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Removing nylon plug from carbon fibre tube

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Sam Spoons31/05/2020 23:04:26
93 forum posts

Thanks John, It helps to talk the process through. I'm trying scraping the varnish off as sanding it seems to be more uneven but I'm also trying an oscillating multitool sander head which works as well. Whatever I do it seems to take ages.

I have a 90mm offcut of 50mm round Derlin on it's way, just need to figure a way to fix it to the topslide* so I can use a router bit** in the chuck to machine the tenon, then I hope it'll be long enough to turn the stepped section and part the finished part off the waste (which, hopefully, will be enough to turn a 50mm x 8mm sheave for the masthead halyard block.

* I'd love a vertical slide with a decent machine vice but I'll be improvising for this job.

** I think, used with care, a router bit will be sufficiently beefy to machine Derlin?

Grindstone Cowboy01/06/2020 02:02:23
642 forum posts
58 photos

Try and get hold of some of the open mesh type sanding sheets, they don't clog up in seconds like the ordinary ones do with paint and varnish. Like these maybe. Other sellers (and makes) are available...


John Baron01/06/2020 06:57:07
471 forum posts
186 photos

Good Morning Sam,

Be careful machining plastics ! The plastics are quite abrasive and will cause the tool to get hot very quickly. The danger is that the hot tool no longer cuts but starts to melt the plastic. A flow of water based coolant helps tremendously.

I've used router bits many times to mill steel and brass. The problem with those is that because there is no rake on the cutting edge they shear the material off. This is fine for brasses and alloys, it works on steel but to get a good finish requires fine cuts. I've never cut plastic with one but I imagine you would need a fairly high speed and fine cuts.

Deralin/Acetal machines quite well when turned.


Sam Spoons01/06/2020 10:02:02
93 forum posts


Thanks clogging is a problem with abrasive paper but the stuff on the multitool seems much less prone, scraping is probably the way though (and perseverance).

The first job I did on the Boxford after re-comissioning was to turn some nylon sliding bungs which had, presumably, absorbed some water and I experienced the overheating/melting issue slightly. Gut feeling that sharp HSS tools with some rake would work better than carbide inserts (which were the only functioning tools I had at the time). Now I have a working bench grinder I can probably clean up some of the rusty old tools that came with the lathe so advice on sharpening for turning Derlin please?

John Baron01/06/2020 14:05:32
471 forum posts
186 photos

Hi Sam,

You've got it about right ! Really sharp tools, about 350-400 rpm, maybe a bit less for that diameter and a nice steady feed. I usually go for about 6 thou per turn. If you do it by hand watch out for the tool biting in and dragging the saddle.

Sam Spoons08/06/2020 21:30:10
93 forum posts

Well the plug is out, I drilled three 8mm holes each side of the tenon and had a bash with the slide hammer and it came out fairly easily. It's probably still usable TBH. It's about 60mm into the tube with about half being hollow and the rest solid (will add pics and measurements tomorrow). I now have plenty of 50mm derlin so attempt to fabricate a new one with a couple of sneaky refinements safe in the knowledge that the old one will still work if required. Wall thickness is, from a quick eyeball, around 2.5mm for the bottom section and the inserted part of the plug looks unmolested so probably standard.

I'm still suffering from a total lack of motivation WRT removing the old varnish (which I've now decided is either epoxy or two pack so especially resilient). I'd guess I've got around half done, scraping with the side of an old chisel seems most efficient but it's bloody tedious, even though I can finish up with a rub with the 'vibrating multitool' (ooh er missus). Even watching my buddies sailing on the club webcam didn't get me jumping off the sofa.....

Edited By Sam Spoons on 08/06/2020 21:32:24

old mart08/06/2020 21:34:55
3185 forum posts
201 photos

Was the old one fitted at the wrong angle?

John Baron09/06/2020 06:56:19
471 forum posts
186 photos

Hi Sam, Guys,

Nice one ! At least you can now move on and get things sorted. I'm watching with interest.

Sam Spoons09/06/2020 10:38:05
93 forum posts
Posted by old mart on 08/06/2020 21:34:55:

Was the old one fitted at the wrong angle?

Yes, slightly twisted so the sail track on the mast was slightly off centre. The original plan was to just realign it and refix.


Edited By Sam Spoons on 09/06/2020 10:38:35

Sam Spoons30/06/2020 12:29:33
93 forum posts

Final update, After much tedious scraping and sanding and three coats of white two pack Polyurethane the mast looks great. I fabricated a new heel plug out of 50mm round Acetal (which did machine nicely John yes). I finally gave up on milling the tenon as I could not devise a practical way of holding the workpiece and used hand tools (tenon saw and belt sander) to make it. It's not a neat precision job but it is functional and fit for purpose.

The trampoline racks now look very shabby so they are about to receive some TLC and white paint then I will post a pic of the boat.


Thanks for the help and advice guys. smiley

Edited By Sam Spoons on 30/06/2020 12:30:56

John Baron30/06/2020 15:19:59
471 forum posts
186 photos

Hi Sam,

Thank you for the update ! It good to know that you have got it sorted, I'm pleased that the Acetal machined well for you, its quite a nice material to use for things like nuts for backlash free lead screws, collars and those sort of things.

The trick to holding round objects on the mill is "V" blocks assuming that you don't have a three jaw chuck that you can use.

Sam Spoons30/06/2020 15:28:48
93 forum posts

I was planning to mill on the Boxford but don't have a vertical slide. I did improvise to mill a 3mm slot down the length of a piece of 16mm aluminium round by mounting the bar in a tool holder on my QCTP. Hight adjustable and it worked a treat (It's not cosmetically perfect but does the job I designed it for). I was contemplating making some hardwood V blocks but in the end I decided to just stick it in the bench vice and cut it by hand.

Edited By Sam Spoons on 30/06/2020 15:29:23

John Baron30/06/2020 16:07:44
471 forum posts
186 photos

Hi Sam,

"V" blocks can be worth their weight in... well you know what I mean.

The technique that I would have used is some long bolts into "T" nuts on the crosslide packed up the "V" block till I got the height I wanted and then a flat bar on top to clamp the whole lot down. Probably another flat bar behind to stop things twisting under cutting pressure. Then either mill two slots and do as you have done cut the scrap off with a saw, or used a fly cutter to take the waste off.

But that is all academic now. yes Looking forward to seeing your pictures.

Sam Spoons30/06/2020 19:26:35
93 forum posts

Yeah I'd pretty much arrived at something like that. The Boxford topside only has a single large tee slot for the tool post so not ideal for that purpose, I did contemplate taking the topside off and drilling and tapping some fixing holes in the cross slide but, in the end, I decided using hand tools made more sense.

I have bought a collect chuck and some milling cutters for the future (and used them on the other job, a 'boat breaker' rigging tensioner) so spent far more than I've saved to date but we need the toys so why not. smiley

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