100 year old South Bend 34 Rustoration

[brino]

I think I may try to create a 3d model for the half nuts and 3d print a set in ABS............................. I have nothing to lose so it must be worth a try.

Please let us know how that works out!

-brino

 

[Grendel]

Well a very rough and ready model in fusion 360 (my first real model in that software, I normally use either autocad or microstation full CAD pakages, but they dont have the instant thread making capabilities that fusion 360 does, even then i had to tweak the acme thread specification file to get the 1" 8TPI thread form, so fingers crossed it works.
excuse the holes, i was struggling to get the rib function working as I wanted it to, but all the important parts are there in the corect relation to each other.

 

[Grendel]

not a great start, it took me nearly 4 hours of the printer not behaving to figure out I had worn out the printer nozzle, fortunately I have a nozzle for each type of material, and i rarely use the one i have set aside for PLA, so as my machine has a quick change extruder, I swapped out for the newer pla nozzle and that is now working spectacularly, i have decided to do a test run with a low infill just to see if everything fits on the lathe, if it does then I will print again with a more solid fill.

 

[MyLilMule]

I recently watched a YouTube video of someone repairing a half nut on small lathe. They made an acme nut out of brass that would thread onto the lead screw. And then epoxied it into a set of bored out half nuts. Then cut the brass in half. You may consider that as an option if the 3D printed one does not work out.

I found it while writing this post:

Sent from my iPhone using Tapatalk

 

[Grendel]

perhaps not the best of omens ( or maybe its a good omen, who knows) I generally run my 3d printing overnight, and I have just woken to find that one half nut has broken away from the print bed, so I am baby sitting the other, trying to remove the filament that is being deposited in fresh air. I can say though that the thread in the one that broke away is looking promising and i do have 3/4 of the ut that broke away (is 3/4 of a half nut a 3/8 nut?)

 

[Grendel]

after the print ended and while the surviving half nut was cooling on the printer, I took the 3/8 nut down to the workshop (as I made my morning coffee) and did a test fit, after an initial hesitation, that cleared as soon as i did a full turn around the lead screw to clear the plastic junk out of the thread grooves, i am pleased to report the thread fits very well.
if you look carefully you can see the honeycomb structure that gives the parts their strengrh in this incomplete nut, sorry the last picture is so dark, but it is still only 6am here in the UK


I will try and get a better picture with both nuts later, right now its time to stat work ( the good part of lockdown, working from home is you can fit your hours in as you like)

 

[Grendel]

and here is the finished half nut, before the crud was cleaned from the threads, this crud was some of the floating filament from the nut that broke away, it wasnt stuck fast and just running a point along the thread was enough to clean it out.
you can see a slicght crack whee the filament has delaminated, i will brush the outside of the part (not the thread) with acetone which will remelt the abs plastic into the crack, actually this is something i generally do as it fuses the outer layers making it less prone to shear between layers.

 

[Grendel]

so the part fits into the half nut housing quite well, I need to make a 1/2" dowel to push into the back to operate it

 

[Grendel]

meanwhile if anyone wants the fusion 360 file to play with, you may need to PM me your email address as I see that the allowed file types dont include STL, f3d or xml. what you do need to do in fusion 360 is edit a copy of the ACME thread data file for the acme thread using notepad, below are the parameters that you need to change to get an 8tpi 1" acme thread in fusion 360 basically you set the TPI to 8 then match the Major, Pitch and Minor diameters to the designation for an 8TPI ACME thread (I got the offsets for the diameters from a thread above that was 8TPI, and amended them for the 1" diameter, copy the file, make the changes and save the file as acme thread modified or some other name, (I recall I lso changed the title up at the top of the file.

 

[dirty tools]

A couple weeks ago someone on EBay had a set of half nuts for sale
I was looking for the worm gear