Half inch whitworth tapping size hole?

niander · Post by **niander** » Sun Nov 18, 2007 7:26 pm

Hi guys i just know some of you guys will know what size hole i need to drill to tap for Half inch whitworth bolt

preferably metric as its easier to get hold of.....

cheers

Vic · Post by **Vic** » Sun Nov 18, 2007 8:45 pm

10.5 mm or 27/64"

40TPI · Post by **40TPI** » Sun Nov 18, 2007 9:25 pm

Worth a bookmark along with quite a few others from Google..

http://modratec.com/mud_tap.php

Peter

niander · Post by **niander** » Mon Nov 19, 2007 4:26 pm

Very good 10.5 mm it is then...
and good site..
anyone know a good source for an extra long drill bit?

Vic · Post by **Vic** » Mon Nov 19, 2007 5:20 pm

That's not going to be so easy. Screwfix do then up to 8mm only.

I reckon you will have to go to a good engineering suppliers and it'll probably cost!. I think what you need is called a "crankshaft drill" dunno why.

If you could set it up to stay straight you could braze a standard drill onto a length of steel bar but you would have to keep clearing the swarf from the hole.

Then I suppose you are going to want a long tap. This is going to be an expensive job.

philj · Post by **philj** » Mon Nov 19, 2007 6:28 pm

Hi,
RS Components will sell long series drill bits
Phil

Charles UK · Post by **Charles UK** » Mon Nov 19, 2007 7:52 pm

For long series drills try (cromwell.co.uk) 10.5mm x 121mm flute length Â£7.60 that was the first I saw, or 10.5 x 200 flute Â£29.17

Make sure you ask for their catalogue, they stock everything.

niander · Post by **niander** » Mon Nov 19, 2007 10:30 pm

ok is it posible to weld a bar on to extend the the drill and tap?
as i can weld easier than braze...

Vic · Post by **Vic** » Tue Nov 20, 2007 1:22 am

is it posible to weld a bar on to extend the the drill and tap

If your welding is up to it perhaps.

You are not going to believe this but this picture is in fact of a 27/64" drill brazed onto best part of 12" of 3/8" bar

It was amongst my father's tools and it's been around for as long as I can remember. I reckon he must have had the same job to do! Its been ground for something in particular though. No matching 1/2" Whit tap.

philj · Post by **philj** » Tue Nov 20, 2007 9:16 am

Hi,
that is a "drill on a stick"
They are used to drill the hole required to pin a cam on to a shaft, they are brazed because it uses less heat than welding. Welding will cause distortion and weaken the drill, but if you are only using it once and will throw it away after, then welding is ok. At this size it will not be so important.
regards
Phil

Vic · Post by **Vic** » Tue Nov 20, 2007 1:27 pm

I suspect this one was made to drill a hole through a wall in the days before you could get long masonry drills. Probably 27/54" because being the tapping size for 1/2"W he would have had loads that size available.

niander · Post by **niander** » Tue Nov 20, 2007 11:09 pm

If your welding is up to it perhaps.

Well it was my job for years:)

so im good enough...actually a plater/welder

mig or stick

but i only have the stick welder at home.

is that drill a masonry it looks it from the side or the point needs sharpening?

if that drill is hss will you sell me it?....

Charles UK · Post by **Charles UK** » Tue Nov 20, 2007 11:15 pm

We are all getting very curious, please explain the purpose of this hole.

Perhaps we should run a sweepstake

niander · Post by **niander** » Wed Nov 21, 2007 10:21 pm

Just bolting some wood to cast iron.