Recently when channeling my Ford Model A I wanted to use Grade 8 fasteners for all of the body mounts instead of just tapping threads into the frame or inserting rivnuts that could fail over time. First of all the 1/4″ wall of the tubing wasn’t really thick enough to give sufficient threads to hold the weight and twist of the body from normal driving. We came up with a slick solution and figured we’d share.
I started by threading a batch of Grade 8 nuts onto a carriage bolt and locking them all together.
I then mounted the bolt into the lathe and cut off the hex portion of each nut leaving us with perfectly round grade 8 threaded inserts. The nuts were cut down just a hair bigger than 1/2″ so they would be a press fit into a 1/2″ drilled hole.
I then counter sunk each hole and threaded a bolt into each insert so I could adjust them so they were straight in the holes. I used the TIG 200 to carefully lay a weld puddle on the edge of the threaded insert melting it to the frame. You must take your time here and be very precise because a rogue dab of filler rod could go over the edge of the threaded insert and make your life hell when it comes time to thread a bolt back into the insert!
Hopefully you can use this method to put some clean, strong threaded inserts in your next project.
-Matt/EW
If you reread the article and look at the pictures you will see I put a bevel in the frame to do just that. The weld bead was flush with almost no sanding needed.
Takes longer but a drill and a file will do the same thing
what do you do with the raised bead, grind it smooth and you have nothing. I would run a 45 degree countersink in the hole before placing insert in it that way you have more weld grip and you can grind it flat
That’s all fine and dandy if you have a lathe if you don’t have access to one what good is it
I don’t know if a push broach (both square and hex) would work in your situation, kinda expensive but sure handy!
great idea once bolted on frame whatever is secured will probably not be taken on and off who cares if hardness dwindles thanks again for some great ideas
Great job and technique, looks as if it works perfectly! Where do you usually get your threaded inserts from?
I just don’t see how you managed to machine what ends up being something that slender and that long? I mean lets be realistic here, that screw is like .2″ on the M.D. those nuts seem to be about 3″ length which ends up like machining a wet noodle. You take passes under .005″ per pass?
One thing to note is that grade 8 hardware is heat treated. When you weld on heat treated steel you run the risk of losing the harder properties that are associated with Grade 8 hardware.
If you have the lathe anyways, why not turn and tap larger steel bushings. Then the bushings has less chance of losing its hardened properties at the threads.
I recently drilled a hole in a piece of steel, dropped in a grade 8 bolt, and welded the head of the bolt to the steel -this apparently changed the metal structure, for VERY shortly thereafter , the head of the bolt broke off of the bolt, leaving me with a bolt head only ( which I had to grind off ) Wouldn’t the same weakness occur to the grade 8 nuts after they are welded ?
I like that very much. I have a metal cutting lathe at my mothers house my dad left me & I have been meaning to get my butt over there to get it. I have already needed it for a few different things & will be needing it for more in the future.
After welding, the heat-treated nuts will no longer be Grade-8. They will end up either brittle or soft, depending on several factors.
As for not having a lathe, you can also fudge this on a drill press. However, why not just buy a handful of weld-on nuts from an on-line industrial supply house or on eBay??
I have taken this to another level. Now that flanged nuts are readily available I take advantage of the “flange” portion using it as a reinforcement and if room permits, will also TIG the flange portion.
very good
I’ve used this technique before without access to a lathe. I just used my bench grinder to round the edges off the nuts. It worked quite well.
that’s a good idea if you’re wanting grade 8 inserts, nothing wrong with that man.
If you don’t have a lathe… Put the nuts on a long bolt. Chuck the bolt in your drill press and while it’s turning ease a 4.5inch angle grinder to the edge of the nuts and grind the hex off. This has worked well for me……Keep checking your diameter and watch the heat…..
That’s pretty slick, but keep in mind they may not be “grade 8′ when you’re done. All that heat will take out any heat treating that was done to the nut previously, and it will also shrink the nut if you’re not careful. Been there, done that and the bolts still fit, but really tight.
Why not just buy a bag of weld nuts for $10? Google “weld nuts” to see them. They’re a common part.
I’ve been using a different process that eliminates the middleman. You can purchase Flange-Nuts, drill your hole and drop one in and then run your bead around the flange. If your worried about the height you dress up the weld with a couple passes with your angle grinder and your done.
grade 8 seems to be over kill for a non competition vehicle,
would you lose the grade 8 rating due to weld heat
great basic idea
, the copper bolt insert is an excellent comment
All good advice. If you do not have any tools, do a search for BUNGKING.
I didn’t have a lathe so I used spring nuts from electrical strut system. Drill hole size, cut spring off of nut, bolt it to the frame so bolt goes in easy and weld the back side to frame. then I boxed the frame. simple.
Great job, i have done a similar process for years but i just drill a larger hole and weld the hex in…the resulting gap makes for extremely strong welds and gives more buffer for the weld bead.
Seems as though the heat from welding would temper the heat treat on the grade 8 hardware. It might be ok if you were really quick about it and if the hardware were made from air hardening steel.
We use weld nuts from Lawson Company or find on line. Any size available. Usually come in a pack of 10. They look just like the ones being made on a lathe but a lot quicker. Thanks Jack
I would like to be able to use this on all kind of things .
If you don’t have a lathe, you can take the same setup and using a grinder, grind the corners of the hexs off and then drill the hole to correspond with the ground nuts. Same result.
Don’t this for 40 years or more and several ways to get same result.This one is time consuming but neat. Faster is bigger hole with bolt in nut and weld around surface ,but you better be good and better have the gear to do it as well as the room. I am spoiled and sometimes turn vehicle on its side or upside down to fabricate.Old age causes this convenience.
For those that don’t have a lathe or the extra time to fabricate them the same style of ” weld nut” is readily available. There are several sizes and styles some have steps to keep them from falling through and help alignment.
I don’t ever “comment” on sites. But I have to comment on the quality of responses, above.
If you don’t have a lathe buy one, you’ll be happy for the rest of your life.
Good idea! A small machine shop or a hobby machinist wouldn’t charge much to do this if you don’t have access to a lathe.
They are not grade 8 after you weld them. Not sure exactly what they are but they are not grade 8 any more.
Even so, it’s a nice job and certainly does what you want it to do.
If the metal is thick enough (such as a frame rail), you can use a grade 8 flange nut as an insert. I use a Unibit to make a stepped hole just deep enough for the nut flange to be flush with the frame rail, then weld it in. It is a very strong insert and no lathe required.
If you have time and don’t have a lathe, McMaster Carr has a good variety of them and they aren’t too expensive. I keep may sizes on hand for quick fixes or alternates to tapping threads where there isn’t enough material to provide a strong joint.
You don’t need a lath.
They don’t need to be perfect.
Chuck the bolt into a drill press,
spin it on low speed.
Then use you air wize wheel or electric
angle grinder to round them off.
I’ve use a a hand held file and
battery powered drill to do it.
BTW:
Most of the value of grade-8 goes away
from the heat when you weld small parts.
I’m under the impression that the heat from welding a Grade 8 nut/bolt will alter it’s mechanical properties such that you don’t have grade 8 anymore. A quick Google search seems to confirm that. Most HW store items are of an unspecified metallurgy, so results will likely vary. If strength is the goal, this seems like a problematic solution.
The thick wall tubing is a good idea, but beware the tubing is no where close to the tensile strength of a grade 8 nut, if you must apply max torque.
I’ve done this but not using a lathe.I put a nut on a screw then put that on a drill and sanded it.super fast way.
Thanks for the reminder.
Not having a lathe, I have put a screw into a drill chuck and rounded the nuts with a metal file … more time consuming but it gets the job done.
Carbon rod threaded and screwed into the inserts will prevent weld from entering the insert also.
I needed the same type fasteners but I did not use a lathe. Here’s how I set this up. I threaded the bolts onto a 10″ long piece of stainless steel threaded rod. I then chucked it into my drill press and ran it at 1000 rpm. Using a file first and then finishing with strips of sand paper I got almost the same results, a perfectly round (well almost perfectly) threaded insert..Your way is much more accurate but this was as alternative as I do not own a lathe.
All these tips I collect as I’m at at a place and
Time I can actually do a complete build.
Thank you.
IMHO, seems like an huge amount of work for an insert! McMaster-Carr sells a wide variety of threaded inserts. Even *properly* installed heavy duty rivnuts (also McMaster-Carr) should be fine for such an application, where the bolt will be tightened and removed only a few times during the life of the vehicle.
Some years ago I replaced the wear bar on a snow plow. The mounting holes did not match up, and I needed to reposition the square holes. This was pre Plasma torch for me, I thought how great it would be to have a square hole insert to weld in place. I would also like Hex holes that could be welded to projects as nut keepers.
Buddy should have used a center drill on the end of the carriage bolt and used the lathes tailstock with a live center to steady the whole assembly while turning it.
If you don’t have a lathe just drill a bigger hole and press in the hex nut. It will take a bit more welding to fill in the gaps. Running my lathe is more fun 🙂
I’ve done the same thing by threading the nuts onto a long bolt or a length of threaded rod and grinding them round with a bench grinder. Not as slick but works just the same. Don’t forget to jamb the nuts together or they will walk on the rod and wear welding gloves…..that rod will get hot.
Unfortunately after welding the bolt is no longer hardened to the grade 8 standard anymore.
Try chucking your threaded rod into a drill press or hand drill affixed to your bench, turn it on, use a grinder with light pressure to round the nuts & follow with a file to clean up.
I thread copper and brass bolts into the serts to keep the threads clean when welding.
Nice job but not everyone has a lathe so using a thick wall tube and tapping it would solve that problem. You may have to find a tube with a inside smaller diameter than the tap and drill it so the tap would work.
Yes I’ve done that and it really is the cats meow. Sure it takes time but the results are worth it. Have also cut out thicker washers with hole saw and threaded them either to weld (where unseen) to not only give a properly threaded piece, but also for some extra thickness where needed. Generally I use this where I have 1/4 or 5/16 fastening challenges.