Kwok - I was worried the nuts would be hard to get out also, but they were no problem at all. I just removed the 3 screws and used the old shaft to wiggle the nut a little and out they came. The super-glue just has a hard time holding onto that steel. I "forgot" to take any photos (mostly out of shame), because my ZBNs are big and bulky, made from 1 1/2" X 2" pieces of 3/4" thick HDPE that I sawed to that size. The one on Z is still thin enough that it fits under the "shelf" where the flange-nut was originally installed, with about 1/2" clearance above the top of the flexible shaft coupler. I wanted to install it that way so the ZBN is holding the weight of Z up, not the threads on the little screws.
The 3-foot length is definitely enough to make both the Y and Z shafts, with enough left over to make the tap from the remaining 2 3/4". I'll get a photo of the tap and post it, tomorrow - - it's bed-time here (midnight).
btw, with the remainder of the sheet of HDPE I bought, I replaced that ugly wooden cutting board my wife was using with a custom HDPE one, so she's happy also. It's very nice, very easy to clean and she will never wear it out.

 

In an other thread dbtoutfit says he is not using HDPE for his ZBN. He says not enough lubrication, I thinks, but didn't say what he makes them out.

Happy New Year to all

Yoram

 

I thought at first Dorsal had some HDPE left over from his PP Mod where he used the HDPE to thicken the table, so I suggested he try the HDPE.

HDPE is what I have made the originals out of but over the years I have changed the chemical compounds.

HDPE will make nice nuts and will feel just like and acts just like my ZBN's but I could not stand behind them to the extent I do with these.
Also threading it very important. I use custom machined taps just for this.

I have a lot of time and research, failures, loss of hair etc trying to get these to be near perfect. lol

Eric

P.S. the plastic is not a secret but I could not begin to tell you what the compounds are. I do hold a patent on it though.

 

I told Kwok I'd post photos of the tap I made from the remnant of 3/8-12 rod, so here they are. The tap is only 2 11/16" (68mm) long, and the lead taper is less than 2 turns. I believe I used a 5/16 (.3125) dia. tap drill even though the calculation says it should be 0.304 - 0.310" diameter - the minor diameter was too tight after tapping the first one, so I went to 5/16" and it was good.
I bought the two jam-nuts when I bought the shaft (same place) and they are very handy for getting the tap through the material the first time with a wrench. Then I removed the nuts, chucked the tap into my reversible drill motor and ran it a couple more times at full speed, until the threads were clean and free. Attached files

 

Dorsal,

Thanks, for the tap tut. But how do you cut lengthwise, like that, with a hack saw? I have trouble getting the hack saw to catch, even when cutting across the diameter. It bounces all over the place; and I usually end up having to pull it backwards, to get it started. Sometimes when it goes bad, there are nicks all over the place.

-Kwok

 

Well, first I clamped the tap horizontally in a vise - gently. Then I put a 32 tpi blade in the saw. Then I just held my finger alongside the blade and drew the blade backwards a few times to get a notch started. I had to keep my finger there while I sawed the notches, because the saw will bounce like crazy if you give it half a chance - don't force the blade down, just let it do the work. It took 40 - 50 strokes for each "slot".

 

By the way, I first sawed the longest piece (for the Y-axis) off of the 3-foot piece, then measured and MARKED the length for the Z-axis shaft, but didn't cut it off. Then I made the "tap" on the remnant end of this (approx. 10" long) piece of shaft. I find it a lot easier to hold, file, shape and use a tap that is longer, and much easier to know when it's perpendicular.
It was only after I had tapped the 2 pieces of HDPE that I actually cut the "tap" end off.

 

Thanks. Will give it a try. I still not 100% sure, if I will initially go with the acme. That's because I already have all the stuff (bearings and cheap nuts) and 5/16" all thread, I was intending to use. Will have to think on it. But regardless, I need a new nut, so will definitely make a tap. I did some careful measurement and my nut is 1/16" low (would have been 1/8" low, if I was using the original pex pipe). I took some pictures of an easy way to measure this. Will post it soon, when I get a chance to start a build log thread. And I like what you posted about HDPE. Planning to just get a $5 cutting board from the supermarket for material.

-Kwok

 

Getting a $5 cutting board is what I was planning to do also Kwok, but when I remembered that nasty thing my wife was using for a cutting board I just had to get the 3/4" sheet and replace it. The original cutting board was built into the kitchen cupboards, so the size and thickness were already established, if I was going to "replace" it.
Your 5/16 allthread should work great - especially since that's what you already have!
Making your own HDPE nuts will make a world of difference, once you get everything aligned properly. Remember, your allthread is 125% the size of the original, so it will be 1.953125% (almost twice) as stiff. Alignments will be twice as critical as before.
It will be sweet!

 

You know, I bet those ($4 ?) acme nut, you bought, can be made from the standard 3/8"x16 nuts. Just fill them with solder or jb weld and retapp them. If done right, you would need 4 nuts per axis. So that's instead of $32 for nuts.

Darn, that ebay seller is out of the 6' rod; so even if I want some, I can't get any. 3' is probably too short. Won't give me th option of using bearings. Hope he going to restock.

-Kwok

 

I would advise against using JB weld as the all thread will cut it up very quickly.
As far as the solder, tin is very soft, wears quickly, would cause binding much like aluminum does but at a much easier rate and most of all you would need a propane torch to heat the nut up to the degree that solder would begin to flow.

I may have missed the type acme nut being used here in this convo' but I would suspect its made of Actel/Delrin which is something solder will not bond to and has a melting temp of about 200 deg (depending on the compound).

Also taping solder is about 2-3 times worse than taping aluminum due to it's softness with any tap, and to do this with anything but a machined tap such as the all thread it self would be a disaster .

But then again I saw a real jet on youtube fly and land with one wing blown completly off (true).

Eric

 

Yea it's made of delrin.

Eric

 

dbtoutfit,

You misunderstand completely. I am not talking about a drive nut. And it's not all thread, as the mod is to convert an all thread nut to acme. But even if it was all thread, people use jb weld, all the time, to fix stipped threads. What I was referring to is a regular metal nut, but with acme threads. Since it's stationary, it doesn't wear. You can see two of them in Dorsal's tap pictures. And it's not like a propane torch is a rare item. I have one, but my first choice would be my soldering gun.

I am pretty confident, with plenty of ideas on different way to do this. You can even mold the threads.

-Kwok

 

Ya I am total lost as to what the nut is being used for now.

Eric

 

The two nuts in my photo of the 3/8-12 Acme tap are only being used as jamnuts to turn the tap now. I got them in case I conjured a way to hold them for use as drive nuts for Y and Z, but I still wasn't happy with the metal/metal setup anyway. That's why I bought the 3/4" sheet of HDPE and eventually tapped / made the 2 Acme drive nuts I now have installed. Eric was adamant that my Delrin material would be very disappointing to use.

 

Gotcha ya, just need some way to be able to grasp the all thread. I see what you guys mean now with the nuts.

About Delrin, it's great and all. It's used all the time but it wears even on acme threads and even more so on all thread from what I have seen. Along with other things I have already mentioned. I honestly cannot tell you way it is used so much for backlash or driver nuts.

The only thing I can think of is due to the fact it's considered the filler between metal and plastic.
And the fact it has been preached to be the commonly used plastic along with metal. It's abrasion resistance is up there but it lacks other things. I have all kinds of Delrin, it has it's place but I just don’t think it holds a candle to other plastics for this type application from my experience.

Eric

 

FYI: Most all (if not all) cutting boards are made from LDPE not HDPE.
If you buy a cutting board and it's flexes or when your machining it, it gums up, it's LDPE also there are many other forms of cheap plastics used for cutting board.

HDPE is hard = chips, when milled/cut
LDPE is soft = gummy/flimsy and tend to throw small balls or semi melted chunks when milled/cut as well as the material wrapping around your end mill while it's being cut.

Unless you throw down a big chunk of change for a cutting board and given it's very hard and not very flexible even a 1/4 thick it's more than likely LDPE or something else. LDPE is cheaper in price.

Eric

 

$89 for a 12" X 48" x 3/4" piece didn't seem cheap, and I'd hoped that TAP Plastics knew which material they were selling me. Should I worry?

 

umm no, lol Tap plastic "cutting board" is HDPE and they should state it they also should sell LPDE cutting board just gotg to make sure you get the right thing. I'm talking more the lines of going to walmart and grabbing a chopping/cutting board, most time they are textured. these are not what you want to use.

I don't want ppl to think they can just grab a cheap cutting board and make one thats gona stand up and that they understood your "cutting board" is HDPE Not from Wally Word

Eric

 

You just saved my bacon, Eric. I have some 3/4 cutting board and was going to make the nuts out of it. Now I know it's LDPE. Darn it!!!

Yoram