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Engineering question...

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Engineering question...

I need to drill a  hole in a section of 15 mm square brass bar... and then tap it for a 6 mm threaded bolt.... do I drill a 6 mm hole, or a 5.5mm hole? 
Any offers ? ( as I don`t have a pillar drill, to make sure it is vertical ).....
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Re: Engineering question...

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Re: Engineering question...

Thanks Jim.... still a bit confused... how do I find the "pitch" of the thread... it is a 6mm x 25mm pan head slot type bolt.
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Re: Engineering question...

A cheap pitch gauge....often included in tap and die sets.
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Re: Engineering question...

best way is to measure it - distance between 20 threads - although it is probably 1mm as I don't think that metric fine is available at M6 http://www.metrication.com/engineering/threads.html
However - as strat infers above you need to buy the correct tap for the thread
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Re: Engineering question...

If I read the read right Shutter is screwed if he goes wrong.
What type of brass is it?
jim:green extremely rude typo changed mod:end
Now Zen, but a +Net residue.
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Re: Engineering question...

Yeah.. I am screwed (?) if it goes wrong..  it is brass bar... solid brass.. that`s all I know about it...    I realise that I need to get the pitch of the "tap" hole the same as the pitch of the supplied bolts... however. I do have an alternative.. and that is to drill a 6mm hole.... then, on the underside... drill a BIGger hole, to allow the insert of the 6mm nut to be soldered in place...  a messy solution, but it works if I can`t get it right ! ! ...
Unfortunately, there seems to be some "lateral" and "end" play on the thread of the nut and bolt, so I would prefer it if I can tap, or get it tapped to the correct pitch for the bolt to be a reasonably tight fit...
The bolt will be used a a fine gap adjuster, and may need a lock nut, or some kind of compression spring to hold the adjustment so set...
EDIT EDIT EDIT
I was considering buying this set...... 
http://www.ebay.co.uk/itm/310926178933?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
but I can`t see a "pitch gauge" in there....

Kevin
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Re: Engineering question...

A quick Google seems to say that a coarse 1mm pitch is the usual for an M6 bolt, therefore you would need to drill a 5mm hole in brass.
http://en.wikipedia.org/wiki/ISO_metric_screw_thread
Kevin.
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Re: Engineering question...

Quote from: shutter
I can`t see a "pitch gauge" in there....

Sad
Pitch gauge on everyone's favourite auction site.
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Re: Engineering question...

Thanks Kevin....  Wink
Thanks Strat .....  Wink
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Re: Engineering question...

Quote from: Strat
Pitch gauge on everyone's favourite auction site.

Why can't you politically correct people just accept that there is actually no harm in saying "ebay" ? - What is wrong with saying that Stat? Instead you tell me that its my favourite auction site - which in itself is not politically correct because it is not my favourite auction site Tongue
Come on.. I want an answer! Too many people dodge names of sites, newspapers, TV programs, usernames etc.. it's all getting rather silly when you can't even say ebay anymore.
I need a new signature... i'm bored of the old one!
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Re: Engineering question...

Wow.... that is really going "off topic"...  Lips are sealed
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Re: Engineering question...

No, that's just going off! Cheesy
Got to agree though, why pussyfoot around? Smiley
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Re: Engineering question...

Correct me if I'm wrong 7up but I believe this was the first time I have used that particular phrase and it will almost certainly be the last.
Please accept my apologies if it offended your sensibilities.
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Re: Engineering question...

Assuming you know the bolt and tap diameters (in this case M6), I've always held the bolt thread against the tap thread, and if the threads match and 'interlock'/'mesh' then it's the correct pitch, and if not you try the next pitch size tap from your tap set !