I want to make some 10BA clearance holes in a piece of
spring steel for the support of a pendulum.
Do I need to anneal first and reharden afterwards, or is there
a better way?
(Ham Radio project - chinese copy of a Vibroplex Morse key)
I think this would depend on what state the steel you have is in and
what you require it to do. I have a few thicknesses of carbon spring
steel , IIRC 1.5mm, 2.0mm and 2.5mm, and it is in an annealed state as
delivered and that is fine for my use. As such it is easy to drill and
machine so for your use you may be able to just drill the material you
have as is, you should though take advice from the suppliers as to it's
strength and therefore determine a suitable cutting speed for the
material you have.
Carbide drills will go through spring steel easily without the need to
anneal, though you would be advised to sandwich it just the same as any
other thin metal being drilled.
Cliff Coggin.
I recently repaired (well, last year) a Gents Pulsynetic, which had a broken
pendulum support spring on receipt. Just measured up the spring, thickness
and width, and then bought a cheap clock spring via ebay, where there is
quite
a selection usually.
A drill wouldn't go near it, so I did anneal before drilling, then hardened
and tempered afterwards...
Regards,
Chris
The way I do it is to fold a piece of brass, make, the required size of
hole, in the brass Then make punch out of silver steel, harden and
temper. It is then easy to put the spring steel between the folded
brass and punch the required hole without the need to annealing the spring
In article , gareth
writes
I have heard of a technique; -never used it personally;-
"Put a piece of steel rod with a square end and of just over clearance
size in the drill chuck; bring it into contact with the spring where you
want to drill the hole and run the drill at high speed with a fair
amount of pressure. The friction will heat up the spring at that spot
and anneal it. Then drill with a normal high speed drill."
If the leading end is still intact you might consider using that. If
the hole needs opening out then a tapered grinding tool from a micro
drill could be considered.
If the material is thin as in a steel tape you could easily make up a simple
punch and die set using silver steel and harden it. you could then punch the
holes easily, have a look at making pendulum clock suspension springs.
Peter
Thank-you Peter. based upon previous contributions that is indeed the way
that I have chosen to go.
Now, being of a nervous disposition, I'll need to use a slitting saw to make
the
slot to take the flat metal spring, both for the die and also for the
Meccano***** rod
that will form the pendulum.
Are there any dos and don'ts for this exercise, because with what will
essentially
be an electric saw running with no guard, it could well be a s*itting saw
for me? *****Meccano still in occasional use here. One "boiler" is used as a
soldering
iron guard.
Carbide drills in 10BA clearance...? (that is ~1.7mm diam...)
The traditional method, given that it is a PIA to drill thin material,
is to make yourself a hardened steel punch. If you want to do the
thing properly, then make a matching punching block (think paper hole
punch) that wil guide the punch & also help to make the punch cut
cleanly, but you can get away with punching through onto soft material
(aluminium block, hardwood end-grain).
Regards,
Tony
But this involves added expense :-). If you are making batches, having the
right tools is probably a good idea, though carbide drills, at least the pcb
drilling types, are very fragile, ime. A stellite drill may be a better
choice,
though it's years since I even saw one.
For a one off, at no expense, it takes only minutes to anneal, drill, then
re harden and temper and it costs you nothing...
Regards,
Chris
Just how long does it take to cut a bit of spring steel strip, warm to
red heat in gas blowlamp, allow to cool, centre punch, drill, warm to
red heat and quench, polish and temper to desired point ?. About 10 or
20 minutes should get the job done.
There's a tendency to overcomplicate all sorts of stuff these days, when
alls that's needed is a bit of common sense...
Regards,
Chris
Find strip
Find saw
try saw
find another saw
try new saw
find dremel
fit rotary abrasive blade
cut strip
warm to
Find blowlamp.
find (empty) fuel canister
go out and buy new fuel canister
heat strip to red heat
ooops, too hot - cut new strip.
heat to red heat
allow to cool,
easy, eh?
centre punch,
find center punch
punch
turn strip over
punch in correct position on other side
drill,
find hss drill
try to drill
darn, cooled too fast, curled up when drilling. Never mind, the hole
would have been in the wrong place anyway.
find Dremel (I _knew_ I shouldn't have put it away)
cut new strip
heat to red heat
allow to cool
drill hole.
warm to
ooops, nothing to quench in - get water.
oops, left in flame too long. start again
ooops, no strip left. Go out and buy new strip.
cut new strip
heat to red heat
allow to cool
drill hole.
heat to red heat
quench
polish
find wire brush for Dremel
oops,broke quenched strip, too brittle,
Gave up on polishing idea.
cut new strip
heat to red heat
allow to cool
drill hole
heat to red heat
quench
and temper to desired point
temper temper!
ooops, no strip left. Go out and buy new strip.
cut new strip
heat to red heat
allow to cool
drill hole.
heat to red heat
quench
temper
About 10 or
ITYM 10 or 20 days?
:)
-- Peter Fairbrother
Or a carbide drill....
But buy at least two, if you buy one it will most likely break. If you
buy 2 or 3 then either all or none of them will break. Buy 4 and no
matter how cackhanded or unlucky you are you should be able to drill one
hole.
Of course circumstances (see my last post) may conspire to increase the
hole requirement - so buy 10. You will get at least six holes from ten
drills. Hopefully that will be enough.
Note, if you buy 2 or 3 then there is no correlation between whether
they all break and whether, if you had only bought a single one, that
one would break.
-- Peter Fairbrother
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.