Chaincase fixing screw thread

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pierodn

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Hi,
I welded and plugged the three holes on the drive side of the cranckcase to rethread for new chaincase fixing screw.
Please, i need to know the stock thread.
Thank you.
Piero
 
L.A.B. said:
062669

1/4" X 20 (UNC).
Click to expand...

Hi Les,
i mean, but i was not too clear, sorry.
I need to make a new three holes (i welded and plugged the previous that had no thread more) into the crankcase and rethread they.
I need to buy the thread tool and need to know the measurement (and the hole to start to rethread).
Thank you.
Piero
 
L.A.B. said:
pierodn said:
I need to buy the thread tool and need to know the measurement
Click to expand...

Sorry, I don't understand what this "measurement" is that you need?

pierodn said:
(and the hole to start to rethread).
Click to expand...

The tapping drill bit size required for a 1/4" UNC thread is: 0.2010" or 5.11mm (although 5.10mm is probably the nearest commonly available metric size).

http://www.gewinde-normen.de/en/unified ... hread.html
Click to expand...
Hi Les,
Sorry for my bed explanation.
If i need to use the 062669

1/4" X 20 (UNC)

i need to buy his tap for rethread: what tap is, and the tip?.
To use his tap i need to make the new holes: if i understood i need to drill with 0.2010.
Regards.
Thank you.
Piero
 
Hi Piero

LAB is correct....you will need to buy a 1/4 - 20 tap. It will be listed as such in a supply catalog. The holes are drilled with a number 7 drill bit which is 0.2010 inch dia. Or use the nearest metric. The tap and drill are all you need, assuming you have a tap handle.

I assume the engine case is on your workbench.....you should set it up on a drill press to drill the holes in straight.

Caio

Roberto
 
pierodn said:
i need to buy his tap for rethread: what tap is, and the tip?.
Click to expand...

Thread taps of one particular size often come as a set of three, or set of two, which are normally used in sequence (most tapered tap first) to cut the thread, however it isn't always necessary to have all three, especially as you will be cutting into reasonably soft alloy and you will not have to cut threads right to the bottom of a 'blind' hole, so you don't really need the 'bottoming' tap, and you can, if necessary, do the job with only one tap, usually the 'second' tap.

Chaincase fixing screw thread

Chaincase fixing screw thread




pierodn said:
To use his tap i need to make the new holes: if i understood i need to drill with 0.2010.
Click to expand...

Yes, although I would think you might have some difficulty finding a #7/.2010" drill bit in Italy, but perhaps not?
 
Since you are starting from new, you can select ANY thread form that you can easily and quickly obtain. There is no specific need to rework the holes and replace the hardware with OEM specification, unless you want to keep the bike unbelievably original.
 
At this size of thread there is nil difference in fit and function betwix SAE and Whitworth and holes small enough with the welded holes & surround now softened enough, one pass with a finish tap should work a treat to glue in SAE studs permanently and quit buggering up the threads to fart with ever again. But it ain't factory issue so a nod to extra work to keep it like factory for ever more.
 
Pierodn,
This is your opportunity to add threaded inserts where applicable. For sure the chain case fastener area is a prime candidate for this. I also used them in the oil drain plug on the 72.

These are available everywhere in one form or another. These are NOT helicoil type crap. Threaded inserts will add much integrity where there was little berfore.

Threaded inserts will supersede (sostituire) OEM trheads.

Example.
Take the pink stuff off and set them with JBW.
http://www.catalogds.com/db/service?dom ... duct=329_4
 
Pete, I like those e-z lok. One of my chaincase holes has a 5/16" thread in it. Is there enough metal in the crank to install those gizmos and it won't protrude too far into the crank? I also did like hobot said and used studs and nuts there with red locktite in the crank side. I always thought those 1/4-20 bolts were a bit whimpy.
 
DogT said:
Pete, I like those e-z lok. One of my chaincase holes has a 5/16" thread in it. Is there enough metal in the crank to install those gizmos and it won't protrude too far into the crank? I also did like hobot said and used studs and nuts there with red locktite in the crank side. I always thought those 1/4-20 bolts were a bit whimpy.
Click to expand...

No problem at all. drill and tap for the external 7/16-14, JBW them in and away you go.

For 72 owners, when you tighten that drain plu,g do you feel shakey wondering if you have gone too far or not far enough, generally the former.

I know there are some pros' who have chime in here on the forum, do all the base stud holes and where ever applicable, and there are many places for these, ie gearbox drain.
 
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