Back in July I posted about having a shear element in a feed gear train
to protect the gears. Of course, I never did anything about it and I
just broke a gear!! My *new* to me Jet 1024. I locked the carriage to
do facing and then forget it was locked as I went to do turning. Damn!
And the gear is inside the apron, of course.

The lathe has an interlock to prevent engaging the threading feed screw
and the turning shaft at the same time. An interlock on the carriage
lock is what I needed.

'Guess it's time to get some skill repairing gear teeth. Sigh.

Bob

Bob Engelhardt wrote:
Back in July I posted about having a shear element in a feed gear train
to protect the gears. Of course, I never did anything about it and I
just broke a gear!! My *new* to me Jet 1024. I locked the carriage to
do facing and then forget it was locked as I went to do turning. Damn!
And the gear is inside the apron, of course.

The lathe has an interlock to prevent engaging the threading feed screw
and the turning shaft at the same time. An interlock on the carriage
lock is what I needed.

'Guess it's time to get some skill repairing gear teeth. Sigh.

Bob
Durn it, some days.
Only an opinion, but I usually rough face, turn to dim., Then finish
face and/or cut off last.
Just habit.

wws

Oh, Sh! T Bob I feel your pain, You idiot, kick yourself in the arse.

You do know you are a dolt, eh? Oh hell......kick yourself again.

But hey, you admitted your screw up. A small slip of attention that
resulted in huge consequences.
Glad no body parts were swarf.
You'll never perform that particulular act again, and as a bonus, you
were "Guy" enough to fess up, on usenet, and teach us all to ...Be
Careful, and THINK.
What would teenut say?

~D




Bob Engelhardt wrote:

Back in July I posted about having a shear element in a feed gear train
to protect the gears. Of course, I never did anything about it and I
just broke a gear!! My *new* to me Jet 1024. I locked the carriage to
do facing and then forget it was locked as I went to do turning. Damn!
And the gear is inside the apron, of course.

The lathe has an interlock to prevent engaging the threading feed screw
and the turning shaft at the same time. An interlock on the carriage
lock is what I needed.

'Guess it's time to get some skill repairing gear teeth. Sigh.

Bob

--
Note, my address is MUNGED

Try contacting the vendor first about a replacement gear. I was
surprised about how cheap a replacement worm and wheel were for a 4 x 6
bandsaw from the supplier. I had the saw for about 5 - 6 years and the
parts were readily available and cheap even with the postage and in
stock, delivered in about 2-3 days. This was machinemart in the UK but I
was impressed, it'll cost you a phone call to find out.

Bob Engelhardt wrote:

Back in July I posted about having a shear element in a feed gear
train to protect the gears. Of course, I never did anything about it
and I just broke a gear!! My *new* to me Jet 1024. I locked the
carriage to do facing and then forget it was locked as I went to do
turning. Damn! And the gear is inside the apron, of course.

The lathe has an interlock to prevent engaging the threading feed
screw and the turning shaft at the same time. An interlock on the
carriage lock is what I needed.

'Guess it's time to get some skill repairing gear teeth. Sigh.

Bob

As a WMH (Jet, Wilton, Powermatic, +) tool dealer I can assure that
parts are really cheap. There is no reason to consider making the
broken gear unless you are in to self humiliation and/or the kind of
person that makes new tires for their car should they wear out. Leigh
at MarMachine

Good news, bad news. Good news is that it wasn't a gear that broke, but
a spring/split pin holding the gear on. 'Course it was down inside the
apron and more work to get to than about anything else on the lathe!

I was surprised than the pin broke - just sheared right off. It was
small (3/32, .094, 2.4mm) and not hard, but still ...

The bad news is that there was also damage in the quick change box. A
couple of gears there had been repaired with brazed-in teeth and one of
those teeth bent. I plan on replacing them (the gears, not the teeth).

I've started experimenting with shear keys. I have some plastic that
looks promising. One test key 3/16 square x 1" long took 70 foot lbs
to shear it. I'm going to start with real small versions and work up
till I get a size that won't shear under normal conditions. Then
hopefully it will shear under damaging ones.

I thought of another approach to gear train protection (for this lathe
anyhow). The first gears off the forward-reverse toggle are two gears
on a jack shaft, keyed together. Instead of keying them, one could
sandwich some friction material between them and create a slip clutch.
It might be kind of difficult to get a consistent slip point, but it
might be worth experimenting with.

Bob

Consider that a slip clutch would be capable of causing un-noticed loss of
sync during threading. I think an easily replaceable shear element would be
much preferable.
Don Young
"Bob Engelhardt" wrote in message
...
Good news, bad news. Good news is that it wasn't a gear that broke, but a
spring/split pin holding the gear on. 'Course it was down inside the
apron and more work to get to than about anything else on the lathe!

I was surprised than the pin broke - just sheared right off. It was small
(3/32, .094, 2.4mm) and not hard, but still ...

The bad news is that there was also damage in the quick change box. A
couple of gears there had been repaired with brazed-in teeth and one of
those teeth bent. I plan on replacing them (the gears, not the teeth).

I've started experimenting with shear keys. I have some plastic that
looks promising. One test key 3/16 square x 1" long took 70 foot lbs to
shear it. I'm going to start with real small versions and work up till I
get a size that won't shear under normal conditions. Then hopefully it
will shear under damaging ones.

I thought of another approach to gear train protection (for this lathe
anyhow). The first gears off the forward-reverse toggle are two gears on
a jack shaft, keyed together. Instead of keying them, one could sandwich
some friction material between them and create a slip clutch. It might be
kind of difficult to get a consistent slip point, but it might be worth
experimenting with.

Bob

xray wrote:
On Wed, 10 Aug 2005 14:30:26 -0400, Bob Engelhardt
wrote:


The bad news is that there was also damage in the quick change box. A
couple of gears there had been repaired with brazed-in teeth and one of
those teeth bent. I plan on replacing them (the gears, not the teeth).


I didn't save the original message, but as I recall you had locked the
spindle. I assume its like my taiwan lathe and that means engaging the
reduction gears and having the pin engaged that locks the pullies to the
spindle gear.

I'm curious how there was a problem in the quick change box? That seems
removed from where I would have expected forces applied. Did I miss
something?

The carriage was locked for a facing operation.
Then the feed was engaged for turning, I think.

Don Young wrote:
Consider that a slip clutch would be capable of causing *un-noticed* loss of
sync during threading. ...

Good point! I didn't need another project, that's for sure. Bob

My 13x34 Jet(Taiwan) uses 1/8" brass rod shear pins in both the feed shaft
and lead screw couplings where they come out of the Q/C box. I have sheared
the feed screw pin two times over the years, but there has been no gear
damage.

Randy


"Bob Engelhardt" wrote in message
...
Good news, bad news. Good news is that it wasn't a gear that broke, but
a spring/split pin holding the gear on. 'Course it was down inside the
apron and more work to get to than about anything else on the lathe!

I was surprised than the pin broke - just sheared right off. It was
small (3/32, .094, 2.4mm) and not hard, but still ...

The bad news is that there was also damage in the quick change box. A
couple of gears there had been repaired with brazed-in teeth and one of
those teeth bent. I plan on replacing them (the gears, not the teeth).

I've started experimenting with shear keys. I have some plastic that
looks promising. One test key 3/16 square x 1" long took 70 foot lbs
to shear it. I'm going to start with real small versions and work up
till I get a size that won't shear under normal conditions. Then
hopefully it will shear under damaging ones.

I thought of another approach to gear train protection (for this lathe
anyhow). The first gears off the forward-reverse toggle are two gears
on a jack shaft, keyed together. Instead of keying them, one could
sandwich some friction material between them and create a slip clutch.
It might be kind of difficult to get a consistent slip point, but it
might be worth experimenting with.

Bob