Video's of making the Ultimate Kelvin connection(major hacking of a Pomona clip)

[Greate]

That is an awsome work!  Can you let us kow how much would it cost? I bet developers would be interested I might recomend your products to my friends.

Sent from my A100 using Tapatalk

[chrome]

I would also say that it's not as easy to get into machining yourself since the equipment is pretty expensive compared to other hobbies.

Not necessarily. You need a good space for a workshop, but there are plenty of less expensive ways to get tools, either new or second hand. Part of the learning exercise is starting with a tool of average quality and tuning it up to have less play, better tolerances, smoother action and so on. Once you have a few tools you can use them to make new and better parts to upgrade what you have.

There are many hobbyists out there who make model steam engines and other mechanical devices in their home workshop. If you're really enthusiastic you can have a home foundry to complement your machine shop and then you can make almost anything.

OK lets say you want a lathe and a mill, how are you gonna find that for say sub 1k$? You almost aren't gonna find that and even then you still need the cutters for the mill and other tools.

Now say you wanna start learning electronics, for <10$ you can get one of those cheap multimeter and for a few dollars you can find some basic parts to start out with.

[dcel]

If there is a lot of interest I would run another batch of them.   I will post what I think they will sell for when I figure that out.

Calculations complete yet?

Chris

[tramjoe]

This is amazing to watch for a guy like me who dreams of machining equipment.

Please keep on sharing that kind of videos, I spent a very inspiring hour watching this one, and I'm sure it's the same for others.

Thank you :-)

[IanB]

If you like that kind of video you should check out Mattiaswandel's channel on YouTube. He does the same kind of precision construction with wood.

[tramjoe]

Thanks for the pointer, seems very interesting too

[robrenz]

For those that asked about availability and price, If there is enough interest to do at least 10 sets they would be $195.00 US  That would be two Kelvin pincers each with a 36" lead with a double Pomona banana plug and a shield lead with stackable banana plug. That setup will allow connecting both shields to the low of the input or to whatever you want to connect the shield to.  The Kelvin probes  or the universal adapters that can attach to these pincers will be separate items. (still finishing them and the corresponding video).

That may sound expensive but a mass produced Pomona 5940 kelvin clip set is roughly $194.00  My purpose in posting was not to sell these but there seems to be enough interest to consider it.

[Monkeh]

Sell the design to Pomona.

[dcel]

Sell the design to Pomona.

Then Pomona would want to sell the perfectly redesigned kelvin clips for $388.00 each!

I kinda figured about $150 would have been the price I was willing to jump at, but I didn't add in the cable, bananas and assembly costs. I don't have a meter capable of milli/microOhms (4 wire) yet, but I'm in negotiations to obtain one, haggling over price. I know he does not have kelvin leads for the meter, so that is why I am intrested.

I never priced kelvin clips before and didn't know they were sooooo expensive.

Have to think about it...

Chris 

[nukie]

I was cringing when you took out the slitting saw at around 30 min mark, it was hard to imagine, how a tiny mistake can ruin all the work done. Then you talk about the jig that holds it, you made it look so safe. It was excellent. Also, you have hands of steel  . May I ask what lathe / mill was that.

[robrenz]

I was cringing when you took out the slitting saw at around 30 min mark, it was hard to imagine, how a tiny mistake can ruin all the work done. Then you talk about the jig that holds it, you made it look so safe. It was excellent.

Remember that slitting saw is super glued on that arbor (adds to the suspense )

May I ask what lathe / mill was that.

Lathe is a Hardinge Toolroom lathe, CNC mill is a Southwest Industries DPM3, manual mill is a Bridgeport that I bought when I was 17 (42 years ago)

[nukie]

Quite true, the tooling will quickly add up $$$. The cheap machines need a lot of work to perform and it requires a wealth of knowledge to tune them. Second hand machines come with problems of their own. Machining is a lot of practical work where EE is half maths and theory. The best way to learn machining is at school or a job at a machining shop then graduate to owning your own machines. If you have the money you can start off buying the best you can afford and learn slowly. I started off buying cheap Chinese lathe and boy it was a steep road ahead.

Rob is extremely lucky to be able to own a mill when he was 17. I had to wait till I was able to own a house with a tiny shed to start with machining.

Nowadays there's another solution, that is to learn Solidworks, then send off the drawing to a machining shop where the CNC machines do their job. This is similar to home DIY etch PCB vs professionally shop made PCB.

I would also say that it's not as easy to get into machining yourself since the equipment is pretty expensive compared to other hobbies.

Not necessarily. You need a good space for a workshop, but there are plenty of less expensive ways to get tools, either new or second hand. Part of the learning exercise is starting with a tool of average quality and tuning it up to have less play, better tolerances, smoother action and so on. Once you have a few tools you can use them to make new and better parts to upgrade what you have.

There are many hobbyists out there who make model steam engines and other mechanical devices in their home workshop. If you're really enthusiastic you can have a home foundry to complement your machine shop and then you can make almost anything.

OK lets say you want a lathe and a mill, how are you gonna find that for say sub 1k$? You almost aren't gonna find that and even then you still need the cutters for the mill and other tools.

Now say you wanna start learning electronics, for <10$ you can get one of those cheap multimeter and for a few dollars you can find some basic parts to start out with.

[robrenz]

[quote author=nukie link=topic=9807.msg134247#msg134247 date=1343870571
Rob is extremely lucky to be able to own a mill when he was 17. I had to wait till I was able to own a house with a tiny shed to start with machining.

No luck involved . I worked my but off in the local hardware store starting at age 12. My used Bridgeport was $1700,00 back then

Nowadays there's another solution, that is to learn Solidworks, then send off the drawing to a machining shop where the CNC machines do their job. This is similar to home DIY etch PCB vs professionally shop made PCB.

I think you will find the costs of that method prohibitively expensive unless you are talking large quantities

[/quote]

Edit:  I just sent off to "firstcut prototype services"  the nose piece and the brass inner piece you saw in the video to be quoted for 10 pieces of each.  I will report back what type of prices I get if any.  I suspect they will balk at the rectangular broached holes in both pieces.

[robrenz]

[quote author=nukie link=topic=9807.msg134247#msg134247 date=1343870571
Nowadays there's another solution, that is to learn Solidworks, then send off the drawing to a machining shop where the CNC machines do their job. This is similar to home DIY etch PCB vs professionally shop made PCB.

I think you will find the costs of that method prohibitively expensive unless you are talking large quantities

Edit:  I just sent off to "firstcut prototype services"  the nose piece and the brass inner piece you saw in the video to be quoted for 10 pieces of each.  I will report back what type of prices I get if any.  I suspect they will balk at the rectangular broached holes in both pieces.
[/quote]

As I suspected Firstcut (machining) and protomold (molding) would not quote the parts because of being below their 1/4" size limit. And the rectangular broached holes were a problem anyhow. 

Email from them:
Thank you for sending us your parts to quote.

Due to the thin walls on the parts listed below, they are not a good fit with the Firstcut manufacturing process.  If the walls can be thickened to at least 0.040 (1mm), please send revised 3D files.  We will provide a quote as quickly as possible.    If you have any questions, please feel free to contact me.

General machining is a different animal than PCB's or things that will be rapid prototyped by any of the current methods.  The latter two don't need much specialist input beyond what is defined in the files sent to the service.  Machining does need a lot of human decision making based on what machines/processes are available even when using a CAM system for the programming of the CNC machines.

[M. András]

some machine shop especially here only do fairly large runs if even do it for a single person not for a corporation. not even talking about 1 off prototypes for bigger metal pieaces/parts.
as for solidworks. i like the software, i dont have any traning for machining(dont ask how i get it). so i can say that i find it easy to learn to use the software. i wish i could buy a lathe+mill combo even if its manual. finally i could statisfy my creativity while creating things for myself which i can use.

question for you Robrenz, can you say some info about the endmills or any kinds of mills what they use for cutting slots into metal, i would like to know what are the milling depths for them at sub 5mm diameter. even on oldish manual/cnc controlled ones, or on a cnc machining centres/mill centers

[robrenz]

question for you Robrenz, can you say some info about the endmills or any kinds of mills what they use for cutting slots into metal, i would like to know what are the milling depths for them at sub 5mm diameter. even on oldish manual/cnc controlled ones, or on a cnc machining centres/mill centers

These charts will give you a general idea. Most plastics can be cut at aluminum speeds. I use mostly solid carbide end mills.
Side milling with end mill
http://www.microcutusa.com/cuttingcond.php

Slot milling with end mill
http://www.microcutusa.com/slotcuttingcond.php

Google "miniature end mill feeds and speeds" and you will get this and lots more.

Everything I made could be done on machines from here.
http://www.sherline.com/

[M. András]

i forgot to write the material i want to get my idea made from is copper. thanks for the help

[robrenz]

i forgot to write the material i want to get my idea made from is copper. thanks for the help

Copper is not fun to machine unless you are using C145 or C147 .  The other grades are very gummy and tend to push and smear if you dont have very sharp cutters and a good lubricant.  This is evidenced by their machineabilty rating of only 20% as good as C360 free machining brass (what I used in the video).  I suggest using C145 Tellurium Copper
 if its electrical properties will allow in your application.

See properties here
http://www.onlinemetals.com/copperguide.cfm

[HLA-27b]

The second video is even more interesting than the first. True mastery and pride throughout! I must thank you for making these, they are very interesting to watch.  The end product is definitely worthy of its own display case and maker's signature.

[robrenz]

Thanks HAL_42b, very kind words. 

Here is part 2 which covers design and making of the probes and universal adapters. This completes the whole system.  There is a lot of content I left out because I am concerned about exceeding an hour and I don't know how many are interested in mechanically oriented stuff.  I hope many find this interesting and informative.

[IanB]

Mechanical stuff is very interesting. I think you have reached a level of fascination similar to Claude Paillard's video of  making vacuum tubes

[chrome]

Thanks HAL_42b, very kind words. 

Here is part 2 which covers design and making of the probes and universal adapters. This completes the whole system.  There is a lot of content I left out because I am concerned about exceeding an hour and I don't know how many are interested in mechanically oriented stuff.  I hope many find this interesting and informative.

For me it wouldn't be a problem if it was longer.
You had very good shots, clear and to the point and well edited in a way that didn't make me lose interest.
So well done.

[tramjoe]

I would watch it if it were 3 hours long. This stuff is most interesting, and you are making such a great job ! Thanks again for sharing :-)

[robrenz]

Thanks everyone for the encouragement.  Lots more to come on other topics.

[digsys]

Your first video was faultlessly awesome, I really appreciate seeing engineering (of any field) done well.
Your second video ... now I hate you :-)