What size is this bolt?

Llaves

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L4630-GST-C with LA853
Jan 17, 2016
21
2
3
Llaves, New Mexico, USA
L4630:
tractor_bolt.JPG


It looks like an M8, but an M8 doesn't seem to fit. The bolt on the tractor has a 12mm hex head; an M8 has a 13mm. I've looked in various tables of bolt sizes and nothing takes a 12mm socket. Is it a self-threading M8? I can't find head sizes for the self-threading screws.
 

TheOldHokie

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L4630:
View attachment 61441

It looks like an M8, but an M8 doesn't seem to fit. The bolt on the tractor has a 12mm hex head; an M8 has a 13mm. I've looked in various tables of bolt sizes and nothing takes a 12mm socket. Is it a self-threading M8? I can't find head sizes for the self-threading screws.
Kubota uses JIS fasteners and the head size on an M8 JIS cap screw is 12MM. I think its very likely that is a standard M8 x 1.25 screw.

Dan
 

Russell King

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You may want to get fine and extra fine thread pitch bolts to try. Kubota seems to love the “not coarse” threads.
 

NCL4701

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Looking at your location, I noticed running down to the local hardware store, which may of may not have what you need, may not be a cost effective strategy.

If you have a bolt that fits correctly (appears you do) but are one short to fill all the holes, you can measure the pitch one of two ways. Ideally you’d have a pitch gauge. If not, you can measure. You’ll need a caliper as it’s a rather precise measurement for the metric pitches. Without a caliper you’ll have to count threads over a longer measured distance and get creative with some math to calculate.


Once you have the thread, pitch, and length it looks like you have Fastenal locations and Kubota dealers in your area, either of which are likely to be able to get you the right bolt. Online, McMaster-Carr seems to have quite a broad selection of fasteners: https://www.mcmaster.com/screws/
 
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GreensvilleJay

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re: Take the other bolt out and take it to a hardware store and match it.

Be REAL CAREFUL if you do remove it....
Murphy would make me sneeze, bolt goes in the 'slot' and get stuck 'somewhere'.....
..my luck,if outside ..... I'd drop it on the ground and never find it...
if in the garage, drop it and never find it...
recently 'lost' my 3/8 drive, 1/2" shallow socket in the garage 'somewhere', sigh....
 

TheOldHokie

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L3901/LA525, B7200DT/B1630, G2160/RCK60, G2460/RCK60
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I'd say pretty definitive. Ordinary everyday M8 cap screw with integral flat washer. AKA flange bolt or what newer Kubota parts manuals now call out as a SEMS bolt. I bet Messicks will ship you a DIN cap screw with 13mm head. Thats what I get from my local Kubota dealer when I hand them a part number like that. Drives me crazy....

I have 4 machines and I try to keep a smalll selection of those JIS screws in the parts bins. Here is a good source:

Generic substitute for Kubota SEMS Screws


Dan
 
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Llaves

New member

Equipment
L4630-GST-C with LA853
Jan 17, 2016
21
2
3
Llaves, New Mexico, USA
Kubota uses JIS fasteners and the head size on an M8 JIS cap screw is 12MM. I think its very likely that is a standard M8 x 1.25 screw.

Dan
It is indeed an M8 x 1.25, but with the JIS 12mm head.
Turns out my problem is a bad thread in the panel where the bolt goes. I'll have to run a tap through it to clean it out.

Thanks to everyone with suggestions
 
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TheOldHokie

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Myersville, MD
I own 4 Kubota tractors and they are covered with those fasteners. Hence my private little hardware store.

Dan
 
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