Machining Nylon

If you can afford it, how about a reamer lubricated with mineral oil?

Maybe somewhere in the production budget but this is a prototype budget.

any other thoughts? cylinder hone of sort but i would think something other than the typical abrasive.

Two strikes against you. Nylon and MoS₂ means nothing will grind it.

Maybe, and this is a big maybe, you could draw a heated rod of the proper dia. throught the ID and melt the grooves flat. It is a thermoplastic.

Is the finish really too rough, or are you just trying to get the best possible performance?

This is a head scratcher.

Really, just best performance possible. It will pretty dang smooth when the boring bar is finished. I just haven't been that next step with this material.

Grinding is out. A cylinder hone,.... conversation with my mechanic buddy and he said... a flex hone is how he finishes his and they are available to 320 grit. they are steel cylinders, of course but being that the hone is cutting with little sharpies, i think it would work well. *pass or fail on the logic test*

Mineral oil sounds good.

For the cost involved, I'd say give it a go.

Where is everybody else?

How about some more brains here.

Where is everybody else?

I hafta work a little!

I was thinking in reverse. Would it be possible / feasible, rather than smooth down the machining marks (making the bore larger)... fill them in? Smear some fill compound around one end, and push thru a rod with an O-ring to wipe... this assumes bore goes thru. Also assumes a suitable fill can be found; foodsafe, withstand hot water, cures with smooth skin, adhere to base material... many things to consider.

???

As I preview this suggestion, I am not too sure. Coefficients of expansion of base and coating, resistant to whatever you find in water (including 'Green Grits'), age decay of coating, consequence of failure... there are probably too many obstacles. I believe it is constructable on prototype basis, but not too sure if it would be long-lasting.

Well, think it over, just a thought...

"I hafta work a little!" Me too.

Not to speak for the OP, but he's using Nylon filled with moly disulfide, so there's no active surface to bond to and what's not nylon is lubricant.

I believe the "as machined" surface will be fine, if the feed rate is slow.

Cheers.

Where is every body else? Currently in Torrance California getting ready to give a presentation on regulatory changes for the Machining Industry at Mazak Distributor tomorrow. For best results on machining rubber, we would freeze it and then machine it cold. I'd bet dollars to donuts that this would also be the case with nylon, as the cold would eliminate the ductility of the chip. Been up since 5am eastern, its damn near a day for me out here PS not all gurus are shameless panderers for Good answers, despite what the good answer value is Some of us are just shameless...<giggle>

milo

Damn.....Milo on the Mark .........again!........freeze it is what I do! Preferably with Co2 or liquid nitrogen. 20' relief angle, negative rake on the cutting tool (HS steel), slow feed.

ps ...Measure while still at room temp. and compensate during machining. Will shrink approx .010" @-90'F.

I agree, "what's the matter with the first time"

Got it!

STOLISMA

Good to have you with us. I have given up to make sense of this site but have found that it is not addiction but magnetism of some kind that attracts me to here. It could be that I am in a state of denial.

I needed a thread on a 20mm nylon rod one day and the only way it could be done was to freeze it. I can confirm that increasing brittleness should help. It worked like a charm in this instance.

Is there a specific reason you use Nylon? Sorry, you might have mentioned it and I didn't pick it up. There are far better materials, with other wise similar characteristics, which would be a joy to work with.

If you could use perspex, or any of its variations, you could end up with a highly polished surface by carefully flaming the piece with a torch. Again, why nylon?

Coming to think of it why don't you make a test and try the torch on nylon. I have never tried it but if I had some laying around I would give it a go and see for my self. The idea is to slightly liquefy the surface. Like I said, speculation is taking over.

Good luck with it all, Ky.

Nylon was what i had seen being used. we do what we see work.

I am not familiar with perspex, torlon, peek or any of the others mentioned but they're on my list to check out.

this is second prototype that would involve the nylon, torlon, peek cylinder. the first is going to be in acrylic tube for demo purpose.

I will check into these others before buying that particular stuff. now, i have nylatron gsm for the endcaps, cause its black and i like that for an endcap. the tube is clear and the piston is uhmw cause it's white and i like that for a piston. spring is steel by the way. yes, color played the major decider for these.

I would be afraid of flaming a bore. i have flamed acrylic and some others. when that surface liquifies, it distorts. like the hot rod method mentioned early on, dont know that i could pull that off successfully.

imagine mounting the ole jewelers torch to the toolpost and getting the temp and feed rate figured out so that you didnt end up with one single bubble in your cylinder wall.

nope, i'm not that talented.

my machines and i have an understanding, we dont ask anything out of each other that we're not capable of!

STOLISMA,

I know UHMW as an abrasion resistant poly-ethylene (not too good but better than the ordinary).

Polyethylene (PE) has nearly zero moisture absorption.

RHABE

UHMWPE has excellent impact resistance at cryogenic temperatures and high abrasion resistance.

Known here as Saxon New-Lite and Simona.

Obviously out to lunch, it is only 3.45

I hope they buy off on this faucet idea...

What other folks/threads are good to watch on here. there is so much, it's a little overwhelming. My name is Shea, by the way, handshake.

Hi Shea,

I'm not sure, exactly, how I got here myself, the first time. I think Vader sent me interstellar, subliminal messages to come here and ask a dumb question.

I'm Lyn and you just have to decide what interests you. Flip through the FAQ's if you haven't already.

We have a cat, squirrel, gremlin, intergalactic war lord, and many other colorful characters who just happen to also be very intelligent minds and scholars.

Terms, such as Guru, are given far too much importance by some. Others have even been known to shamelessly solicit GA's, but that's another matter.^{_{(Cat's fur stands up, back arches)}}. If you stay around long enough, this will all make sense to you.

You may have noticed that participants are sprinkled all over the world and bring diverse languages and cultures to the forum.

You seem to be a tinkerer and craftsman and aspiring bridge owner. (Hows the snow maker going?)

You'll find that this can be addictive.

Welcome!

Lyn,

Glad to finally be here. I have been searching for it for about three years. My previously mentioned mechanic buddy has a bmw tech group that he belongs to and uses frequently for just this type of 'hey, who knows what i need to'. this is the first one that i have found that has any participants that know what they are talking about. I'm sure that I'll be able to phrase a question better than "I need a bridge" in the future.

I figured out facebook, i think... so this ought to be a piece of cake.

The snow was a learning experience for the next one.

That's the quicky that i drew for a buddy of mine. saw it on a link from here. It's the pro version. would be relatively simple to construct. I told my bud that we can build this and then when the weather permits, put the signs up around town -'CALL THE SNOWMAN, WE MAKE HOUSE CALLS!". $100 bucks an hour. mount this on the truck, pull a water tank behind and go mobile.

Yes, I am addicted to yet another... at least this one isnt unhealthy!

Too many variables to consider. I think it comes down to patience with the process.

Good thought train though. like the hot rod method suggested earlier. cool idea but dont know that i could pull that off.

like I said, I'm just shooting for the best that I can get. What ever falls off the table is chalked up to experience. I work by myself and dont get many 'let me run this by ya' conversations.

Keep steering toward north and eventually you'll get close enough for a short walk.

Let me introduce you to the reply button. It's down there in the lower right corner by the report button.

If you hit that, your reply goes directly to that person, as well as everybody else.

Maybe you already know that.

I have to go.

Later.

Noted, but what's the dif if it goes to everybody else as well. I'll watch how its' applied.

you better quit checkin here if you have to work... It's a dic tive...

The best is to buy the right sized tube...the factory finish is usually great...but if you must the burnish it

I'd grind the boring bar to be very rounded (in top view) at the cutting tip, and leave it at that. The tip could span two or three times the feed per revolution, cutting off high spots as it goes. So finished, I doubt that any typical seal (lip seal, o-ring) would leak air.

I'd endorse this reply, use a good rad on the tool tip, if you are using tip tools can you use one with a circular tip?

Hi,

buy a tool with a long nose-radius made from natural diamond,

use a near perfect machine (Professional Instruments, Hembrug, Hardinge),

and you will get the best possible result.

2 Problems remaining:

Nylon is very flexible, so distortion is very likely by small forces.

Nylon will dissolve large amounts of water, so change dimensions.

If Nylon is necessary, then allow for a metallic outer cylindrical part and press fit the Nylon into it and then machine to dimensions.

Else try POM or the many other better materials.

What about TORLON or PEEK, reinforced or not, lubricating particles inside?

What about glass or mica reinforced Teflon?

RHABE

Lets say I am giving up a trade secret here...but what else are secrets fore.

We, depending on the size, drop the parts in liquid Nitrogen for a tad...then either machine or polish. We have been able to produce finishes within a couple of microns.

Thats the best I can do...just experiment a little...it's easer than you would think.

Cold is good, unless your wearing shorts.

Good Luck!

EXCELLENT ON THE LIQUID NITROGEN AND THE FREEZE.

That would certainly harden it up. Will that change its' physical properties when thawed?

ALSO, EXCELLENT ON THE LARGE RADIUS. I probably would have chosen the larger when i went to pick cutters.

Not familiar with POM, TORLON and PEEK. I will check into those.

Rhabe, explain nylon dissolving water and changing dimension. I am unaware of this.

Dont take this the wrong way but I think I am falling in love. Finally, a place to ask the burning questions and get real answers! My wife doesnt seem to understand my infatuation with the conference room.

Thanks guys, I look forward to ....

Perhaps the better word to have used would have been "absorb" water. Weigh some pieces, dry them in an oven for a couple of hours , then weigh them again and if your scale(balance) has suffficient resolution you will note the difference. That is water driven off. I haven't used the liquid nitrogen method we just put in regular freezer (say -10 F) or our lab freezer (- 30 F ) Since we're being semantically careful, are you asking about physical properties,(conductivity specific heat, etc) or mechanical properties- tensile strength, Yield strength, %elongation, hardness etc. I believe someplace earlier someone mentioned moly disulfide, I don't know what will happen to that at cryogenic (liquid nitrogen) temps. Glad you are enjoying CR4 milo

I will certainly try that, and yes, i do have a scale that is capable, i think.

So, that to say, it will swell slightly? I will have sufficient clearance between cylinder and piston, so if it were to swell, I would be increasing the seal factor of the lip seal? If that's the case, I can live with that!

I cant see that I would have any deleterious effect from property changes in this application, but yes, my question was will freezing change the physical properties in an adverse way. Ultimately, there are not forces on this that would cause failure with sufficient wall thickness right? I think I will stick with the freezer instead of the liquid nitrogen.

After machining smooth bore with abrasives the use a nylon stocking wrapped on a dowel to burnish the bore.

Most critical is the dimension of the o-ring groove in producing the extruded lip seal.

Here you will find examples of tube stock

I'll be sure to have a 'nylon' on hand whilst machining.. watch that lead screw!

I'll ask when i get teh u cups for the seal but what kind of fit would be ideal? I would think compressing half of the angle of the lip??

You don't mention the diameter or depth of the hole you're dealing with or how critical the bore diameter or straightness is, but...

A light touch with 600 grit metal paper quickly does wonders for finishing nylon, though it clogs the paper quickly. If the bore is deep, double back tape it to a wooden dowel. Very quick and simple on a lathe.

Freezing it seems to me to be a bit of overkill.

Hooker

You shoulsd try machining with the sharpest round nosed cutting tool and continuosly apply a cold water/oil soloution to the tool.

What type of oil? Mineral was mentioned..

Yeah, freezing might be overkill but I feel like it would add to not take away from. might even learn something new

I think we are obsessing over smoothness without knowing if it is important or not.

I say if it looks like the grooves in a phonograph record, it's smooth enough.

_{Those of you who don't know what a phonograph record looks like can find a picture of one on the web}.

I also think there are too many favorite material recommendations here from some.

If Shea likes Nylon (it should be capitalized) and it has worked in similar applications let him go with it.

Cheers.

Agreed.

I did want to see how far it went before somebody called the ref on it.

I'll keep yall posted.

I'm also sure that I'll have another hair brain idea soon that I have forgotten about!

Still listen to the LP's now and then but mp3 w/rhapsody makes it tough. spun the jackson 5 just the other night!

freeze it for a couple of hours in a conventional freezer , you need to make sure its core temp is as close to the out side temp as possible, freezing it will make its crystal structure larger and a little more brittle but manageable

Nylon is not a crystal. It will not expand when frozen, but the advice here about homogeneous temperature through section is excellent.

it gets awful hot inside a machining center, and with the temperature change you are dealing with dimensional stability issues...........ie what your turn too oh say 6.375" diameter after its been out of the hot booth from the machining center and gets cooled down it may be 6.282" diameter final diameter

good point phoenix.

i think that i will machine at room temp and leave a few thou for the flex hone. that ought to be a pretty good finish.

Hello STOLISMA, Here a couple of idea. If your cylinder is not too long or the id's not too small.

It is a hand scraper there are several type. What I had in mind is whats called three corner scraper and a curved scraper. They are usually used for deburring holes and internal surface of bush bearings.

Also some woodworking methods like hollow form turning may apply if your cylinder is large enough.

These were just some ideas that may give you a smoother finish. If the larger radius cutter with small steps for overlap like has been suggested, leaves the finish not as smooth as you need.

Charles

Thanks Charles.

I think the large radius/small feed is going to give a good enough surface. Talking to my seal provider, he said that will be ideal surface!

I have a scraper but I would see the chatter being the issue. Basically doing the same as a large radius cutter??

shea