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What steel are grade 8 nut and bolts made off?

Laverda

Cast Iron
Joined
Mar 24, 2014
Location
Riverside County, CA
I need to make some 5/8"-22 nuts. This thread size is not available off the shelf and the hex size will also not be standard. They need to be equivalent to grade 8 or better. What steel is commercial hardware of this grade made of? Are they heat treated? I would rather not get some oversize grade 8 bolts and use the head as my stock to machine the thread and hex to size. But it may be my only option????
 
I need to make some 5/8"-22 nuts. This thread size is not available off the shelf and the hex size will also not be standard. They need to be equivalent to grade 8 or better. What steel is commercial hardware of this grade made of? Are they heat treated? I would rather not get some oversize grade 8 bolts and use the head as my stock to machine the thread and hex to size. But it may be my only option????

The j429 spec Steve references includes a purposely loose material spec. It includes any medium carbon steel like 1040 or 1050. What is locked down in the spec are the mechanical properties, so most any steel can be used if the mechanical specs are met after heat treat. It does not preclude alloy steels like 4140. $$ usually will do that.

As a side note, the temper temperature specified is 800 degrees. This along with the mechanical properties means the fasteners are tempered martensite. You won't reach ductility without it. So no cheating in heat treat. Also if 800 degrees is reached or exceeded in the end use, the fastener will continue to soften and eventually be grade 2. So much for all the strength specs. Under the 800, no significant hardness or strength degradation.
 
Check the diameter of the shank first before buying a bunch of any bolts. If the threads are rolled you may find the actual shank size is a touch less than you need to cut threads.
 
Oversize grade 8 bolt could be your cheapest option as you end up with lot less wasted material. (Works unless you are making these in hundreds on bar feed machine.)
 
Check the diameter of the shank first before buying a bunch of any bolts. If the threads are rolled you may find the actual shank size is a touch less than you need to cut threads.

Would that make a difference? I think he’s making nuts.
 
I used ETD 150 at my last job to make custom high strength thread adapters. Available from McMaster, easy to get and machines great.
 
I suggest pre heat treated 4130 . Meets the bottom end of the Grade 8 specs. I suggest this because it's commonly available and machines readily if a bit abrasive. If your customer is picky you may need specific heat treatment.

If one bolt and nut is required I suggest you buy a grade 8 bolt having a long un-threaded shank so you can crop the existing threads and cut new threads suiting the customer. The nut you can make - well, 4130 pre-heat treated will work fine. My vote is make it all from scratch and HT to suit the specs. Do they want a test specimen or a sample to break?

22 threads? Why? Not even a preferred thread.
 
Went back and read the original post again. Making nuts out of grade 8 bolt heads? I thought all grade 8 bolts were case hardened. If you are making grade 8 strength nuts you should start off with a material that is already that strong as suggested or make them from scratch out of a material that can be heat treated to that strength. The center of a bolt hex when drilled will not have the surface hardness/strength I think a great 8 bolt has on the outside.
 
Another voter for ETD-150. Matches the yield and tensile of Grade 8 with excellent machinability.

http://www.niagaralasalle.com/pdf/etd150casestudies.pdf

Look at both specs. 4130 and ETD-150 are nearly same except ETD-150 has an added tellurium.selenium or sulfur content to aid machinability. Not arguing one over the other but this is a distinction making little difference. Mechanical specs of 4130 and ETD-150 are both on the minimum side of the Grade 8 spec.

Grade 8 specs serve the fastener industry where shear, fatigue, bending, and stress reversal are not factors. If the customer wishes this for an application requiring unusual resistance to shock or fatigue he should provide better material specs than "Grade 8.".
 
A few more details. The nuts are 5/8" 22 thread with a 1 1/16" hex. They are only 1/4" thick which is why they are such a fine thread. Need to make 12 of them and they are going on to an old piece of machinery. They will be torqued to 75 ft lbs. As for the grade 8 spec, who knows what the original ones were made of but as they are only 1/4" thick I want to be safe. Can't buy a tap this size so will be single point threading. Would like to be able to buy a piece of hex stock the correct size to begin with but don't know what type to order. I do have a heat treat oven so am not worried about this. If I have to I will get some grade 8 bolts with a head bigger than 1 1/16" and mill to the correct size and on to the lathe and bore and cut the threads. On the original nuts beside being rusty and chewed up from it looks like a pipe wrench you can see the threads were stretching. I have made parts out of scrap grade 8 and 9 bolts laying around and with carbide if cuts easy.
 
Another voter for ETD-150. Matches the yield and tensile of Grade 8 with excellent machinability.

http://www.niagaralasalle.com/pdf/etd150casestudies.pdf

Watch out. Due to the added sulfur or other element to increase machinability, the ductility of ETD-150 is about half that of 4130 pre-hard. The thing that makes chips break can also, in a sense, help the material itself break. ETD-150 is great, but check that its ductility is adequate for the application.
 
Liability if they fail? I will need to make another set. And an unhappy customer as it will take hours to replace them. So let me ask the question another way. First, lets forget about grade 8 nuts. I want you to make me some 5/8" 22 nuts 1/4" thick that I can torque to 75 ft lbs. That's the only info you have. What steel would you use?
 
Must they be 1 1/16?

I can find 1 1/8 hex bar stock. How about that in 4140 then harden?
 
maybe you could buy one grade 8 bolt, 8 or 10 inches long. Cut out the shank with out the threads...Now you have a piece of stock you could hex all at once. ( you could leave the head on to use in timing the hex. You could also put a hex collet block on the end of the shaft and use it to time the hex- clamp in the vise on the material and use a level on the hex part or indicate on the hex if you need more accuracy).
Prolly drill and thread about an inch deep and cut off three 1/4” nuts at a go
 
It looks like ALRO has 1-1/16" 4140 cold finish annealed hex. Fry Steel lists cold finished 4130 prehard and 4340 normalized and tempered in 1-1/16" as well.
 








 
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