I've read that the best way to open out a hole accurately is not with a drill bit but with a five-sided reamer. Depending on the thickness of the material this can leave a slightly tapered hole, but once one aperture is at the final size, a bit can be used. I've never had occasion to try it though.
Typical blaming someone else when you brag that you are the expert!
A poor workman *always* blames his tools and a poor employer *always* blames his employees!
May not be a problem with the drill bit, but perhaps you should try varying the speed of the drill (lower) and using a lubricant on some metals - and even making sure that you have the right cutting angle on the tip of the bit for the metal being cut.
Before you start your usual invective, just have a google and you will find the answer (try the wikki pages) - or even read a decent engineering book.
A 2mm enlargement to a pre-drilled hole - easy enough for all but the least experienced!
So what about you using your "great expertise" to resolve the problem, rather than blaming someone else?
What about someone doing something that he knows little about ?
Was "Desmond" using the power drill at its maximum speed thus causing the bits to overheat (that would explain the "wearing out") and any number of other reasons of misuse causing the snapping of the bits.
All the above presumes that these "special" brackets made out of mild steel and not some exotic metal - as you have failed to give some fairly basic information yet again.
Its certainly easier in a drill press, however assuming these were mild steel brackets, then even if not ideally suited to the job, a HSS bit should have done it relatively easily.
(your favoured bosch mm bits would have probably done a better job).
What did TMH do to deserve that invective? He was relating his account of a job and asking if Silverline-brand bits were crap or if it was to be expected of this sort of job. Seemed reasonable enough to me: guy's a handyman not a specialist machine-shop engineer.
Did he upset you in another thread? Your "great expertise" quote suggests a reference to a post elsewhere. I might be more inclined to employ Dave as a handyman than as a diplomat, but I don't think anything he said in this thread merited that response.
I have had mixed experience with Silverline items.
Opening out a hole without adequate clamping and hand held tools is always going to be difficult. Particularly where there is so little
*uncut* material to support the cutting edge of the drill bit.
One technique I was shown as an apprentice is to *back off* the cutting points. I have long forgotten the actual cutting angle on a properly sharpened bit but, if this is made nearer to 90deg. by judicious use of the ubiquitous angle grinder, the cut swarf will not *snatch* the drill so easily.
And being on site no good secure means of holding the brackets? The speed is a little high for handheld but let the tool do the work. Just hold it as firmly as you can into the hole and don't push hard. Pushing hard will make the drill cut deeper and with such a small amount of metal involved very likely to grab, twist and snap the drill...
For on site a 10mm round file might have been a better bet than trying to use drills or, unless it was a long way. back to the workshop and the pillar drill and not charged for the time.
Yeah but a pilot hole shouldn't be much bigger than the little line on the main drill where the ground faces meet in the center. That must have a name...
You had a "pilot" hole nearly as large as the wanted size, just 1mm of metal all round to remove. A twist drill should manage it *if* you can control it, keep it centred and don't feed to fast. That was never going to be easy hand held.
Ignore it John "Unbeliever" and TMH don't hit it off. "Unbeliever" is a troll and TMH (normally) feeds the troll...
TBH "Unbeliever" appears perfect but *everyone* makes mistakes he just hasn't the bottle to ever admit them or acknowledge that there may be gaps in his perfect knowledge. Unlike TMH and many others who are happy to ask "the stupid question" or admit to fups.
Presumably, you were also taught to select the pilot drill be holding it up to the web of the larger drill, to check they were the same size or, at most, marginally larger. The web has no cutting edges and the pilot hole reduces the load when drilling with the larger drill. It is also useful as a guide when everything is not firmly clamped or if the main drill is not absolutely sharp and might otherwise tend to produce a slightly triangular cut.
To open up a hole that is not far off the finished size, you need something that uses the existing hole to guide its cut, such as a taper reamer or a step drill with the right sizes of step. A two flute drill does not do that. A three flute drill would be better, but are not common. You can get away with a two-flute drill, but only if the work piece is firmly clamped in a pillar drill and the hole and drill have been properly aligned.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.