I have a set of grade 8 bolts that are holding my CV driveshaft currently. I was wondering if it would be possible to drill a hex into the head to make it easier to tighten and remove. Currently it very difficult to get a wrench on it to tighten it properly.
Short answer, NO!
Long answer:
- Grade 8 bolts are hardened steel and very difficult to machine.
- You canât âdrillâ a hex hole. You need something like a rotary broach, which we donât have, and if we did would not be useable on a grade 8 bolt.
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Machining a hex socket into an existing bolt would be difficult at best even with mild steel and the right tooling, if we had it. Hardened grade 8 steel? Might as well kiss the expensive tooling good bye before even buying it.
Look up grade 8 bolts with the same thread pitch and length on https://www.mcmaster.com/ that have a hex socket, if they exist.
If they donât, it may be because of the other issue - how much torque can be applied without stripping out the socket? Small socket on a hefty bolt, or a bolt that requires a high amount of torque (like with holding a drive shaft in place), it may not be possible to apply the correct amount of torque without stripping out the socket, even with a hardened steel bolt.
Youâd want to form the head with a die anyway, and then add the threads with a lathe. Machining a die and getting the metal hot enough to form, then threaded, then hardened properly again would be a monumental task.
And the other issue is - what happens if the bolts you make fail when youâre going down the road at speed? On a door panel, it might not be anything major, on a drive shaft, it might be a fatal accident for you or someone else.
Engine and drive train bolts are not something you should really do yourself, at least if itâs on a vehicle that sees use on public roads.
Nah, best case (and worst case) is that we get rid of a few bad driversâŚ
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Worst case is if itâs on a car, on a public road, and takes out a minivan full of kids on the opposite side of the highway in a head-on collision. Ideally, other people shouldnât die for our mistakes.
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Well that got darkâŚ
Jesus guys. That escalated quickly.
Is this a CV joint on a driveshaft, or on an axle shaft? If itâs an axle shaft, the failure mode for mount bolts is non-catastrophic and wonât cause an accident, so do the McMaster-Carr thing. If itâs a driveshaft (for example on a RWD or 4WD vehicle) then make sure your replacement bolt heads are capable of holding the required clamping force and wonât deform at the torque setting that generates that clamping force.
But while that failure mode is typically catastrophic, it wonât cause your car to veer out and kill somebody, youâll just lose your ability to accelerate. And probably need a replacement driveshaft.
Bolts is bolts. As long as they are made to the appropriate specification and installed correctly, thereâs no need to be afraid of using âthe wrong onesâ in an automotive application. The only thing to watch out for is mitigating the effects of vibration- donât want anything to back out. Thread locker is typically sufficient for this.
Iâm curious what kind of vehicle weâre talking about, what their current configuration is (i.e. what is the current tool requirement), etc. I find that most DIYers are using the wrong tool, or using it improperly, when I encounter complaints about difficulty in the âCV axleâ area (which, for the record, are separate components; the axle is the shaft, the constant velocity joint(s) is(are) the bendy bit(s), but I suppose they ARE usually retained as a unitâŚ).
Itâs a driveshaft. I bought 12 point bolts from a manufacturer in Nevada. On that note Iâm now the owner of 25 count of 5/16, 24, 1-1/4 if anyone ever needs a set of those bolts.
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Itâs the driveshaft plate that holds the driveshaft to the yoke.
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Roger that.
And this.
My question remains, what kind of vehicle/application/current configuration?
From your original description, it sounded like you meant internal 12 point, which would look more like this
that you wanted to âdrill outâ to a hex shape, like this
Iâm guessing with â12 point, 5/16x24x1-1/4â bolts", weâre talking external 12 points?
Like so
It seems like finding some 6 point grade 8 5/16x24/1-1/4" bolts would be MUCH easier than trying to machine (grind) those downâŚ
https://www.fastenal.com/products/details/0118797
If you actually meant the former, we do not have the broaching equipment to make that happen (and although I read about folks turning grade 8 bolts, I have no experience, and if Walter says donât do it, the machine shop chair is likely to take that stance as wellâŚ).
I currently have home Depot grade 8 bolts. Everytime I pull the driveshaft its a pain the ass. So I just went and bought outer 12 point bolts. I was just trying to figure out if there was an easy way to convert regular hex bolts to internal hex bit bolts.
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Ah.
No.
You did the right thing, ordering those. 
To not derail this thread overmuch, Iâll keep it short hah. FUD (fear, uncertainty and doubt) is an evil sales tactic, notably used by Microsoft. The reason itâs notorious is because as Microsoft practiced it, there was no real truth behind it - the evils of open source were anything but what they said.
Thereâs no FUD when it comes to making unsafe repairs or modifications to things that keep your car from crashing. âIâll make my own driveshaft boltsâ is fine if you know what youâre doing, but when someone is asking these sorts of questions, they donât.
If someone isnât aware of how things can go wrong, itâs better to explain what could go wrong than to stay silent. Especially when thereâs a reasonable potential for getting themselves killed or others on the road. If there was none, sure, itâd be akin to chicken little, but if your driveshaft bolts strip out while going down the road at speed, and one end drops while the other stays in place? Itâs not unreasonable to say it could be a very bad day for both the driver and others on the road.
To date, I have had one complete loss of steering event caused by work done at a top rated professional shop, when they failed to torque and cotter pin the taper joint between the pitman arm and the power steering sense valve, and if fell apart giving a total loss of steering while on the public roadway.
I have another professional shop case where tie rod adjustment clamps were installed not in the manufacturer recommended orientation leading to damage to the power steering valve, that could have lead to loss of power assist, and fluid spilled on the roadway, neither of which are great for public safety. It did do a fair bit of damage before I identified what they did wrong.
My father had a shop fail to tighten the oil drain plug on a car such that it fell out about 400 miles down the road.
Iâm sorry, but the professional shops arenât setting a very high bar to beat in terms of public safety, if you have even a basic understanding of your limits.
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Good to know, but they were expecting and planning for failure. People get killed because theyâre distracted and spill their coffee or look down for a second to change the radio station. It doesnât take much. And sure, a tie rod, or an axle or even loose lug nuts might make for a worse day. But it takes very little to cause an accident, it doesnât hurt to do things the right way when one potential side effect is getting killed. Stick with the original OEM bolts? Worst comes to worse, itâs a pain in the rear to get them on and off. Or make your own and worse comes to worse, get in a wreck because they fail unexpectedly?
Everyone has their own measure for what they consider acceptable risk.
No argument?
Sure, crappy work by crappy mechanics is possible. And good work by non-mechanics is possible, if you know what youâre doing.
If youâre asking about machining a hex socket into bolts that were never designed for that⌠Itâs a reasonable sign that someone doesnât know what theyâre doing.
Here are a few local hardware sources for next time:
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Elliottâs Hardware on Inwood near I-35E (best hardware store selection Iâve seen in Dallas)
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Crouch Sales Company - on Irving Blvd down near Parkland Hospital http://www.crouchsales.com
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All Size Supply - on Irving Blvd just east of Hwy 12. http://www.allsizesupply.com
-Dave
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Iâd ask you to take that accusation back.
I am not saying âDonât make somethingâ, Iâm saying âIf youâre working on something that can get you or others killed, you need to know what youâre doing before you make something. If you have to ask this question, you donât know what youâre doing. Please listen to those around you before proceeding, there may be another way to achieve your goals without risking life and limbâ
Iâd say the Makerspace, new though I may be to it, believes the same - a lot of the machines in the machine shop have required safety training, because you can main yourself with a lathe if you donât know what youâre doing. A car is capable of the same, and due caution should be exercised in the same manner.
Do you still stand by your accusation?