[Mr.Ed]

Hi guys,

In my first machine i used 12mm threaded iron rod for transporting the gantry. The nut is made of a copper-zink alloy (Messing, dont know the English word).

It works, i compensated backlash by means of two springloaded nuts, no fancy stuff. But it's no ballscrew.

So i started thinking of using Teflon. Dont know the English word either, but it's the stuff used in cooking pans. (duh... )

Anyway, did anybody recently try this with teflon? It's tough, it's wear and heat resistant and it slides like...well, more like a ballscrew than copper-zink does.

Being tough, it might be hard to drill accurately, and tap 12mm thread into the hole.

Anybody want to share thoughts about this? A beer for the first reply! :cheers:

Thanks,

Ed.

[duluthboat]

I could use a pint.

Teflon is very easy to machine, it requires very sharp tools and several clean up passes to get tight tolerances. I think it would make a backlash free nut, but I’m not sure how strong it is and it suffers from contamination. What I have been thinking about is to put Teflon inserts into a standaed nut that could be tightened and replaced.

Gary

[Chagrin]

Teflon works, but I think Acetal/Delrin is better. Acetal has a slightly lower coefficient of thermal expansion (nobody likes it when their nuts tighten up from the heat, right?) and is just easier to machine.

[Mr.Ed]

Right from the start, when i began building my machine, i had difficulties in getting the right materials. So Delrin / Acetal... pooh.. I dont know about that, though i take your word for it that it is better than Teflon.

Another hobby of mine has to do with Radiotransmitters and all that. Teflon is relatively easy to come by when you're in High Frequency stuff. I could get kilos if i wanted to.

That, sofar, has been the greatest challenge when building a machine in Europe. Just where to get your materials. Shure, there must be resources, we're no dummies. Sofar most of my stuff comes from Ebay, US. Add taxes and postage and you see my problem(s).

Anyway, Duluthboat, CHEERS ! :cheers:
I see some strong points in your comments. keep them coming !

Ed.

[BigDaddyG]

Hello All,
Don't forget the casting Polymers! Take a small peice of thread and a tube, and cast a perfect anti-backlash nut! With todays technologies this stuff is avialable all over the place and cheap. Take some care with the set-ups. I have been machining threads on tubing (or you can use any mounting configuration like all the common anti-backlash nuts out there), machine a small plug for one end (which can be used over) and pour the casing full of Plastic! You get a perfect nut, with Metal outside and your ready to go! One quart of casting compound will last for a very long time and make many nuts, and drive others nuts trying to figure out how you did that (Take if from me, I know)!Cheap, long lasting and you will impress your friends!!!!!!
Good Luck All,
Glen

[ESjaavik]

One problem with Teflon(Tm) or PTFE is that it's not holding a shape. I have a 2m long rod of 25mm PTFE. I had it lying on top of some other things, and when I needed it the rod was far from straight. It had followed gravity and taken that shape. The fix was to put it into a straight tube, and after a while it was straight again.
I believe the polymer casting idea. It shrinks appx. 0,1mm when cast in 3mm thickness. Hopefully that will not tighten it around your rod but rather create the needed room for lubricant. Remember the release agent on your threads.

[DareBee]

Teflon has an extremely poor tensile strength rating. Definately would not be my choice.
If you want to use thermoplastic I suggest Nylon 6/6 or Delrin.
You can actually purchase Nylon hex nuts from fastener suppliers here.

[RotarySMP]

Hi Ed,

I used Moly disulphide impregnated nylon "Nylotron" nuts from www.maedler.de for my Z axis leadscrew nuts.

[Mr.Ed]

Thanks Rotary,

I started looking through the products that they have and it looks promising. The case is, i'm allso looking for Schneckenräder . Unfortunately, they don't go higher than 150 teeth. I would need something like 320 or so... :tired:

Anyway, thanks for your contribution. I'll be looking into it...

Thanks,

Ed.

[RotarySMP]

Hi Ed,

Here is a write up on making your own worm gears.

Why 320:1?

Mark

[RotarySMP]

Oops, here it is...

http://bedair.org/Worm/Worm.html

Mark

[Mr.Ed]

That's it !

It's meant for my Telescope, you guessed it !

The example is for 200 teeth. I mentioned 320 teeth. Both are fine i guess. There seems to be a standard rule of thumb stating that the diameter of the Wormwheel should be about the same size as the diameter of your Telescope's tube.

My Telescope is 200mm across, and i would like to make or buy me a Wormwheel of 200mm in diameter. That would come to something like 200 up to 350 teeth, depending on teeth distance.

This is only the second site that i encountered ever, that explains making your own Wormwheel. Amazing !

Something tells me that you know more about the subject!

Start talking, you got my attention now ! :banana:

Ed.

[RotarySMP]

Hi Ed,

Sorry, that is not my site (it's Steve Bedair who hangs out on the 9x20lathe Yahoo group sif you want more info.

http://groups.yahoo.com/group/9x20Lathe/

I am interested in making a worm gear for my 7x12 spindle so I can do dividing with a powered spindle on the cross slide. Not a really high priority, so it isn't really moving up my to do list.

[Woodie1]

BigDaddyG says to use Polymers. Wich one? There are many!

[chuckknigh]

It's not hard. Heck, my first experiment with making a gear was done by hobbing it with a homemade hob, hand filed from a "lag bolt." Amazing what you can do with a Dremel tool and a chain saw file.

It's not hard. Basically, you need a blank of the right diameter, and a cutting tool which is, ideally, self feeding. IOW, a screw. ACME thread works quite well.

Steve added a layer of complexity -- he uses a dovetail router bit to make "slits" in the blank, which then act to index the cutter -- the cutter, he produces with 1/2" ACME rod from ENCO. Seems to work quite well, for him.

Then, you drive the cutter (worm) and let it cut into the wheel.

After it's hogged out most of the material, just apply a lapping compound, and let the hob produce a nicely finished wheel. It's not hard...just a little bit time consuming.

-- Chuck Knight

[Mr.Ed]

My biggest concerns are these.
You have to take into acount that though i own a lathe, i am not doing magic with it. So making a blank would be a challenge on its own. But i think i would manage to make one. Bronze or Messing (Copper-Zink) would be ideal but it's quite expensive. Aluminium is easy to come by, but softer and does not have the same caracteristics as with bronze. But anway...that's one.

Secondly i worry that i will not be able to make one ongoing thread on the worm wheel. If diameter and cutting depth are not correct, then after one turn of the worm wheel, the second time it will go round, it will eat the first thread that was cut. Know what i mean? I do want a continuous thread being cut so that theoretically the telescope would be able to run enlessly without jamming on fallsely cut thread. I do not own a devider head, and they cost about a fortune overhere. So cutting the first "slots" in the right amount of teeth is virtually impossible for me. Again taking into acount that metalworking is not my occupation, though i do know how to improvise.

Finally, how slow would the lathe have to rotate to cut without destroying the worm wheel? I dont know if my lathe will do turns that slow.

Ed.

[ger21]

BigDaddyG says to use Polymers. Wich one? There are many!

Usually Moglice. McMaster-Carr has a polymer filled epoxy, which is probably the same thing, but it's pretty expensive.

[High Seas]

Usually Moglice.

Any On-Line source I can order from? Looking to try it out - but no one in my area stocks it - and an on-line order can be placed today!
Cheers - Jim

[chuckknigh]

Looking into casting polymers a while back, I discovered that J.B.Weld has very similar properties to Moglice, and is a fraction of the price. Don't know if it'd work as well, but at a few dollars for a tube, it won't cost much to experiment.

http://www.jbweld.com

-- Chuck Knight

[High Seas]

Ya Chuck
I've used JB Weld to fix a few bits in remote places - did a Thermostat (waterneck) on a diesel in wayoutback Mexico in 1996 - and its still running today! No leaks - but got a real spare now too!
JB Weld doesn't have the slippreyness (wot kinda word is that?) I'm looking for - kinda like that slide stuff you found!
Thanks though - Jim