I still haven't been able to access my buddies wood shop but I have now priced the MDF for this project ($46 CDN incl. taxes) and in the mean time I have been busy making some parts that I can work on here. The first project was a set of three self-adjusting AB nuts. I decided to go with this design rather than a split type with adjustment screw as I had some round nylon bar available plus it gave me a chance to play with another toy of mine.
I have a Unimat SL/DB200 table top lathe/mill (early 70's vintage) and I was just about on it's limits in terms of size with these parts. 1.5" is about the maximum diameter you can hold in the chuck (with the jaws reversed) and the stock nylon bar was 1.5" diameter. Unfortunately the torque at that diameter meant I could only take 10 thou cuts otherwise the belts would slip so it took a long time and lots of winding those tiny handles to turn these parts but it was interesting and gave me a sense of achievement when it was done.
The slots were cut with the Unimat in mill mode using a .120" burr from my Dremel. I could only take small cuts again as I didn't want to break the only suitable cutter I had plus it tended to flex on the male part if the cut was too large.
The springs I found in the local hardware store and have a free length of 1.5" and compress to .5". They are 5/8" diameter and use .040" diameter wire. They load up nicely and have enough tension to do the job.
I made a tap out of a piece of 'all tread'. I turned a taper on one end and cut the slits with a cutting wheel in my Dremel. I also centre drilled the end so that I could support it on the lathe. With a centre in the end the tap started into the hole square and true. It worked quite well considering what it was but I may have to run it through the nylon a few more times (or open up the hole one drill size) as it is a bit 'tight' on the 'all thread' and I can see the motors having to work hard just to turn the leadscrew in the nuts.
I have attached a few photos for your viewing pleasure
. More info to follow as the project progresses. It will be next weekend before I can start on the wood so I think some handles/knobs for the motor shafts are going to be next.
Larry