Joining 2 things with different thread/bolt sizes

[KD]

Hi all, I've got to try to join two 'things' together. They both have threaded inserts already in place. Problem is, one has 6mm insert and the other has

8mm insert. Re-drilling and inserting is not an option. I have 2 options (a) not bother and (b) try to find if there's any reasonably easy way to connect something that needs an 8mm bolt to something that needs a 6mm bolt. Are there any neat solutions out there or should I just take option a.

Cheers, Keith

P.S. For info the two things are a floorstanding loudspeakers with 8mm inserts and a wooden 'speaker feet' with 6mm inserts.

[The Natural Philosopher]

Oh ..I see.

I was going to say glue 6mm stud in the 8mm bit, but that is a bit drastic for speakers.

Hmm. Could drill and tap an 8mm bolt for 6mm I suppose..

If you have a lathe and 6mm and 8mm dies, it is of course the work of a moment to turn up a stepped shaft and thread it..

[Newshound]

Even easier to turn and thread a bit of 8 mm studding

[Roger Mills]

One possibility is to get a 6mm and an 8mm bolt, and weld them head to head, and then cut the threads off to an appropriate length. The two things being joined would, of course, be separated by the thickness of the two bolt heads.

You could reduce this to one bolt-head thickness with the alternative solution of taking an 8mm bolt, and drilling and tapping a 6mm thread down the middle from the head end, and screwing - and probably Loctiting - in a short length of 6mm threaded bar. If desired, you could cut the head off the

8mm bolt before screwing the 6mm bar in - just giving you a double-ended threaded adapter - but you'll need the head prior to that for holding it while drilling and tapping it.

As always, run a nut onto any threaded bolt or bar before cutting it, so as to be able to clean up the thread as you wind the nut off.

[Lurch]

On Sat, 14 Apr 2007 12:11:47 +0100, "Newshound" mused:

My first thoughts. No need for a lathe either, so maybe that could be a downside?

[TMC]

Take a small piece of metal say 3mm thick drill 8mm hole for bolt to go up into speaker drill a 6mm hole alongside but clear of the foot and countersink it to take a 6mm csk head screw down into the foot

Tony

[mike]

You've not actually thought that through have you?

[KD]

Hi all, Thanks for the advice so far. Given my inherent laziness and my hope that someone was going to say 'oh, you just want one of those double threaded bolts specifically for the purpose' I think I'm just going to send the feet back and not bother. I still might try your ideas though.

Cheers, Keith

[Lurch]

On Sun, 15 Apr 2007 08:46:36 +0100, mike mused:

I can't see where the problem with that is. Feel free to point it out.

[Lurch]

On Sun, 15 Apr 2007 09:52:48 +0100, "KD" mused:

Well, if you really are that lazy I'm sure someone could be persuaded to make you some of those aforementioned double ended studs for a reasonable sum. ;)

[KD]

... was wondering that :) Seriously though, I'm not sure it's not worth the effort when I can return the spikes to the retailer and use the rounded ones provided by the speaker manufacturer (for laminate flooring). I did try to be a HiFi pedant a few years ago but I'm not so enthusiastic any more about funny spikes, bizarre cables etc. In fact, the only reason I'm having to do this all over again is because I managed to knock over and destroy one of my previous speakers - the stability was somewhat affected by having spikes fitted. I really should learn my lesson. Apparently I can just glue them on but that's mentioned as the second best option and I've got to use the best option if possible :O) Oh dear.

Cheers, Keith

[KD]

Hi again, I'm probably off near a shed this afternoon so I may invest in some 8mm studding and try the tap and die thingy. Could be good for a laugh. Shame I know nothing at all about it :O) SWMBO is not going to be too impressed when all house work stops for me to fiddle with bolts. "But it will make the speakers look nice" will have to be my argument.

Thanks, Keith

Can't believe that they don't sell double width bolts just for numpties like me who order the wrong thing.

[Owain]

It will make them easier to clean under, too :-)

Owain

[KD]

... like your thinking ;o)

[KD]

Hi TNP, Being somewhat rubbish at anything to do with manual tools I simply nipped down to the Screwfix trade counter and bought a tap and die set in some haste. Thinking (stupidly) I could somehow convince a 6mm die onto an already threaded 8mm stud and man handle the thread down. I've been a 'bit' daft. I'm not ignoring the tips mentioned so far but are there such things a dies/cutters tapered from 8mm to 6mm that could chew the difference off. Does this make sense ? I'm quite happy to invest the time in sanding part of the 8mm bar down to 6mm if that's the only way to do it. I'm not sure I'm capable enough to tap a 6mm thread inside and 8mm bar (which I believe has been suggested) and welding is way out of my league. The idea of having a piece of metal to form a common interface between the

8mm and 6mm bolts could be a possibility (which Tony 'TMC' has suggested) but I'd prefer to go down the one bolt method until I'm convinced otherwise :O)

Sorry if it appears that I'm making a mountain out of a mole-hill here.

Thanks, Keith

[Roger Mills]

You won't easily reduce an 8mm bar to 6mm with sandpaper - you really need a lathe.

Failing that, have you got a (preferably horizontal) drill stand which enables you to use an electric drill in hands-free mode? If so, mount the drill in the stand, hold the 8mm bar in the chuck of the drill, turn the drill on and use a file to reduce the diameter of the free end of your bar until you can get the 6mm die to start on it.

When cutting the thread, put a couple of 8mm nuts onto the 8mm thread and tighten (lock) then together using two spanners. Hold the bar - by means of these nuts - in a vice. The nuts will prevent the 8mm thread from being damaged.

[John Laird]

Sounds unusual - I would've thought they'd be more stable. Unless you mean the speakers were sitting on spiked stands. I mounted some bookshelf speakers on floor stands and the bottom of each cabinet is now very badly scratched as a result of being knocked off their perches (although they were never quite knocked to the floor). Spiked floor-standers seem (to me) much more stable on their spikes.

-- "Nodding the head does not row the boat."

[adder1969]

Open up the speaker and put a 6mm bolt through to the feet?

[KD]

Hi John, They were spiked and stood on marble floor tiles to avoid scratching the laminate floor. A slight knock resulted in the speaker skating gracefully off the tile and, with a cry of timber!, falling over and destroying my laptop which I'd just placed on the floor while I plugged the charger in. Not a good evening that one :O) Well, not for the insurance companies anyway.

Keith

[KD]

It would be even easier than that to be honest. The speakers are themselves bolted to small platforms so I would just need to take these platforms off and alter them. I was originally looking for solutions involving changes to bolts so as not to affect the cosmetic appearance of the speakers in any way but it looks like simply adding some 6mm inserts, similar to your idea, is going to be the way forward.

Cheers, Keith