93 replies to this topic

[mike.]

Well an update. Got my bolts through from the US from dave.

They're still going to be too short because of the stripped threads.

Don't get me wrong, the bolts would be fine, but since i'm missing the first 5-8mm of thread, i still end up with the same amount of thread engagement i had before.

These pictures will explain.

Heres the new bolts, compared to the others i was supplied which led to the stripping of the block:



Here, as you can see, the new bolts still won't engage the same amount of threads the standard bolts would have if I had not been fitting a centre main strap:



And here, this shows that once these new bolts have cleared the damaged threads in my block, they'll still only be screwed into 5mm or so of thread. So basically the same as they were before and i'll just end up ripping more threads out of the block:



This picture is with the bolt screwed all the way into the block (full depth engagment) then back off a couple of turns. This shows how much longer the bolts ideally need to be:




I've measured it and the bolts ideally need to be 15mm longer. This would allow full depth engagement in the threads, as well as fitting the CMS and washers.


I'm going to email dave. See if he can supply them, but just incase he can't (and to be honest could do with getting the bolts ASAP rather than waiting for delivery again) does anybody know anywhere that'll make me some bolts suitable for this application that they've used before?

[Ethel]

Or look for a slimmer strap?

Have you looked in the Moss catalogue? There might be a suitable bolt used elsewhere.

[mike.]

Thats a good point actually, I could just get 10-15mm machined off the strap. Is there any issue with doing this?

I'll have a look at moss now...

[mike.]

Right i'm going to make some enquiries about some bolt manufacturers.

Just need to be clear with what im asking for.

I need to ask for some 7x16" UNF bolts, that are shouldered with roughly 30mm of thread and need to be at least grade 5.

Is that right?

Or I could get 10-15mm machined off the strap. However that'd make the strap about half an inch thick. But to be honest, i'm regretting bothering with that anyway. Having a half inch thick strap will be better than none at all right?

Edited by minimadmike, 23 June 2009 - 11:18 AM.

[mike.]

Rite well, just rang up a few nut/bolt/fastener places near me. All of them said there no chance anywhere will keep 7x16 UNF in stock. They said they might be able to get some made up, but only in a large batch of around 50 minimum!

Theres a machining guy literally 10 mintues walk from my house who said he'll be able to machine the strap down by half an inch. That'll give me all i need then to get good thread engagment.

What do people think of that? No problems with doing that is there?

[turbodave]

Right i'm going to make some enquiries about some bolt manufacturers.

Just need to be clear with what im asking for.

I need to ask for some 7x16" UNF bolts, that are shouldered with roughly 30mm of thread and need to be at least grade 5.

Is that right?

Or I could get 10-15mm machined off the strap. However that'd make the strap about half an inch thick. But to be honest, i'm regretting bothering with that anyway. Having a half inch thick strap will be better than none at all right?

If those are too long, then you need to be looking for 4.5" long bolts. In a grade 8 at that. You may, or may not find them easilly as bolt-places start to carry sizes in 1" at those kinds of lengths, and finding grade 8 is definately difficult.

Personally, I'd find a machine shop that can whizz 1/4" off that super-thick strap. That strap is ridiculously thick; all it's doing is adding weight, anything over 7/8" is probably overkill. Anything over 1" is DEFINATELY overkill.

That would be easy to get done, and cost you 10-15 quid at a guess.

[mike.]

Great. Well thats good news.

I'm going to go and measure up and see just how much i need to get removed...

[turbodave]

Just remember what i said about machining off both sides of the strap if you're going to take 1/2 and inch off.

I'd personally only take it down to 7/8 minimum - but still take it off both sides...

[mike.]

Right so i've been out an measured. Looks like i need 10-12mm taking off the strap.

So your saying I need to ask for 6mm to taken of both faces of the strap?

[Ethel]

I think Dave means gets both ends cut down not just the one that will go with the dodgy thread.

If the use an end mill, similar to a drill, they can make a sort of Tee shaped strap.

[mike.]

Oh i see.

Well i've gave it to the guy anyway and asked for 10mm to be taken off. So hopefully that'll be ok after that

[mike.]

Rite just got the strap back, now 10mm shorter and £10 less wealthy

Anyway, compared to my full depth engagement bolt looks perfect:



Much more like it:



However, I didn't really think about the other bolt, without the damaged threads.

So now, the other bolt, the shouldered part of the bolt hits the undamaged threads (i.e fully screwed in) way before reaching the depth of the CMS.

As seen here:




Is there anything wrong with just using more washers to take up that space?

That'll mean i have one washer under the damaged thread bolt and probably about 4 under the other bolt. I can't see this causing any problems really, i'll be using the supplied extra grade 8+ washers supplied with the bolts and they'll still be torqued the same.

[DaveRob]

take a die from the box that you should have ... you know the one that has the TAP in it that you used to clean the threads in the block before you started the reassembly and thread the bolt the extra half inch...... please try to keep an imperial thread with some imperial dimensions and dont mix metric with imperial.... ( sorry pet hate ). If you dont have this die.... <SHOCK>.... take the bolt back to the machine shop.... have hime thread the bolt the extra HALF inch.... and preferably both bolts.... then they are the same. Dont try bodging it...... £5 to thread the bolts a bit is better than looking at it later and saying...... thats just not right.

Just my thoughts

Rob

[MRA]

Yes, don't use more washers as they can compress..... simply use a clearance drill for 7/16" and ensure you only go down enough to do the job.... also as Turbodave mentioned did you get the strap machined off both sides ? as this is very important to avoid residual stresses bending the strap and affecting the main cap and bearing etc....

If you are having trouble with UNF bolts we can either make them or buy them in sufficient quantities but at a reasonable price... we thread roll which is a lot better than thread cutting, Turbodave would use bolts manufactured in the same way.

Regards Martin

[mike.]

Yes i've had it machined all the way along, so its still all flat.

I've just assembled it to see how many washers i'd need to use. Found i'll need to use 5 to get it all assembled right and get enough clearance for both bolts to be torqued up without bottoming out...



Doesn't exactly look like the best way of doing it...

I've not got any taps/dies, i took it to the headshop to get the thread cleaned.

So really my options are to get the shouldered part of the bolt threaded another 10mm.

Or

The machine shop i've just had the strap done at, all it is, is a local guy round the corner from me who has aload of mills/pillar drils and things in his garage. Not sure if he'll have such a big range of taps/dies to thread the bolt abit more.

So i'm thinking another solution would be to get the block on his pillar drill and get him to simply drill out the first 5-8mm of thread in the block. So that both sides have the same amount of thread. Any swaft could just be vacuumed/blown out and then the threads would be the same...

It'd save me driving up to warrington again just to get the headshop to thread the bolt.

What do people think of this?