I am sure this has a simple answer
Was tuning up my band saw and adjusting motor pulley, which uses a set
screw. Guess I turned it too tight, rounded off the allen wrench and
now it just turns. It is a metric 3.0 wrench. I also assum the set
screw itself is probably also damaged.
My only solution I see is to eposy the wrnech to the set screw and
then replace both when I get it loose, but don't know if you can buy
individual allen wrenches..
any helpful suggestions?
| I am sure this has a simple answer
| Was tuning up my band saw and adjusting motor pulley, which uses a
| set screw. Guess I turned it too tight, rounded off the allen
| wrench and now it just turns. It is a metric 3.0 wrench. I also
| assum the set screw itself is probably also damaged.
| My only solution I see is to eposy the wrnech to the set screw and
| then replace both when I get it loose, but don't know if you can buy
| individual allen wrenches..
| any helpful suggestions?
You _can_ buy individual Allen wrenches. If your local hardware store
doesn't have a 3mm, try www.use-enco.com (who does have 'em).
DeSoto, Iowa USA
Rather than buy a new Allen wrench, cut or find off the rounded end. Then
again if yours rounded off you may want to buy a better quality wrench.
If possible, replace the set screw with a set screw that has a head, it will
use a larger wrench to adjust and will be less likely to round off in the
wrench and replace the set screw..
I recently had the same problem on a lathe pulley... after I got the old set
screws out, I replaced them with hex head machine screws...
I could see no problem with interference or anything and they are a lot easier
to use now..
Please remove splinters before emailing
Highly unlikely you'll find any epoxy that will have more shear strength
than required to break the set screw loose.
If you rounded over the wrench, you can hope it was because it was a
cheap one and the screw head, being harder is basically intact. I agree
it probably was 1/8", not metric and so the wrench being undersized
slightly contributed to the problem.
My suggested solution is to get a good quality wrench instead, use a lot
of penetrating oil to help first, then apply some heat to the outside of
the boss holding the screw to expand it a little, then it should pop loose.
I sharpen the multispur bits for the plumbers and the pilot screws are
locked in with an allen set screw which is often frozen.
I make my own extractor from a piece of handsaw file ground to be
sharp and turned with vise grip pliers. The ends of the file have a
nice taper and you can pick the closest size match and drive it in to
"bite" the insides of the rounded off allen.
Grind down your hex key wrench to expose an unrounded surface, they
are prety much usable until too small to hold onto.
I'll add some cheesy tricks I've tried in the past and that have worked:
Grind a new flat end (on the proper size allen wrench) and you want to leave
a slight burr on the new re-ground end.
Now - after applying the requisite amount of penetrating oil and leaving it
set - then insert the re-ground end of the allen wrench into the hex head.
With the hex being rounded, it may be difficult to feel the edges of the hex
head hole but do your best. When you have the best feel - lightly tap the
other end of the re-ground allen wrench into the hex head. Do not slam it
so hard you widen the head and lock it in solid. A slight tapping is all
that is needed to jam the burr into the hole edges and hopefully provide
sufficient purchase for you to turn the screw out.
Failing that - all is not lost. Someone mentioned an EasyOut and that is a
good suggestion provided the hex screw is not so deep that the EasyOut can't
reach it. I've had success with simply drilling a hole into the hex screw
and once a small hole is drilled, use the next size drill to further enlarge
the hole without damaging the threads (be sure the drill stays perpendicular
to the shaft. You can also purchase drill bits that drill into material
with the drill set to the reverse position. If a standard drill is
considered an Up-Spiral bit, then you would want a Down-Spiral bit or as
I've seen one set advertised "Left-handed" drill bits. That may not be
technically accurate but it does get your attention.
If you do use a left-handed bit, the hex screw will probably come right out
while you're drilling. If using a standard drill bit, then an EasyOut would
be your best bet. But anything that you can fit and jam tight into the hole
that can then be turned would also work. (i.e., a finish nail bent like the
allen wrench and then flat ground on the end like a small screwdriver and
tapped into the hole).
As a last resort. Consider that a hex head screw tightened against a shaft
is held in-place by a locking force applied against the fragile and most
likely, softer material threads and the shaft. It is the forced expansion
of the screw pushing on the shaft and threads that needs to be overcome - by
only a very small amount. Again - using a small hammer, tap (decisively)
right over the hex head screw. This will (if lucky) somewhat compress the
thread material just enough to reduce the force holding the screw if the
thickness is not to thick or the hex screw is in real deep. This idea is
iffy since it's prone to permanent damage but if so - read below.
If the blow to the head doesn't work, purchase a small tap set and matching
drill bit that is about the same diameter as the hex screw now stuck. Drill
out the old screw and drill a new hole and tap it for the larger size hex
head screw. It's Miller time.....
After that - there's always dynamite........
An E Z Out or one of the newer versions of screw removal bits might work,
but drilling out a set screw will be very hard to do as set screws are
usually hardened to almost as hard as standard drill bits. It will likely
take several bits to make any headway in cutting it. I would try to fit a
freshly cut end of an allen wrench into it, and if that didn't work I would
clean out the hole with solvent and then try to epoxy the allen wrench into
the set screw before trying to drill it out.
Some years ago I bought a set of left handed drill bits that I keep around
specifically for getting out broken bolts. They are available from
industrial supply houses for just slightly more than the cost of a set of
standard drill bits. When using these, the drill bit is turning the same
direction that you are trying to turn the broken bolt to remove it and the
bolt will usually unscrew itself and come out long before the drill bit
makes it all the way through the bolt. If it doesn't, then the E Z Out or
other methods can be used on the remaining part of the bolt or it can be
further drilled out until the only thing that remains are the threads from
the offending bolt. Then a tap of the right size can be run in to clear them
I have yet to find a hex screw in a piece of machinery used for tightening a
pulley to a shaft that is hardened to the extent that it is hard to drill.
What you do not want to happen is to create galling or denting of the
shaft - which makes getting the pulley off even more difficult - which a
hardened screw would do. The better grade hex screws have a "plastic" (of
some sort) on the tip that pushes against the shaft when tightened.
They certainly do make hardened screws but I have not come across one that I
haven't been able to drill out - yet. Not that I do that many but YMMV.
Here's the neatest solution I've ever heard of:
Get some valve grinding compound. I suppose fine sand would work.
Mix a little oil with it. Dab it into recess in the set screw. Get a
new, proper size wrench. Now wiggle the wrench into the hole so the
gooey grinding compound can squeeze up to fill in the possible rounded
corners of the set screw head. Then loosen. This works pretty well.
One other poster mentioned tapping on the wrench, (but not too hard) to
"jar" the screw threads. I like this one, too, but I go for hitting it
pretty hard. In order to do this though, you can't realy hit an L-
shaped "allen wrench" straight enough to do the job.
I cut one leg off the wrench so I can hit straight down. This, of
course means you'd have get an extra wrench. I'd cut off the old,
rounded wtench to use as the "driving" tool. Support the under side of
the pulley so you don't bend the shaft. If you are not an accurate
person, hold the one-legged wrench with a pair of vise grips. And, of
course, wear eye protection.
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