What size threads for 3 point bracket?

[Alpaca Farmer]

Hello - I am new to the group, and also to tractor ownership.

We have just bought an Iseki TX1510 and also a topper. What we were not told at the time is that we needed various attachments to get the topper to fit onto the tractor - namely a 3 point linkage system which we have now bought. Now we have found that the bracket that goes onto the tractor itself is also missing so I have one on order, but do not know what size bolts it needs - the top ones seem smaller than the bottom ones. I have tried some bolts on the lower ones but they are not quite correct. Can anyone tell me even if they are metric or imperial and if so, what are the correct sizes?

Thank you in advance.



(I have found an operators manual online, but not a service or parts manual)

 

[Agvg]

Metric, it's a Japanese tractor

 

[smstonypoint]

Just curious. What is a "topper"?

Steve

 

[Gary Fowler]

Without a manual reference, I suspect that you will just have to go with a series of different thread per inch or what ever the metric equivalent is. With a caliper, you should be able to get the correct OD of the bolt and then get a sample of each different metric thread type that is available. I do know that the metric threads are a bit more varied than our American which is either SAE coarse or SAE fine so you will just have to experiment.
If you have a tap and die set, you may find it easier to find the correct thread and size bolt easier than just buying a bunch of bolts.

 

[Alpaca Farmer]

Thank you Agvg - that makes it easier for me to narrow down the sizes needed!

 

[Alpaca Farmer]

Thanks Gary for your reply. The metric system of bolts is quite narrow in choice, so it makes it a whole lot easier to find what I need now - I can go by rough diameter of hole and then go for the M number that is that size.

 

[Alpaca Farmer]

Hi Steve - a topper is a three bladed mower that fits to the PTO of the tractor and goes behind it cutting the field/meadow/pasture or whatever you want to call the land.

You can adjust the height of cut to "top" the grass.

 

[Agvg]

Start with std metric, 10 or 12mm bolt may be 14mm.

 

[Alpaca Farmer]

Thanks again Agvg! I am waiting for the bracket to arrive - hopefully tomorrow then I can get on and get the topper fitted and cut the fields.

 

[ericm979]

Metric threads are named by diameter and pitch, for example 6x1mm. There's usually a coarse and a fine option for most diameters. You'll most likely need the coarser one if it's threaded into a casting. Make sure the bolts are the right length. Too short and there's a danger of breaking the casting. Too long and they'll bottom out and break the casting. Cast iron is brittle. Even with bottoming taps the last few threads in a blind hole are not good, you don't want the bolt to go there.

Many bolts have an unthreaded portion. It's usually larger and wont' fit into the threads. But it is better at locating a part than threads, so often it's designed so the part near the head that goes through the bracket is unthreaded and the threads start a ways into the hole. If that's the case you want bolts with about the same unthreaded length.

Last is bolt strength. The system was designed for a certain strength of bolt. Lower strength bolts may fail under load. Metric 8.8 is common and that's probably what was used but not for certain.

For all these reasons it's best to either find the official bolts or the spec for them. I think there's an Iseki forum, maybe someone there can measure theirs and tell you what the markings on the head (that indicate strength) are. Then you can order replacements from McMaster-Carr.

Knowing the torque value would also be good but if you don't have that spec you can use the standard value for the bolt size.

 

[Alpaca Farmer]

Hello ericm979 and thank you for a comprehensive reply with very logical reasoning.

 

[Agvg]

Std metric you should not need to spesify pitch as there are only one for the diameter bolt, if it's fine pitch then things can get complicated...

 

[Alpaca Farmer]

SOLVED....,.

Just to update you all, we finally got the topper sorted. The bolts were all the same size - I had to clean out the threads very thoroughly as I was worried at first that excess force would strip the threads.

It was not all plain sailing though as the centre rod supplied was actually too short and I ended up sending the tractor and topper back to the place we bought it for them to fit. They did not do a great job as they removed some stabiliser bars that stop the main support from swinging into the rear tyres when turning so I had a local firm make me up some parts that I fitted onto the cross bar to restrict its movement. They charged me a days labour for what could have only been a couple of hours at best and they did not even lubricate the gearbox or anything, but at that point I just wanted the machinery back so I could get on. I have used them now several times and also made modifications to the arms of the wheels as they kept working loose. Also, one of the wheels has fractured off the arm which is not great for a new item so again I will go back to my local firm and get them to weld it back on for me. I am learning all the time. Biggest lesson is that not all of these companies that supposedly specialize in farm machinery actually know their stuff. Again, thanks everyone who contributed help and suggestions!

I think it is important on these forums to actually post a final "report" as such on how things went otherwise nobody benefits.