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Old 23rd Jan 2021, 7:44 pm   #41
ms660
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Default Re: Centre drills vs Spot drills.

Here's a few holes cut with a hole saw (Bosch) it was to see how many the drill would do continuously on one fully charged battery....almost 6 holes, the timber is tough stuff (Spruce) I have a full set of Bosch ones and a special for doing 110mm for the large waste pipes, I mainly used that one with a mains powered drill that I could extend the side handle on.....

Lawrence.
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Old 23rd Jan 2021, 8:03 pm   #42
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Default Re: Centre drills vs Spot drills.

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Originally Posted by Radio Wrangler View Post
If you pre-drill a pilot hole right through, use a bit of rod mounted in the holesaw. It won't enlarge the pilot hole by cutting sideways with the flutes as a drill bit would.
Most these days are hex shank drills.

If the proper drill bit is used it shouldn't drift because of the type of flute, it ensures a tight hole, it's that tightness that is used to eject the plug, at least it is with the Bosch system.

Lawrence.
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Old 24th Jan 2021, 8:06 pm   #43
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Default Re: Centre drills vs Spot drills.

Thanks David for the information in Post No.32. (link to Marius on YT very useful)
I so rarely have to use a holesaw ('tank cutter') bit that i never learnt how to do it properly. Following the advice i completed three 2" holes in thin ply without the heat build-up, jamming and clogging. Obvious when you think about it- if you don't get rid of the sawdust you may as well be a boy scout starting a fire with friction.

A couple of things to add- look out for off centre cheap arbors and cheap slightly oval holesaws....and attack the wood from the reverse side to finish the hole if possible.

Dave
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Old 25th Jan 2021, 12:38 pm   #44
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Default Re: Centre drills vs Spot drills.

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Originally Posted by robinshack View Post
Before Xmas, a set of the stepper cones was offered for I think £4.99. Can't remember if it was Aldi or Lidl. Not going to be professional grade at that price, but probably ok for occasional hobby use. Besides, they always have no quibble guarantees as well.
Trade names are Parkside (aldi) & Workzone (lidl). Ferrex is another brand I have seen.
Rob
I used my Ferrex ones on Saturday to put some holes in the cases for my latest project, 2x phono (RCA) and power. Pretty impressed with them. Ferrex is an Aldi own brand.
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Old 25th Jan 2021, 10:01 pm   #45
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Default Re: Centre drills vs Spot drills.

Going back to my engineering apprentice days, We were shown how to apply a blob of plasticine onto the end of the closed drill chuck, push a needle into it and then centre the needle by touching the needle as it rotated. Once centred, the pin was lowered toward the centre punch of the hole and carefully lined up, looking the front and the side. Once lined up, the hole could be drilled (small pilot to start it), followed by the correct size.

We never had any holes out of alignment.
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Old 26th Jan 2021, 12:04 am   #46
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Default Re: Centre drills vs Spot drills.

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Originally Posted by David G4EBT View Post
If you don't do it as shown in the video at the link below, you'll probably conclude that either the hole-saw is rubbish, or your typical DIY pillar drill which most of us have - myself included (usually about 350 Watts) is underpowered. Neither is the case - there's only one way to successfully use a hole-saw and it's demonstrated here:

https://www.youtube.com/watch?v=1ZSse6AW2cA
Brilliant video, David, thanks for sharing.
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Old 26th Jan 2021, 4:35 pm   #47
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Default Re: centre drills vs spot drills

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Originally Posted by Station X View Post
Centre drills are for drilling centre holes in the end of shafts so that they can be mounted "between centres" on a lathe and shouldn't be used for anything else. They're very prone to snapping off if you're not careful and the remains are a to get out.

To start holes I either use a centre punch or a spotting drill.

I also remember being taught that all holes over 1/4" diameter must have pilot holes. The diameter of the pilot hole should be slightly larger than that of the larger drill's tip.
Similar to my training. But I've found over the years that in addition ( and sometimes in the absence) of a centre punch, using a small bit in a cordless on a low speed in reverse can provide an accurate start point.
Thin metal needs a support or the metal can bend. For larger holes I'd recommend something like a Qmax hole punch.
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Old 28th Jan 2021, 8:20 pm   #48
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Default Re: Centre drills vs Spot drills.

In Lidl this morning, which is the day they display their latest 'Lidl in the Middle' 'when it's gone it's gone' offerings. Coincidentally, they had a set of six bimetallic hole-saws - 22mm, 25mm, 35mm, 44mm, 68mm and 73mm diameter. (Tested and certified in Germany). Couldn't resist them at £9.99.

Lots of other electrical and hand tools including a rotary 'Dremel' style tool, variable speed from 10,000 to 40,000 RPM, flexible shaft, keyless chuck, routing base, stand, 42 attachments, and an LED (battery powered) light attachment. (£19.99).
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Old 29th Jan 2021, 12:26 am   #49
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Default Re: Centre drills vs Spot drills.

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Originally Posted by David G4EBT View Post
In Lidl this morning, which is the day they display their latest 'Lidl in the Middle' 'when it's gone it's gone' offerings. Coincidentally, they had a set of six bimetallic hole-saws - 22mm, 25mm, 35mm, 44mm, 68mm and 73mm diameter. (Tested and certified in Germany). Couldn't resist them at £9.99.

Lots of other electrical and hand tools including a rotary 'Dremel' style tool, variable speed from 10,000 to 40,000 RPM, flexible shaft, keyless chuck, routing base, stand, 42 attachments, and an LED (battery powered) light attachment. (£19.99).
.....lead us not in to temptation, and deliver us from evil during lockdown...
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