aquaholic
Active member
Is it possible to tap a new thread into a resin? If s which type of resin s best to use, also will it take a self tapping screw instead?
Tapping a thread in resin
- Thread starter aquaholic
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howardclark
Active member
Did an epoxy course at West Systems and they say you can tap a machine thread into their resin. of couse it will be weaker than metal but OK if lightly loaded. Cannot remember if they said to use a particular mix - suggest you ask them direct
Avocet
Well-known member
A lot depends on the resin and the reinforcement. It's definitely possible to tap a thread in most resins - just use a tap as if it was metal, but how much load it will take is a different question. Self-tapping screws are more difficult because you need to be careful you get the pilot hole just right. Too small and there's a chance you'll crack the resin. Too big and the threads will pull out. If you can get back with a description of what sort of resin, how thick, whether or not there are any fibre or powder reinforcements, and what sort of magnitude and direction the forces acting on the fastener will be, it might be possible to have some further thoughts. Is this a block of resin that exists already or that is yet to be made? If the latter, there are a great many other options available.
BACUS
New member
Could you not drill a larger hole and epoxy a form of captive nut in place
Regards
Bacus
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Bacus
nigelmercier
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I suggest a course in reducing the size of an avatar.
TQA
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JB Weld is what I would use.
It will take a thread or a self tapper.
It will take a thread or a self tapper.
cryan
New member
You can tap resins but probably stronger to use a captive nut encapsulated in resin.
Poignard
Well-known member
This info from WEST might be useful:
http://www.westsystem.com/ss/bonding-hardware/
Instead of tapping a hole for the screw I would enlarge the hole, fill it with epoxy and cast the screw in place (wax the screw if you might want to remove it later) .
This method is very strong. I saw it demonstrated on a test rig during a WEST training course and the timber to which the fastener was bonded broke first.
http://www.westsystem.com/ss/bonding-hardware/
Instead of tapping a hole for the screw I would enlarge the hole, fill it with epoxy and cast the screw in place (wax the screw if you might want to remove it later) .
This method is very strong. I saw it demonstrated on a test rig during a WEST training course and the timber to which the fastener was bonded broke first.
AMCD300
New member
HAHAHAHAHA.....
Although I can see why he wants to show his yacht off..she's a beauty
Daydream believer
Well-known member
HAHAHAHAHA.....
Although I can see why he wants to show his yacht off..she's a beauty
Should be on the MOBO forum!!
Daydream believer
Well-known member
Do you need to tap the resin?
Possibly set a stud in place using west 404 filler as an option ( i think 404 is the correct one it is super strong)
CreakyDecks
New member
If you want to be able to remove and refasten the screw often then maybe use a helicoil thread insert like you would with aluminium (in a non-marine environment). Helicoils are stainless steel so if the screws are also there would be no corrosion issue.
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macd
Active member
+1
Thread inserts can work well used in this way (although my preference is for Recoil rather than Helicoil...simpler system), but the load-bearing capacity will not be as great as an insert or a tapped hole in metal. They're best used in an epoxy/microfibre mix.
Stemar
Well-known member
Depending on the application, a rivnut might be more reliable than a tapped thread but, for high loads, I'd agree with those who suggest casting a nut in place.
I've never needed to do it, but I think plan A would be to grease a bolt, thread the nut on it and cast the whole lot in position. Once the resin's gone off, unscrew the bolt.
I've never needed to do it, but I think plan A would be to grease a bolt, thread the nut on it and cast the whole lot in position. Once the resin's gone off, unscrew the bolt.
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Poignard
Well-known member
I like that idea but how do you keep the epoxy out of the inside of the Helicoil?
macd
Active member
The mix is allowed to cure, then tapped (for the insert) in the normal way. No harm in putting a smear of epoxy on the outside of the insert before inserting, then after locking it, running a lightly oiled nut through the insert. Alternatively, run a tap through while the mix is green.
I'd stress that this is not appropriate for very high loads, but makes for neat 'blind' fixings.
D
Deleted member 36384
Guest
You only need the same cross sectional area (CSA) of threads cut in the epoxy, as a 'cast in' nut CSA to achieve the same strength. It therefore follows that if you have sufficient depth of epoxy you should be able to achieve a very strong fastening where the primary substrate is epoxy. Clearly though over drilling an old metal stud hole and filling it with epoxy is not going to have the same strength as a metal thread. However, if the tapping into an epoxy base, say GRP mount for a cockpit spray hood, then tapping the GRP maybe good enough if the depth is good. I suspect in many instances there is insufficient depth of GRP and a cast in nut is probably more robust when it comes to frequent removal and insertion of the threaded item
West does have figures, from tests, where wood screws (in solid wood and ply) had the screw holes wetted out and the screw inserted into wet epoxy and then backed out before they set i.e. are not epoxy glued in place. In some pull test cases the head of the screw sheared off before the cured epoxy soaked threaded holes striped out.
West does have figures, from tests, where wood screws (in solid wood and ply) had the screw holes wetted out and the screw inserted into wet epoxy and then backed out before they set i.e. are not epoxy glued in place. In some pull test cases the head of the screw sheared off before the cured epoxy soaked threaded holes striped out.
Poignard
Well-known member
macd
Active member
Understood - thanks for the advice.
ps I guess you mean 'screw' not 'nut'
I guess you're right. Sorry.
srp
Well-known member
www.bighead.co.uk make a range of fasteners for bonding to composites etc. Unfortunately, they don't seem to want to bother supplying small quantities, and they are a bit expensive. I think you can buy them from eBay sellers.
