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Hi -
I'm hoping someone here can help me work this one out..........

I need to drill holes up to 16mm diameter through the very corner of a pvc window frame, right in the corner of a deep window alcove, and from inside the house, not from outside.

I know from previous experience if I try with my existing standard bits and drills, because of
a) the width of the chuck and the drill body itself and
b) the relatively short length of standard drill bits
that I won't be able to get right into the corner of the alcove to drill a straight hole, and the chuck is likely to cause surface damage to the wall as I try to get into the corner where I need the hole to be.

So I need extra long drill bits, minimum 300mm long, so I can keep the chuck and the drill well back and out of the alcove and still drill straight in the very corner of the frame in the alcove.
I've found 300 mm HSS drill bits on Amazon which have the range of sizes I need, and the length is good, but all the bits are straight shank so the larger diameter bits are beyond the 13mm chuck capacity of my current drills.

I want standard HSS metal drill bits, not masonry, SDS, wood augur bits etc as I don't think those would be as good for drilling a neat hole thru the pvc.
The bits from Amazon are standard metal bits so seem ok, but have the straight shank issue.

I cannot find larger diameter extra long HSS bits with reduced shanks to fit a 13mm chukh, even blacksmiths bits which usually come with a reduced shank unfortunately don't seem to come in extra long lengths.

An alternate thought is perhaps I can get a bigger chuck (that will take up to 16mm straight shank bits) to fit one of my drills, but I can't find one of these either, and presumably it would depend on the model of drill anyway ? Or are they 'standard' fitting?

So I'm wondering if anyone knows of a supplier of extra long and wide HSS bits with reduced shanks, or a supplier of larger chucks that I can approach?
Or, am I missing something obvious that I simply haven't thought of........always possible !?

Many thanks.

Update - since posting above, I have found 16mm chucks .......mostly it seems for lathe work so not suitable I don't think, but I've found a couple that look like they are for hand held power drills.
So I guess that may be an option if I can work out just what mount is required for one of my drills ............

What depth is the cut, UPVC windows have some aluminium core which I think you know, hence your choice of HSS bits.
My trial would include 1st drilling a smaller bore hole to test what lies beyond the external finish, if just plastic then choice of wood bits possible.
I would consider a long round, rat tail, file held in the chuck, low speed, though the fit, with some taper, would be sensitive to overload looseness, safety care called for.

Hi, many thanks for your reply.
I'm not sure what you mean by "depth of the cut"..........the window frame is about 65mm deep/thick, so that's the distance I need to drill a neat hole through. To me it's a hole, not a cut.
Agree re drilling a smaller hole first, and then moving up the drill sizes appropriately to 16mm.
Not sure re a rat tail file.......for now will hold out for bits and/or chuck I hope !

found this https://www.rennietool.co.uk/products/f ... u-EALw_wcB 13mm shank, PLEASE NOTE this is not a company I have used so cannot recommend ...

Thanks wine~o, that's a good find !