Ron78Z&66Vette

I'm FINALLY ready to bolt the front suspension together. I ran my hardware in my tumbler for a good 12 hours, but they all atill look like cr@p.

I'm having a hard time finding "Grade 8" hardware, so I was wondering if "Grade 5" would be a suitable & safe substitute? I'd hate to use crummy looking hardware next to my powdercoated comtrol arms, but if it's a safety issue I guess I'll have to.

GCD1962

Look for a larger ACE Hardware store. My local ones has a huge stock of all sizes including Grade 8. I used the grade 8 on my front suspension. If you can't find I might have the "correct" ones that Corvette Central sells (I didn't use them)

63C2splitter

Ron,

I am anxious to see responses from the technical experts on this. My guess is that you should use grade 8. I live in the Wichita area, and several places you may find them are: the Ace hardware on w. 13th (Indian Hills) - they carry a lot of bolts and fasteners, another is the Yard store, and a last recommendation is a hardware store at the corner of 47th South and K-15 - they have a lot of stuff as well (not a fanchise HW store, just an old fashioned "have everything" type of place). I haven't been in the one on 47th for many years, but I think it is still in business. Good luck.

Dave

firstgear

Tractor Supply store also has them and even check at Home Depot, not sure but they have a large special bolt area as does Lowes....but I would only put GRADE 8 in there....why take the chance?

Also, do a search for any local Fastenal stores, there is a web site that you can order the parts you need and then pick up at your local Fastenal store and for sure you will be able to get what you need from them. Not sure how far these guys are from you...but they have to be close and you can get any bolt of any type from them....or even take your bad bolts in and tell them you want ones just like those but new and grade 8....
Fastenal
Location Address
Store Code: KSWIC
Wichita, KS 67217 2461 South Leonine Street
Wichita, KS 67217
P: (316)941-4400
F: (316)941-4404
Store Code: KSWI1
Wichita, KS 67219 3040 N Ohio
Wichita, KS 67219
P: (316)265-1961
F: (316)265-0721

http://www.fastenal.com/web/home.ex

good luck, Herb

Sky65

Not sure what part of your suspension you are talking about but I wouldn't use grade 5 in stress areas. Bump stops I would use grade 5. No what I mean Vern?

BADBIRDCAGE

Come see us at the local NAPA store in the country. We supply farmers with bolts for everything they own and we have grade 8 in all sizes you might need for the front end rebuild.

I am in Virginia Beach but I am betting you have a good one local there.

Rich

Hitch

You will find that Lowe's has the best selection when it comes to on the shelf and that Fastenal can get you anything you want. The problem with Fastenal is that you usually have to buy 20 when you need one and 100 when you need more than 5.... Dave

67L36Driver

Only an idiot would sub a grade 5 for a grade 8.

Hitch

You would be surprised at the amount of grade 5 bolts in your midyear

66since71

Suspensions, I agree.

Into cast iron (blocks and heads) Grade 5. For aluminum (Muncie housings) ungraded or max grade 5. Depends on what you want the failure mode to be (when you over-torque it)!

Harry

chris ritchie

My local Lowes has a huge selection of Grade 8 nuts and bolts. The local Home Depot isn't bad either.

Don't use stainless steel. Has little strength. Less than Grade 5.

Maker sure you use all the "castle" nuts and cotter pins where called out in the AIM.

I'll bet the usual Corvete parts vendors also sell these nuts and bolts.

kcust62

Grade 5 bolts have about 70% of the compressive load strength of a Grade 8. Example: a 1/2"-20 TPI Grade 5 bolt (medium carbon 1038) w/ a stress area of .1599 tightened to the recommended torque between 65-85 ft/lbs will yield ~10200 lbs of compressive load capacity. A Grade 8 (medium carbon alloy 4140) in the same size at the recommended torque of 90-120 ft/lbs will yield ~14375 lbs. So, you can see a significant difference in strength. The use of Grade 5 or Grade 8 depends largely on the application and the associated mechanical strength requirements needed. Arbitrarily substituting bolts could be hazardous to your health if not done wisely. If in doubt, play it safe!

Ron78Z&66Vette

Well, I'm glad I asked!!

I had to do a lot of hunting, but I found Grade 8 to use where I need it. There was a couple of larger bolts that I couldn't find in fine thread, so unless anyone sees a problem with substituting course instead, I'll have to reuse the old hardware.

If any of you wichita area guys ever need any, Hupp True Value Hardware (around 700 block of E Harry) has a HUGE selection and I was able to find most of my stuff there. I never made it over to the hardware store on 13th, maybe tomorrow if I see I'm missing anything or am really bothered by the few old pieces I have to use.

Time to go out and start wrenching & thanks again!

Cris

I recently rebuilt my front suspension and a local mechanic who was coaching me through the process said he would never buy a bolt from a hardware store. He said too many counterfeit grade 8's are out there. I went home and researched the problem and he was right. In fact, the aircraft industry has banned grade 8 hardware for this reason. The other problem with plated (gold zinc) grade 8 hardware is hydrogen embrittlement. If the bolt manufacturer is not careful in the plating process he can trap hydrogen which migrates into the steel and embrittles the bolt.

I found US and Canadian bolt manufacturers still make very high quality bolts and they have addressed the issue of hydrogen embrittlement. If you buy a bolt from them, they are the real deal. How do you know if the bolt is from them? All certified grade 8 hardware carries a manufacturer's stamp. Two very common stamps are Infasco (raised filled triangle), and Lake Erie (LE in raised letters). Infasco is Canadian and I have talked to their engineers about their process, Lake Erie is a US company. (And the offshore companies sometimes counterfeit these manufacturers stamps.)

If I have time I buy my bolts from a local supplier that only stocks US or Canadian bolts. If I am in too much of a hurry, I head down to my local hardware and look through their bolts for the right manufacturers stamp.

firstgear

All of my bolts that I got with my suspension pieces from Myers Racing were FINE thread GRADE 8. I couldn't figure out why, because getting coarse threaded bolts was so much easier. But this is why after I did a
research...

Are bolts with fine threads stronger than bolts with coarse threads of the same grade?

Yes, bolts with fine thread will produce about 10% more clamping force than coarse bolts of the same grade. This is due to the differences in cross-sectional areas. The thread roots of the coarse threaded bolt are deeper than those of the fine threaded bolt. Therefore, the fine thread series has a larger stress area and can support more load.

A few items to know...

Are Grade 8.8 metric bolts as strong, or stronger than, Grade 8 cap screws?

No. Metric bolt heads are marked with their property class, in this case, Class 8.8. Class 8.8 is the tensile strength of the fastener, expressed in Megapascals, and is basically equivalent to grade 5. If a bolt is needed that is of grade 8 strength, the metric equivalent to use would be class 10.9. Again, the class marking will be on the head of the bolt.

Are stainless steel bolts as strong as Grade 5 or Grade 8 bolts?

Most commercial stainless steel fasteners available are made with austenitic stainless steels (200-300 series). These are commonly known as 18-8 (304) and 316 grades. These grades are not that high in strength and should never be used in applications calling for grade 5 or grade 8 fasteners. In fact, they are in the strength range of grade 2 fasteners (approximately 75,000 psi).


Above is just a few tid bits from this site http://www.4asource.com/FastenerFacts.html#Anchor4


and just a few more with VIBRATION resistance the key for suspension pieces...

A quote about Coarse vs. Fine threads. "I bought all coarse thread for my body mount hardware, cuz I figured it'd be easier to take off (less time with a ratchet). But in longer bolts, I was unable to find coarse thread." Another digester said something recently about mistakenly buying coarse thread... What's
the deal?

Coarse (UNC) threads are used for general assembly work, especially where frequent assembly and disassembly is necessary. They should not be used in designs in which vibration may be encountered. They should always be used in nonsteel metals like brass and aluminum. The rule of thumb is always use coarse threads unless a specific factor of design indicates otherwise.

Fine (UNF) threads are widely used in automotive applications where vibrations are likely to occur. Only used with steel.

Interestingly, fine threads are only about 10% stronger than coarse threads. A 3/8-16 thread has a tensile stress area of 0.0775 sq.in., 3/8-24 0.0878.


above from http://www.binderbulletin.org/faq/11.htm


So, if I was you, find time to get the RIGHT bolts with FINE threads and you never have to look back...

67L36Driver

Welcome to 'Fasteners 101'. All of the gearheads on this forum should read this thread.

SPLITRAY

Well done Firstgear, great info!

Also, Do not attemt to torque a coarse thread to the Fine thread specs provided in the AIM... as you may over torque the bolt beyond its elastic point.

When the AIM calls for a specific torque in a specific location, it assumes the proper fastener is being used.

John McGraw

I would not substitute a coarse thread where a fine thread was used. They usually used a fine thread because the additional clamping force was required. McMaster Carr is another good source of fasteners, and they ship fast and usually have no minimums.
There are Stainless bolts that are stronger than Grade 8, but they are not cheap! I use them exclusively on my hot rods because of the look of the highly polished, small hex, flange head blots. Totally Stainless sells all sizes of high-strength stainless bolts in both metric and fractional sizes as well as lower strength stainless bolts. Some of the larger sizes like 5/8" X 8" can run in excess of $15 for a single bolt, but they sure look good!

Regards, John McGraw

firstgear

YIKES!!!!

JohnZ

Yup, there's no substitute for ARP bolts when you're building a project car; quality fasteners cost money, but they'll never let you down.