I've got a couple of sets of plug cutters - for cutting wood plugs to fill screw holes, etc. But what to use for the perfect hole to fit them to? The same nominal size Forstner bits produces too large a hole for a tight fit. I do have by chance a router bit that is ideal for 1/2" ones - but nothing for the other sizes. Other wood bits tend to leave a rather ragged edge.
Welcome to the club.
Only solution I ever found was to get a cheap set of the flat wood bits and spend time with a vice and file until the core matched the hole from the filed bit.
As the bit edges are flat they are not too much trouble to file.
Lip and spur bits. The very good makers of plug cutters (Clico - try Axminster) do matching lip and spur bits for their plug cutters, but IME any reasonable lip and spur bit (e.g. Bosch) is up to the job.
I normally use a lip 'n' spur bit. Gives a clean hole, and the size match is usually ok.
I just bought this set:
in which the screwdiggers seem to produce the right size of hole for the plugs the cutters produce.
The reviews don't look encouraging ...
The snag with those is I may not always want a through hole - I've used plugs to replace old screw holes etc rather than filling. I do have some of those drills and they're very slow at making the countersunk hole.
They tend to give a pretty rough edge to the hole - no better than a twist drill. They're really designed for speed rather than accuracy.
I've got some lip and spur drills but it's the same problem - they give a clearance rather than interference fit. Although I must admit not having a big selection of them - perhaps I just need to buy ones which are the actual correct size for what I need.
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Have a look at Axminster part number 300532. This is a set of plug cutters and shaped drills for the holes which match properly. You can adjust the drills such that the front thinnest part is very short and not a through drill.
Indeed you can - I've got several of this sort of combination bit and forgot you can adjust the position on the drill. But I'm actually ok for hiding screw heads - I have a router cutter which is the right size and works ok in a drill. It's the larger sizes that are more of a problem.
What I think I need is Forstner bits designed for the job. I don't have a big selection of these so perhaps need to see if there is a metric one which gives the correct hole for an imperial plug cutter - or vice versa. Lip and spur drills tend to pull themselves in rather too easily if you're working with a hand held drill.
You shouldn't need to do this. Are you drilling on a drill press or in situ? If it's the latter then you could fit a small portable stand/depth stop to the drill to prevent it from pulling in.
Could you actually give some numbers for the diameter of plugs you're using please?
Plug cutters over half an inch are less common, and lip and spur are available up to that size.
Above that size, I'd look at using auger bits rather than forstner bits (and definitely not flat bits!). IME lip and spur don't tend to pull in at all, whether on a drill press, handheld power drill or hand drilling. By their nature auger bits do pull in (and forstner can be all or nothing), so augers are not suitable for a drill press at all, and power drills need very good low speed control - but they produce good parallel-sided holes in larger diameters.
As ever, sharp drill bits make all the difference - a dull bit will still cut, but will require too much drilling pressure to be easily controllable.
Be better to find a cutter that does the job properly IMHO.
1/4, 5/16, 3/8, 1/2, 5/8.
They are - and are ok except when an existing hole is there. Ie ok when drilling fresh wood. But the same applies - a 1/4" one gives a 1/4" hole and leaves the plug loose.
I obviously need some form of mill rather than drill. The forstner ones I have would be ideal (to me) if only I could get the right size.
[Thinks] - perhaps I could get them ground down to what I need?
I've never had a problem with sets like this into either soft or hard woods. The plugs end up being a good interference fit. I can imagine that trying to drill the holes with a hand held drill is not going to be optimal though.
You sound to be making this difficult - plugs should be EASY!
Go out and buy a new plug cutter and lip & spur drill:
(for cabinet work, you leave the plug slightly proud until the glue goes off, and plane in)
I just gave my set away on Freecycle. ISTM that a better design would have been to have to designed them so that each drilled a hole that would fit the next larger one's plug (largest excepted of course). You'd need to drill a slightly undersized starter hole first of course.
Yup - that had occurred to me too.
lip and spur drills.
My requirements are different to yours, then.
Is there any other way?
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