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resolvedI read today of an interesting bit of DIY where someone made custom chainring shifting pins by drilling holes in the chainring, tapping them, putting in a small screw and then filing the screw down.
I'd like to give this a bash on a spare ring but I don't know the first thing about tapping (nor do I want to spend a fortune on equipment for something that might not work!
Can anybody help?
I have a tap and die set. I'm quite pleased actually because my lost M5 tap turned up today. My tapping wrench though was one of the cheap collet chuck designs and died a while ago, but my 5" adjustable spanner works better in some cases.
I imagine that for creating chainring shift pins you'd want M3, possibly M4, since the machine screw heads will need to be quite small. I'm not sure if I still have my M3 tap or not. The process for tapping a thread in metal is quite straightforward but precise and relies heavily on feeling the tap biting and tightening. I've broken off too many taps in blind holes to be slapdash about it! But in a chainring you have only a small thickness of material to work with, so that risk is pretty small. You also need to have the right size of drill to create the pilot hole. In aluminium, and in a thin section, you can fudge it a wee bit more. M3 will take a 2.5mm bit; M4 will use 3.2mm (Edit: strictly speaking it's 3.3mm, but you never see that size in DIY multisets).
The rule of thumb for hand tapping, once the tap is engaged, is half a turn of cutting, then a quarter turn of reverse to clear swarf, repeat, rinse as required, and use cutting paste. In a pinch you can use lithium or moly grease, and if cutting into nylon or glass-filled nylon, you often don't need any lubricant. On a lathe or machining centre you can constantly douse the workpiece with cutting fluid and just keep on turning.
Given the small thickness and resultingly few turns of thread (M3 pitch is 0.5mm, remember), you might also want a dash of threadlocking compound to ensure it doesn't back itself out. Loctite 243 usually covers most bases.
My tapping wrench though was one of the cheap collet chuck designs and died a while ago, but my 5" adjustable spanner works better in some cases.
A spanner is not going to let you apply force to two sides at the one time which Vic (of Vic's Tools, Dumbarton Rd, Partick) said was important.
LIDL were selling a tap and die set for £5.99 - no idea of quality, I believe likely to be inferior but cheap.
A spanner is not going to let you apply force to two sides at the one time...
Hand tapping by its very nature relies on precise alignment of tap and pilot hole. Of course you can't put a spanner on the end of a tap and just crank on it; it takes much more care and attention to apply torque and compensate for the tendency for lateral movement. I've been doing this stuff for years. :-)
A proper tapping wrench doesn't use a collet chuck anyway, but two v-clamps and a leadscrew. You don't get those in Lidl!
I can confirm that the lidl tap and die set for £5.99 is £5.99 well spent. Santa gave me one for christmas and it works well in 8mm flat bar steel so chain rings should be no probs. Engineers drill bits are what you need....go to wilkinsons in arthur st.
"A proper tapping wrench doesn't use a collet chuck anyway, but two v-clamps and a leadscrew. You don't get those in Lidl"
The set I got did.........
OK - so it sounds possible. I even have a spare worn chainring or two to experiment on first!
I was thinking M4 as the chainring is quite bulky - it's a 70 toother and weighs about 350g!
Can you not just use chain oil as a lubricant, or is that a terrible idea?
I did previously have reasonable results shifting up onto the ring as it is, but it was more temperamental than I'd have liked. It's a big jump from 50 to 70 teeth!
3-1 would probably be better than bike lube.
Actually i'm not really sure why i say that its just a hunch. 3in1 is cheaper though....
as a cutting fluid iron bru works well, if a little smelly.
I'm not sure why I need a tap and die set but i know i need one...
Good spot!
No workshop's complete without one!
Interestingly the original impetus for this project has largely evaporated, since my bike shifts crisply enough between 50 and 70t chainrings without outside DIY assistance :-|
Ooops
Nicholson Street Lidl is now 'food only'.
Can't get to another store before about 2.30 - how are stocks??
Almost forgot. I'll be heading to Dalry shortly and popping past either Granton and Leith or Craigmillar and Musselburgh on the way home if unsuccessful.
19 left in Dairy after I take mine. Lots of calipers left, too.
18
Might one enquire how this tool is put to use on or around the bike frame?
Erm. You could tap yourself some extra bottle-attachment points, if you don't mind weakening the frame a wee bit considerably?
I'm going to use mine to chase out the gunged thread on the tension-adjusting thing on my front brake. Might also be useful when constructing myself an Ortlieb-defeating quick-release light-holding handlebar-addendum.
Ooooh calipers look good...
"Might one enquire how this tool is put to use on or around the bike frame?"
Basic - mudguard eyes - paint, gunge or metric instead of BA - sometimes thread for first time.
I also have some nice brakes where the adjuster screw has seized and broken off.
Dave shifts crisply enough between 50 and 70t
That's an impressive jump. Though I had a bike that did 39 to 60t - a 21t step!
This week LIDL appear to have more tools in the form of drill bit sets, screwdriver sets, variable pliers, screwdriver bit sets, wall-box organiser-tray things, toolkits, hose/Jubilee clips, trainer socks, arc welders and sack barrows.
I'd only popped in to see if they still had the odd pannier sitting about but (from the choice above) can only really justify getting some more drill bits after losing, snapping or burring most of my last cheap set (bought in 1997).
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