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Forum topic by Fezz posted 12-18-2018 08:01 PM 829 views 0 times favorited 17 replies Add to Favorites Watch
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Fezz

5 posts in 251 days


12-18-2018 08:01 PM

Topic tags/keywords: workbench bolt knockdown

Hello,

I’ve got myself a real mystery on the last step of assembling my new workbench. I’m just getting started with woodworking and this was my first project. All went fairly smoothly until the final assembly.

The joint I used one the stretcher to leg assembly is a simple blind mortise and tenon that is drilled all the way through from the outside face of the legs about 3 inches into the stretcher to fit a 3/8in bolt. This bolt then exits into a 1 1/4inch holedrilled perpendicular to the bolt, where I can attach some washers and nut to tighten everything down. This is a basic setup I have seen on many other knockdown benches.

After a test fit of the front stretcher, I went to loosen the bolts so that I could fit the rear stretcher as well. Only problem was that the bolt turned about a half turn and then jammed very solidly. I cannot for the life of me figure out what is going on. It is happening on both ends of the stretcher. both bolts are not jammed in the wood, they’re free to rotate on their own and there’s plenty of clearance in the hole. The nut was simply jammed on the bolt threads. I ended up having to use a breaker bar and turn the bolts until they sheared to separate the joints. Can anyone give me some insight as to why this happened?

My only thought was that I got exit fever, and ended up not flattening the inside face of the 1 and 1/4 inch hole. Perhaps the washers digging into the rounded side caused the threads to go out of whack? but this was just a test fit and I really didn’t torque them that much.

See attached picture perhaps to clarify if my words were not clear.

Thanks!

Nate


17 replies so far

View Lee's profile

Lee

135 posts in 1298 days


#1 posted 12-18-2018 08:38 PM

Well, the only thing I can think of is you cross threaded the nut. Did you spin the nut on by HAND not with a wrench till the bolt protruded about 1/8” past the nut before getting tight.

-- Colombia Custom Woodworking

View Jack Lewis's profile

Jack Lewis

452 posts in 1498 days


#2 posted 12-18-2018 08:40 PM

Use a dremel cutter and split the nut!

-- "PLUMBER'S BUTT! Get over it, everybody has one"

View bondogaposis's profile

bondogaposis

5453 posts in 2771 days


#3 posted 12-18-2018 08:58 PM

Chop the opening into a “D” shape with a chisel so that the washer can lay flat.

-- Bondo Gaposis

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lew

12807 posts in 4175 days


#4 posted 12-18-2018 09:05 PM

I’ve had threads gall if the nut/bolt was over tightened or if the steel was really soft. COuld be that happened.

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View johnstoneb's profile

johnstoneb

3115 posts in 2592 days


#5 posted 12-18-2018 09:31 PM

X1 Lee
That nut should have turned on very easily. I would bet that it crossthreaded and you torqued it on in. It is very easy to crossthread in a situation like your photo.

-- Bruce, Boise, ID

View Fezz's profile

Fezz

5 posts in 251 days


#6 posted 12-18-2018 09:54 PM

Right, I should have included this in the original post, but I am fairly confident that it was not cross threaded. I was able to thread both nuts on by hand until the bolt was through the nut before tightening. Although I agree this does still seem to be the easiest explanation for what happened. The hardware I used was nice stainless 18-8 stuff from McMaster.

I will have to see if I can fit my dremel in the hole to cut the nut, or else it’s back to the lumber yard to remake this stretcher…

Thanks all

View Kazooman's profile

Kazooman

1325 posts in 2372 days


#7 posted 12-18-2018 10:16 PM

I am not an expert when it comes to nuts and bolts, but I think you might have an issue with galling. Basically the pressure exerted by tightening the bolt can virtually weld the threads together. This is more of a problem with stainless steel bolts than plain old vanilla carbon steel bolts. I have no way of knowing if this is what actually happened to you, but it is a possibility.

Stainless steel is great for situations where corrosion is anticipated, but it shouldn’t be necessary for a workbench. As pretty as it looks, SS is not always the best choice. Same goes for wood screws. Some SS versions are easier to shear right off than other metals.

Here is a Fastenal reference on fasteners. Check out the discussion on galling starting on page 6.

https://www.fastenal.com/content/documents/FastenalTechnicalReferenceGuide.pdf

Go to the big box store and purchase whatever bolts they have in the bins. They will work just fine for your bench.

Note added later: As far as the wood screws go, I just recalled what happened when my contractor was trying to install the custom kitchen cabinets we had built for us. The frames were all solid maple. They were trying to fasten pairs of side by side cabinets by drilling pilot holes and running in some nice stainless steel screws. They kept shearing the heads off the screws. I recalled a document I had from the McFeeley screw company that compared the shear strength of various screw materials. Stainless steel was not the best choice. The installers switched screws and had no more problems.

View LittleShaver's profile

LittleShaver

554 posts in 1039 days


#8 posted 12-18-2018 10:48 PM

If you insist on using Stainless, get some graphite on the threads before you tighten the nuts. A little lubrication from the graphite should stop the galling. The stuff they sell for lubricating locks should work just fine. Way back in my submarine days we did this on SS fittings to prevent galling.

-- Sawdust Maker

View Kazooman's profile

Kazooman

1325 posts in 2372 days


#9 posted 12-18-2018 11:10 PM


If you insist on using Stainless, get some graphite on the threads before you tighten the nuts. A little lubrication from the graphite should stop the galling. The stuff they sell for lubricating locks should work just fine. Way back in my submarine days we did this on SS fittings to prevent galling.

- LittleShaver

Whoa! Do you mean to tell me that my wild-ass guess has been confirmed by a former submariner! That is way cool! A submarine would be a logical place for corrosion resistant stainless steel fasteners. For most everyday applications SS is not the best way to go.

The Fastenal reference mentions lubrication, but I don’t recall if they suggested graphite. That would be a lot neater than having oil dripping down the legs of your bench.

PS: Being somewhat claustrophobic, I am always in awe of anyone who could serve on a submarine. It must have been an incredible experience. The technology fascinates me, but only from the comfort of my armchair. Sort of like mountain climbing.

View Fezz's profile

Fezz

5 posts in 251 days


#10 posted 12-19-2018 02:13 AM

Thank you! Now having googled “galling” and done some reading, this is exactly what happened. Great to know, had no idea stainless was the wrong choice. I just assumed it was a bit more insurance and pleasant on the eye.

Now I just need to think of a way to cut these nuts out of a 2 inch deep hole so I don’t have to remake the stretchers.

View Kazooman's profile

Kazooman

1325 posts in 2372 days


#11 posted 12-19-2018 02:54 AM

I wish I had an instant fix on cutting the stuck bolts out, but this is probably one of those situations where the best scenario is to suck it up and move on. If the bolt and nut are truly stuck (and I believe that they are), then you have few options. I cannot imagine the amount of time, materials, finesse, etc. that it would take to cut through a stainless steel nut deep down in a hole with a Dremel tool, or any other tool for that matter, without damaging the stretcher. About all I can imagine is driving some wedges (some sort of metal perhaps?) into the hole to trap the nut and then trying brute force to remove the bolt. It sounds like you have already tried things like that.

New stretchers, some new hardware and you are good to go!

View Kazooman's profile

Kazooman

1325 posts in 2372 days


#12 posted 12-19-2018 03:10 AM

Wow, I just reread through this thread and saw that Lew beat me to the finish line on the galling scenario. With over 12,000 posts I would imagine he has some experience to bring to bear! Good call!

View therealSteveN's profile

therealSteveN

3101 posts in 994 days


#13 posted 12-19-2018 04:52 AM


Thank you! Now having googled “galling” and done some reading, this is exactly what happened. Great to know, had no idea stainless was the wrong choice. I just assumed it was a bit more insurance and pleasant on the eye.

Now I just need to think of a way to cut these nuts out of a 2 inch deep hole so I don t have to remake the stretchers.

- Fezz

If you’ve got a Tractor Supply, or a local store that sells several different grades of bolts, buy the costy ones, and you won’t have much of a problem going forward. The bulk hardware is getting softer, and cheaper by the day. If you really don’t need hardware it works just fine, but if you need something strong to pull parts together, or remain sound while holding back a bit of force, the shiny ones hardly work. Go for the dull black or grey stuff, and you will be good.

The head will have 6 radial lines on the cap, those are Grade 8, which are medium carbon alloy steel, quenched and tempered. Working strength is 150,000 PSI. Some places call that Grade G. No Galling there.

The SS will be ok in wet conditions, but unless you are doing water woodworking you should be ok with non SS and a shot of oil.

-- Think safe, be safe

View LittleShaver's profile

LittleShaver

554 posts in 1039 days


#14 posted 12-19-2018 01:23 PM

If you insist on using Stainless, get some graphite on the threads before you tighten the nuts. A little lubrication from the graphite should stop the galling. The stuff they sell for lubricating locks should work just fine. Way back in my submarine days we did this on SS fittings to prevent galling.

- LittleShaver

Whoa! Do you mean to tell me that my wild-ass guess has been confirmed by a former submariner! That is way cool! A submarine would be a logical place for corrosion resistant stainless steel fasteners. For most everyday applications SS is not the best way to go.

The Fastenal reference mentions lubrication, but I don t recall if they suggested graphite. That would be a lot neater than having oil dripping down the legs of your bench.

PS: Being somewhat claustrophobic, I am always in awe of anyone who could serve on a submarine. It must have been an incredible experience. The technology fascinates me, but only from the comfort of my armchair. Sort of like mountain climbing.

- Kazooman

At least that’s the way we did it back in the late 70’s. I was involved with operating the nuclear power plant parts of the submarine. Needless to say, we used a LOT of stainless. Galling was a constant concern. Tough to get parts and make repairs a few hundred feet under water and in the middle of a patrol. As a nuke. we had a saying “Nuke it out” which translated roughly to use what you know and apply logic to the problem to figure out a solution. I think this thought process/skill has stayed with me as much or more than anything else I learned.

It was indeed a fascinating time. My first three patrols were constant learning even after I earned my Dolphins, after it became more routine. The best part of my job was to be the first person to go topside after extended time under water. There is nothing like the view of the coast of Spain at dawn after 72 days under water.
There is also nothing like the feeling of launching 4 ICBMs rapid fire (it was a test).

As does every old sailor, I have many “sea stories”, but I’ll spare you the time. To tell the difference between a sea story and a fairy tale, listen to the opening line.

A fairy tale begins with “Once apon a time…”
A sea story begins with ” This is a no sh*tter…”

-- Sawdust Maker

View Monty151's profile

Monty151

69 posts in 261 days


#15 posted 12-19-2018 01:32 PM


Thank you! Now having googled “galling” and done some reading, this is exactly what happened. Great to know, had no idea stainless was the wrong choice. I just assumed it was a bit more insurance and pleasant on the eye.

Now I just need to think of a way to cut these nuts out of a 2 inch deep hole so I don t have to remake the stretchers.

- Fezz

If you ve got a Tractor Supply, or a local store that sells several different grades of bolts, buy the costy ones, and you won t have much of a problem going forward. The bulk hardware is getting softer, and cheaper by the day. If you really don t need hardware it works just fine, but if you need something strong to pull parts together, or remain sound while holding back a bit of force, the shiny ones hardly work. Go for the dull black or grey stuff, and you will be good.

The head will have 6 radial lines on the cap, those are Grade 8, which are medium carbon alloy steel, quenched and tempered. Working strength is 150,000 PSI. Some places call that Grade G. No Galling there.

The SS will be ok in wet conditions, but unless you are doing water woodworking you should be ok with non SS and a shot of oil.

- therealSteveN


Tell me more about this water woodworking you speak of.

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