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Old 01-10-2016, 16:01   #16
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Re: Help find chainplate bolts

I'm matching existing.

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Old 01-10-2016, 16:13   #17
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Re: Help find chainplate bolts

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Are there any other sources people know of for Slotted Truss Head bolts made of 316, larger than what's available on McMaster. Additionally, they only have 18-8 in the larger sizes. By large I mean 1/2" bolts by 9 inches long. Thanks!
I did not see exactly what you are looking for on Boltdepot.com. They have several things that might work for you.
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Old 01-10-2016, 16:26   #18
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Re: Help find chainplate bolts

In this case, I would be inclined to use button head screws with an Allen socket in t hem. Similar in appearance to the originals (that seems important to the op) but far better in terms of "drivability", and commonly available in 316 grade s/s.

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Old 01-10-2016, 16:47   #19
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Re: Help find chainplate bolts

For the OP and Sailor Russell, simply but 316 SS carriage bolts and a 1/4" square file. A minute amount of elbow grease and you do not even need some one holding the other side with a driver.
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Old 01-10-2016, 17:12   #20
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Re: Help find chainplate bolts

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Originally Posted by Freerider View Post
I find them hard to tighten, and un-tighten. A flathead screwdriver is no match for the socket wrench on the other side.

When i disassembled my boat for her refit, all the lifelines were through bolted with slotted bolts and it made me want to inflict pain on the builders.
you are right use hex drive bolts n screws or for screws square drives invented for aircraft industry
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Old 01-10-2016, 17:38   #21
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Re: Help find chainplate bolts

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Originally Posted by Sailor_Russell View Post
Are there any other sources people know of for Slotted Truss Head bolts made of 316, larger than what's available on McMaster. Additionally, they only have 18-8 in the larger sizes. By large I mean 1/2" bolts by 9 inches long. Thanks!
Have been struggling myself to source 3/8" truss head bolts. Even the MacMaster Carr is not a proper truss head.

The ones I'm trying to replace are machined. Probably explains why they are bloody hard to find. The originals are slotted head not internal wrenching. Slotted are useless but maintain the original look.

I'm considering NC machining internal wrenching mushroom head bolts which are easy to source. There are no strength issues as the tensile loads are low.

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Old 01-10-2016, 17:51   #22
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Re: Help find chainplate bolts

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ArtM,

Stainless bolts on a sailboat are often the first thing that sufferes from crevice corrosion. They are typically under enough stress to cause what's called stress crack corrosion, plus the threads are prime candidates to start crevice corrosion. This is a pretty big subject, and there are a lot of seperate things that work together to cause stainless corrosion.

There aren't really the same type of proof bolts in stainless as there are in steel. That is because the stainless grades are much more descriptive than occurs with steel alloys. So for instance a 316 bolt from almost anyone is going to be very close in properties to a 316 bolt from anyone else. With steel that isn't true, there are hundreds of steel alloys (if not thousands) so proofing is pretty necessary.

That being said, there are a number of stainless grades, and you need to know what you are replacing to match it. Or go with the strongest option you have available. That being said most boat manufacturers use either 304 or 316.
Not quite sure what you're claiming here. Structural steel hardware is rated in numerical grades for imperial and 100MPa UTS increments for metric. All the rest is just junk with no provenance.

The only hardware properly rated, by strain, are aerospace fasteners and engine bolts.

You should not be using any hardware on a boat loaded to induce strain. Double shear is the preferred installation.

Corrosion of the austenitic 3xx grades of stainless steels occurs in stagnant sea water. Titanium is an obvious replacement option. If using stainless regular inspection is the key to managing crevice corrosion which is readily detectable by inspection.

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Old 01-10-2016, 17:52   #23
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Re: Help find chainplate bolts

chain plates bolts are in SHEER
Sheer strength = 60 % of tensile

ss fastenings , one has no idea of tensile the heads are not marked grade 5 0r eight as in steel
in fact i bolt alloy plates to the structure inside alloy yachts using grade 8 steel 4 at 5/8 which is far stronger than the rigging
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Old 01-10-2016, 17:58   #24
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Re: Help find chainplate bolts

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Not quite sure what you're claiming here. Structural steel hardware is rated in numerical grades for imperial and 100MPa UTS increments for metric. All the rest is just junk with no provenance.

The only hardware properly rated, by strain, are aerospace fasteners and engine bolts.

You should not be using any hardware on a boat loaded to induce strain. Double shear is the preferred installation.

Corrosion of the austenitic 3xx grades of stainless steels occurs in stagnant sea water. Titanium is an obvious replacement option. If using stainless regular inspection is the key to managing crevice corrosion which is readily detectable by inspection.

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Old 01-10-2016, 22:07   #25
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Re: Help find chainplate bolts

I'll give boltdepot a call. Thanks Murdoch.

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Old 01-10-2016, 22:28   #26
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Re: Help find chainplate bolts

Some of the nices "bolts" I've seen are threaded aircraft "rivets" or bolts. They have an allen head on the same side as the threads and a polished carriage bolt head with a round shoulder. Makes sense on a surface exposed to air, weather, etc.

To tighten you just put the nut on the inside and tighten. When it wants to start turning you just insert the allen wrench.

Sometimes you can find these things surplus
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Old 03-10-2016, 14:33   #27
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Re: Help find chainplate bolts

I ran into the same problem. It appears my bolts were originally carriage bolts that had the square portion machined off and a slot cut into the head. All I can say is that must have been a lot of work to make them.

I got 316 stainless carriage bolts from BoltDepot.com and a 1/2" square broach from McMasterCarr. Some say that having the square hole in the chain plate gives it a point to start cracking at. I weighed that possibility with the fact that my chain plates are 1/2" thick and external, so they are strong and easily inspected.

It helped that the round holes in the plates were already the correct start size for the broach. It also helps to have access to a hydraulic press with 12" of travel to broach the hole in one pass, instead of re-positiong the press blocks every 4" or so. That adds a lot of time to broaching 50 holes.

Looking back now, I probably could have found a machine shop that could do rotary broaching on all 50 holes for the price I paid for the manual broach ($200!) and saved me time too. Probably worth looking into if you go down this road. Very interesting videos on youtube on how they drill a square hole. Yes, you read that correctly, drill a square hole.

Oh yea, add a few extra bucks and have someone polish the heads of your bolts for that finishing touch.
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Old 03-10-2016, 15:32   #28
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Re: Help find chainplate bolts

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Originally Posted by Celestialsailor View Post
For the OP and Sailor Russell, simply but 316 SS carriage bolts and a 1/4" square file. A minute amount of elbow grease and you do not even need some one holding the other side with a driver.
If the op's chain plates are any where near the thickness of mine doing this with a file would be a long, tedious process.

In my case that would be filing 200 corners! Even if it could be done in 3 minutes a corner, that would be over 10 hours of filing. My hands are cramping just thinking about that!
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Old 03-10-2016, 15:35   #29
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Re: Help find chainplate bolts

ever consider domed head, the look classy
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Old 03-10-2016, 15:36   #30
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Re: Help find chainplate bolts

https://www.google.com.au/search?q=d...w=1440&bih=794
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