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Drilling and Tapping

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Quote Me Happy



Joined: 15 Jan 2005
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PostPosted: 12:14 - 21 Feb 2011    Post subject: Drilling and Tapping Reply with quote
Hello everyone,

I've got a bash plate to fit to my XT to replace the bars which are currently fitted. The common wisdom is to drill the holes on the frame out from M6 to M8.

A quick Google suggest using a 6.80mm tap drill - does that mean a 6.8mm HSS drill bit to make the hole then use a M8 tap to make the thread?

Is this advisable for a mong with a handheld electric drill to attempt?

Cheers
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virus
World Chat Champion



Joined: 16 Aug 2006
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PostPosted: 12:19 - 21 Feb 2011    Post subject: Reply with quote
m8 has a 1.25 mm pitch gap, so you take 1.25 from 8 to get6.8 or thereabouts as you have done, drill carefully with a hand drill, then tap away with your m8 being careful not to get that in on an angle, you want to keep the tap square to the hole at all times otherwise you get a nasty thread with either a bolt sticking out at a jaunty angle, or it pinches on one side tighter than the other.


Its no massive job to do really, note taps come in 3s, start with the one with the finest point, and if the hole doesnt go all the way through then finish with the one with the squarest end to get thread right to the bottom.

Cheers
John
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Suntan Sid
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Joined: 07 May 2009
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PostPosted: 12:23 - 21 Feb 2011    Post subject: Reply with quote
M8 (Coarse) = 6.75
M8 (Fine) = 7 or 7.25 or 7.5 (Weird)

Shouldn't be too difficult if youve got M6 holes already there, would be pretty difficult not to get things lined up!
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Bezzer
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Joined: 14 Apr 2005
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PostPosted: 12:37 - 21 Feb 2011    Post subject: Reply with quote
Suntan Sid wrote:
M8 (Coarse) = 6.75
M8 (Fine) = 7 or 7.25 or 7.5 (Weird)

Shouldn't be too difficult if youve got M6 holes already there, would be pretty difficult not to get things lined up!


As previously stated 6.8 is the accepted tapping drill size for standard M8x1.25, they are readily available not so 6.75.
M8 fine could be any pitch from 1.0 down so 7.5 for a 0.5 thread is rare maybe but not weird.
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.....
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Joined: 15 Jan 2005
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PostPosted: 12:51 - 21 Feb 2011    Post subject: Reply with quote
virus wrote:
you want to keep the tap square to the hole at all times otherwise you get a nasty thread with either a bolt sticking out at a jaunty angle


Extra marks for using 'jaunty' - one of my favourite words Thumbs Up

Quote:
Shouldn't be too difficult if youve got M6 holes already there, would be pretty difficult not to get things lined up!


Believe me, if anyone can get this wrong, it's me.

Does the tap need any cutting fluid?
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tatters
Exxon Valdez



Joined: 04 Jan 2004
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PostPosted: 12:59 - 21 Feb 2011    Post subject: Reply with quote
Hetzer wrote:
Joe wrote:

Does the tap need any cutting fluid?


Bit of WD40, unless you're tapping under power. And I use WD40 for that too, coz I is badass.


Dont forget to back the tap out every other 2nd turn to clear away the swarf.

I,ve got the right drill bit and tap as well as a proper tapping wrench and cutting fluid if you want to borrow them.


I would,nt try and use the tap in a drill if l was you as it will most likey snap leaving a nice chuck of hardened steel in the hole.
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MarJay
But it's British!



Joined: 15 Sep 2003
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PostPosted: 13:42 - 21 Feb 2011    Post subject: Reply with quote
I use power steering fluid as cutting fluid, and I do 3/4 of a turn, then back off 1/4 of a turn each time. Takes a long time, but does the job.
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Pete.
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Joined: 22 Aug 2006
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PostPosted: 14:23 - 21 Feb 2011    Post subject: Reply with quote
The No1 cause of snapping a tap is not starting it in line with the drilled hole. Next is using a blunt tap. Get it straight and that's half the job bone.

For tapping ally I use WD40 for steel I use normal engine oil in my oilcan. I have a can of rocol tapping lube which I save for important jobs and stainless.
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Joined: 15 Jan 2005
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PostPosted: 14:44 - 21 Feb 2011    Post subject: Reply with quote
tatters wrote:
I,ve got the right drill bit and tap as well as a proper tapping wrench and cutting fluid if you want to borrow them.


Cheers, will probably take you up on that - I'll bring the chain tool if you want and you can ditch the split link?

Hetzer wrote:
Gawd, I've realized how my post could have induced disaster.


I don't need help inducing disaster Laughing

MarJay wrote:
and I do 3/4 of a turn, then back off 1/4 of a turn each time. Takes a long time, but does the job.


Cheers, slowly does it then.

Pete. wrote:
The No1 cause of snapping a tap is not starting it in line with the drilled hole. Next is using a blunt tap. Get it straight and that's half the job bone.


Stupid question, is there anyway to make sure it's going in straight other than by eye?
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virus
World Chat Champion



Joined: 16 Aug 2006
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PostPosted: 15:11 - 21 Feb 2011    Post subject: Reply with quote
put the tap in then remove the tap wrench and check using a set square if youve got one, thats the prefered method

as long as its as square as possible and you keep on the same kind of heading rather than correct halfway through you'l have useable thread.


Cheers
John
____________________
own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance.
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Pete.
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Joined: 22 Aug 2006
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PostPosted: 17:12 - 21 Feb 2011    Post subject: Reply with quote
Quote:
Stupid question, is there anyway to make sure it's going in straight other than by eye?


If you have a small pillar drill you can make a tapping guide by drilling a hole the diameter of the tap through some scrap material (all, plastic, wood) and run the tap through that first then hold it flat over the hole and keep tapping.
Failing that, find something square/rectangular and line it up alongside the tap as a visual reference. Something about the size of a matchbox would be good.

As Hetzer said, a taper tap will tend to start quite straight but it's not guaranteed, and most cheap tapping sets only contain second taps anyway. One thing they won't want to do is correct themselves once started.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
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Quote Me Happy



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PostPosted: 20:09 - 21 Feb 2011    Post subject: Reply with quote
Pete. wrote:
As Hetzer said, a taper tap will tend to start quite straight but it's not guaranteed, and most cheap tapping sets only contain second taps anyway. One thing they won't want to do is correct themselves once started.


Thanks Pete, out of ratings for today.

I've been looking at tap and die sets online and they vary hugely in price. Can anyone recommend a set?
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stinkwheel
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Joined: 12 Jul 2004
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PostPosted: 21:20 - 21 Feb 2011    Post subject: Reply with quote
Could you not just go all the way through with a good quality nut and bolt?

Be a hell of a lot easier to get out again if you bend it. Fitting a bash plate implying it stands a good chance of getting bashed at some point.
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stinkwheel
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Joined: 12 Jul 2004
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PostPosted: 21:33 - 21 Feb 2011    Post subject: Reply with quote
Joe wrote:

I've been looking at tap and die sets online and they vary hugely in price. Can anyone recommend a set?


You can buy individual HSs taps in a little red plastic box in most steel stockholders and places like machine mart.

I invariably find the ones you buy individually seem to be a lot better than the ones in a set.

Dormer is a very good make.

I have a set of Teng ones that are very good quality.

Both of the above are pricey. The clarke ones you get in machine mart are fine for most jobs though and are a lot cheaper. Also on Ebay.

Up to a certain price, a tap-wrench is a tap-wrench and you don't need anything particularly fancy for what you're doing if you were buying a single tap.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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