Best screw type to fix skin fittings to steel hull

[Robbo]

Hello,

Whats the best method to fit skin fittings that require screwing down (like diesel tank fill inlet).    I was thinking tap and using machine screws?  What is the best material? Stainless steel?

Cheers,
Richard.

[Dalslandia]

SS or welding if similar material

[dmr]

1 hour ago, Robbo said:

Hello,

Whats the best method to fit skin fittings that require screwing down (like diesel tank fill inlet).    I was thinking tap and using machine screws?  What is the best material? Stainless steel?

Cheers,
Richard.

Brass machine screws into tapped holes would be my choice, but brass is surprisingly soft so they will shear off if you over-tighten them. Stainless steel is OK. There is reputed to be a dis-similar metals corrosion issue with stainless steel into mild steel which causes the stainless to turn into powder. In my experience this is only a real issue in salt water environments.

Best of all is probably bronze but I bet you can't find any.

..............Dave

[ditchcrawler]

I used brass fittings with brass 5mm countersunk screws tapped into steel deck  

[Neil Smith]

I used SS machine set screws tapped into the shell.

Neil

[Robbo]

Cheers for the confirmation I was on the right track.  Prob use SS as my fittings are.

[artleknock]

For bronze machine screws fleebay is your friend.

[dmr]

15 minutes ago, artleknock said:

For bronze machine screws fleebay is your friend.

Well, I was about to be humbly corrected, but if I type bronze machine screw into eBay I see a load of bolts (and a couple of machine screws) that I reckon are steel painted in some sort of bronze coloured paint. "Bronze Tone" is the clue. Its a bit like "smoked style cheese". Found a bit of proper smoked Lancashire cheese in Waitrose yesterday though, but no sign of any bronze bolts.

These long bronze painted bolts are very popular for self assembly furniture. I think you can still get proper bronze screws (wood screws) from some specialist vintage wooden boat chandlers.

..............Dave

[rusty69]

20 minutes ago, artleknock said:

For bronze machine screws fleebay is your friend.

Got a link? 

[Slim]

Brass if you're talking brass fittings After tapping the thread run a quality steel screw in first to ensure the tapping is cleared.

 

[nb Innisfree]

To ensure screw heads sit properly in their countersunk make sure tapped holes are dead central in fitting holes and square on to metal, easier said than done. 

Edited December 6, 2017 by nb Innisfree

[WotEver]

3 minutes ago, nb Innisfree said:

To ensure screw heads sit properly in their countersunk make sure tapped holes are dead central in fitting holes and square on to metal, easier said than done. 

Just stick the arse end of the boat on a large pillar drill.

[WotEver]

 

 

 

More seriously, self-centre drills would be a good start. Change the supplied tin drill bit for a decent cobalt one. 

https://m.ebay.co.uk/itm/4PCS-Door-Lock-Hinge-Drill-Bit-Set-Self-Centering-Hinge-Drill-Bit-For-Plastic-UK-/192359089241

[nb Innisfree]

9 minutes ago, WotEver said:

Just stick the arse end of the boat on a large pillar drill.

Some drill! 

When I was wondering how to fix brass ports on Innisfree I decided against drilling and tapping after seeing several boats done like that, all of them were cockeyed. Instead I drilled oversize holes and used machine screws, nuts and washers. Not that that is poss with the OP. 

[nb Innisfree]

7 minutes ago, WotEver said:

 

 

 

More seriously, self-centre drills would be a good start. Change the supplied tin drill bit for a decent cobalt one. 

https://m.ebay.co.uk/itm/4PCS-Door-Lock-Hinge-Drill-Bit-Set-Self-Centering-Hinge-Drill-Bit-For-Plastic-UK-/192359089241

To drill square to surface I use a short length of bar with ends turned square in a lathe with a concentric hole drilled through for a pilot drill. With bar held against the surface a pilot drill will be square on. 

[artleknock]

13 hours ago, rusty69 said:

Got a link? 

Here's one

Enter marine bronze, or phospher bronze into search box.

If you do a Google on bronze screws you will find a few wooden boat chandlers that do wood screws and nails.

 

[rusty69]

1 minute ago, artleknock said:

Here's one

Enter marine bronze, or phospher bronze into search box.

If you do a Google on bronze screws you will find a few wooden boat chandlers that do wood screws and nails.

 

These are bolts, not machine screws

[MtB]

3 minutes ago, rusty69 said:

These are bolts, not machine screws

 

And for those wondering what the difference is, a machine screw has the thread going all the way up to the underside of the head. 

 The head is usually round with a screwdriver slot or cross too, but not necessarily. A hex head bolt with thread all the way up is a actually a screw. 

[artleknock]

Thre are some here.

If you have a lottery winners bank balance.

[rusty69]

2 minutes ago, artleknock said:

Thre are some here.

If you have a lottery winners bank balance.

So ebay, isn't as much a friend as it was yesterday

Unless you live in the states

Edited December 7, 2017 by rusty69

[artleknock]

18 minutes ago, rusty69 said:

These are bolts, not machine screws

http://www.nenutsboltsfasteners.co.uk/product/m8-x-27mm-long-phosphor-bronze-hex-head-screw/

[rusty69]

6 minutes ago, artleknock said:

http://www.nenutsboltsfasteners.co.uk/product/m8-x-27mm-long-phosphor-bronze-hex-head-screw/

Very nice, although I'm not sure what your point is

[MtB]

2 minutes ago, rusty69 said:

Very nice, although I'm not sure what your point is

 

The listing is for hex head screws, illustrating (I suspect) the point I made earlier about screws sometimes having hex heads.

[rusty69]

1 minute ago, Mike the Boilerman said:

 

The listing is for hex head screws, illustrating (I suspect) the point I made earlier about screws sometimes having hex heads.

Perhaps he should have quoted your post then

[Neil Smith]

58 minutes ago, Mike the Boilerman said:

 

And for those wondering what the difference is, a machine screw has the thread going all the way up to the underside of the head. 

 The head is usually round with a screwdriver slot or cross too, but not necessarily. A hex head bolt with thread all the way up is a actually a screw. 

The machine screws I used had hex in for tightening with an allen key.

Neil