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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 12th Apr 2022, 12:20 pm   #1
Wendymott
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Default Hole enlarger.

Hi Peeps.... Often, when I am building something, the holes can be an inconvenient size... I have a hand reamer, but sometimes it gets a bit "boring" forgive the pun.. to make the correct size. I have two of those "stepped" cone drills, but they are often oversize on the steps. So for holes from 3mm to 12 mm, I bought a tapered reamer with a "T" bar, that fits nicely into my 13mm pillar drill chuck...... at slow speeds, works a treat... NO more rat tailed files,
Yes I Know ... the safety police will be hammering on my door... but with umpteen years of experience, we know what's safe and what's unwise.. now where's that first aid box.... just kidding
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Old 12th Apr 2022, 2:31 pm   #2
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Default Re: Hole enlarger.

You can get stepless smooth cone drills, I've got a couple somewhere.

https://www.lawson-his.co.uk/cutting...ter-drill-bits
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Old 12th Apr 2022, 6:09 pm   #3
G6Tanuki
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Default Re: Hole enlarger.

"Cone-cuts" are brilliant for this sort of thing; I use them a lot when I need to open-out a hole in a chassis to fit a modern B9A valve-socket in place of the older obsolete B8 version (for example when fitting a UL84 in place of a UL41) - _usually_ a B9 base will fit the same hole as an old B8 but occasionally you come across one that doesn't, and a cone-cut is a good way to ream-out the hole.
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Old 12th Apr 2022, 6:39 pm   #4
wireman
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Default Re: Hole enlarger.

I have all of these (step drills,cone drills,hand reamer) and they really are a revelation if like me you used to use normal drills for sheet material and from time to time tried to jump too many sizes with terrible results.
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Old 12th Apr 2022, 11:10 pm   #5
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Default Re: Hole enlarger.

Dont forget though, that if a tapered reamer chatters, you will get a lovely hexagonal hole.

Joe
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Old 13th Apr 2022, 7:38 am   #6
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Default Re: Hole enlarger.

I changed over to the Rotabroach mini system. I found that they cut a very clean hole with no burrs to clean up. The system works like a std hole saw. You have a Arbor and then interchangeable cutters to the size that you need. The small Arbor fits from 6mm – 19mm then the larger one for 20mm and above.
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Old 13th Apr 2022, 10:42 am   #7
Wendymott
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Default Re: Hole enlarger.

Joe... Thats why its a multi fluted reamer... and running at moderate speed.
Bob..... no good to me..finite sizes.. not variable..
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Old 13th Apr 2022, 10:53 am   #8
joebog1
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Default Re: Hole enlarger.

Yes Wendy!!! I MEAN a multi fluted reamer!!!!. If it chatters you will get a hole with as many lumps as flutes in the reamer!!!!.
I will send some photos.

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Old 14th Apr 2022, 5:33 am   #9
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Default Re: Hole enlarger.

.....which is why they make larger reamers with many more flutes and you have to clamp the workpiece down tightly.

My old boss used to say when a 'mistake' was made "bigger holes, bigger washers...."
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Old 14th Apr 2022, 1:49 pm   #10
Wendymott
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Default Re: Hole enlarger.

Good job Im not making nano metre accuracy then .
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Old 18th Apr 2022, 8:43 am   #11
SiriusHardware
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Default Re: Hole enlarger.

The main hazard with using both types of enlarger is the high possibility of keeping it going for a little bit too long and ending up with an oversized hole.

If using a pillar drill with an adjustable height bed my 'top tip' for using a stepped or cone type hole enlarger is to wind the position of the bed down to the point where the correct sized step or correct diameter of the cone only just reaches the workpiece when the drill head is wound all the way down and hits the end stop, making it impossible to push the enlarger any further into the workpiece.
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Old 18th Apr 2022, 11:19 am   #12
David G4EBT
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Default Re: Hole enlarger.

I do have reamers but I generally don't find step drills an issue in being over or under sized for holes. They go up in 1mm steps, so if a hole is drilled oversized that's only 0.5mm gap around the circumference. (The larger the diameter, the less significant 0.5mm is). Incidentally, step drills are also available in Imperial sizes. A set of three HSS titanium coated step drills from Toolstation will cover from 1/8" to 3/4". (1/8" - 1/2", 3/16" - 1/2", 1/4" - 3/4"), in 1/32" steps, so each step is 0.79mm larger than the one below it. Three for £16.98:

https://www.toolstation.com/hss-tita...ill-set/p30591

Step drills are a joy to use - they don't judder or snatch, and are essential for plastics such as thin acrylic sheet. They have their limitations - they can only be used for thin material up to maybe 5mm thick, (such as a die-cast alloy project box), but that covers much of what we do. In thicker material such as steel plate, normal fluted engineering drills are needed, but for larger holes they need to be run at slower speeds or they'll judder, snatch and won't cut cleanly. Always best to use a chunky drill vice bolted to the table of a pillar drill when possible, to firmly anchor the workpiece and avoid injury. EG:

https://www.axminstertools.com/axmin...CABEgLKqvD_BwE
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Old 4th May 2022, 2:59 am   #13
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Default Re: Hole enlarger.

I found when using a stepped cone drill that on thick metal (Like a rack panel) it was very easy to go too deep trying to cut the entire hole to size, and make the hole too big.
My solution was to drill as deep as I could with the correct size on the cone drill, then flip the metal over and finish the hole from the bottom or back.
Worked like a charm for me. Correct sized hole and no burrs.
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Old 4th May 2022, 8:21 am   #14
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Default Re: Hole enlarger.

For woodworking, rough edges to large holes are a perpetual problem. The solution there is to make a pilot hole in some scrap, and clamp that onto the workpiece and drill through it.

I appreciate that you can't always do that with a chassis, as you don't want to denude it of components and there isn't room otherwise, and I've had similar issues, such as chatter when enlarging through thin sheet. I have several solutions, depending on the nature of the problem and size of hole:

1. use a "Q-max" type of punch to the correct size. This is far and away the neatest result, and usually I can fit the punch in with minimal clearance. It even works well on Eddystone boxes (die-cast ones), as long as you use a bit of oil on the threads and the surface - I've fitted many Neutrik behind-panel mount XLR sockets that way, and DIN-sized connectors.

2. use a core drill, with a wooden guide and a backing "board" to drill into. Works well for larger sizes (such as for clamp-mounted can capacitors), but you do need the space to squeeze the sandwich tightly together).

3. for repairs, cut a neat hole in a pice of aly sheet (or steel as appropriate), and pop-rivet that over a larger one made with an Abrafile, or similar. It's often the only way to change a connector from an obsolete to an available one.

4. Diamond burrs in the Proxxon (Dremel-like) mini-drill. I have a set like these and they are ridiculously useful. You need varispeed on the tool though, as the different diameters need very different speeds to work well. Also beware of softer materials especially aluminium, as they just clog the cutters. Big plus points are controlability (with practice), and the fact they don't resonate (to give you faceted holes). If I am able to mark out the hole I want, I can usually shape it neatly and cleanly with these. I think they're great value for money, but I haven't yet found a way of cleaning them once they clog. The bur tools with spiral cutting edges do work, especially in soft materials such as acrylics, but they are a lot less controllable. Most kits from Lidl, etc. come with mini sanding drums, and these will clean up holes in aluminium, but wear very fast.

4. This is a last resort: I have an electric-drill driven, Chinese-made, panel nibbler. It works, but it's not very controllable (and you still need space surrounding the hole for all the gubbins). You have to accept then that the hole will either be very rough or need a fair bit of cleanup with a rat's tail file (which rather defeats the object).

By the way, am I alone in hoarding Abrafiles? It saddens me that they're no longer available - so useful. If there's an equivalent available new, someone please post a link!
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Old 4th May 2022, 8:03 pm   #15
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Default Re: Hole enlarger.

You are not alone in hoarding abrafiles Simon. I ordered a couple of dozen for work about 30 years ago and had been able to liberate one or two over the years for home use. I was disappointed when I went to re-order about 10 years ago to find that the makers had folded. As luck would have it, I bought about 40 up at the car boot a few years ago for a pound in their original packaging. The modern equivalent would appear to be tile saws that fit into a frame similar to a hacksaw frame, but with a shorter length. I agree, a much loved and much missed product.
Neil
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