Sunday, July 31, 2016

Improving A Cheap Set of Forceps/Tweezers

Over at The Whole Garage Catalogue recently, I posted an item about a cheap pair of forceps/tweezers. Here's the post:

- - -

A Pair Of Forceps/Tweezers Of Some Sort

There's no maker's name on them, and they look cheaply constructed. The pivot is a bit sloppy, and the tips align poorly.

With a bit of work, I could improve the thing, and possibly have a useful tool for something-or-other.

I'll stash these in my spare tools drawer against the day that I feel like getting after them.

# # #

Well, I feel like getting after them. So here's what I need to do to improve this tool:
  • Strip off and possibly replace that rotten sleeving.
  • Reconstruct the sloppy pivot.
  • Align the jaws.

That wasn't difficult to scrape off with a utility knife. The tool is reasonably clean now.

I have some red 3/16" heat-shrink tubing on hand that might make excellent replacement sleeving. That can wait until I've dealt with the pivot and the alignment.

The Pivot

The original pivot was a 1/8" diameter rivet. I cut off its end and discarded it.

The pivot holes are slightly oversize -- that accounts for the sloppiness that I observed in the pivot's action.

I can drill out the pivot holes slightly to accommodate a 6-32 screw, but there's a caveat regarding the use of a screw as a pivot pin. It's a very poor practice to have a pivot point operate on a screw thread. You want a pivot point to operate on a full rod/cylinder. So, what I need here is a 6-32 screw that has an unthreaded shank portion that's just the right length to serve as the pivot point, while providing thread enough to be fastened by a Nyloc nut.

I have some 1 3/8" long 6-32 hex socket head cap screws with unthreaded shank portions to them, but the unthreaded portions are too long. So, I threaded one of the screws further, and now I have a screw that should serve nicely as a pivot (once I've cut it down to correct overall length). Here's a view of the screws I've just been on about.

At the left is an unmodified screw. At the right is a screw that I've threaded further. That one's going to be my pivot screw.

The pivot holes need to be enlarged slightly to accept a 6-32 screw, and it's important that I get as close a fit as possible so as to minimize slop in the pivot. Consequently, I didn't just go with the conventional 6-32 clearance drill size of 9/64". I miked the screw's shank, and chose a drill size based on that result.

The screw's shank measured 0.135". The closest clearance drill size is No. 29 (0.136"). So I went with a No. 29 drill, and that gave me just the outcome I was after -- a relatively slop-free pivot. Here's a view of it assembled without a nut.

Now I just have to cut the screw down to correct length, add a Nyloc nut, and my improved pivot will be done.

- - -

And here we are.

A slop-free, reasonably tidy pivot.

All that's left is to lubricate the pivot, align the jaws and add new sleeving.

- - -


I've got a decent set of forceps/tweezers from what was a piece of offshore junk. Very satisfying.

# # #

# # #

No comments:

Post a Comment