Need to know how to cut/thread plastic
John Coates | 18/11/2012 19:35:59 |
![]() 558 forum posts 28 photos | One of our toilet handles has broken and none of the repair kits fit as they are larger and too big for the hole in the ceramic cistern Basically imagine a threaded cylinder with a flange at the end to stop it sliding through the hole in the cistern. To tighten this against the cistern is a locking nut. These are plastic and trying to repair the existing one by plastic welding with a soldering iron results in a weak joint that just breaks. Having replaced the syphons in two toilets and spent most of the weekend doing this and stopping them leaking (close coupled) it's time to turn to that recalcitrant handle SWMBO is getting fraught that one toilet is still out of commission and I thought "I have a lathe and this is just a turning job, right?" So any tips on how to turn a replacement fitting on the lathe? Will my normal metal cutting tools work on plastic? I intend to just screw cut the cylinder to match the existing lock nut (one less job) and reckon on using nthreads to use my set of change wheels to get somewhere close I've only cut and threaded steel (FC and stainless) and brass so plastic is new to me. Think the existing is ABS but will see what the supply store has in stock tomorrow during lunch break Thanks for any help John |
Stub Mandrel | 18/11/2012 19:38:04 |
![]() 4318 forum posts 291 photos 1 articles | Sharp tools, don't go too fast so it doesn't melt.
Hope you get it fixed in time Neil |
John Coates | 18/11/2012 19:59:24 |
![]() 558 forum posts 28 photos | Thanks Neil I'm mainly in trouble because I paid the maintenance guy from work £60 to fix the two toilets that weren't working very well. This was three weeks ago. He said he fitted two service kits but neither toilet was much better. He said he would "do me a deal" on two replacement cisterns if they weren't fixed So I searched the t'interweb, read about replacing the syphons, bought two new ones and fitted them yesterday and today. In the process I found he only fitted one service kit (or else the new one deteriorated bloody quickly in 3 weeks) so was extra angry. Hence sorting the broke handle is top priority to recover some of the cash I paid to this muppet
John |
roy entwistle | 18/11/2012 20:11:07 |
1716 forum posts | Just a thought Why not make a metal one preferrably brass |
John Coates | 18/11/2012 20:13:30 |
![]() 558 forum posts 28 photos | Roy I thought of that but am worried that metal will grind/wear against the ceramic cistern - the flat part (imagine a top hat with the cylinder going through the hole in the cistern) Do you reckon brass will be okay? |
Paul Barter | 18/11/2012 20:48:43 |
112 forum posts 8 photos | Hello there, probabley no need to torment yourself or your wife! The sheds and plum center, thats how they spell it, sell handles for cisterns. The sleeve is usually polythene and thus un gluable, but it can be easily harvested from the handle kit if you do not fancy the handle supplied and your original substituted. I hope this helps |
John Coates | 18/11/2012 20:52:09 |
![]() 558 forum posts 28 photos | Cheers Paul That's the problem with weekends - the plumbers merchants all close at midday on Saturday and my problem didn't synch with their opening hours! Will give them a visit tomorrow
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Robert Dodds | 18/11/2012 20:54:40 |
324 forum posts 63 photos | John, The bigger concern with using a metal bush is that to prevent stressing in the ceramic and consequent cracking of the cistern you should fit 1.5 - 2mm thick rubber washers both inside and outside the cistern wall. It is not quite so important with a plastic bush and nut but even there you need a little compliance against the ceramic. You won't have any trouble cutting plastic in the lathe but whats wrong with going for a Screwfix replacement handle for £4.49 ? It comes complete with new plastic bush and nut for you to use as you like Bob D |
John Coates | 18/11/2012 21:07:37 |
![]() 558 forum posts 28 photos | Cheers Bob, will look at Screwfix Our handle shaft is 18.5mm OD whereas the Wickes kits were about 22mm |
Andyf | 18/11/2012 21:56:31 |
392 forum posts | Being part of a plumbing fixture, it could well be a BSP thread, John. I've just measured the plastic bush in my cistern, which appears to be 1/2" BSP, with a major diameter of 0.825" and 14 TPI. If your bush is also BSP, it must be a larger size or have pretty thin walls if the handle shaft passing through it is 18.5mm/0.729". Maybe 5/8" BSP with major diameter 0.902"/22.91mm, or 3/4" BSP with 1.041"/26.44mm, both of which are also 14 TPI. The major diameters are nominal, and may be a bit less in practice. BSP is a 55 degree Whitworth thread form. That must drive them mad in more metric parts of the world; it has wide international use for plumbing. Andy
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Sam Stones | 18/11/2012 21:59:51 |
![]() 922 forum posts 332 photos | Hi John, The trouble with injection moulded plastics nuts and bushes, is that there is (almost) always a weak(er) weld line opposite the gate (feed point). This results from the fact that the melted material has to travel around both sides of the mould core, and rejoin (weld). That aside, when machining plastics, treat the job as if the material was wood, ie. lots of top and front rake. There’s less tendency for the cutting tool to rub, and the swarf is (usually) propelled away from the workpiece rather than getting wrapped around it. Static electricity can become involved too, adding to the problem. Plastics materials which are reasonable to work with, but not all that cheap are polyacetal (Delrin), and rigid PVC (RPVC). Both are more rigid than polyethylene and polypropylene, but will still deform in the chuck unless care is taken. As has been suggested above, I’d be buying brass nuts/bushes and padding the ceramic/brass contact faces with rubber. Or, if you don’t mind the extra cost and extra work, machine your own from brass. Regards, Sam Edited By Sam Stones on 18/11/2012 22:01:39 |
Les Jones 1 | 18/11/2012 22:58:13 |
2292 forum posts 159 photos |
Hi John. Les. |
Terryd | 19/11/2012 07:34:48 |
![]() 1946 forum posts 179 photos | Hi all, I would have thought this question would have been better and more quickly solved by visiting a Plumbing forum such as this one as such items are cheap and readily available. Not worth the waste of workshop time to make them I would have thought. By the way Paul it is spelled Plumb Center. Useful to spell correctly when searching. Best regards Terry |
John Coates | 20/11/2012 07:16:00 |
![]() 558 forum posts 28 photos | Terryd - agreed but at the time the local suppliers didn't have what I wanted and SWMBO was getting very irate and buying some plastic from the local supplier and turning it seemed the quickest way out of my domestic hell In the end it was Les who provided the solution as Toolstation were on the same road my lad works on in Doncaster (25 miles away). He picked one up yesterday and I fixed it this morning at 7am (was out watching Skyfall last night). Got a a hug from SWMBO so domestic bliss is restored. Didn't know about Toolstation but I do now!
Thanks all. John Edited By John Coates on 20/11/2012 07:16:27 |
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