delrin on delrin any good or bad idea?

[jack404]

Hi folks

i'm making a machine filer , not a model but will definatley help with making them

i was going to use a lineal bearing for the main bearing but i am now thinking about all this delrin i have here

the action of a filer is up and down often and fast, do you think delrin would handle this ok?

in the drawing below, the yellow is the delrin surround ( bearing) and the orange is also delrin ( shaft )
as is the blue swarf guard to prevent swarf or metal filings getting into the bearing section

think this would work?? the blue and orange sections would be going up and down between 1500 and 4000 times minute and have a travel length of about 10 mm ( 3/8")

i think it would be ok if i greased it ok but i aint a materials expert ( in fact i just dont know )

cheers

jack

 

[rodbuilder]

The problem you might run into it the heat generated from the friction, I do not know how much heat will develop. What kind of tolerance are you looking at for shaft and bearing.

As far as plastics go take a look at Rulon its a modified PTFE and has a low coefficient of friction. I have heard of it referred to as the greased plastic.

 

[greenie]

Hi Jack, just my five cents worth on this subject (cost of inflation here in Australia, thanks to the septics and the sub prime crap).

Might need to do a re-think on using Delrin in that particular application, think what the file is going to remove and just what they are going to do to that bit of plastic. You might make it with a couple of thou tolerance, use it a few times and you gunna have something like 20 thou tolerance.
Possibly an OFF THE SHELF bronze bush with a fibre washer on the top to clean away any gritty bits would be more appropriate, you could even add an oiler to the bush as well. By using an off the shelf bush, if it ever wears, just go get another.

regards greenie

 

[jack404]

Greenie

yeah but theres a steel ( maybe 2011 Alu ) holder to be mounted in the top to hold the file and the file its self will be only 2 " plus tang ( maybe 1/2") but you maybe right i've not used delrin for this fast a action or one that will repeat so often.

as for the other line

that a bit outta place mate

the fact is a very few greedy slime did some shonky business and yes its screwed us here big time but the worst is gonna hit in the US and to folks who had nuthin to do with that at all but they'll pay the most.
the SHTF just has been delayed there for a while

and again its not the whole of the US but a very few ( a handfull) of cowboys who thought thier person profit was more important than honesty and we have a few here as well ( we have 3 in parliment now!! and we voted em in!!) theres low lives everywhere mate no race or creed or religous restraints on being scum

eh

cheers

jack

 

[Maryak]

Hey Greenie,

This is an INTERNATIONAL forum about Model Engines

Not a place to use derogatory comments or blame one particular nation or ethic group for the worlds problems.

The forum, in the main exists, due to the hard work and efforts of the very people you've put down.

Please confine yourself to the topic being discussed.

Thanking you
Bob :-[ :-[ :-[

 

[tel]

Back to our regular broadcast ....

I agree with the consensus here Jack, I think the side load imposed by the machine would give you problems - far better stick to a metal to metal arrangement

 

[CrewCab]

I'm a bit lost on Aussie politics to be fair .......... OK read that as "completely lost" ............ but Bob's dead right ...... there are plenty of forums to express your opinions about world politics, this just doesn't happen to be one of them guys 8)

Lets keep it "Engineering" related at least please

Cheers Chaps ;D

CC

 

[tel]

I'm a bit lost on Aussie politics to be fair .......... OK read that as "completely lost"

CC

So are we mate, so are we.

 

[CrewCab]

Thanks Tel,

I've got to say that my gut feeling is Delrin might not be up to the job, It's used on the side door roller mechanism's on my Van, and all 3 rollers needed replacing after 3 years, the Van had light use so lets assume the side door was opened 5x per day (probably much less really) ........... in 3 years that's close on 51/2k time up and down ......... your looking at that sort of use in less than 2 minutes :-[ ............ :'(

OK I know it's not model engineering related but I think the principle applies 8)


hth

CC

 

[jack404]

Cheers CC

i'll stick with the lineal bearing idea

i've some smooth actions outta delrin but its used few and far between

Guide for a keyway broach i made

1/2" DRILL ROD AND LINEAL BEARING IT SHALL BE
the LB 's are rated at 100 million repetitions minimum at the pressures i'll be using

ill save the delrin for the swarf guard under the top plate

thats not wearing surface just a deflector

and i'll use a peice of inner tube from a bike and some hose clamps as a seal on the shaft entry to ensure no filings get into the bearing

first ideas are often the best..

cheers

jack

apologies for my "educational" stance delete if its upsetting folks

 

[Stan]

My first thought was bronze or oilite bushing but if you want to go first glass use the linear bearings with the recirculating balls and seals on both ends. I have bought several on ebay at reasonable price Here is link to the type of item I am talking about.

http://cgi.ebay.com/Thomson-SPB-8-L...yZ111618QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[jack404]

cheers for that Stan

here the ones i'm bidding on now

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=230304991615

 

[greenie]

If your going to use those bearings, then make sure that the rod used with them is HARDENED, using normal drill rod in the un-hardened state, can and will pick up bits of the shaft, not too good for that type of bearing.
Paper cup making machines used those type of bearings and if you used the normal drill rod, life expectancy of the bearing was in the weeks, using hardened rod, then it was maybe a year or two.


regards greenie

 

[jack404]

Good tip

thanks mate will use the oil tempered

got some from offcuts gallore the other week

its rated 68 Rc ( 70 on my test unit but it may be over reading)

if i get a 40 mins a day for a year out of it i'll be happy to remake another in a year

i expect ( hope) 2 hours a week total use max, if i'm getting more i'm making $ or lots of models so its all good

cheers

jack

 

[Dhow Nunda wallah]

G'day Jack
these folks have pretty fair prices on linear slides and rail.

http://www.homeshopcnc.com/LinearGuide2.html

Cheers,
Lin

 

[Stan]

Jack: Nothing wrong with SKF linears but that is just a replacement insert. You will have to make the mounting block and maybe get seals.
I built an elevator for my wife's wheelchair that goes from ground level up two feet to the back door landing. It rides on four 1" Thompson blocks on standard 1" cold rolled round bar. The bearings haven't given any problem in six years but it certainly isn't high speed.

 

[BobWarfield]

And now for a dissenting view on the Delrin.

I wouldn't go Delrin on Delrin, but a Delrin bushing with a steel shaft would work great IMHO. This is being used all the time to make CNC machines that work quite well. Delrin has some nice properties in terms of a tendency to "spring back" too. What that means is when you bore the hole to size it will be slightly undersized so that it makes for a pretty precise linear bearing.

Here is one such CNC machine that uses this style of shopmade linear bearing:

http://www.cnczone.com/forums/showthread.php?t=21872

I've learned a lot from the Widgitmaster and he has become a friend. He's a retired professional machinist and his stuff works well. I have one of those little routers and its a kick to play with.

Cheers,

BW

 

[jack404]

Stan i'm going to have to mount them anyway, so thats no real issue but know what you mean
cheers eh

Cheers

Bob sorry mate but i'm banned from CNCZone one of the clowns there is from a gun forum
I was a member on until i bought some stuff and never got it, sadly the dramas followed me for months
Practical Machinists site as well as some others

its was easier to get me banned than to pay up or apologuise until the law grabbed the low life and i finally got my money back ( a tad over $6000 USD less legal and police and court costs in Tiawan)
but CNCZone values paying advertisers and vendors ( even rip off dealers) way more than members
so i'm banned for getting my money back ,

the quote was " how dare you get the police on to Sunny ( the rip of guy), dont you know how much he pays us a month?" my reply was "no and i dont care" ... BANNED but hey, thats income driven sites for ya

but thanks for the link and Info

cheers

jack