Bolt/thread size for L2900 rops???

[Black Dog Chainsaw]

Hey guys just got this new to me L2900. The PO took the rops off and didn't put the bolts back in the axle. So of course they got lost and the axle treads are rusty and full of dirt.[emoji35][emoji35]

Anyway I want to chase/clean the treads out with a tap before reinstalling the rops. Need to know what size the bolts are. I think they look like metric 14-1.5???


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[Black Dog Chainsaw]

Oh here's the new tractor!

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[Stubbyie]

I've had similar problems with bolt holes.

Blow well with air, repeatedly.

Use a dental pick to clean holes as much as possible.

Blow with air again, repeatedly, during process.

Use lots of lube (Relton Rapid Tap Paste) and then try a selection of metric bolts---I've found metric bolts on ours having thread pitches of 1.0, 1.25, and 1.50, depending on application and location.

Use a flat-face bottoming tap ONLY by hand, lots of lube, carefully feeling your way along or risk dinging a thread. Blow debris out with air, holding rag over hole (lube splatter).

I like using a bolt instead of a tap, less likely to hurt a thread. File a tapered angle on the end of the bolt, remove burrs, use the bolt like a less-aggressive tap. Can also slot the end of the bolt with a hacksaw or dremel blade and again remove burrs then use in suspect hole.

Be patient and take it slow. Don't get rough with a tap wrench.

Please post back your continuing experiences so we may all learn.

 

[Black Dog Chainsaw]

Looks like I'll need to drill and re-tap. The threads are 1/2 stripped from being seized and had force removal... Might just go SAE next size up...


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[Stubbyie]

Might consider using HeliCoil or similar if you want to stay OEM bolt size.

Can't for the life of me think of the name of the alternative to HeliCoil---it's a short externally (and internally) threaded insert that has four (4) little prongs sticking up on the top.

You follow directions for installation then when the threaded insert is fully seated into the hole the little prongs or fingers are driven down, locking the insert into the hole. The propngs are sort of diamond shaped in cross-section---one sharp edge of the diamond scores and locks into the hole wall.

I've successfully removed the occasional HeliCoil but have no idea how this other critter may come out if required for some reason.

Please post back your continuing experiences so we may all learn.

 

[Black Dog Chainsaw]

Probably going with helicoils. If I haven't already bought 12 new m14x1.5 Rops bolts, I would have switched over to m14x1.25 bolts since the local hardware stores sell them much cheaper!


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[rbargeron]

......I like using a bolt instead of a tap, less likely to hurt a thread...... Can also slot the end of the bolt with a .....dremel blade and again remove burrs then use in suspect hole.....Be patient and take it slow. Don't get rough with a tap wrench........

great advice - try this before you drill any more material out of the holes

 

[Black Dog Chainsaw]

great advice - try this before you drill any more material out of the holes

The below pic is a $5 snap-on thread chaser designed specifically for clearing out threads without harming them. Cheap and easy for the holes with threads left.

However when the original bolts came out like this there isn't much hope...

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[Black Dog Chainsaw]

Here is where I'm at.

Helicoil kit 5544-14 (554414)
14mm x 1.5 thread x 21mm inserts.

$60 Kit comes with tap, install tool, and 6x 21mm long inserts. Tap is proprietary so using one you already have wont work.

21mm insert package is part number: R3745-14
Just in case you need more than 6 inserts. $15

I spoke with and engineer from Stanly (company that makes helicoil) because there seemed to be confusion on whether or not to use a thread locker with helicoils. The engineer said regular helicoils are designed based on the outward force of the m14 bolt pushing the insert outward into the cast iron to lock it in place. Because of the increase in thread size on outside of insert the holding power is greater than the original bolt.

The reason for thread locking inserts or keensert (as brought up above) is for applications in soft metal or high vibration areas where the insert needs to be held in place in order not to come loose or to reduce possible damage of the surrounding soft metal during operation. Cast metal (rear axle kubota) is considered abrasive soft metal, so a keyed insert is probably the best choice. However either will work.

Grainger does not carry a keyed insert with an internal m14 thread size. They stop at m12. McMaster-Carr does carry the 14m-x-1.5 key locking inserts with the tools to install them. You can get them in 18-8 stainless or black phosphate. The down side to these is that they call for a 18.75mm drill bit which doesn't convert to anything standard size and still be close enough. 18.75mm = 0.738 inch so the closet drill bit size would be a 47/64 = 0.7343in. The other downside is that 4 inserts with tools cost $131 + $26 per extra insert in stainless. Black phosphate is significantly cheaper at $61.36 for the tools and 4 inserts + $8-$10 for each additional insert.

You also need to keep in mind where and what you are tapping. The bolt holes on those kubota axle are considered "blind holes" or holes that don't go all the way through the metal. So you should not technically use a plug tap that is used for through holes. For the holes I'm doing I will need a "bottoming tap" that will run threads all the way to the bottom of my blind bolt holes in order to have full threads for my inserts.

That being said I know most of us aren't machinists here so we don't want to spend hundreds of dollars on something that will be used once in a blue moon. So I will probably buy the standard helicoil kits which will be much cheaper in the long run since I have 7-10 holes needing inserts. I'll run the drill and tap as deep as I can until the bottom out in the hole. If I can't run the full length of the insert into the freshly tapped hole I will clip off 1-2 threads from the bottom. If these helicoils are actually stronger than the original bolts I should have at least the original designed strength.

I will post more as I go. The bolt holes may turn out to be 20mm deep and only need 16-18mm in which case this discussion on bottoming taps was pointless.

Advise to new people buying new kubotas. Buy a bottle of blue loctite and take your external hardware out and reinstall with loctite. This will seal any bolts that will be exposed to moisture and rusting between 2 different metals.


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