The solution you worked out for yourself is actually the same as I suggested
for the Q&D method, and it should be satisfactory. Mert
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-----Original Message-----
From: 7x12minilathe@...
[mailto:7x12minilathe@...]On Behalf Of Andrew
Sent: Wednesday, October 12, 2011 5:07 PM
To: 7x12minilathe@...
Subject: RE: [7x12minilathe] Damaged compound
Mert,
I had a look at clearing the hole, adding an insert of sorts and
re-tapping. I did not feel comfortable doing that as it might do more
harm than good.
My work around seems to be OK for now. Only time will tell if the
remaining threads will handle the stresses of machining.
I also noticed that the parting tool holder from A2Z had slipped past
its reference point. On the top there is the adjustment knob made from
brass. It has slipped past its stop point and most likely caused the
tool to be below its ideal height. My next project is to make a larger
adjustment knob.
Thanks for the comments and encouragement.
Andrew
On Wed, 2011-10-12 at 07:07 -0400, MERTON B BAKER wrote:
If I have the problem correctly, you have a hole, formerly threaded
for the
stud which secures the toolpost, with the first two or three threads
either
torn out, or damaged. Assuming that I have the right idea of the
situation, here is what I would do. The hole in the topslide is tapped
all
the way trough the casting. I don't know this, it may not be. No
matter,
take the top slide casting off the lathe. Now, there are two choices;
first, the easy one. Make sure the original threads go all the way
thru the
casting. I know the hole does, but the threads are an assumption. If
they
go through, fine, if they don't, find the right tap and see that they
do.
File off any burrs left on the top of the casting that might have been
left
when the original stud tore out. Next, get, or make, a replacement
stud.
Maybe a piece of all-thread. In any case, it wants to be longer than
the
original one by 6 or 8 threads, we need it to thread deeper into the
topslide casting. That's the "quick & dirty" method. Now, a more
elegant
one.
Drill out only the damaged threads, no more, and make a steel plug
that's a
close sliding fit in the drilled out portion of the hole, and drill it
through with the tap drill for the thread on the stud.
It wants to fit a few thou below the topslide surface when in place.
Put it
in with hi-strength Loctite, let it set up a day or two, and going in
from
the good threads below, tap it for the stud. More elegant still, use a
tap
drill to remove the damaged threads, and thread the drilled insert
before
installing it with loctite. In either case the bottom of the plug
should be
turned conical to the same angle left by the drill. Otherwise, there
will
be a gap, filled with swarf from tapping the plug.
The stud should stand at right angles to the top of the slide. If the
bottom of the toolpost is undamaged, whether the stud sticks up true
is
moot, when things are tightened up, the toolpost will make it so.
Hope this helps.
Mert
-----Original Message-----
From: 7x12minilathe@...
[mailto:7x12minilathe@...]On Behalf Of Andrew
Sent: Tuesday, October 11, 2011 6:34 PM
To: 7x12minilathe@...
Subject: Re: [7x12minilathe] Damaged compound
I was thinking of seeing if a "helicoil" could work. Of course where
do
I get it done?
More importantly, does the toolpost bolt have to be absolutely square
to
the surface?
Cheers,
Andrew
On Tue, 2011-10-11 at 15:23 -0700, Jerry Durand wrote:
If I remember right from my mechanical engineering classes two full
threads of a bolt *should* be all you need. That's assuming the bolt
and nut are cut to spec out of proper materials.
Other than that, do you have room in your tool post to use a larger
diameter bolt? If not you'd have to make the hole quite a bit bigger
and put in a threaded insert.
On 10/11/2011 03:14 PM, Andrew wrote:
G'Day to all,
My task yesterday was to work on the cylinder for my Webster
engine.
I had hogged out the fins, the lower portions and drilled the inner
diameter to 13mm. The last operation was to part off the work from
stock when I noticed a lot of chatter. I stopped, cleaned up all the
cast iron swarf and tightened the gibs. I tied again and the chatter
was just as bad. I sharpened the tool which look OK and still no
luck.
When I tried after tightening the carriage and compound do nothing
would move I tried again and the A2Z tool post (LMS #2461) came out
of
the compound. The holding bolt pulled the threads out of the
compound.
When examined I noticed the bolt only penetrated a 3 or 4 turns. I
knew this as the threaded part was still there like a spring on the
bolt.
At this time I need to either fix or replace the compound. I also
plan to buy or even make a suitable replacement for the supplied
bolt.
The reason for this post is to ask advice on if the compound is
worth repairing and to warn others before they have problems.
Cheers,
Andrew in Melbourne
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Jerry Durand, Durand Interstellar, Inc. www.interstellar.com
tel: +1 408 356-3886, USA toll free: 1 866 356-3886
Skype: jerrydurand
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