8.8 vs 10.9

[skulldrinker]

Looking to stock my new bins with Metric and SAE nuts and bolts. For the Metric should I go with 10.9 or will 8.8 be good enough.

For the SAE I will be going with Grade 8.

This is just for the home garage and I'm am looking at the USBoltsKits dot com for purchase.
Thanks for your replies.

 

[ddawg16]

Looking to stock my new bins with Metric and SAE nuts and bolts. For the Metric should I go with 10.9 or will 8.8 be good enough.

For the SAE I will be going with Grade 8.

This is just for the home garage and I'm am looking at the USBoltsKits dot com for purchase.
Thanks for your replies.

Really great question.....one can assume anything from China is grade 3. I really see it on the cheap *** screws supplied with something you screw to the wall.

You got me doing a look on the comparison....one of the 'rumors' circulating is grade 5 had better shear values. It appears that is not true.

This is a nice reference

https://rtstools.com/are-grade-8-bolts-more-brittle-then-grade-5-8-8-vs-10-9-metric/

The real question, do you need grade 8?

Is it worth the cost difference?

Me? I'd do grade 5 until I had a real need for grade 8

 

[Lucid Moments]

I recently stocked some of my bins and decided to go with grade 10.9. It is overkill for a lot of the things I need, but I don't need enough to keep multiple sets around and I decided it is better to go too high a grade than too low. I wonder about the issue of brittleness where something like a grade 5 might actually be better but I honestly don't really know how big an issue that might be.

 

[plinker]

I dont remember the exact details off hand, but 8.8 is similar to grade 5 and 10.9 is similar to grade 8 from what I do remember. 10.9 would cover things pretty well. Some stuff is grade 5 (or equivalent) for a reason though.

 

[plinker]

You got me doing a look on the comparison....one of the 'rumors' circulating is grade 5 had better shear values. It appears that is not true.

When I was working building hi rail trucks, the guy doing the rail gear said the bolts were supposed to be grade 5 on the rear rail axle mounts specifically because they would shear off in case of derailment and not tweak/damage the frame. I had heard it talked about one other time where Grade 8 was used and it caused some damage (3rd-4th hand info though).

Some farm equipment (older baler's in particular) also say not to use anything harder then grade 5 in shear bolt application if needed.


Most of the automotive hardware I see is 10.9 with some 12.9, not much 8.8.

 

[ItsNemo]

I dont remember the exact details off hand, but 8.8 is similar to grade 5 and 10.9 is similar to grade 8 from what I do remember. 10.9 would cover things pretty well. Some stuff is grade 5 (or equivalent) for a reason though.

Yup, this.

Honestly I just do TSC by the pound grade 5 stuff for my regular bolts on hand. For almost everything around the house/garage this is plenty to bolt together a couple things or whatnot. The higher grade stuff is useful for repairs on vehicles, but often times they end up being a flange bolt or fine thread when you only have course thread or similar, so it's easier to onsie twosie on those.

 

[M635_Guy]

It really depends on application. I wouldn't waste the money on Grade 8 for most things I do (I have bought Grade 8 where specified for my cars, and I used Grade 8 bolts when I installed my vise on the bench, but other than that I can't think of anything that would benefit from G8 vs. G5...)

 

[HoosierBuddy]

I typically buy the higher grade for my projects unless a particular finish is required.

The "benefits" of Grade 5 over Grade 8 have been argued for years via anecdote, but when you look at the numbers, a Grade 8 bolt is simply superior. A shear bolt, however, is not a "bolt" in the normal sense...so just take those off the table when considering grade.

The only advantages I see for lower grade bolts is they are cheaper and easier to drill out after they break.

Phil

 

[M635_Guy]

I typically buy the higher grade for my projects unless a particular finish is required.

The "benefits" of Grade 5 over Grade 8 have been argued for years via anecdote, but when you look at the numbers, a Grade 8 bolt is simply superior. A shear bolt, however, is not a "bolt" in the normal sense...so just take those off the table when considering grade.

The only advantages I see for lower grade bolts is they are cheaper and easier to drill out after they break.

Phil

I see you hail from the "Anything worth doing is worth over-doing" camp

I have times when I flip into that mode - half the reason I do so much work on my cars myself is to close the equation to do a more complete job (e.g. I'm not just replacing the water pump, I'm probably replacing the thermostat, the radiator and all the various hoses/etc. since all of that stuff is generally right there and is probably within sight of needing replacement as well. Sometimes there are reasons not to do that too though...)

I guess it's very situational for me - I built big storage shelves in the upper spaces in my garage, and while I'd definitely care if it fell, it's all Grade 5 bolts/lags/etc. But the design has multiple layers of safety. So it's probably over-spec'd as a whole, but the hardware isn't.

My wife wouldn't describe me as frugal, but I do have a line between "purposefully overbuilt" and "wasteful" - I'm just not sure I could fully articulate it other than through things like the example above.

 

[Dave455]

I was in the same situation a few years back. Loads of bolts and screws, little metric.

I bought a load of 8.8. To be honest, no regrets. It cost very little, and it’s all been useful.

For automotive applications though, you generally want at least 10.9, and that’s what I’m buying now. The 8.8 always seemed very soft compared to my older stocks. It’s not just the thread strength to be considered, but also the bolt head or screw slot too.

I’m buying, and use, 10.9 for most applications. If strength isn’t an issue, then I tend to use stainless. Started to use a lot of stainless maybe 10 years back, and it’s been brilliant. The premium for stainless isn’t what it was, but it’s been a game changer for me in the wet U.K.

 

[JZiggy]

That link shows a nice graph that shows there's a grain of truth in the the tell-tale "higher shear strength" of grade 5 bolts, even though that statement isn't true. The higher elongation at break of grade 5 means it is in fact tougher -- it will dissipate more energy before a fracture. So there is in fact a tradeoff...

But most of the time we don't really care about that. The bolt's function is to apply enough preload to keep the joint from separating regardless of load direction. A higher strength bolt lets you apply more preload.

Higher strength bolts are also more susceptible to hydrogen embrittlement, if you want to go down that rabbit hole: https://www.boltscience.com/pages/t...is-not-necessarily-the-case-for-fasteners.pdf

I suppose if you're using a bolt as a pin then there could be a good reason to use a softer, tougher grade 5 bolt.

 

[bobcatdan]

My metric bolt in the bins are 10.9. I didn't actually request 10.9, that is just what I got. When I asked about it, I was told the price difference between 8.8 and 10.9 is so little, they don't mess with 8.8 unless asked for. For comparison, grade 8 is about 50% more than grade 5. When I was looking at the assortments, I thought about being that guy that uses grade 8 for everything, then I saw the real cost. If I need grade 8, the supply house is 3 miles from the shop.

 

[Al Borland]

Really great question.....one can assume anything from China is grade 3. I really see it on the cheap *** screws supplied with something you screw to the wall.

You got me doing a look on the comparison....one of the 'rumors' circulating is grade 5 had better shear values. It appears that is not true.

This is a nice reference

https://rtstools.com/are-grade-8-bolts-more-brittle-then-grade-5-8-8-vs-10-9-metric/

The real question, do you need grade 8?

Is it worth the cost difference?

Me? I'd do grade 5 until I had a real need for grade 8

The next page on the RTS Tool site (Next article link) is about why 6 points are better than 12. (Just to poke a dead horse)
https://rtstools.com/always-choose-6-point-ratcheting-wrenches-unless-working-with-12-point-bolts/

 

[Strouty]

*** mentioned sometimes grade 8.8 (5) is better than grade 10.9 (8), all depends on the application. There are some really decent assortments out there, but you may look at what you normally use, the kits are selling you a lot of what you might never use. Remember the 399 piece tool kit with 100 hex keys???? Unless you are in some remote location, buy what you use all the time, or the most common sizes you think you will use, then when you find you need another size, buy a bunch of that size. I find that I can get by with a good assortment of 1/4 and 3/8 hardware in both fine and course. If I need 5/16. or 7/16, I will buy a bunch then I have it for next time. I rarely use 1/2, 5/8, or 3/4 unless it is structural or flange bolts. Of course you are dealing with metric, but the same logic applies.

 

[Leaflessshadetree]

I try and keep a good selection Grade 5 and 8.8 with Zinc coating.
Then there is harder, softer, stainless, galvanized and a variety of styles that accumulate due to overbuying when I needed something special.

 

[Strouty]

My friends joke that they come to me before a hardware store when looking for almost anything.

 

[Ralf11]

10.9 is more brittle sometimes

 

[laser3kw]

it doesn't matter (sort of) if you don't torque the fastener to correct preload. The fastener has to develop "clamp load" to be effective as designed. A 10.9 torqued to its proper rate will have greater clamp load than a 8.8 torque to its proper rate.

 

[ToolRoom]

Here in the U.K. 8.8 is the "standard grade" for most general purpose applications.

10.9 and 12.9 are the other common ones encountered and tend to be for specific scenarios where the properties are required (e.g. automotive suspension bolt) or often used for cap head screws

4.8 is mainly found on imported Chinese tools.

A2 (304) and A4 (316) stainless grades are also quite common, with A4 being used in harsher environments.

Rarely will you see anything else.

Most of my stock are 8.8 as they are cheap, easy to get hold of and suitable for most applications.

 

[American Locomotive]

Grade 5 and Metric Grade 8.8 bolts are way more than strong enough for most of the stuff the average person will do in their shop.

Put it this way, a humble Grade 5 1/2-20 bolt will have an ultimate tensile strength approaching 4,000 pounds. You could literally hang a small family sedan from a Grade 5 single 1/4-20 bolt, and it will not break. A single 1/2-13 Grade 5 bolt has a tensile strength of 17,000 pounds! You could lift a whole box truck with one!

Metric bolts work similarly. A Grade 8.8 M12x1.5 bolt has a tensile strength of 16,500 pounds!

Grade 5 and 8.8 bolts are super strong! Unless you plan to only be replacing suspension and head-bolts, I see absolutely no reason to spend the extra money on Grade 8 or 10.9 stuff.

 

[Ralf11]

what grade are seat belt bolts?

 

[JjKk40]

I've came across a bunch of 9.8 fasteners on vehicles before as well. Maybe a compromise between 8.8 and 10.9.

 

[Super Mech]

what grade are seat belt bolts?

I’m almost sure they are 12.9

 

[Theruse]

While we are on the subject, where is a good place to buy metric nuts/bolts in bulk. I am tired of running to the store because I want three or six or whatever bolts to all match when I am doing some job.

 

[Ralf11]

Wurth has quality kits. McMaster-Carr, Belmetric, etc. do mail order.

You have to be careful at the "Hardware Store" anyway as you may get sold some Chinesium, tho True-Value and some others seem reliable.

I'll just post this Public Service Announcement: Be careful! Check the manfs. parts list for anything that might a safety issue. If an engineer call out 12.9 don't jam 8.8 in there.

 

[tonyciambrone]

Shouldn't you really be buying everything in 12.9?

4.8 is plenty for most everything I do with bolts.
8.8 and 10.9 are cool to have around for automotive stuff.
12.9 are also used on cars, but I mostly see very specialized fasteners in this grade.

I would get 8.8 and if you ever really need a 10.9 in a pinch there is McMaster carr or whatever

 

[seber]

On the rare occasion that a grade 8 bolt is needed, you won't have the correct size anyway. If it is needed then it needs to be the exact size and length specified. I had that available at the plant I worked but the selection meant hundreds of sizes. You just can't justify that in a home shop. Stock grade five and order the specials as needed. I bet it won't happen even once a year.

 

[MoonRise]

General use: Grade 5 and 8.8.

They are 'graded' and pretty strong for most uses. Minimal risk of hydrogen cracking/embrittlement, either from any plating done on them or from environmental exposure.

If you NEED a stronger grade/class bolt, then get some Grade 8 or 10.9 or 12.9 for those uses.

IMNSHO.

Just like you probably won't use some ARP bolts everywhere.

 

[theoldwizard1]

For the SAE I will be going with Grade 8.

Grade 8 is overkill more most application and you will hurt your wallet, deeply.

 

[Ralf11]

Shouldn't you really be buying everything in 12.9?

Not what I'm told. Metallurgists say that as the strength of an alloy goes up, they become more brittle.

This has to do with malleable and ductile properties based on the fine grain structure in the alloy, and is above my pay grade. So I just do what they tell you to do in the parts diagram or repair manual. Saves me a whole bunch of brain cells.

 

[Steve_P]

Shear strength is directly related to tensile strength. Textbooks say shear is .50 to .577 of tensile ultimate. Testing says it can be almost as high as 90%. I always use .50 in calculations to be conservative; don't assume 90%.
SAE grade 8 is not that hard: RC 33-39; with ~15% elongation at tensile failure. This is not very brittle: basically a 1" screw will stretch to 1.15" before failing. If you think that's brittle, well, I think you have issues.
SAE grade 5 is ~RC 19-30 with 27% elongation at tensile failure.
More strength is not always better if you're threading into material instead of a nut. If you use a grade 8 screw into an aluminum plate and only have equal value of thread engagement to the diameter, you can strip the threads if you use grade 8 and torque to the specified value; you should have 2X+ depending on the aluminum alloy.

 

[skulldrinker]

I went with Grade 8 for SAE and 8.8 with the metric. Over 5000 pieces. Just need some labels. Probably just use white electrical tape.

 

[2ndGearRubber]

I deeply respect your bolt game, sir.

 

[macgee]

Sounds like its time to invest in a label maker. Very recent thread here talks all about it and its not expensive.

https://www.garagejournal.com/forum/showthread.php?p=8927756#post8927756

 

[Stick-man]

I know this is an old thread, but at US Bolt Kits, the difference in cost between the grade 5 and grade 8 is ZERO! And, the difference between the 8.8 and 10.4 is $44.00. These are the largest sets they have. Earlier in the year I went with the grade 8, and now I am going to be ordering the 10.4. It seems, because I am old school, all the new shtuff is metric.

 

[john.k]

Chinese 10.9 &Gr 8 is brittle for sure .........had a lot of breakage with these ,while the 8.8 would be OK...........if you want quality bolts that wont break ,buy off Caterpillar ...........once upon a time ,German made Unbrako was tops,now its Indian made and both low tensile and low quality.

 

[Junkdrawer Dog]

I had an application at work that used (3) grade 5 bolts for a clevis pin retainer. They were constantly stretching and working loose. I replaced them with grade 8 bolts and all that did was pop the heads off the bolts leaving me to extract all 3. Went back to grade 5 bolts and periodic replacement.

 

[tool_scrounge]

Chinese 10.9 &Gr 8 is brittle for sure .........had a lot of breakage with these ,while the 8.8 would be OK...........if you want quality bolts that wont break ,buy off Caterpillar ...........once upon a time ,German made Unbrako was tops,now its Indian made and both low tensile and low quality.

I am so sorry to hear about Umbrako quality dropping. They were always expensive in the past, but worth it when you really needed the strength.

 

[john.k]

Im told the Chinese bolts are all the same material ,and the Gr 8 rating is achieved by extreme hardness.......This is obvious if you use them for lathe turned parts ..........Caterpillar bolts machine easily with a nice finish ..........in fact ,its worth buying a bulk lot of Cat bolts from one of the tractor dismantlers .........used ,but still good

 

[dutchgray]

Chinese 10.9 &Gr 8 is brittle for sure .........had a lot of breakage with these ,while the 8.8 would be OK...........if you want quality bolts that wont break ,buy off Caterpillar ...........once upon a time ,German made Unbrako was tops,now its Indian made and both low tensile and low quality.

I pick up all the old stock I come across from the old quality bolt makers, hard to find anything off the shelf in my location that is really good now, everything is Chinese or Indian sourced.