Graham_Wright
Well-Known Member
M8?! what is it a 2cc toy engine? Mine are M12 and long!
Can you tap epoxy?
- Thread starter ridgy
- Start date
M8?! what is it a 2cc toy engine? Mine are M12 and long!
sailorman
Well-Known Member
the thickness of the solid part of the screw or slightly less, it is the cut thread that needs to grip into the material
Tranona
Well-Known Member
Interestingly they don't seem to show up in the usual tables. However, I have used both M6 and M8 recently and used a pilot hole 2mm smaller - so 6mm for M8 with a short countersink for the unthreaded part. Both into hardwood. Used a socket to screw them in. The M8 were for engine mounts and I have had them out subsequently and they screw back securely.
You might want to experiment on a piece of scrap wood so you get a fell for what is required to screw them home.
You might want to experiment on a piece of scrap wood so you get a fell for what is required to screw them home.
Tranona
Well-Known Member
Nanni 14. Matches the holes in the engine mounts. Each of 4 mounts has 2 screws. 70mm long from memory into oak. Previous ones were the same for a Yanmar 1GM. Stayed there happily for nearly 20 years and came out cleanly. New ones slightly different spacing so plugged the old hole with dowels in epoxy and redrilled for the new ones. Expect they will outlast me.
TQA
Well-Known Member
- Joined
- 20 Feb 2005
- Messages
- 6,815
- Location
- Carribbean currently Grenada
" J-B WELD can be formed, drilled, ground, tapped, machined, filled, sanded, and painted. It stays pliable for about 30 minutes after mixing, sets in 4-6 hours, and cures fully in 15-24 hours. It's water-proof; petroleum-, chemical-, and acid-resistent; resists shock, vibration, and extreme temperature fluctuations, and withstands temperatures up to 500° F. J-B WELD is super strong, non-toxic, and safe to use. Before it sets, you can clean up with soap and water. "
I have used it on a low stress job and it did what is says above.
I have used it on a low stress job and it did what is says above.
oldbilbo
...
Parsifal is 'spot on', as usual. The above reference is a good explanation, as is the 'Gougeon Brothers on Boat Construction', where this process is described as 'potting-in of hardware'.
KenMcCulloch
Well-Known Member
You may find the sort of coachscrew you need here:
http://www.a2a4.com/acatalog/HEX_HEAD_COACH_SCREWS_A_2.html
http://www.a2a4.com/acatalog/HEX_HEAD_COACH_SCREWS_A_2.html
tim_ber
Well-Known Member
And my post:
Must be the first time (and probably, only) that I have ever got anything right on here (although WEST didn't suggest their hard wearing graphite additive). Warm cozy feeling...
Good luck with the installation.
oldsaltoz
Well-Known Member
Many advocate the use of a dowel to replace the old hole and insert the coach screw into that.
But none of them add an epoxy prior to inserting the screw.
Any large screw going into timber MUST have the hole treated or moisture will recreate the same problems later.
Not to mention that the timber used in the dowel will most likley be of a lesser (softer) quality than the original block mount.
Never drill a hole in timber and screw into it without first adding some epoxy unless you enjoy replacing them again and again.
Good luck and fair winds.
But none of them add an epoxy prior to inserting the screw.
Any large screw going into timber MUST have the hole treated or moisture will recreate the same problems later.
Not to mention that the timber used in the dowel will most likley be of a lesser (softer) quality than the original block mount.
Never drill a hole in timber and screw into it without first adding some epoxy unless you enjoy replacing them again and again.
Good luck and fair winds.
sailorman
Well-Known Member
Many advocate the use of a dowel to replace the old hole and insert the coach screw into that.
But none of them add an epoxy prior to inserting the screw.
Any large screw going into timber MUST have the hole treated or moisture will recreate the same problems later.
Not to mention that the timber used in the dowel will most likley be of a lesser (softer) quality than the original block mount.
Never drill a hole in timber and screw into it without first adding some epoxy unless you enjoy replacing them again and again.
Good luck and fair winds.
assume you let the epoxy cure first or do you glue your screws in
Poignard
Well-Known Member
But is screwing into a dowel a good idea, because you are screwing into end grain?
Tranona
Well-Known Member
The sort of coach screw we are talking about in a pilot hole is never going to move. Thgere are 8 of them holding down the engine mounts, which themselves take the load from the engine. My original Stuart Turner was solidly mounted with coach screws into the Oak bearers. Never moved in the 15 years or so it was bolted down.
oldsaltoz
Well-Known Member
it is better to have a full cure but anything can be unscrewed form epoxy with a little heat as it starts to soften around 90*C so no problem, small scews only need a soldering iron them for minutes.
William_H
Well-Known Member
Screws into epoxy
Any of the wood screw/ self tapping screws do a fair bit of material damage and compression as they screw in. This is normally OK in wood provided you don't split the wood.
To put a wood screw into hard epoxy would just shatter the epoxy.
To put a wood screw in with unhardened epoxy will be OK and help to hold and seal the screw.
If you use epoxy in the hole then let it harden and cut a thread using a tap for metal thread type bolt you will get a good grip. The strength of the whole grip depending on the depth of the epoxy and thread.
So the OP first idea is good. olewill
assume you let the epoxy cure first or do you glue your screws in
Any of the wood screw/ self tapping screws do a fair bit of material damage and compression as they screw in. This is normally OK in wood provided you don't split the wood.
To put a wood screw into hard epoxy would just shatter the epoxy.
To put a wood screw in with unhardened epoxy will be OK and help to hold and seal the screw.
If you use epoxy in the hole then let it harden and cut a thread using a tap for metal thread type bolt you will get a good grip. The strength of the whole grip depending on the depth of the epoxy and thread.
So the OP first idea is good. olewill