Restoring blunt cable cutters.

[gaz]

My Park Tool CN-4s have stopped cutting cleanly. I mostly use them for outer cables, having a set of CN-2 for inners. On gear cable they now leave a strand in place. I've tried adjusting them as per the Park Tool website instructions but without success.

I've had my moneys worth from them but I wonder if there is anything I can try to restore them before setting them aside for spoke cutting duties. I don't have access to any angle grinders, just a set of cheap hand files.

CN-10s already purchased. I've nothing to lose but would appreciate any tips so my efforts are made in the right direction.

[profpointy]

Maybe be able to do something with a diamond file or mini oilstone (ie oilstone "sticks" size of a crayon - used for carving tools etc) . Need to be careful that the jaws still meet if they are wire-cutter style. I scicsors style then need to ensure the mating surfaces are both still flat & flush. If the latter and the come apart then you can flatten the mating surface - but if rivetted don't touch this surface. I've never done any of this but theory is ok - and if they're stuffed anyway nothing to lose

[reohn2]

Don't touch the mating surfaces or attempt to 'sharpen' them you'll make a gap between the jaws rendering them useless.
Only sharpen the bevels on each jaw (following the existing profile)as state above diamond stones or slip stones are ideal for this.
Diamonds stone used to be expensive but are reasonably priced these days and are now available in all shapes for all sorts of sharpening jobs including cutters and scissors.
The method should be stroking the stone on the jaw bevel toward the cutting edge (where the two jaws meet) until a small burr is felt on the mating surfaces side of the jaws.
It can also be done with Dremel type tool with the right sized stone in the chuck,but care must be taken to keep the profile.
Leave the burr on where the cutting surfaces meet,when the cutters are closed the burr is sliced off by each jaw,completing the sharpening.
Depending how dull the jaws are it may take a bit of time to get them something like sharp but there's no reason they can't be made as good as new with a little perseverance,and once sharp a touch up now and again will keep them in top shape


PS, if you don't fancy buying a sharpening stone or don't have a Dremel,pop them in the post to me and I'll do them for you.

[Brucey]

FWIW I agree with R2's comments but I'd additionally comment that

-that model of cable cutter wasn't park tool's finest effort; they do just wear out, especially if you use them on index housing (which appears to be made of many piano wire strands). However they also break, and when they break they get exchanged under warranty.

-if the sliding faces of the cutters are in any way marred, you should carefully lap them back flat before you sharpen the angled cutting edges as R2 describes.

- if you remove much material from the cutting edges when sharpening, you may find that the jaws don't close fully. If this is the case, you may need to shorten the handle stops.

-when sharpening tools like these, be careful; excessive heat can temper the steel so that it isn't hard enough any more.

Bike cable cutters are usually manufactured pretty cheaply. If you go to buy industrial tools for doing this kind of job they cost a fortune; for example a set of CK side cutters (~10" long) is a super tool that will cut cables, housing, and tyre beads. An LBS uses these, and a set will last about a year in daily workshop use, but cost the thick end of £40 to replace when the time comes. If you want to cut single strands of piano wire regularly, a set of 'lindstrom' cutters is a good idea; last time I checked a 4" set cost about £50....

Since the jobs are rather different from one another, I'd suggest keeping one set of cutters for cable inners (and maybe spiral wound housing too, which is normally soft steel) and then using something different for prepping index housing.

Since I like to grind the ends of the housing flat anyway (which makes a super job) I generally cut cable housing using an ultra-thin cutting disc in a grinder these days. My cable cutters are lasting a lot longer; I only use them on inners now.

cheers

[reohn2]

......if the sliding faces of the cutters are in any way marred, you should carefully lap them back flat before you sharpen the angled cutting edges as R2 describes...

But all of the sliding surfaces need to be lapped flat including where they're bolted together and not just the cutting portion.
This ensures there is no gap between the cutting jaws where single stands can get folded over between them.the lapping also needs to be done evenly across the whole of the jaws and pivoting area on a flat stone.

[Redvee]

Can't find a price of Park cutters mentioned by OP but I've been using a pair of these Knipex cutters. Not cheap but still going strong after 15 years of cable, outer and spoke cutting duties.

[Brucey]

......if the sliding faces of the cutters are in any way marred, you should carefully lap them back flat before you sharpen the angled cutting edges as R2 describes...

But all of the sliding surfaces need to be lapped flat including where they're bolted together and not just the cutting portion.
This ensures there is no gap between the cutting jaws where single stands can get folded over between them.the lapping also needs to be done evenly across the whole of the jaws and pivoting area on a flat stone.

agreed, but for practical purposes it is usually appropriate to simply remove any raised areas on the sliding surfaces, rather than dress out any small holes in the surface too; that is a more substantial undertaking. If any raised areas are left on the sliding faces, you can undo all the sharpening effort in no time.

cheers

[Dynamite_funk]

Can't find a price of Park cutters mentioned by OP but I've been using a pair of these Knipex cutters. Not cheap but still going strong after 15 years of cable, outer and spoke cutting duties.

Spoke cutting Surprised they lasted 15 years!

[tim-b]

Hi
I bought a pair of boltcroppers from Aldi for stranded outer, mudguard stays, etc. I think that these items benefit from tidying with a file in any event
I keep the smaller cutters for inner cables and spiral outer casing, which seems to help them last longer
Regards
tim-b