316 SS machine screws - Passivated or not

yoyo

Anarchist
691
267
Throwing this out there to get some present day experience from the brain trust. 

I am re bedding an 80's vintage aluminum toe rail and need to purchase a bunch of flat head machine screws.  It looks like I can order standard 316 SS flat head machine screws or passivated 316 SS.  Is the incremental price increase for passivation worth it?  Salt water / ocean service.

Also - what drive do you like and why?  The originals were straight slot.  It looks like most common availability is phillips but I can also get hex drive.  Not planning on having the boat long enough to pull and re bed again but would like some insight to ease of installation and removal.  What are the cool kids using......  

Any other suggestions for toe rail?  Favorite bedding compound for aluminum / stainless, etc.

Thanks in advance for your help.

 

snubber

Member
161
63
Idaho
Throwing this out there to get some present day experience from the brain trust. 

I am re bedding an 80's vintage aluminum toe rail and need to purchase a bunch of flat head machine screws.  It looks like I can order standard 316 SS flat head machine screws or passivated 316 SS.  Is the incremental price increase for passivation worth it?  Salt water / ocean service.

Also - what drive do you like and why?  The originals were straight slot.  It looks like most common availability is phillips but I can also get hex drive.  Not planning on having the boat long enough to pull and re bed again but would like some insight to ease of installation and removal.  What are the cool kids using......  

Any other suggestions for toe rail?  Favorite bedding compound for aluminum / stainless, etc.

Thanks in advance for your help.
I am not a cool kid, but I have been upgrading my hardware from Phillips, to Roberts or Robertson drive (square). As long as you prevent epoxy or goo from getting into the screw head, it eases removal. I have twisted a drive-bit and had to replace it, but never fragged a screw head, so the Robertson screws seem to enjoy a longer service life. I like Bolt Depot for my hardware. 

That's all I have. Fresh water for me these days. Others WILL have opinions about bedding compound. 

Snubs

 

slug zitski

Super Anarchist
5,124
829
worldwide
Throwing this out there to get some present day experience from the brain trust. 

I am re bedding an 80's vintage aluminum toe rail and need to purchase a bunch of flat head machine screws.  It looks like I can order standard 316 SS flat head machine screws or passivated 316 SS.  Is the incremental price increase for passivation worth it?  Salt water / ocean service.

Also - what drive do you like and why?  The originals were straight slot.  It looks like most common availability is phillips but I can also get hex drive.  Not planning on having the boat long enough to pull and re bed again but would like some insight to ease of installation and removal.  What are the cool kids using......  

Any other suggestions for toe rail?  Favorite bedding compound for aluminum / stainless, etc.

Thanks in advance for your help.
Sikaflex for bedding  3m 4200 is another choice 

if your fitting accepts countersunk Allen heads ... use them

slotheads don’t like extrerior mountings 

 

slug zitski

Super Anarchist
5,124
829
worldwide
A toe rail takes a long time to mount 

use the slowest  cure bedding compound 

consult the product catalogue ... many times  shops don’t carry slow cure  ...special order 

 

slug zitski

Super Anarchist
5,124
829
worldwide
And always use a drill guide to keep fastener centered ,  perpendicular and to avoid eroding the anodizing

typically custom made by the  machinist in the yard  for each type track or toe rail

top photo is a drill guide for the last Genoa track I mounted 

It is simply an Old prop prop shaft cut and machined 

cost 75 $

second pic is an off the shelf drill guide 

handy for general purpose  but tedious if you must blow thru a few hundred  holes 

B037F605-F76E-4FB3-9762-E6C05D95120C.png

3A6C39E7-2B64-4E8B-8F8F-5DFE47A8610A.png

 

Zonker

Super Anarchist
9,139
5,051
Canada
I've seen the odd Robertson head s.s. machine screws but they are extremely rare. I'd go with the hex head too. I doubt the originals were "passivated". (Machining s.s. to form threads can make the surface more active. If you're really worried you can DIY  https://www.pemnet.com/design_info/plating-guidelines/passivation-of-stainless-steel/#:~:text=The passivation process involves submerging,to thirty minutes is typical.  But it will self-passivate to some degree as well. 

Good idea on sourcing long open time caulking. Pick a cool, dry day (polyurethanes cure by moisture in the air). Check the expiry date on the tube.

 

yoyo

Anarchist
691
267
Thanks for the info on passivation.  I doubt the old ones were passivated and I'm not sure they were even 316 but they appeared to be in relatively good shape.  Probably good quality stainless from days gone by.

Slow cure sealant makes sense.   It will definitely take some time to refit the rail one screw at a time while bending it into place.  I was amazed that when removed the aluminum rail straightened out after having been curved for almost 40yrs.

Any thoughts on polysulfide?  I remember hating that stuff in the past because of the mess.  But it has a long tack time and multi-day cure cycle.

 

El Borracho

Sam’s friend
6,347
2,385
Pacific Rim
The trick is not getting any sealant on the threads as the screw is pushed thru.

No fan of the Phillips design. But they (or anything) are a better choice than slotted for a toerail: appearance and seal. Be sure to clock whichever you choose.

Passivating does make a difference. Quality hardware will be polished as well. Passivating is rather pointless if the surface is rough.

 

Zonker

Super Anarchist
9,139
5,051
Canada
Yeah, I like polysulphide for longevity. I think it actually has a longer life than most polyurethanes like Sika 291 / 5200 etc.

Polysulphide is very "stringy" so it pulls away in long strands as you use it; the trick is keep the caulking gun on the work; release the trigger and pause, then pull it away while wiping the tip a bit.  For this job I'd look into a powered caulking gun (rental) due to the amount of sealant you'll have to pump

 

longy

Overlord of Anarchy
6,297
894
San Diego
If you don't have ooze all around, odds are high you will have leaks later. This hard part is having just enuff to slightly extrude, but not waste a lot. Tape off edges, use putty plastic putty knife for first clean up, then alcohol & 1/2 sheets of paper towels. Have a large open top box close by - swipe a section ^& toss the paper.Have sealant around the shoulders of the fastener, a dry joint here will lead to corossion later.(look at old Swan toerails -every bolt head has a circle of crud around it). Dry bolt threads will result in leaky bolts later. Ever seen a rusty nut/washer underdeck? salt water wicking down the threads.

 

slug zitski

Super Anarchist
5,124
829
worldwide
If you don't have ooze all around, odds are high you will have leaks later. This hard part is having just enuff to slightly extrude, but not waste a lot. Tape off edges, use putty plastic putty knife for first clean up, then alcohol & 1/2 sheets of paper towels. Have a large open top box close by - swipe a section ^& toss the paper.Have sealant around the shoulders of the fastener, a dry joint here will lead to corossion later.(look at old Swan toerails -every bolt head has a circle of crud around it). Dry bolt threads will result in leaky bolts later. Ever seen a rusty nut/washer underdeck? salt water wicking down the threads.
Yes indeed 

Bog up both the male and female threads  ...bolt threads and hole  ...both .need to be bogged up or the joint will leak .  Water must be kept out of the counter sink or corrosion will form on the shoulders 

Caulk is cheap ... use plenty of caulk 

Take care on the boat interior by protecting delicate furniture from bog blowout 

masking off the joint can help contain the mess on deck 

have plenty of solvent ,paper towels  and disposable gloves handy 

All those caulking  bogs  are monstrous... the black stuff gets everywhere

when finished you might even go “ black face “

be alert on your walk home  or a riot may form 

 

yoyo

Anarchist
691
267
Thanks for the responses.  I like the Allen hex drive. 

I'm leaning towards polysulfide for the extended working and cure time. 

Thanks for the reminder on sealing the shoulder.  That should also add some limited separation/isolation between the aluminum and SS to reduce corrosion.  

Taping off the edges sounds like it should help a bunch with preliminary cleanup.

 

longy

Overlord of Anarchy
6,297
894
San Diego
White colored goop cleans easier than black (or at least tiny bits don't show) Bk seems to take twice the effort to clean

 

yoyo

Anarchist
691
267
Butyl has an infinite working time and much less mess...
Alex,

I thought about Butyl tape and have used it in other applications.  I do like it, especially the cleanup aspect. 

The problem I see is with this toe rail application.  The rail has to be slowly and forcefully bent into a curved position one bolt at a time.   The recommendations I have seen for butyl tape is to make a ring seal around the fasteners, push in straight and then tighten nuts without rotating the machine screw then retighten 2-3 times to fully compress the excess butyl.  I wont be able to insert each machine screw until I get the rail aligned with each hole. 

Is there a different method for Butyl tape or product you would suggest? 

 
Last edited by a moderator:

Alex W

Super Anarchist
3,306
296
Seattle, WA
I would test what I'm proposing first.  The only toe-rail that I've rebedded personally wasn't aluminum and so it wasn't as hard (wood and plastic both curve pretty easily -- my toe rail was a combo).

If you counterbore the holes I think you can put a donut around the hole in the toe rail (very close to the hole but not touching).  When you push the toe rail into position you can now push the bolt through.  When you tighten it the counterbore will squeeze butyl up tight around the bolt's shaft.

 
Top