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Plastics Expert.....Its arrived

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Cncpaul

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l’m looking for a some advice on a plastic that would be suitable replacement

My laser rise and fall table developed a worn threaded bearing, these are 50mm dia x 20 mm thick

They are available at £85 each plus shipping and vat, when it arrives in Ireland it attracts another 23% vat
making a grand total of 152 euro’s :shock:

I can make them on my cnc router, so l plan to machine 4 replacements and some spares, my problem is the best choice of material either Nylon, Nylon 66, and Acetal




Any advice would be greatly appreciated
 
You should be able to buy tax free for export with the appropriate invoice from the supplier, only pay VAT when it arrives in your country. Will that make it worth buying rather than making?
 
Sweet Jesus, an expensive piece of plastic!

I'd personally be making them in Phosphor Bronze if it was something that needed to last a long time without wearing other components, is it literally just a plain piece with a threaded bore and four other holes or is there something more to it than meets the eye?

Alternatively, Acetal/Delrin would work well.
 
sunnybob":28egh264 said:
You should be able to buy tax free for export with the appropriate invoice from the supplier, only pay VAT when it arrives in your country. Will that make it worth buying rather than making?
Click to expand...


Apparently not, at the moment things are up in the air here, if you buy a car in the uk and bring it to Ireland
you will pay 21% tax even on the vat you paid in the uk, you have 30 days to register and pay the tax if not they will impound the car if you are stopped by the garda.
 
Trevanion":2cix0dry said:
Sweet Jesus, an expensive piece of plastic!

I'd personally be making them in Phosphor Bronze if it was something that needed to last a long time without wearing other components, is it literally just a plain piece with a threaded bore and four other holes or is there something more to it than meets the eye?

Alternatively, Acetal/Delrin would work well.
Click to expand...

Yes, Phosphor Bronze would be the best choice but l would have to find an engineer to make those, the bearing do not sustain continual use, the rise and fall is only used when you change material thickness to focus the laser. l can machine Nylon/Acetal/Delrin, they only a 50mm dia x 20mm disc with 4 x 3mm holes and a M20 thread in the center, so nothing exotic
 
Nylon is self lubricating where as delrin (which isnt the same acetal) isnt, what is is though is highly abrasion resistant. For cost id go with nylon. For ability to machine it id go with delrin.


Tough call,if its something you dont mind swapping out and have the machines to work it, then it doeant really matter.

Looks like an aluminium head so phosphur bronze isnt suitable really,coef of friction being to similar and wear on both parts being more likely. Id rather have a plastic bearing to replace than a whole shaft.
 
novocaine said:
Nylon is self lubricating where as delrin (which isnt the same acetal) isnt, what is is though is highly abrasion resistant. For cost id go with nylon. For ability to machine it id go with delrin.


Tough call,if its something you dont mind swapping out and have the machines to work it, then it doeant really matter.

Looks like an aluminium head so phosphur bronze isnt suitable really,coef of friction being to similar and wear on both parts being more likely. Id rather have a plastic bearing to replace than a whole shaft.

The aluminium housing each end of the shaft has ball bearing, the nylon nuts just support the table

EEF1F6DA-9382-4020-A356-601D6FC21285.jpeg

many thanks
Click to expand...
 
Ohhhhhh its not a bearing as such, its a nut, I see now.

Bronze doesnt like threads.

Aluminium would be my choice metal but the reason they are plastic is to reduce backlash by deforming slightly on direction change and to reduce noise an vibration from thread movement. Delrin will be to hard, they actually look like hdpe from the machine marks but nylon will be perfect.
 
Cncpaul":nvziymq3 said:
Yes, Phosphor Bronze would be the best choice but l would have to find an engineer to make those, the bearing do not sustain continual use, the rise and fall is only used when you change material thickness to focus the laser. l can machine Nylon/Acetal/Delrin, they only a 50mm dia x 20mm disc with 4 x 3mm holes and a M20 thread in the center, so nothing exotic
Click to expand...

There are a few people on this forum that could help you out with that if you want to explore that path :)

novocaine":nvziymq3 said:
Bronze doesnt like threads.
Click to expand...

Really? I've always thought Bronze would be the go-to material for this kind of thing where the screw might be in continual use as the female threads on my lathe are bronze as far as I know but an acme thread form rather than a regular coarse metric which might make a difference.
 
I'd use nylon in any of the grades Paul or even ptfe if you can find a bit. Depends on your method of machining whether block or rod, from memory we used to sell 50mm round bar, you may be able to persuade one of the semi finished plastics suppliers to send you a free sample thick enough. £85 seems extremely expensive but I guess it's down to labour and profit.

Just a thought another material could be SRBP (Tufnol), most grades are suitable for bearings though I don't know for this application, possibly a bit of lignum vitai is another option?

If you get stuck I could possibly post you a bit enough for 1 bearing from my stash from when I was in the plastics industry but I don't know the cost of postage.

Bob
 
Sorry let me clarify

Phospher Bronze is fine with larger thread forms like acme, large pitch etc. And I'm confusing it with oilite because im an idiot. :D

The other reasons mentioned still stand.
 
I forgot to say though you likely already know, search for plastics stockholders, engineering or semi finished plastics suppliers, there will be some in Ireland.
If you want to try for samples I would phone rather than email as you'll get a salesperson looking for future business and if your marals allow just say you're experimenting making up bearings, looking to compare materials and could they send you samples of what they recommend, in the size you need to make up prototypes.it will work most of the time foc or at worst a minimal cost.
It's only a teeny lie and I've heard the Irish can tell a good story. :eusa-dance: ;)
Cheers
Bob
 
One of the plastics that I like to machine is Ertalyte TX. I bought some 25mm rod for a particular job about 20 years ago and still have a tiny bit left. It’s nice to machine, dimensionally stable and has a very low coefficient of friction due to included PTFE.
 
Well l purchased some 50mm dia x 500mm Nylon 66 for £29.76, bargain, l had it sent to my AddressPal in uk
who used to ship items to Ireland up to 20kg for €3.95 since Brexit its €6.50 still a bargain, it then took 8 days to transport it from Hatfield to Heathrow a day later they informed me they value the item at €38.76 and I need to pay a further €11.63 or they won’t deliver it.

Dick Turpin is now living in Ireland

I have been told that the UK and the EU had an agreement that the importation duty‘s were suspended for 6 months unfortunately the EU haven’t kept up their side of the agreement. :eusa-naughty:
 
Cncpaul":3i8gjy3l said:
Well l purchased some 50mm dia x 500mm Nylon 66 for £29.76, bargain, l had it sent to my AddressPal in uk
who used to ship items to Ireland up to 20kg for €3.95 since Brexit its €6.50 still a bargain, it then took 8 days to transport it from Hatfield to Heathrow a day later they informed me they value the item at €38.76 and I need to pay a further €11.63 or they won’t deliver it.

Dick Turpin is now living in Ireland

I have been told that the UK and the EU had an agreement that the importation duty‘s were suspended for 6 months unfortunately the EU haven’t kept up their side of the agreement. :eusa-naughty:
Click to expand...

Welcome to the new world order, where everyone is out for a quick buck and it's all their fault not ours. :)
 
novocaine":279zxgwt said:
Cncpaul":279zxgwt said:
Dick Turpin is now living in Ireland
:eusa-naughty:
Click to expand...

Welcome to the new world order, where everyone is out for a quick buck and it's all their fault not ours. :)
Click to expand...

I agree 100% , I am looking very hard at my box making business as all my materials are imported and 99% my sales are exported, this will have a serious effect on my market.
 
Well, my nylon66 has arrived with enough material to make 10 ball nuts.

49E549CE-0D93-4D3C-829B-EBC6595C65A8.jpeg

Purchased on ebay £29 arrived in Eire 20 days later €57, at least l have a few spares
 
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