Is it my turn? Anything to do with lathes, mills and other shop tools

I'm bushing a kickstart idler gear to fit a cr80 transmission in an xr100.
20210310_195632.jpg
 
Though those of you with an old lathe and worn out half nuts might find this useful. I sure did! New half nuts are about $250 from Logan, repaired half nuts are $125 on eBay. I saw a post on one of the home shop machinists forum about making them from Acetal plastic by heating up a piece of Acme rod and forming the Acetal around the rod. Seemed like a cool idea so I decided to try it. First I had to bore out the old worn out threads in the existing half nuts. The tricky part was figuring out how to do it with the tooling I had. So I put centers in the piece of acme rod I bought to form the threads on and then put that between centers. I then clamped the half nuts in the half nut mount I removed from the apron. There is a steel bar under the half nuts you can't see that is keeping them held tight around the acme thread. When everything fit nice I clamped the mount to the face plate, removed the acme rod and bored out the half nuts.

full


Next step was to bore out the piece of Acetal and split it, then clamp it around the Acme rod while I heated it with a Propane torch. It holds on to the Acme thread after it cools so I put it the rod back between centers to machine it to fit the old half nuts and add the flanges.

full


When everything fits well, I split the nut and put the two halves into the old half nuts. I don't have a picture but after this step I added two socket head cap screws to each half to hold it in place but honestly it fit tightly enough that it likely would have kept it secured without them but I didn't want to trust it.

full


So for a total of $35 for the Acetal rod and Acme screw I have a set of half nuts that will likely outlive me and whoever gets the lathe next.

If you google Acetal Half Nuts and dig a bit you will find the original posting and pictures by a gentleman named Evan. (hence the Evanut nickname) Hope this helps someone who was in the same position I was. I cut a thread on a piece of scrap just to try it (another first for me) and it worked perfectly.
 
The thing that gets my goat with lathes is how many guys will run them forever with the dial worm engaged till it wears out or has teeth on it that are paper thin and make guessing where the half nut engagement is a bugger
 
Thankfully I didn't have that problem.

My guess is the guy used the half nuts instead of the power feed as the apron had no oil in it, (not even oil residue-dry as a bone) and not much wear to the gears but the half nuts were razor thin. And the gears in the QC gearbox were so packed with oily wood chips it was almost impossible to change gears, some would engage and some wouldn't.
 
Though those of you with an old lathe and worn out half nuts might find this useful. I sure did! New half nuts are about $250 from Logan, repaired half nuts are $125 on eBay. I saw a post on one of the home shop machinists forum about making them from Acetal plastic by heating up a piece of Acme rod and forming the Acetal around the rod.
<snip>
Next step was to bore out the piece of Acetal and split it, then clamp it around the Acme rod while I heated it with a Propane torch. It holds on to the Acme thread after it cools so I put it the rod back between centers to machine it to fit the old half nuts and add the flanges.
<snip>
If you google Acetal Half Nuts and dig a bit you will find the original posting and pictures by a gentleman named Evan. (hence the Evanut nickname) Hope this helps someone who was in the same position I was. I cut a thread on a piece of scrap just to try it (another first for me) and it worked perfectly.

An interesting way to make a part to fix a worn out set of nuts. No comments on that last sentence!
Well as I had not heard of Acetal before I did a Google search on that and found this:

Polyoxymethylene (POM) plastic, also known as "acetal" or "polyacetal", is a polyacetal (and a polyether), and a polymer of formaldehyde. 1,1-Diethoxyethane (acetaldehyde diethyl acetal), sometimes called simply "acetal", is an important flavouring compound in distilled beverages.

That last part got me a bit by surprise!
 
It does smell weird when you're cutting it, either on the lathe or with a saw. I suppose it does smell a little like formaldehyde so what you say makes sense, however I draw the line at tasting it. It cuts super nice though.
 
Commonly referred to as Delrin, generally found in either off white or black. A pretty stable and easily machinable plastic. I've worked with it a lot. More firm than Nylon and not abrasive to tools like garolite/glass laminate or phenolic.
Makes great bushings/plane bearings
 
Last edited:
Hi RC4MAN.
back 'ome (1950s UK) they wouldn't let an apprentice into the design office until he'd worked 3 years on the shop floor.
Alas no such rigor in Canada. Had a new start (1st job after drafting school) draw up a radioactive materials tote bucket.
( 1 gallon s/st can with 1/2" thick lead lining)
His design had a 10 gage wire carrying handle.
"What's that thing weigh ? HTF you gonna pick it up?
"I did the stress analysis. that handle's good for it"
"without it cutting your fingers off?"
"Oh."

There are Many Aspects in that Approach ..mid 70 ies
After Military service and after 6 Months short job in a Sheet Metal Shop
I got a job working at construction sites installing Air condition..
Much better pay and more interesting work .
In those days it was not so Safety secured and a dangerous place.
Could fall down and I did without getting hurt landing soft
And the 2 people I worked with more senior was one Magician and one Genius
The Magician could weld 1 mm sheet metal with an 3 mm stick
The genius could remember measurements and read drawings perfect..
None of them had much formal schooling .
The Magician told me " First year you keep Your mouth shut and do as You are told "
I doubt that is possible today.
But I did not mind ... coming out of the Military service. Used to taking orders
The salary was .. performance based ..more installed under shorter time.
And the paycheck was bigger.
And I quickly realized working with a Genius and a Magician ---Whats wrong with that
Work less for Higher pay They were smart enough to organize and plan .. and perform ..They were not difficult to work with
But besides the skills learned about the Profession one also learns to cooperate with the people at the floor
so to speak . Talk The talk
I makes cooperation simpler .. Further on .. I changed work but i Have always had use for that.
I Learned there then.
 

Attachments

  • 1003969A.jpg
    1003969A.jpg
    17.4 KB · Views: 78
Nothing better than learning from talented people. Did my apprenticeship with a company that made medical equipment, kidney dialysis machines and blood centrifuges. All materials were stainless, aluminum or plastics and tolerances were close. My mentor there was an expat brit tool and jig maker. His parents had been "in service" in England, his father was butler for a lord and mother the head housekeeper. High enough they had a cottage on the grounds to live in.
Wasn't his cup of tea so he went into the mechanical fields, did millwright work machining bases for gun turrets and somehow ended up in the states.
This was in Laurel MD and a huge horse racing town, one of the 3 state approved horse tracks and a trotters track which ran at different times of the year.
His father had taken him to Ascot as a child and taught him to study and bet the horses. There was one of the machinists that was a bookie and people from all over the plant would stroll through the shop and drop bets in the top of his tool box all day.
While the horse track was in season, at quitting time, 3;00 pm people would bolt for the track to catch the last few races of the day. MD split the years horse events between 3 tracks in the state, Pimlico where the Preakness is run, Upper Marlboro and Laurel, 4 months each.
 
Last edited:
Back
Top