Do-it-yourself dilemma

[Hawkmoon]

I set out to make a new battery hold-down for my riding mower. Shouldn't be any big deal -- two J-bolts (actually just straight rods with a small, L-shaped leg on the bottom and with the top threaded), and a cross bar that spans the battery.

The holes in the tractor battery shelf are too small for 1/4" rods, so I decided to use 3/16". Well, for starters, Lowe's didn't have any 3/16" round steel rod, so I had to trek to Home Depot. They had it. Fine.

I've checked multiple web sites, and they all tell me that a #10-24 bolt has a major diameter of .1890". 3/16" rod is .1875" in diameter. I figured that, for a non-critical application like a battery hold-down, the loss of .0015" off the major diameter wouldn't matter. So I clamped the rod in a vise, dug out my tap and die set ... and found that I could NOT get a 10-24 die to even think about starting on the rod. I had to use a 12-24 die. I had bought some 10-24 wing nuts. Naturally, they wouldn't fit.

http://www.fasnetdirect.com/refguide/Machinescrewthreads.pdf

So today I went back to Lowe's in search of 12-24 wing nuts. And ... they don't have them. They don't have ANY nuts, bolts, or washers in the #12 size. They skip from #10 right to 1/4-inch. So I'm going to have to order some 12-24 nuts from Amazon.

But I can't figure out what's wrong here. 3/16" is .1875. The minor diameter for a #12 thread is supposed to be .2078" -- a 3/16" rod should fit right into that and, when I tested it on the thread sample board at Lowe's, it did.

If the major diameter for a #10 thread is .1890" and a 3/16" rod is .1875" -- why couldn't I thread it using a 10-24 die? Why did I have to use a 12-14 die?

[Brad Johnson]

Like this?

https://www.jackssmallengines.com/jacks-parts-lookup/part/mtd/9110222a





Brad

[Hawkmoon]

A whole lot like that, in fact.

[dogmush]

So either the rod you bought isn't 3/16, or the die you used isn't 10-24.

Did you put calipers on the rod?  Perhaps some jerk put some 5mm rod in the 3/16" box?

[230RN]

Not for this case, but I screwed (no pun) myself oncet on accounta I had reset the zero on my sooooper-doooper 'lectonic calipers accidentally and unknowingly.

Drove me nuts for a while wondering why this male thing didn't gazinta that female thing.

I now rezero almost religiously before measuring.

[zxcvbob]

I needed a battery hold-down for my dad's old John Deere tractor.  I used some small diameter polypropylene rope; tied a trucker's hitch to cinch it down tight.  That was a couple of years ago and it's still tight and the rope hasn't degraded from the acid.

[griz]

If a 10-24 die will not start on a rod a tad less in diameter than the finished thread, something isn't as labeled.

By the way, if it was me, I think I would just use all thread if I got to the store and they didn't have the right nuts.

As an aside, number 12 screws seem to be fading away.

[dogmush]

I needed a battery hold-down for my dad's old John Deere tractor.  I used some small diameter polypropylene rope; tied a trucker's hitch to cinch it down tight.  That was a couple of years ago and it's still tight and the rope hasn't degraded from the acid.

I used a 24" zip tie on my [lawn] tractor battery.  Works great.

[K Frame]

No det cord?

Slackers.

I agree, something wasn't labeled correctly.

Oh, and if you have a complete tap & die set, make your own nuts out of bar stock. I've done that before for non critical hold applications.

[brimic]

Did you measure the rods? They are probably hot rolled steel and may just be 'close-enough' for their nominal labeled diameter. Plus, the pieces are likely to be cut off using some sort of shear, distorting the ends even more ('upsetting' -making thicker).

[Hawkmoon]

I did measure the rods. 3/16" is .1875". The rods (at least the one I'm using) measure .1850", so slightly undersized for what's supposed to be a #10 screw shank. And I know about upsetting -- I always dress the end with a file or roll it against a grinding wheel to clean up the end and apply a slight chamfer before I try to thread.

But then, last night, I found an unopened pack of 10-24 machine screws I had apparently bought at Lowe's for some long-forgotten project that never happened. I measured one of those, and came up with .180". (According to the standards I've found on-line, that major diameter is less than the specified minor diameter for a 10-24 thread.) The ID of a Lowe's 10-24 nut (measured with a caliper, which is not perfect) is only .150". The specified minor diameter for 10-24 is .1818". Can we say "interference fit," class? Of course we can!

So it appears the Chinese hardware the big box stores are selling today don't meet the standards. Lowe's doesn't sell any 12-24 or 12-32 nuts, bolts, or screws, so I ordered some 12-24 nuts from Amazon. If that doesn't work, I'll take the Lowe's 10-24 wing nuts and drill them out and retap them for 12-24 to match my threaded rod.

[K Frame]

Sounds like a major conundrum...

of minor importance.

That's a slow pitch...


Just read up again on major, minor, and pitch diameter. Been awhile.

[griz]

You may be confusing the minimum major diameter with the minor diameter.  For a 10-24 thread the minor diameter is about 0.138 depending on the class of fit.

[Brad Johnson]

Just a thought... are you sure it's not metric thread?

Brad

[Hawkmoon]

You may be confusing the minimum major diameter with the minor diameter.  For a 10-24 thread the minor diameter is about 0.138 depending on the class of fit.

Perhaps, but there's no confusing that the nominal size for a 10-24 thread is .190", and the major diameter should fall within a range of .1890 to .1818. A rod with a diameter of .1850 is well within that range, yet I could not get a 10-24 die to even start on the rof, even after dressing and chamfering the end. And there's no confusing the fact that the 10-24 machine screw I took out of a sealed baggie and measured was only .180, which is smaller than the purported minimum standard of .1818.

Conversely, the nominal diameter for a 12-24 thread is .216. The major diameter range is .2150 to .2078. I can't find any charts on-line that give the minor diameter for a 12-24 but, when I was at Home Depot buying the rod, I stuck the end of it into the 12-24 female thread on their bolt sizer and it went in. So the minor diameter of 212-24 should be larger than my .1850 rod, yet I was able to put a real thread on it using a 12-24 die.

'Tis indeed a conundrum. I'll make it work, but what should have been an easy project has become a minor PITA project.

[Hawkmoon]

Just a thought... are you sure it's not metric thread?

Yes.

[brimic]

It sounds like the only reasonable solution to your battery tie down problem is to procure a lathe for your work space, and single point cut your threads until they fit.

[Brad Johnson]

All-thread? Or maybe the units I linked above (a mere $8.50)? Seems you're going to a lot of trouble and expense for something that doesn't really merit it when there are multiple convenient and cost-effective alternatives.

Brad

[Hawkmoon]

All-thread? Or maybe the units I linked above (a mere $8.50)? Seems you're going to a lot of trouble and expense for something that doesn't really merit it when there are multiple convenient and cost-effective alternatives.

Initially, I wanted a new hold-down NOW, so the easiest solution seemed to be buying a length of rod (which is supposed to be the right size for a standard #10 screw thread, cut a couple of pieces to length, bend over one end of each, and thread the opposite ends.

Except that nothing is as it should be. It would still be simple if Lowe's or Home Despot carried #12 machine screws, but NOOOOOOOOO. I guess #12 is to close to quarter inch, so they jump straight from #10 to quarter inch.

What I ended up doing was to take the 10-24 wingnuts I bought, which didn't fit, and drilling them out and retapping them to 12-24.

[RoadKingLarry]

Have you tried turning it off then turning it back on again?

 

[HeroHog]

Question: Why not just enlarge the holes so you can use 1/4"?

[Hawkmoon]

Question: Why not just enlarge the holes so you can use 1/4"?

The mower is a very old Wheel Horse that I inherited from my mother. I don't want to modify it. The battery hold-down has disappeared, so I much prefer to make the hold-down fit the tractor rather than the opposite.

[Scout26]

Did you try going to an Ace or other local hardware store ??  They generally have a better selection and people that know what they are doing.

[Hawkmoon]

Did you try going to an Ace or other local hardware store ??  They generally have a better selection and people that know what they are doing.

Too far. There used to be a Sears Hardware store within a tolerable distance, but that closes maybe a year or a year and a half ago.

[dogmush]

Do you have some kind of small knock off Home Depot/Lowes?

They normally carry #12 hardware. I just checked, and the ones around here have both #12 machine screws and wing nuts in stock.

I thought the big boxes were more homogenized than that.