit this subforum feel free to relocate it. 

Some of you might have noticed that I have somewhat unhealthy obsession with sewing kits for a man. Case in point: http://forum.multitool.org/index.php/topic,55594.msg1022668.html#msg1022668
 
So far so good. I think this might be the most complex and at the same time small sewing kit out there. If you know of any that surpass this one do tell me about it. 

But before I ever made this one I had an idea for the container for the sewing kit. It would also be a capsule with a thimble on top / inside (back than I didn't even know they used to make them). But in addition it would have some way of holding a sewing machine needle on the other end to function as an sewing awl.

I made a prototype back then from a aluminium capsule bought on DX and some holes drilled in to a M8 screw. I might post the pictures of that if I can find the prototype. But the prototype didn't work all that well because I didn't have access to a decent drill press so the holes were all askew.

Skip forward a year and I decided to give it another try. This time I wanted to design it in some kind of a CAD program and then have it made by a professional machinist on a lathe. So I started learning the FreeCad and came up with this:







For now it is only a concept. For now all I know is that the thing is supposed to be about 5 cm long when closed (the second picture but without the needle). From here on I need some help. I don't even know all the things I will need your help with yet so for start I will just make a list of questions:

1) Can someone who has experience using a lathe tell me if this thing can even be made on a lathe? I presume so as most of the geometry are rotational bodies and that is kind of what lathe do right? 

2) How hard would it be to make the little holes on the thimble for catching the needle (the holes are missing form the CAD model for now). Alternatively can a knurling finish be made on a sloped part (of the thimble)?

3) What about lathes and cutting threads (the threads that are supposed to hold the body and the thimble together are also missing from the CAD model...  )? Is there some kind of a primer for idiots I can look up to get to know the topic? Like how thick must the wall be where the threads are cut in to it...

4) I think we have a member of two that make their own flashlights body and all? I think that making a body for a flashlight would be similar to what I will need to do.

5) Should I be trying to make this thing waterproof? You know for all those times you need to sew something up 10 meters under water... 

6) Some sewing awls are able to feed the thread form their handle. Is anyone that uses one of those around? Is that a feature that you simply can not do without? I think I will have some problems if I want the sewing awl to be water proof and be able to feed the thread form the handle at the same time?

7) What material should I be thinking for this application? For now I am thinking steel...

I will probably think of some more questions later. 

[hiraethus]

Good stuff so far.

1) Yes, you could make that on a lathe.  Probably not that easy, but manageable.  The flat bottom of the the main hole would be best if it's left as a drill point - typically 118 degrees.  Then it could be drilled instead of being bored out.  That would fit nicely into the tapered region above the needle holder.

2) Lots of small holes in the thimble should be ok - that sort of thing would be best on a CNC milling machine, or a dividing head on a milling machine.  Expensive to set up for one part but ok if you're making a batch.  Alternatively, you could 3D print it in metal with the holes already in place.  I think you should be able to do a knurled finish on an angled part - never tried it though.

3) Wall thickness really depends on the material and what load you're putting on it and machining very thin sections is tricky.  Threads have a major (outer) and minor (inner) diameter.  Depending on whether you're cutting a male or female thread you'll need to leave a bit of material outside or inside the thread to give it some strength.  The finer the pitch of the thread, the closer the major and minor diameters are - so for a thin-walled part like your sewing kit you'd need a fine thread.  Something like M20 x 0.75 - that's a 20mm outer diameter male thread with 0.75mm between each thread.  Loads more info on Wikipedia: http://en.wikipedia.org/wiki/Screw_thread and for specific sizes try here: http://www.roymech.co.uk/Useful_Tables/Screws/Screw_Threads_1.html

4) Flashlight bodies would be a very good place to start.

5) No to waterproofing.  More effort than it's worth, IMO.  O rings and the like are perfectly doable, but add a level of complexity you probably don't need.

6) No idea about the internal thread passage. I do sew, but only with a needle and thread.  Hopefully someone else with more experience can chime in.

7) Steel needs a finish to protect it, but it's cheap and easy to machine.  Stainless steel is harder to machine and won't need painting/coating but threaded parts can gall and bind together unless you're careful.  Aluminium is easy to machine and probably strong enough for what you need.  You can anodise it nice colours too.  Brass would also work well - easy to machine, need no protective coating, looks good.

Looks like you're thinking about this a lot, and taking the time to translate your ideas into 3D CAD really helps.  I find it hard to judge the scale of things in CAD though, and keep designing stupidly fiddly little mechanisms that are hard to assemble.  It all looks so easy on screen.

[lister]

That is some good stuff there Hiraethus! 

so my comments on the answers:

1) That is exactly what I wanted. I need to know ''tricks'' that will make this easier to make and thus less expensive. This will probably turn out to be one of my more expensive gadgets, despite me beeing the designer... 

2) I figured that I would need to go via the cnc route for that. I might choose to make things simpler by placing an ordinary thimble inside the body, it might be less of a hassle and it would be more adaptable if anyone else would want to use it. I am still working on the 3D cad concept...

3) This one will take me some more time to do my research.

4) I've noting to say here... 

5) I agree but it would be cool. 

6) This will be more doable if I forgo the waterproofing part so so far so good.

7) I was thinking of the stainless steel. I knew that it was harder to machine (hardness and slow heat transfer) but I was unaware of the galling. I will need to research that further... Brass would be nice I think. But how about the screw that is supposed to hold the needle in place? Will it be a problem if I use steel screw in a brass body? Would if strip the threads?

Unrelated to my problems: What kind of projects do you do? Fiddly little mechanisms sound interesting... 

Ps: If anyone else wants to chime in feel free to do so, I don't bite. It is not necessary to delve so deep in to the technical side as Hiraethus did, you could also just vote on the water waterproofness and the internal thread feeding. Or suggest some other possible functions? I already had an idea that might be totally useless: To make a drill bit that goes in to the holder and provide some  grooves to make this in to a bow drill... 

[NKlamerus]

If your not planning on forming this; i really think flashlight bodies would be the best place to start.

It seems like a Mini-Mag light almost fits the dimensions.

Do you have a local machine shop.

[lister]

If your not planning on forming this; i really think flashlight bodies would be the best place to start.

It seems like a Mini-Mag light almost fits the dimensions.

Do you have a local machine shop.

I don't know, but I am sure there must be some. I will start asking about...

[NKlamerus]

If your not planning on forming this; i really think flashlight bodies would be the best place to start.

It seems like a Mini-Mag light almost fits the dimensions.

Do you have a local machine shop.

I don't know, but I am sure there must be some. I will start asking about...

This is so close, i dont know if it opens up or not.

I do like the needle holder though!

http://www.ebay.com/itm/261753073787?redirect=mobile

[zimchaz]

Apart from what the others have said, I can only offer advice on
#6 I have used a speedy stitcher in the past,but now I tend to use it without the self feeding bobbin.
2 reasons for that, you have to manually wind the thread on it (which is a ball ache) and if it snags, the tension on the thread tends to snap the needle.

Other than that I would be interested to see how a machine needle holds up in manual stitching, the machine oscillates the needle in a very specific vertical plane, that can't really be replicated by hand, add to this the fact that the needles are very brittle and I reckon you will be snapping needles pretty often.
I have tried using them manually before and this was my experience.
Good luck I look forward to seeing it.

[lister]

Apart from what the others have said, I can only offer advice on
#6 I have used a speedy stitcher in the past,but now I tend to use it without the self feeding bobbin.
2 reasons for that, you have to manually wind the thread on it (which is a ball ache) and if it snags, the tension on the thread tends to snap the needle.

Other than that I would be interested to see how a machine needle holds up in manual stitching, the machine oscillates the needle in a very specific vertical plane, that can't really be replicated by hand, add to this the fact that the needles are very brittle and I reckon you will be snapping needles pretty often.
I have tried using them manually before and this was my experience.
Good luck I look forward to seeing it.

The needles snapping is not good news... 

[zimchaz]

Apart from what the others have said, I can only offer advice on
#6 I have used a speedy stitcher in the past,but now I tend to use it without the self feeding bobbin.
2 reasons for that, you have to manually wind the thread on it (which is a ball ache) and if it snags, the tension on the thread tends to snap the needle.

Other than that I would be interested to see how a machine needle holds up in manual stitching, the machine oscillates the needle in a very specific vertical plane, that can't really be replicated by hand, add to this the fact that the needles are very brittle and I reckon you will be snapping needles pretty often.
I have tried using them manually before and this was my experience.
Good luck I look forward to seeing it.

The needles snapping is not good news... 

Do a test mate and check, I would say cut a 2 inch long piece of broomstick and whittle it down to a comfortable handle. Drill a small hole (with an MT awl if it's easier) to take the needle and see if it holds up with some test pieces.

[NKlamerus]

Looks like these come apart. Not quite what you want but maybe you could order the cheaper one (like 2 USD) and mod it?

[lister]

I will do some tests. 

And I'll order one of those 2 usd things to see what's what. 

[hiraethus]

That is some good stuff there Hiraethus! 

No problem.

2) I figured that I would need to go via the cnc route for that. I might choose to make things simpler by placing an ordinary thimble inside the body, it might be less of a hassle and it would be more adaptable if anyone else would want to use it. I am still working on the 3D cad concept...

I wonder if making a body that fits snugly inside a readymade thimble might be easiest - use the thimble as a push on lid - find a thimble with a non-tapered opening and machine the tube of the holder to fit it.

7) I was thinking of the stainless steel. I knew that it was harder to machine (hardness and slow heat transfer) but I was unaware of the galling. I will need to research that further... Brass would be nice I think. But how about the screw that is supposed to hold the needle in place? Will it be a problem if I use steel screw in a brass body? Would if strip the threads?

Steel screw in brass body should be fine.  Just don't tighten it too hard.   A knurled thumbscrew should hold the needle securely, but prevent you from over-tightening.  M3 thread or something like that.

Unrelated to my problems: What kind of projects do you do? Fiddly little mechanisms sound interesting... 

Work mostly - my home projects are much simpler - fluid control valves for trucks.  Lots of self-centring and spring return mechanisms for solenoid valves.

[lister]

@zimchaz:

a) What are the shank dimensions of the super sticher needles?

b) Can you buy them easely and seperately?

c) What kind of material should I use? A few layers of leather? And how fast should the needle break in your experience?

@Hiraethus:

I am thinking along the same lines (push on lid). But I was thinking of a cap in the shape of a thimble on which you put an ready made thimble and a magnet to hold in place (kind of what I have at the moment in my sewing kit). In this way you avoid all the holes but retain strenght which I think the thimble lacks.

[zimchaz]

@zimchaz:

a) What are the shank dimensions of the super sticher needles?

b) Can you buy them easely and seperately?

c) What kind of material should I use? A few layers of leather? And how fast should the needle break in your experience?

@Hiraethus:

I am thinking along the same lines (push on lid). But I was thinking of a cap in the shape of a thimble on which you put an ready made thimble and a magnet to hold in place (kind of what I have at the moment in my sewing kit). In this way you avoid all the holes but retain strenght which I think the thimble lacks.

I will have a look when I get home after work for dimensions for you.
As for the test I would be impressed if a machine needle stitches something useful out of a few layers of leather. Remember to test it with thread as well because the gauge of thread will change how easily the needle passes through leather etc.
As to how long they will last, I may be a clumsy impatient oaf and that's why they break on me, they might last you forever, but in my experience they tend to break relatively easily. The speedy stitcher needles are a lot sturdier and can be bought separately on ebay. The only problem is that the needles plus some thread are only marginally cheaper than the whole setup.

[lister]

I believe you that the sewing machine needles will break often, that's why I wonder if the same design of needle holder could hold both kinds of needle. 

By the way could you also measure the length of the speedy stitcher needles? I need that measurement to see if I could store them inside the sewing awl handle.

[zimchaz]

Sorry for the delay hopefully these pictures will load

[zimchaz]

55mm long and 2mm diameter.

Hope this helps.

[lister]

No problem, thanks for the measurements. 

It seems like the diameter of sewing machine needles and easy stitcher needles are the same, so I can use both in the same design. But the latter are a bit longer, so I will need to make the handle of the awl a bit longer so I can store both types of needles in it.

[lister]

This is how it would look like if there was enough room inside the handle to store a normal thimble:



The thimble could be held in place with a spring between the end of the spool and the thimble.

I don't like the looks of this one as much as it is less elegant (because the handle has to have a larger diameter to accommodate the thimble). 

[lister]

Additional thoughts:
1) As there were no standards worked out before the deities went around creating us there are so many different sizes of fingers and as a consequence there also different sizes of thimbles. This could be a problem for my first design, the second should be fine for all sizes.

2) I have another option of adding a thimble to the kit. In that incarnation the cap of the body would be shaped like the inside of the thimble so the thimble could be put on it. It would be held in place by a neodymium magnet glued in to a hole on the top of the cap. But then again I would have problems with different sizes of thimbles. Also I need to make a cad model to see how it would look like...