Thread size

[Hubie]

Hi all,

Am just wondering if anyone can tell me the thread size of the three chaincase bolts that go through the outer and inner chain case covers and into the crank case.

Cheers,

Hubie.

[MG]

5/16" x 18 TPI x 2" long

HTH. Markus

[Hubie]

Thanks fellas,

I don't have recoils for 5/16 whit but I do have loads in bsf so I might go down to the bolt joint and get some bsf bolts instead, might be the easiest way to do it.

Cheers,

Dave.

[Desburnett]

Hi do not use bsf. You need a course pitch thread in alloy to prevent stripped threads. Des

[chaterlea25]

HI Hubie,
Be VERY CAREFUL
If you are going to fit thread inserts at this location use solid inserts (timesert) of the correct length
recoils could move inwards in the future when the screws are replaced and the inserts will foul the crankshaft
I always measure the depth from the outside while turning the crank to find the nearest bit to the case
and then make the screw 1/8th shorter than that,
The  screw length depends somewhat on the thickness of the spacer plate and gaskets between crankcase and primary
also the drilled depth of the outer case
REMEMBER  to fit the required thickness spacer /or washers between the rear inner case to frame mounting soas nort to distort the inner case
It should be easy enough to find UNC inserts and allen screws (UNC and BSW are both 18tpi at 5/16 dia)
screws and inserts will then match

HTH
JOhn O R

[Hubie]

Thanks fellas,

Found a place that has whitworth inserts.  I will get the correct size and will be loctiting them in with 620 so they don't go anywhere.  A mate has the tap, I have the correct drill size and the inserts are only 10 bucks so I'll be heading down to pick them up this week.

Cheers,

Dave.

[Goldy]

Hubie.  Many of the bolt sizes on listed on this website. All the best Goldy   http://www.stainlessbits.com/link12.html

[wilko]

BSF is commonly used in alloy on british bikes.

[groily]

With you Wilko.
Should have been called 'BS Finer' or 'BS Fine-ish' I'd say. It obviously wasn't fine enough for our friends elsewhere who came up with UNF, widely adopted as the standard in the UK and only ousted when we went metric. No need for a BSC equivalent in US factories then, although there was always UNEF in extremis.
BSW is, I reckon, a pretty limited thread form, for having too small a minor diameter. Ditto UNC. Good in alloy of course.  But BSF can be perfectly OK and I have no compunction in using it where it can readily be adopted for an oversize fastener with minimal loss of parent metal. Repairing stripped 1/4 20 BSW/UNC with 5/16 22 BSF or M8 1.25 comes all too naturally to me, and I've never had a problem, be it simple bolt, set screw or a stepped stud where necessary.

Going a step further, any AMC twin owner will be only too familiar with 2BA screws into crankcases for timing covers . . . a step too far I'd say, but they must have had their reasons!

[BSA_54A10]

Hubie.  Many of the bolt sizes on listed on this website. All the best Goldy   http://www.stainlessbits.com/link12.html

This site was down for over a year.
The owner has obviously put it back up because he wanted to have a rant and more than likely because he is an enthusiasts of some sort.
Just compiling the data would have been a monumental task.
I suggest that every one downloads the charts while they are still available.
While not 100% correct and having a few omissions you will not find a better thread reference table any where else in the world.
Perhaps this forum could adopt it and add the missing bits as they are found out and fix the few mistakes.
It would be a very valuable project and make like a lot easier for many generations to come.

[Hubie]

Thanks again chums,

I have the inserts drill bit and tap now.  Just curious as to opinion with loctite.  Was down at the local parts shop and they had low strength, medium and permanent.  Any thoughts on which to go for - am leaning to either permanent or medium (for the inserts that is).

Cheers,

Dave.

[MG]

The green Loctite stuff (that is the highest strength one, that could be your "permanent" one?) will loose it's grip when heated to about 200°C, should the insert ever have to come out again, so no problem using that one for added peace of mind.

[Hubie]

Well I got the recoil inserts in no worries and there's no way they'll come out!  Problem now is that it is so tight I can only get the bolts in a few turns before they will go no further and it's not enough to fasten the inner and outer cases to the crank case.  Wondering what to do now....

[Brian]

Thats a common problem with thread inserts, not usually in alloy though.

What you need is a split die. Head off to your local engineering supply place and find a die in the 5/16" size, you need to get one that is split with a small screw in the side of it. Should be easily available, at a pinch you could use 5/16" UNC but try and get a witworth one if they are the inserts you used. Put the die in the stock and run it down the thread on your bolt, if the bolt still wont screw in easily then unwind the tiny screw in the side of the die about half a turn and try again, keep going  until they screw in ok. When you put the die in the stock (die holder) tighten the screw that holds it in very tight, this will compress the die slightly. If the screws you bought are zinc plated you may find just running a die down them will cure your problem.

Another option is if you have a friend with a lathe who could screw cut a couple of thou out of the thread.

Remember, we do this for fun 

[Stu55Flash]

Sorry if this is stating the obvious but UNC = 60 deg pitch and Whitworth is 55 deg pitch, so even if both are 18 tpi they will pick up or bind. Don't know if this helps?

Stu