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1st Mar 2017, 3:22 pm | #1 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,846
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What's the best way of re-cutting the slot on a damaged screw?
Hello,
During my work on radios and clocks, I come across lots of screws (especially countersunk woodscrews) where the slot has been damaged by somebody using a poorly-fitting screwdriver, or even where it's been badly manufactured. Sometimes, I just fit new screws but invariably, these stick out like a sore thumb or aren't quite the right size. It would be nice to be able to neaten-up and deepen the slot of the old screw and re-use it. I've found ways and means to deal with very big screws, but what do people here recommend for the tiny ones e.g. No.4 and smaller? Thanks, Nick. |
1st Mar 2017, 4:55 pm | #2 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,947
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Re: What's the best way of re-cutting the slot on a damaged screw?
I use a diamond cutting disc in a cheap Dremel clone. I bought the disc from a tool store in Oxford market, but sadly they're long gone. You can probably find them on eBay.
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1st Mar 2017, 5:26 pm | #3 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,846
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Re: What's the best way of re-cutting the slot on a damaged screw?
Thanks Paul. How thin are they? My Dremel ones someone gave me are rather too thick for what I need them for.
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1st Mar 2017, 5:26 pm | #4 |
Dekatron
Join Date: Nov 2003
Location: Near Leeds, West Yorkshire, UK
Posts: 4,609
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Re: What's the best way of re-cutting the slot on a damaged screw?
I use something like this, Nick:
http://www.ebay.co.uk/itm/like/261620596449?lpid=122
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Mike. |
1st Mar 2017, 5:29 pm | #5 |
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Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,947
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Re: What's the best way of re-cutting the slot on a damaged screw?
You can buy cutting discs in a range of sizes.
Mike has a point though, can't you rescue some dental cutting discs when they're no longer suitable for medical use? |
1st Mar 2017, 5:30 pm | #6 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,846
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Re: What's the best way of re-cutting the slot on a damaged screw?
Thanks Mike, that looks promising.
It was a nice Elliott clock that I'm working on at the moment which prompted this thread. It's 70 years old and yet looks brand new... except where some clown's scratched the dial, presumably in part because of the very shallow and rounded slots on the 3 screws (hidden behind the chapter ring) which hold the movement in place. |
1st Mar 2017, 5:37 pm | #7 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,846
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Re: What's the best way of re-cutting the slot on a damaged screw?
I do a lot of that kind of thing, Paul, but cutting discs are generally something a dental technician would use. We clinicians tend to use burs and flexible abrasive discs (1/2" circles of sandpaper with a metal centre boss which snap onto a mandrel).
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1st Mar 2017, 6:08 pm | #8 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,947
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Re: What's the best way of re-cutting the slot on a damaged screw?
How do you chop off a tooth when you're doing a crown?
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1st Mar 2017, 6:22 pm | #9 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,107
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Re: What's the best way of re-cutting the slot on a damaged screw?
I was pleased to find traditional slot (brass) woodscrews in c/sink and dome head- small sizes like No.1,2,4, and even silly lengths like 1/2" and 5/8". They were in Reeves in Maldon who are an independent, but at least it shows they are still being made in brass.
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1st Mar 2017, 6:39 pm | #10 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,208
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Re: What's the best way of re-cutting the slot on a damaged screw?
When I had to make some special screws (ever tried to by M3*0.6mm ones?) I cut the slot with a slitting saw on a milling spindle. OK, not everyone has such facilities, but... Slitting saws come in just about any thickess from about 5 thou upwards, so you can cut the slot width you want.
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1st Mar 2017, 7:21 pm | #11 |
Dekatron
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 5,339
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Re: What's the best way of re-cutting the slot on a damaged screw?
Razor saws are available from model shops and the likes of Axminster tools, who offer them with 0.25mm thick blades. Intended for wood or soft metlas, but would probably cut brass and mild steel.
http://www.axminster.co.uk/victor-jeweller-s-saw-910295 I haven't had to re-cut slots in very small screws, but I wonder if it would be possible to carefully grind either side of the teeth of a fine toothed HSS conventional or junior hacksaw blade to the desired thickness? As only a shallow slot is needed it would not be necessary to reduce the thickness of the entire blade, and in principle only a few inches need be treated. I have only had to tackle large screws where a standard hacksaw blade produces a slot that it too thin, and for this I used a suggestion I found in a book, which was to use two or more blades in the same frame according the the thickness of slot required. |
1st Mar 2017, 7:39 pm | #12 | |
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Re: What's the best way of re-cutting the slot on a damaged screw?
Quote:
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1st Mar 2017, 8:00 pm | #13 |
Moderator
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Re: What's the best way of re-cutting the slot on a damaged screw?
Fret saw blades are very thin.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
2nd Mar 2017, 6:55 am | #14 |
Nonode
Join Date: Aug 2010
Location: Resolven, Wales; and Bristol, England
Posts: 2,608
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Re: What's the best way of re-cutting the slot on a damaged screw?
When faced with this problem on oboes and clarinets (an everyday occurrence) we use a piercing saw with a blade of the correct thickness.
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Richard Index: recursive loop: see recursive loop |
2nd Mar 2017, 9:46 am | #15 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,983
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Re: What's the best way of re-cutting the slot on a damaged screw?
We're a bit off topic, however:-
My dentist (Robin Nagi at Iffley Dental, Oxford) always removes the minimum amount of tooth and fits a thin crown. His perspective is that leaves lots of options down the line, whereas the method of chopping a tooth down to a peg and then using a massive crown leaves absolutely nowhere to go if something goes wrong later on. I've now got four or five in various materials. Last dental hilarity was root canal work, which I was not looking forward to apart from the fact I was under so much pain. Three really easy two hour sessions and it has been absolutely perfect since. Craig |
2nd Mar 2017, 11:27 am | #16 |
Heptode
Join Date: Feb 2011
Location: Southend, Essex, UK.
Posts: 802
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Re: What's the best way of re-cutting the slot on a damaged screw?
On some chewed up screw heads I have supported the screw vertically in something solid like a bush on my vice and 'planished' the chewed up bits back into position then tidied up the slot by one of the above methods and finally used a piece of fine abrasive paper or scotchbrite on the head.
Recovery 'can' be better than replacement! Alan |
4th Apr 2017, 7:53 am | #17 |
Hexode
Join Date: Oct 2010
Location: Box End, Beds. UK.
Posts: 271
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Re: What's the best way of re-cutting the slot on a damaged screw?
I always use a junior hacksaw for the small ones, and a full size hacksaw for the bigger ones. May not be the best, but I have them, as do most other practical folk.
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4th Apr 2017, 10:15 am | #18 | |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,761
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Re: What's the best way of re-cutting the slot on a damaged screw?
Quote:
I've just tried a No 4 5/8" c/s/ woodscrew with a 22mm diameter diamond disc. The screw slot is 35 thou wide (0.92mm), and the diamond disc is 23 thou (0.6mm) thick, so will fit the slot nicely. The width of the screw head is 5mm diameter, and with the 22mm diameter disc at the bottom of the slot, it cuts into adjacent timber. A junior hacksaw blade fits the slot, even with the set on the blade, but I can't possibly see how a hacksaw blade could be used to clean out the slots of countersunk screws. To make clearer what I mean, I've attached a sketch. 16mm diameter diamond discs aren't commonplace, but are available. The set here for example includes four 16mm diam ones and two 19mm from a UK supplier: http://www.ebay.co.uk/itm/6pc-Diamon...-/222450496787 The other problem with most Dremel type drills is that they run at far too high a speed for ticklish jobs - typically 10,000 RPM, though the '4000' goes down to 5,000 RPM. I use a small PCB drill and a speed controller for tasks such as this. Hope that helps a bit.
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