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Lack of Round 1/2" Shoulder Bolt Extensions with 3/8-16 Threads for Mower Wheels

etcetra

Plastic
Joined
May 11, 2024
Location
USA
I have a Poulan Pro lawn mower with wheels mounted on shoulder bolts that are part a height adjuster.

I want to put larger diameter wheels on the mower so that maximum cutting height of the grass is taller to put less stress on the grass.

In order to use larger wheels I need longer axle wheel bolts as all the aftermarket wheels I have found have wider hubs that the original Poulan wheels.

The bolts are not removable from the height adjustors as the company wanted to sell you the whole height adjustor assembly and their own replacement wheels.

So I need to lengthen the existing 1/2" diameter shoulder bolts which have a 3/8-16 male end for a nut.

3/8-16 hex coupling nuts are very common and I have a couple, but these will not work as they are too wide and they need to be round. The closest round coupling I found was on Amazon, with the correct internal threading, had a outside diameter was 12mm and were not intended for outdoor use.

A round coupling would work by inserting an additional threaded rod to act as a mounting surface for the nut - with everything being secured by threadlock.

A bolt extension would be more ideal as it would be one piece and have a prexisting female internally threaded end and a externally threaded male end nut; however, I've found none.

I've also looked using terms such as "stud extensions, standoffs, bongs, post extensions" and so forth.

Another idea was to perhaps purchase some longer shoulder bolts and have a machinist cut the heads off and internally thread the headless end. I am guessing this would be overly expensive.
 
My local hardware store has a whole wall of fasteners and misc hardware stuff. They even have those bolts for mower axles. I’ve replace them on several push mowers. I’d check there.
 
My local hardware store has a whole wall of fasteners and misc hardware stuff. They even have those bolts for mower axles. I’ve replace them on several push mowers. I’d check there.

The bolts are not replaceable on this mower.

They are not normal shoulder bolts.

They have specially shaped heads and are compression fitted into a thick height adjustor face plate.

As they exit the height adjustor plate they form a large washer size rod that is larger that the main shoulder bolt. This saves having to have a separate large thick washer in that area.

They then transition to a 1/2" should bolt with 3/8-16" terminating threads.

The height adjustor also includes a bearing for a drive rod running from the front gear case as this was a push mower with optional self propulsion.

The height adjustor is in turn attached to the deck with two bolts.

The front drive case and belt has been removed as it would interfere with putting larger wheels on and. The 190cc motor would never have enough power to cut the thick grass here, bag the grass and pull the mower. Its also way too slow to use.

The goal here is to increase the cutting height of the mower to match a commercial mower as most consumer mowers have a lower limited cutting height.
 
The closest they have are some 3/8-16 round coupling nuts in black oxide, stainless steel or 316 stainless steel from 3/4" to 2" in length but with a diameter of only 31/64" and not 1/2".

The original mower bolts are some type of hardened steel.
 
The closest they have are some 3/8-16 round coupling nuts in black oxide, stainless steel or 316 stainless steel from 3/4" to 2" in length but with a diameter of only 31/64" and not 1/2".

The original mower bolts are some type of hardened steel.

One of these should work. Cut to length and tap the cut end. I would expect the thru hole to be 5/16". The link I posted goes to this:​

Hollow Female Threaded Rods​

97311a111-@halfx_637153777720135558.png


Connect and separate threaded rods, studs, and other components. These hollow rods have internal threads on both ends, so you can make connections and still pass wiring and other objects through the center of the rod. Made of zinc-plated steel, they resist rusting in wet areas. All meet ASTM B633, an international standard for zinc plating.
3D CAD models available
For technical drawings and 3-D models, click on a part number.
Lg.Thread
Lg.
ODWall
Thick.
Tensile
Strength, psi
click to learn more about
HardnessSpecifications
Met
Each
Zinc-Plated Steel
3/8"-16
click to learn more about 3/8-16
6"5/8"1/2"0.063"60,000Rockwell B49ASTM B63397311A111$22.96
1 ft.5/8"1/2"0.063"60,000Rockwell B49ASTM B63397311A11244.06
2 ft.5/8"1/2"0.063"60,000Rockwell B49ASTM B63397311A11369.92
 
I would cut off and then drill out the existing wheel stud. Use any size wheel bolt and washers,tubing as needed for clearance. Sounds like the stud head was formed in place after the stud was in the hole.
BilL D
 
Could you cut down the existing stud and bolt on a plate with it's own longer stud. Is there clearnace for this. Or weld on a extension.
BilL D
 
31/64 is 1/2” for lawn mower wheel tolerance.
Do you need “hard steel”.

Here is 1/2 od, 3/8 thread, “hard” stainless. https://www.mcmaster.com/product/97851A364

“Have you checked mcmaster?” Solution to 76 percent of all basic hardware needs.
This is suppose to act as an extension of an existing actual 1/2" shoulder bolt - not a 31/64" that will act as a axle for a plastic based mower wheel.

Not going to work.

---

That product link is not usable.

The only way to use the barrel at all would be to cut off the head, leaving less than a 1" in length for $25.55 each. Likely shipping is more. The remaining length is short as the hub width on 14" wheels is 2 1/2 +/- plus any additional room that may need to be added to clear the existing hardware.

Yes, I've checked McMaster and they have nothing, as explained in another thread.
 

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They do not have anything.
If you have a hacksaw and a 3/8"-16 tap, Mcmaster Carr has what will work, I showed you. Or get a piece of 1/2" round stock and make it all yourself. Cut to length, hand drill a 5/16" hole, tap, then repeat till done.
 
Take your adjuster brackets,
Use a grinder,
Cut off the welded in step studs,
Weld in to your brackets some 3/8-16 hex nuts,
Use regular shoulder bolts.
All other attempts to buy a bolt on solution end up
with an inferior and weak assembly.
Yer killin me with all this jockey jabber.
It's not gunnaa work.

-D
 
I have no idea why this place deletes threads that mention anything to do with "hobby machines" but, permits no-post n00bs to ask questions about lawn mowers, debate the inaccuracy of Pi and other such nonsense.

Look: I will fix all four of your axles. Send me your four wheels, the four adjusters and eight, crisp $100 bills. I will return the parts in 7 days with the axles appropriately mounted. Not worth $800 to make a custom solution for your $600 lawnmower? Well now you've found the crux of the issue. That's about what it will 'cost' for anyone to create a custom solution. That might even be a bit low.

This is not going to get fixed with COTS hardware and you're wayyyy too fast to poo-poo all the suggestions you've already been given. Hey, I feel your pain. I did exactly this modification to my mower back around 2000. It was the first thing I did with that lathe: custom axles out of some giganto screws I bought. I know how long that took.

If you don't have the ability to drill or grind off the existing axles and draw up exactly what you need, maybe even needing to weld the new axles to the old pivots, what do you expect people to come up with? Oh, here, lemme make you something custom for free?
 








 
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