Need help in Measurement

[Tractorhead 9,064]

Hi,

i tried today to reattach my Mowerdeck.

While i‘m changing the defect Engine in my 212 Horse, i destroyed the magneto clutch by try to unmount.

Now i have a new one, but the Screw‘s i have does not fit.

 

Im not familar with US inches, so i have a small problem i can measuring with my caliper, but it shows me just a comma Value.

Can anybody please help me in getting the right value in US?

 

The Screw i need is 7/16 UNF -20 with a length of 12cm - what my caliper imterprets as 4,71 inches.

How this 4,71 is written in fracts? 

Thanks in advance

Stefan

[ebinmaine 67,279]

4.71 is going to be for thousandths of an inch shy of 4- 3/4 "

[formariz 11,987]

It is exactly 4- 45/64", shy of 4-3/4" as Eric said

[ebinmaine 67,279]

It occurred to me after I sent my post that maybe there's a manual that would show that bolt size in US thread measurement?

[Tractorhead 9,064]

Thanks fella‘s,

cause i need to order new Screw, but i cant find them in commata.

 

will order now 👍

[Tractorhead 9,064]

Just find 4 1/2“ here no chance to get a 4- 3/4  or 4- 45/64.

so i ordered and will try if it fits...

[Ed Kennell 38,024]

For maximum strength, the thread engagement should be 1.5 X the thread diameter.     For your 7/16-20 bolt this would be 0.66inches.    If the 4 1/2 " does not provide this thread engagement, you could buy 5" long bolts and cut them to the correct length. 

[ebinmaine 67,279]

1 minute ago, Ed Kennell said:

For maximum strength, the thread engagement should be 1.5 X the thread diameter.     For your 7/16-20 bolt this would be 0.66inches.   

That's great info there.

Is that an industry standard?

 

I've wondered about this in the past and never found an answer.

 

[Ed Kennell 38,024]

1.5 X the thread diameter is a standard rule of thumb that will usually  allow a bolt to break at the shank before the threads shear in the tapped hole.  Of course many factors will affect the results i.e.   material strength, temperature, torque, thread lubrication.

[formariz 11,987]

Is he perhaps measuring bolt including head?That makes it about 4-3/4".

[Tractorhead 9,064]

2 hours ago, formariz said:

Is he perhaps measuring bolt including head?That makes it about 4-3/4".

No, i‘m measured without head.

the difference was, because old Clutch was directly sticked on the bottom of shaft, and the new Warner Clutch has a 

thicker end, so i measured the old screw what has in metric counted 12 cm.

I can‘t use the old screw further, because it was a smaller type, guess close to 9 mm.

 

 

I found also several grade values, i think same to hear for the stability of Screw Steel.

i found grade 5 and grade 8 screws, while awg is opposite to our sqaremillimeter, how about the grade?

 

Should be grade 8 fine?

 

Thanks again

[ebinmaine 67,279]

4 hours ago, Tractorhead said:

found also several grade values, i think same to hear for the stability of Screw Steel.

i found grade 5 and grade 8 screws, while awg is opposite to our sqaremillimeter, how about the grade?

 

Should be grade 8 fine?

Stefan on the OLD bolt... Are there marks or dashes on the top of the bolt head?

You can determine hardness of the original, then use this chart to get the new one.

 

https://images.app.goo.gl/8h8y81zsRia7hxyu8

 

The marks are a little different from metrics to inches but that link should help.

 

[Tractorhead 9,064]

2 hours ago, ebinmaine said:

Stefan on the OLD bolt... Are there marks or dashes on the top of the bolt head?

You can determine hardness of the original, then use this chart to get the new one.

 

https://images.app.goo.gl/8h8y81zsRia7hxyu8

 

The marks are a little different from metrics to inches but that link should help.

 

Thanks for that Link Eric,

 

i have to use a 7/16-20 unf Bolt. From my side this was US Bolt, because 11mm screws are in metric system nearly not available. Here we have 8mm, 10mm and 12 mm. That was most usable sizes.

This diameter was given by Loncin, the Engine manufacturer.

So far i can use most of the Older parts, even the Shaft self, lucky, that the bore inside was big enough.

But while i used it in Winter just with reworked FEL i didnt mount the Magnetic clutch and held it back for spring,

 

Curious, what will be solved additionally.

The lockpin must also be a bit extended, then the Mowerdeck shall be back in Service again.

The rest seems to be fit.

 

Edited April 23, 2019 by Tractorhead

[Sarge 3,463]

If you have any automotive scrap yards - many Japanese seatbelt anchor bolts are 11mmx1.25 thread pitch, extremely close in tolerance to the common 7/16"-20tpi Imperial thread sizing that was used on that engine. A simple metric tap will allow the metric bolt to be used instead of the US Standard 7/16" - it may be a solution for sourcing the part needed on your side of the pond.

Those crankshaft bolts are commonly Grade 8 - which is close to the metric 12.9 class.

 

Sarge

[Tractorhead 9,064]

2 hours ago, Sarge said:

If you have any automotive scrap yards - many Japanese seatbelt anchor bolts are 11mmx1.25 thread pitch, extremely close in tolerance to the common 7/16"-20tpi Imperial thread sizing that was used on that engine. A simple metric tap will allow the metric bolt to be used instead of the US Standard 7/16" - it may be a solution for sourcing the part needed on your side of the pond.

Those crankshaft bolts are commonly Grade 8 - which is close to the metric 12.9 class.

 

Sarge

Thanks for this info!