LowThermal Binding Post CAD

[leighcorrigall]

LowThermal 2758 binding posts http://www.lowthermal.com/cables-and-connectors.php are fairly common in metrology because they use tellurium-copper for its combined low thermal electromagnetic electromotive field electromotive force (EMF, https://download.tek.com/document/LV_LR_e-hnbook_91113.pdf) effects and machinability. These posts have decent insulative properties, are multi-functional, and are aesthetically pleasing. Other features are detailed in the datasheet http://www.lowthermal.com/pdf/2758-series-data.pdf. Varients of LowThermal posts can be found in commercially available designs (i.e. Agilent, Fluke, Guidelines, etc.) and can be directly purchased in small quantities for a moderate price (~ 30 USD/unit).

Some hobbyists may be satisfied with the dimensions specified in the datasheet. For my personal designs, I would like to have a CAD assembly available. I decided to address this obstacle so that others may also benefit from my effort.

A few months ago, I purchased posts for a design I am working on. TiN was very helpful when I reached out to him in that he provided a collection of damaged posts for reference so that no one needed to sacrifice a brand new post for the cause. 

Attached is the reverse-engineered CAD assembly. Use 7-Zip https://www.7-zip.org/ to extract the STP file.

Please note that there are likely some differences in the dimensions. For example, I am uncertain what the interface between the plastic mould and the metal barrel looks like for the front chassis flange, even though it has no impact on the effective use of the assembly. I also did not count the knurls for the plastic end cap or the metal components. These are guestimations until accurate information comes along. If anyone does encounter significant discrepancies, please let me know so that a revision can be made. I will not take any responsibility for the CAD. Use at your own risk.

Enjoy!

Revisions:

REV5: The through-hole wire connection termination is now correctly aligned with the D-hole conduit. Refer to the picture where changes have been outlined in blue.

[martinr33]

Thanks for doing that  - it is useful for many things.

I don't think that Fluke uses the Low Thermal posts. I picked up some Fluke parts for an 8508A DMM project, and they are slightly different.

That said, the major parts are interchangeable between Fluke and Low Thermal.

Also, Fluke parts are unplated copper, LT are gold plated.

I don't understand why the Fluke posts do not corrode - they seem to stay bright. 

And while we are here - anybody got a good source for #8 copper or gold plated copper nuts? I have managed to either source or have made the copper washers, but no luck with nuts.

(BTW, Fluke posts alone - the copper shaft with the captive terminal nut assembly - is a deal at about $8 each, and will replace the ones I busted in my Low Thermal parts. Don't overtighten).

[CalMachine]

low thermal electromagnetic field (EMF)

Just a random correction I need to make.  EMF in this case is the electromotive force, not the electromagnetic field.

[leighcorrigall]

EMF in this case is the electromotive force, not the electromagnetic field.

Thanks. I was not thinking when I wrote that.

[quarks]

https://www.jswilley.com/low-thermal-accessories
is also selling LowThermal parts

[leighcorrigall]

The ring terminals (2758-ring) sold by LowThermal might be custom Panduit connectors.


If I were to guess, they are similar in dimensions to the P18-8R Series. Part Drawing: https://www.panduit.com/content/dam/panduit/en/products/media/6/56/256/9256/29256.pdf

Actual LowThermal dimensions:

material thickness: 1/32"
overall length: 0.71"
outer ring diameter: 5/16"
inner ring diameter: 11/64"
crimp terminal length: 17/64"
outer crimp diameter: 17/128"
inner crimp diameter: 1/16"

[quarks]

Panduit is also my guess, because on the 2758-Fork is a stamped in letter P

[Conrad Hoffman]

I can't stand machining pure copper. It cuts poorly with poor accuracy. It bends in the machine too easily. It reacts with many cutting oils. It tarnishes at best and corrodes at worst. Threads tend to gall. Lousy stuff. BUT, if you're going to use copper, it sounds like oxygen free is the way to go- https://samdongamerica.com/blog/ofhc-copper-vs-etp-copper/ Based on that description, I've probably never machined oxygen free. Regardless, tellurium copper is going to be way better from a manufacturing standpoint.

[leighcorrigall]

I can't stand machining pure copper. It cuts poorly with poor accuracy. It bends in the machine too easily. It reacts with many cutting oils. It tarnishes at best and corrodes at worst. Threads tend to gall. Lousy stuff. BUT, if you're going to use copper, it sounds like oxygen free is the way to go- https://samdongamerica.com/blog/ofhc-copper-vs-etp-copper/ Based on that description, I've probably never machined oxygen free. Regardless, tellurium copper is going to be way better from a manufacturing standpoint.

Hi Conrad,

I have no intention of machining these parts. The purpose is to provide members with dimensions / CAD models so they can refine their designs. I thought it would also be useful to provide members with specifications so they can make informed decisions about their purchases.

I used to work with copper a lot in my research. If you are having problems with tarnishing, place your parts in a bath of strong acetic acid (vinegar) for a given time. On removal, immediately wash with deionized water followed by a towel dry. The parts will come out very shiny provided that a thick oxide layer hasn't already formed prior to treatment. I included a photo of C101 and Zry-2 samples that were roughed with a coarse abrasive and then treated with acetic acid as an example.

OFHC (C101) is nearly pure copper. Oxidation takes a long time compared to OFE (C110). Always handle with gloves to prevent contaminating the surface. I believe Te-Cu (C145) and Be-Cu (C172) were designed for machining and corrosion resistance. Any other copper grades will be much more challenging to keep untarnished.

Regards.

[HighVoltage]

Thanks for making the CAD files
However, I am getting some rebuild errors.

Can you post the single files, so I can open them as parts and not the assembly?

[leighcorrigall]

...

Can you post the single files, so I can open them as parts and not the assembly?

Hello HighVoltage,

Sorry that you are having difficulties loading my assembly.

I would prefer not to save individual parts because then I would have to maintain non-native file duplicates (i.e., STEP files instead of ASM/PAR files).

Here is what I suggest:
1) Make sure the problem isn't with SolidWorks. I work often with my university technicians who use SolidWorks and MasterCAM. They have not mentioned problems with my files before. This is why I am confused about your problem. EDIT: Has anyone else had issues loading my step file?
2) If you cannot solve the problem on your end, then maybe I have to look at how I exported the STEP file with SolidEdge. We can email each other until a solution is found. My email should be part of my profile. Otherwise, PM me.

We can work it out.

EDIT: By the way, it looks like they are warnings, not errors.

Regards.

[E-Design]

leighcorrigall,

Very nice model - looks like this took some time. Nice work.

I opened your Rev5 with both a viewer and another MCAD tools which checks for errors. Both reported no errors, no warnings.

[HighVoltage]

Could you save it as IGES file?
Sometimes that works better in Solidworks

[leighcorrigall]

Could you save it as IGES file?
Sometimes that works better in Solidworks

[HighVoltage]

Thank you for the .IGS file
But the errors persisted in Solidworks on two totally different SW installations.

I think I found the problem.
Take a look at the attached samples of your parts.
It seems you saved them as surface parts only and not volumetric parts

Can you save them again with standards STEP or IGS settings, then it should work well.

[leighcorrigall]

...

Can you save them again with standards STEP or IGS settings, then it should work well.

The STEP file and IGS were exported with default settings. I have not changed the default settings at all. 

[HighVoltage]

There is a setting in the STEP export to have only surface data exported.
Then the user can not change the model.
This is why I can look through the nut (above attachment)

I have seen this many times before, when vendors do not want to publish full
volumetric data and keep their IP. Only when I have asked them to send a full
volumetric data STEP, then it worked.

You might want to look at the detailed option settings in your CAD software
for the STEP and IGS exports.

[HighVoltage]

After importing your STEP file in to an old version of SpaceClaim, I saved it again as a STEP file.
Then I saved all parts individually and assembled them again in Solidworks.

At the end it was perfect inside of Solidworks.
Thanks again for your great work!