Hello,
I am thinking of buying a cheap set of augers from Screwfix. Are their "erbaurer" brand any good?
The diy faq says that you cannot use spade bits to enlarge an existing hole. It doesn't say anything about augers. Can augers be used to widen a hole or do you need a hole saw for that?
Thanks, Stephen.
None of the ones that require center guidance will work. You can fill the hole with a scrap of dowel or similar and then use a spade if you want. Or you can put a scrap of wood over the hole and drill trough it with a spade.
I doubt an auger bit would be much more successful. I would expect particuler difficulty getting it started.
What size and depth hole are you wanting to increase, and to what new size? A router would be a good option in some cases.
Non are really suitable as they all use some form of centering.
Could you glue a bit of dowel in the hole and start again, as it were?
Other way might be with a router and suitable cutter.
You can do this with an auger (a helically twisted one at least, not an old spoon bit) provided that you give it a start by bunging the top of the hole up with a temporary plug that's at least one diameter deep. Once you have it started, it'll carry on guiding itself from the sides (for knife-and-fork levels of quality).
A spade bit OTOH won't guide itself from the hole walls at all, and it needs a centre point all thwe way through.
If you're getting fussy about quality, buy yourself a cheap set of sawtooth bits (similar to Forstners). If you also do some work on their edges with a small diamond hone beforehand, the "tenner a set" happy-shopper ones are usable.
========================================= A Forstner bit would be a better bet as it has a cutting edge on the outer perimeter of the bit. Success would depend to some extent on the original hole size and the planned new hole size. Example here:
Even they require a central support for guidance. He needs to plug the hole first or route it wider.
A Forstner bit would be a better bet as it has a cutting edge on the outer perimeter of the bit.
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========================================= No, they don't.
Positioning the bit centrally over the existing hole can be done by measurement but the main cutting edge is the outer edge and doesn't need a central gimlet to pull the bit into the wood.
I've just done a test hole - 20mm hole enlarged to 35mm giving a perfectly clean cut with no central guidance from the enlarging bit.
Cic.
Thanks for the fast replies.
I drilled a 25mm hole for some Pb 22mm pipe. I would think filling such large holes would be tricky? I was interested in the second idea about covering the hole with a scrap of wood, but what happens once the spade breaks through that? Surely it would just start to bounce everywhere?
Anyway, I used a holesaw and that did the trick. I might still pick up some augers though, I understand they are neater than spades. What is the Screwfix own brand "erbaurer" like?
Thanks,
No more than when it is breaking through a normal hole as the scrap stabalises it a bit. It works even better with forstner bits which is what i think you probably want as they are more versatile than augers, Something like
I have no idea. I have some cheap aldi forstner bits and they are OK for what I do.
,
Bear in mind that many of these auger sets have 13mm shafts and might not fit your drill chuck.
Are you from Lancashire Chuck. :-)
Thankfully no. :-)
They don't. They'll even drill a clean hole if they're only drilling timber abbout 2/3rd of the hole diameter (i.e. a chord of the hole is overhanging the edge). Obviously starting the cut needs _either_ a centre guide point, or a fairly rigid drill press to hold it together.
However most "Forstners" for sale are actuallt sawtooth bits (teeth on the edge). These are less stable and self-guiding than the true smooth- edged Forstner (as Screwfix sell), but they'll still do a reasonable job.
Thanks for the tip about the shank size.
I have not heard of forstner's before, so I will look into those. One obvious disadvantage is that they look quite short, so they can't replace a 400mm auger.
It's a shame that the Screfix sets have a 15mm rather than 16mm bit: a
15mm hole might be a bit tight for a 15mm pipe.I had a quick read on wikipedia and it seemed to suggest they require some force and cannot be used in hand drills. Is this so?
It looks as though they are like hole saws but with the advantage that you can drill to any depth, whereas with a hole saw you have to come out the other side.
========================================= They are quite short - typically about 90 / 100mm overall. They do require some force AND a fairly strong grip if you're using in a hand drill. My technique is to press the bit firmly into the wood and start the drill on a slow speed whilst maintaining strong pressure. If you're trying to enlarge an existing hole you do need strong pressure to prevent the drill wandering off. If you've got a woodworking brace you can use a Forstner bit in that but it is very hard work. If you're using a bench drill it's easy work and the depth of hole is only limited by the length of the bit.
If you only have one or two 15mm holes to enlarge to 16mm it would be easier to use a file saw in your drill, a round wood rasp or even a blacksmith's drill. Blacksmith's drills are quite expensive but rasps are usually available from cheap shops like Poundland.
Cic.
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