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What Andrew said!!!! and much better than I did and I haven't been to
the pub. 8-(

John Dammeyer

Automation Artisans Inc.

Ph. 1 250 544 4950

John's right. When a leadscrew is used to cut a pitch of its own "nationality", the right place to engage the half-nuts turns up frequently. Imagine holding two rulers, ruler 1 graduated in 16ths of an inch (representing an imperial leadscrew) and ruler 2 graduated in (say) 28ths (representing a 28 tpi thread you want to cut). The graduations will coincide exactly very frequently - every quarter inch (because 4/16 = 7/28). So,the right place to engage your leadscrew, as indicated by your thread dial indicator, occurs very frequently.
Now, imagine you want to cut a 1mm thread, and that you have a 127 tooth gear to do an exact conversion from your imperial leadscrew. This time, ruler 2 is metric, and you will only get an EXACT coincidence of the graduations every 127 inches (10' 7"). The "right place" is only going to turn up infrequently on your TDI, and you will need a microscope to distinguish it from all the near misses which will turn up while you wait for it. Of course, you haven't got a 127T gear, so you have to use some fancy geartrain involving 57T, 42T, or whatever to get something which is almost, but not quite, 1mm (25.4 tpi). This might make matters worse.
I worked out that, though I could use my imperial leadscrew to cut a 1.25mm pitch thread accurate to 0.02%, the "right place" on a TDI would occur only once in about 30,000 revolutions of the spindle. The gearwheels would only be in precisely the same juxtaposition every 30,000 revs. At an unlikely 1,000 rpm, this would occur every half hour, and would be beyond my eyesight to recognise from all the near misses which intervened.
So, if you want to cut a reasonably accurate thread which is "foreign" to your leadscrew, the only option is to leave the half-nuts engaged, and reverse the lathe to get back to the beginning of the cut.

Does this make sense? It does to me, but I've only just got back from the pub!
Andy

John Dammeyer <johnd@...> wrote:
Hi Ian,

You are making an assumption that when the lead screw is at a specific
point when the spindle is at an equally repeatable location. That's
essentially how the thread chasing dial works. If you were cutting a
thread that required engaging the half nut at any line it means that the
lead screw and spindle are linked in multiples of your lead screw pitch.

But if you are cutting a thread where the #3 position and only the #3
position is the right place it's possible that the spindle is 90 degree
offset for the #2 position, 180 for the #1 position and 270 offset for
the #4 position.

Now follow that same line of thinking for metric and you may find that
the nut would have to be engaged at the #1 position the first time. The
1.27 position the next time and so on.

John Dammeyer

Automation Artisans Inc.

Ph. 1 250 544 4950

Hi Ian,

I have had a knowledgeable response from John Dammeyer but I am not
sure I fully understand it.

Half the time I don't understand myself either so don't feel bad. ;-)


Put a handle on the spindle and install the required for metric gears
onto the lathe and walk through some turns with a piece of tape on one
of the three jaws so you can keep track of it.

You'll find you will be able to engage the lead screw at several places
and the jaw will be at the wrong place for some of them.

Do it for imperial threads and it's always in the right place.

Slow motion....

John Dammeyer

G'day John.
I saw the timing of some of your missals; quite late.
With a metric LS the chaser dial does not have the same relationship
to the thread as for imperial. Apart from really odd-ball threads or
threads with TPI much greater than the LS TPI the chaser dial will
always work for imperial even if you can only use one digit as your
reference, eg 12 o'clock.

I have had a knowledgable response from John Dammeyer but I am not
sure I fully understand it. It seems to me that if the saddle is
always in the same starting position and the lead screw at the same
angle for engagement of the half nuts then the outcome is repeatable.
I haven't made a saddle stop yet so I haven't had a chance to try out
my theory. I have a picture in my my mind of an old machinist with a
chalk mark on the last change gear wheel waiting for it to line up
before he engaged the nuts.

I am seeking to come up with a way that doesn't need a chaser dial; I
am sure a methods must exist other than "granny driving" to reverse
out.

One good turn deserves another. (tongue in cheek)
Regards,
Ian

--- In 7x12minilathe@..., "born4something" <ajs@...>
wrote:

Hi Ian,

An extended tag - I'd never interpretted that passage quite that

way!

Just thinking out loud, if you had your RH carriage stop and always
started from there, dropping the half nuts in at the first arrival
at a digit on the dial (don't care what digit) then successive
passes will always retrace as long as you always use the same

digit.

At least, I think that's right - I had a 3 o'clocker last night and
haven't had any caffeine yet!

John

Hi Ian,

An extended tag - I'd never interpretted that passage quite that way!

Just thinking out loud, if you had your RH carriage stop and always
started from there, dropping the half nuts in at the first arrival
at a digit on the dial (don't care what digit) then successive
passes will always retrace as long as you always use the same digit.
At least, I think that's right - I had a 3 o'clocker last night and
haven't had any caffeine yet!

John




--- In 7x12minilathe@..., "steam4ian" <fosterscons@...>
wrote:

G'day all.
On another topic, John (born4something) and I have been discussing
thread chasing dials. If you have a metric lead screw you need a
range of pinions on the dial to suit different threads. This is
tedious. to cut an imperial thread (with metric lead screw) you

have

to keep the half nut closed the entire time and reverse the lathe

out

between cuts, also tediuos.
There are two common methods to keep the tool "in the groove" for
each pass, namely, using the thread chasing dial or reversing

between

cuts.
I think there is a third method, does anybody know of it?

In the wee small hours of the night, my designing time, I dreamt

up a

method. It involves using a saddle stop at the RH end of the cut
(assuming R to L cutting). At the end of each pass you dissengage

the

half nuts, withdraw the tool and crank the saddle back hard

against

the stop. You set you tool and then gently engage the half nuts by
feeling them into position. This last process would be made easier

by

a circular clip on the lead screw to set indicate when the screw

is

at the same point of rotation corresponding to the first

engagement.

The gib for the half nuts would need to be well adjusted.

Comments and advice is sought, over to you.

One good turn deserves another. (Luke6:31 Machinists Bible)
Regards,
Ian

Hi Ian,

You are making an assumption that when the lead screw is at a specific
point when the spindle is at an equally repeatable location. That's
essentially how the thread chasing dial works. If you were cutting a
thread that required engaging the half nut at any line it means that the
lead screw and spindle are linked in multiples of your lead screw pitch.

But if you are cutting a thread where the #3 position and only the #3
position is the right place it's possible that the spindle is 90 degree
offset for the #2 position, 180 for the #1 position and 270 offset for
the #4 position.

Now follow that same line of thinking for metric and you may find that
the nut would have to be engaged at the #1 position the first time. The
1.27 position the next time and so on.

John Dammeyer


Automation Artisans Inc.

Ph. 1 250 544 4950

G'day all.
On another topic, John (born4something) and I have been discussing
thread chasing dials. If you have a metric lead screw you need a
range of pinions on the dial to suit different threads. This is
tedious. to cut an imperial thread (with metric lead screw) you have
to keep the half nut closed the entire time and reverse the lathe out
between cuts, also tediuos.
There are two common methods to keep the tool "in the groove" for
each pass, namely, using the thread chasing dial or reversing between
cuts.
I think there is a third method, does anybody know of it?

In the wee small hours of the night, my designing time, I dreamt up a
method. It involves using a saddle stop at the RH end of the cut
(assuming R to L cutting). At the end of each pass you dissengage the
half nuts, withdraw the tool and crank the saddle back hard against
the stop. You set you tool and then gently engage the half nuts by
feeling them into position. This last process would be made easier by
a circular clip on the lead screw to set indicate when the screw is
at the same point of rotation corresponding to the first engagement.
The gib for the half nuts would need to be well adjusted.

Comments and advice is sought, over to you.

One good turn deserves another. (Luke6:31 Machinists Bible)
Regards,
Ian

Chris,
The best bet is to find a good supplier of unbranded lathes that come from the same manufacturers as the branded models but cost from ?260 - there's no need to pay more. You can get a model with DRO of the spindle speed and a tailstock lever lock and top quality for 270 sovs. Just got to look in the right place! And if you buy on the internet, eBay etc. go and take a look first before buying.
Hugh

G'day Chris.
CORRECTION. The guy was Andy Franks not Alan. My apologies Andy.
One good trun deserves another.
Regards,
Ian
--- In 7x12minilathe@..., "steam4ian" <fosterscons@...>
wrote:

G'day Chris.
Have a look at the machines close-up if you can. A guy named Alan
from the UK sent me a picture of his lathe, I think it was a Chester,
and it had some significant improvements over the "standard" Sieg.

G'day Paul,
Just to say what you said is great.
Making tools, to make tools, to make tools..........
One good turn deserves another.
Regards,
Ian
--- In 7x12minilathe@..., "Paul Moir" <paul.moir@...>
wrote:

Just to get the terminology down for lathe work -

Turning - reducing the diameter of the work.
Facing - reducing the length of the work from an end.
Parting - cutting work off on the lathe.
Boring - enlargening a hole in the work.
Centre-drill - a special bit that cuts the seat for the tailstock
centre. It is also used for precisely starting drilling operations
since it's short and rigid.

- That should be enough

Since you're working on pipe 10" long, I would suggest getting at
least a 7x12. Work much longer than 8" gets really tricky on the
7x10. The 7x12, despite the numbers, is actually a full 4" longer
than the 7x10.

3/4" and slightly larger diameters will fit fine through the

spindle,

so theoretically you could work on one end of a very long pipe. But
the stock 3" chuck will on only pass 5/8" work. 4" chucks almost
universally pass 3/4" work though.

I don't know the American market for these lathes very well, but a

lot

of people like the cumminstools.com 7x12 for the amount of

accessories

they get. The steady rest is useful for working on very long stock
too, replacing the tailstock. It's probably available somewhere

else

a little cheaper though.

Threading is no problem at all. If you buy just about any US lathe,
it'll be equipped to make perfect imperial threads. Usually the

gears

used will be 40-65-35 gears. The metric leadscrew minilathes can
approximate a 14 TPI pretty well too. Making left hand threads is
pretty simple as you just drive the leadscrew backwards - no trouble
at all, just flip a shifter.

That said, 14 TPI is pretty steep and can get pretty hairy on any
lathe pretty quickly. So something that course is best done by
turning the lathe with a hand crank rather than by power. Usually
it's a pretty simple matter to just make your own hand-crank for the
spindle out of scrap, etc.

Which gets us to the crux of the matter. All the 7xs, with the
possible exception of one of the nice tuned up 7xs like the

Micromark

7x14 (6" longer than the 7x10), are best described as "lathe kits
assembled for your inconvenience" While you can take them out of

the

box and start turning, it won't be very nice and you won't enjoy

it.

This is why these lathes are so popular among us hobbyists as we
actually enjoy spending time tuning them up and dialing them in. If
you don't enjoy fiddling with machines you just want to get straight
to work, spend 2 or 3 times more money and get a real lathe.

Either way you go, the operation sounds pretty straight forward to

me.

I'll explain how I would do it on my 7x10, presuming I could fit

the

work between the centres. I'm also going to presume that I'm

making a

few different length pieces but only a few different ID pipes.

Clearly

OD is our choice.

1). Make some top-hat shaped pieces out of aluminium (or
what-have-you) to make caps to fit each ID pipe I'm using. Probably
about 3/4 inch long, centre-drilled to fit the tailstock. The thin
portion of the top-hat will closely fit the ID of the pipe, and the
flange will 'cap' it and allow the pipe to be held by the dead

centre.

Here's how their made simply:

1.1). Set the AL stock so it's sticking out of the chuck about 1".
With a left-hand turning tool set squarely in the toolpost, turn

down

the stock cutting from tailstock end toward the chuck end, stopping
after about 5/8". Make light cuts to this point until the pipe just
slips over it. Lay a file at an angle on the end of the work, and
form a quick chamfer (slight point) to make inserting the plug

easier.

Then with the cutoff tool set square, cut the stock off 1/8"-1/4"
past the turned down part, forming a flange.

1.2). Remove what remains of the stock and mount the top-hat in the
chuck, flange side out. There will be a nib left over from parting,
you can file it off or simply face the whole top-hat with the

turning

tool. Finally, centre drill the peice with a centre-drill bit held

in

a tailstock chuck.

1.3) A word of warning here - these are not "precision" unless you
indicate the part with a dial indicator when you chuck it a second
time. You can expect 0.002-.005" error if you don't.

2) Get cutting pipe. Cut your peice about an inch longer than you
need it. About 1" of an end will be held in the chuck and is
essentially unworkable without some serious juggling. Cap the other
end with your new cap and fit the tailstock and dead centre. Turn
down your pipe to the OD you want as close to the chuck as you

dare.

If bits of the top-hat flange are in the way, just blast through

them.

3) Back off the tailstock far and part off the pipe, loosing the
chucked end. Remount the pipe so it's only sticking out of the

chuck

1-1.5" (assuming it fits through the headstock & chuck). Chamfer

the

end of the pipe with a file or with the threading bit set at 45
degrees (appx.) to make the pipes thread on easily. Setup and cut

the

threads (whole other lesson!).

4) Flip pipe, face to desired length using turning tool, then repeat
step #3.


I hope that explains it. As you can see, lathe work (and most

machine

work really) involves a lot of setup. This is why machine shops
charge so much less for batches than 1-offs. Also, you see how half
the time you setup for a job, you begin by making tools. Sometimes
you end up making tools to make the tools!

-Paul Moir


--- In 7x12minilathe@..., "harleyknall" <knall@> wrote:

I am looking to buy a cheap lathe to do the following work.
I will be working on some 10" long pipe under 3/4" diameter.
I need to make small sections of it thinner ( face?), and

be

able to cut the pipe to length ( part? )

I am specificaly interested in THREADING, I NEED to be able

to

make 14x1 left hand thread.
Are the cheapo harbor freight ones suited to this? Which

is the

best to buy?
This lathe will be LIGHTLY USED, I do not need an industrail
machine. I am simply wondering what INEXPENSIVE lathe can

perform

the task and HOW to perform the threading task ( what gear set up

ect ).

Harbor freight has 2 7x10 lathes listed that look

identical,

there is a $10 price diferance...... which is better? what is

the

diferance? Will either do the required task?

G'day Chris.
Have a look at the machines close-up if you can. A guy named Alan
from the UK sent me a picture of his lathe, I think it was a Chester,
and it had some significant improvements over the "standard" Sieg.
The tail stock, which is a weak point with Sieg, appeared much better
and I think the bed had a separate prism for it to run on. After
corresponding with Alan off group I looked up the suppliers in the
UK; there are definitely better variants of the 7x12 around.

In the last day I have been airing my differences with John
(born4something) regarding refinements my lathe has over his which is
a more "standard" Sieg. You may find the points of interest.

If all you want to do is face those Aluminium bars then the cheapest
7x12 will do the job but IMHO you would be better off payig a bit
more for a more refined version. Some distrubutors/retail chains set
certain quality and finish standards for the manufacturer rather than
just buy a container load of lathes. Even the dearest 7x12 variant is
still incredible value. The again if I had more money and space I
would have a 10x24 or similar.

Have fun, enjoy the drooling phase.
One good turn deserves another.
Regards,
Ian


--- In 7x12minilathe@..., "mozziesplat"
<katiechris4evr@...> wrote:

Thanks Andy and Ian it sounds like the 7x12 will do the jobs i have
in mind for it so i will be putting an order in soon for iether a
sieg c3 or a chester conquest i think they are the same machine...
Chris

A rule of thumb for the max projection from the chuck jaws is 2-3 times the diameter so a 3" long piece would be fine

Gerry
Leeds UK

From: "steam4ian" <fosterscons@...>
Reply-To: 7x12minilathe@...
To: 7x12minilathe@...
Subject: [7x12minilathe] Re: 7x12 capability
Date: Tue, 13 Mar 2007 23:06:15 -0000

G'day Moszziesplat.
The job is well within the capacity of the 7x12 lathe. My concern is
the overhang from the chuck. There is a risk that the work could skew
in the chuck due to the cutting forces. Being aluminium doesn't help,
it is softer to hold. If the work was any longer I would definitely use
a fixed steady to give support at the work face. Use a steady to be
sure. Consider getting steadies with the lathe, often they come as a
cost effective package.
BTW, with an handle like Mozziesplat and spelling Aluminium correctly
you must be Australian.

One good turn deserves another.
Regards,
Ian

--- In 7x12minilathe@..., "mozziesplat"
<katiechris4evr@...> wrote:

I'm thinking of buying a 7x12 minilathe but i need to know if the
standard chucks are cabable of holding 3 inch lengths of 1 inch round
aluminium stock tight enough so that i can face both ends off.
I would be a complete novice to this hobby hence the simplistic
question.
Could anyone please advise.

_________________________________________________________________
MSN Hotmail is evolving - check out the new Windows Live Mail.

The 7x12 standard chuck would have no problem with that

Gerry
Leeds UK

From: "mozziesplat" <katiechris4evr@...>
Reply-To: 7x12minilathe@...
To: 7x12minilathe@...
Subject: [7x12minilathe] 7x12 capability
Date: Tue, 13 Mar 2007 15:59:28 -0000

I'm thinking of buying a 7x12 minilathe but i need to know if the
standard chucks are cabable of holding 3 inch lengths of 1 inch round
aluminium stock tight enough so that i can face both ends off.
I would be a complete novice to this hobby hence the simplistic
question.
Could anyone please advise.

_________________________________________________________________
MSN Hotmail is evolving - check out the new Windows Live Mail.

Chris, Warco do one, too, and they are all basically Seigs. Their machines have a few rudimentary checks made before being sent out. Their travelling steady is ?18. I don't know how their prices compare. Plenty of dealers on ebay, too (but perhaps they are narrower targets if the machine is faulty). Macine Mart offer one, as well.
If you anticipate cutting any threads, decide whether they are going to be imperial or metric; the machines come fitted either with a 16 threads per inch, or with a 1.5mm pitch, leadscrew. It's a lot easier to cut imperial threads than metrics on the 16tpi version, and vice versa.
Have fun
Andy

mozziesplat <katiechris4evr@...> wrote:
Thanks Andy and Ian it sounds like the 7x12 will do the jobs i have
in mind for it so i will be putting an order in soon for iether a
sieg c3 or a chester conquest i think they are the same machine...
Chris

--- In 7x12minilathe@..., andrew franks <andyf1108@...>
wrote:

Chris, I had a 3.25" length of 1" diam. aluminium handy, so I've

just tried facing it in my 3-jaw, without using undue force to
tighten the chuck. In fact, the chucked end was a smaller diam. for a
quarter of an inch, so the effective grip was on less than 0.5" of
the job. Using modest (3 thou or so) increments, it faced up nicely -
can't see any appreciable light getting through when holding it up to
the window, against a straightedge.Would be a long job, though, if
there was much metal to be removed to achieve the right length, and
a travelling steady, as Ian recommends, would enable more ambitious
cuts.

Andy


mozziesplat <katiechris4evr@...> wrote:
--- In 7x12minilathe@..., "steam4ian"

<fosterscons@>

wrote:

G'day Moszziesplat.
The job is well within the capacity of the 7x12 lathe. My concern

is

the overhang from the chuck. There is a risk that the work could

skew

in the chuck due to the cutting forces. Being aluminium doesn't

help,

it is softer to hold. If the work was any longer I would

definitely

use

a fixed steady to give support at the work face. Use a steady to

be

sure. Consider getting steadies with the lathe, often they come

as

a

cost effective package.
BTW, with an handle like Mozziesplat and spelling Aluminium

correctly

you must be Australian.

One good turn deserves another.
Regards,
Ian

--- In 7x12minilathe@..., "mozziesplat"
<katiechris4evr@> wrote:

I'm thinking of buying a 7x12 minilathe but i need to know if

the

standard chucks are cabable of holding 3 inch lengths of 1 inch

round

aluminium stock tight enough so that i can face both ends off.
I would be a complete novice to this hobby hence the simplistic
question.
Could anyone please advise.

Cheers Ian the work skewing due to the tool forces at the end of

the

work were exactly my concerns. What is the maximum diameter of

stock

that will fit through the fixed steadies ... You chaps down in
Australia still spell aluminium correctly like us in the uk, the
reason for my handle is another story that doesnt involve dead
insects on your windscreen/shield?
regards,
chris






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I stop grinding the top rake just about when the grinding wheel gets to
the cutting point. I'm only using two different tools for most of my
work at this time but it been working for me. The shim is a two inch
square with a hole drilled through it so you just drop it over over the
bolt and put your tool post on. Haven't had any problems with it
slipping yet. Kevin.

By the way, I would suggest still checking tool height.


--- In 7x12minilathe@..., "steam4ian" <fosterscons@...>
wrote:

G'day Kevin.
Lateral thinking!! Good.
Do the shim/s under the tool post allow it to slip?
How do you sharpen each tool to be exactly the same height?
On account of these questions I would not endorse following your idea.
Personally I have five tool post which allows me to have at least 10
tools set up; I have had three tools in one holder, use half length
HSS blanks.

I don't have shares in LMS but I do support Chris's recommendations
regarding multiple tool posts as an alternative to a QCTP. The tool
posts are half the cost of the QCTP holders and can take at least two
tools each.

Keep up the lateral thinking it is part of the skill of the craft. If
an idea doesn't yield the result you want (I didn't say "fails") then
think it through and learn and experiment again.

One good turn deserves another.
Regards,
Ian


--- In 7x12minilathe@..., "kevin" k.hand@ wrote:

5/16 is about .014 under center line on my cummins. Rather than

shimming

each tool bit, I shimmed the tool post. As long as I'm using 5/16

tool

bits no more shimming. Kevin


--- In 7x12minilathe@..., "Damon Wascom" <kc5cqw@>

wrote:

I have to shim my 1/4" and 5/16" tools on the stock 4-way tool

post. I

found that it always

totals 3/8" to get them on center. Should I order some 3/8" tools

or

stick with the shims?

Thanks, Damon

Thanks Andy and Ian it sounds like the 7x12 will do the jobs i have
in mind for it so i will be putting an order in soon for iether a
sieg c3 or a chester conquest i think they are the same machine...
Chris

--- In 7x12minilathe@..., andrew franks <andyf1108@...>
wrote:

Chris, I had a 3.25" length of 1" diam. aluminium handy, so I've

just tried facing it in my 3-jaw, without using undue force to
tighten the chuck. In fact, the chucked end was a smaller diam. for a
quarter of an inch, so the effective grip was on less than 0.5" of
the job. Using modest (3 thou or so) increments, it faced up nicely -
can't see any appreciable light getting through when holding it up to
the window, against a straightedge.Would be a long job, though, if
there was much metal to be removed to achieve the right length, and
a travelling steady, as Ian recommends, would enable more ambitious
cuts.

Andy


mozziesplat <katiechris4evr@...> wrote:
--- In 7x12minilathe@..., "steam4ian"

<fosterscons@>

wrote:

G'day Moszziesplat.
The job is well within the capacity of the 7x12 lathe. My concern

is

the overhang from the chuck. There is a risk that the work could

skew

in the chuck due to the cutting forces. Being aluminium doesn't

help,

it is softer to hold. If the work was any longer I would

definitely

use

a fixed steady to give support at the work face. Use a steady to

be

sure. Consider getting steadies with the lathe, often they come

as

a

cost effective package.
BTW, with an handle like Mozziesplat and spelling Aluminium

correctly

you must be Australian.

One good turn deserves another.
Regards,
Ian

--- In 7x12minilathe@..., "mozziesplat"
<katiechris4evr@> wrote:

I'm thinking of buying a 7x12 minilathe but i need to know if

the

standard chucks are cabable of holding 3 inch lengths of 1 inch

round

aluminium stock tight enough so that i can face both ends off.
I would be a complete novice to this hobby hence the simplistic
question.
Could anyone please advise.

Cheers Ian the work skewing due to the tool forces at the end of

the

work were exactly my concerns. What is the maximum diameter of

stock

that will fit through the fixed steadies ... You chaps down in
Australia still spell aluminium correctly like us in the uk, the
reason for my handle is another story that doesnt involve dead
insects on your windscreen/shield?
regards,
chris






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Just to get the terminology down for lathe work -

Turning - reducing the diameter of the work.
Facing - reducing the length of the work from an end.
Parting - cutting work off on the lathe.
Boring - enlargening a hole in the work.
Centre-drill - a special bit that cuts the seat for the tailstock
centre. It is also used for precisely starting drilling operations
since it's short and rigid.

- That should be enough

Since you're working on pipe 10" long, I would suggest getting at
least a 7x12. Work much longer than 8" gets really tricky on the
7x10. The 7x12, despite the numbers, is actually a full 4" longer
than the 7x10.

3/4" and slightly larger diameters will fit fine through the spindle,
so theoretically you could work on one end of a very long pipe. But
the stock 3" chuck will on only pass 5/8" work. 4" chucks almost
universally pass 3/4" work though.

I don't know the American market for these lathes very well, but a lot
of people like the cumminstools.com 7x12 for the amount of accessories
they get. The steady rest is useful for working on very long stock
too, replacing the tailstock. It's probably available somewhere else
a little cheaper though.

Threading is no problem at all. If you buy just about any US lathe,
it'll be equipped to make perfect imperial threads. Usually the gears
used will be 40-65-35 gears. The metric leadscrew minilathes can
approximate a 14 TPI pretty well too. Making left hand threads is
pretty simple as you just drive the leadscrew backwards - no trouble
at all, just flip a shifter.

That said, 14 TPI is pretty steep and can get pretty hairy on any
lathe pretty quickly. So something that course is best done by
turning the lathe with a hand crank rather than by power. Usually
it's a pretty simple matter to just make your own hand-crank for the
spindle out of scrap, etc.

Which gets us to the crux of the matter. All the 7xs, with the
possible exception of one of the nice tuned up 7xs like the Micromark
7x14 (6" longer than the 7x10), are best described as "lathe kits
assembled for your inconvenience" While you can take them out of the
box and start turning, it won't be very nice and you won't enjoy it.
This is why these lathes are so popular among us hobbyists as we
actually enjoy spending time tuning them up and dialing them in. If
you don't enjoy fiddling with machines you just want to get straight
to work, spend 2 or 3 times more money and get a real lathe.

Either way you go, the operation sounds pretty straight forward to me.
I'll explain how I would do it on my 7x10, presuming I could fit the
work between the centres. I'm also going to presume that I'm making a
few different length pieces but only a few different ID pipes. Clearly
OD is our choice.

1). Make some top-hat shaped pieces out of aluminium (or
what-have-you) to make caps to fit each ID pipe I'm using. Probably
about 3/4 inch long, centre-drilled to fit the tailstock. The thin
portion of the top-hat will closely fit the ID of the pipe, and the
flange will 'cap' it and allow the pipe to be held by the dead centre.
Here's how their made simply:

1.1). Set the AL stock so it's sticking out of the chuck about 1".
With a left-hand turning tool set squarely in the toolpost, turn down
the stock cutting from tailstock end toward the chuck end, stopping
after about 5/8". Make light cuts to this point until the pipe just
slips over it. Lay a file at an angle on the end of the work, and
form a quick chamfer (slight point) to make inserting the plug easier.
Then with the cutoff tool set square, cut the stock off 1/8"-1/4"
past the turned down part, forming a flange.

1.2). Remove what remains of the stock and mount the top-hat in the
chuck, flange side out. There will be a nib left over from parting,
you can file it off or simply face the whole top-hat with the turning
tool. Finally, centre drill the peice with a centre-drill bit held in
a tailstock chuck.

1.3) A word of warning here - these are not "precision" unless you
indicate the part with a dial indicator when you chuck it a second
time. You can expect 0.002-.005" error if you don't.

2) Get cutting pipe. Cut your peice about an inch longer than you
need it. About 1" of an end will be held in the chuck and is
essentially unworkable without some serious juggling. Cap the other
end with your new cap and fit the tailstock and dead centre. Turn
down your pipe to the OD you want as close to the chuck as you dare.
If bits of the top-hat flange are in the way, just blast through them.

3) Back off the tailstock far and part off the pipe, loosing the
chucked end. Remount the pipe so it's only sticking out of the chuck
1-1.5" (assuming it fits through the headstock & chuck). Chamfer the
end of the pipe with a file or with the threading bit set at 45
degrees (appx.) to make the pipes thread on easily. Setup and cut the
threads (whole other lesson!).

4) Flip pipe, face to desired length using turning tool, then repeat
step #3.


I hope that explains it. As you can see, lathe work (and most machine
work really) involves a lot of setup. This is why machine shops
charge so much less for batches than 1-offs. Also, you see how half
the time you setup for a job, you begin by making tools. Sometimes
you end up making tools to make the tools!

-Paul Moir

A couple of questions.

When you say "I need to make small sections of it thinner" do you
mean make the outside smaller or the inside larger?

When you say a "14x1 left hand thread" do you mean a 14mm diameter
piece with a 1mm pitch?

These answers will held decide what you need.

As far as the 7x10 lathe it will be to short for a 10" long piece.

Paul M

--- In 7x12minilathe@..., "harleyknall" <knall@...>
wrote:

I am looking to buy a cheap lathe to do the following work.
I will be working on some 10" long pipe under 3/4" diameter.
I need to make small sections of it thinner ( face?), and

be

able to cut the pipe to length ( part? )

I am specificaly interested in THREADING, I NEED to be able

to

make 14x1 left hand thread.
Are the cheapo harbor freight ones suited to this? Which is

the

best to buy?
This lathe will be LIGHTLY USED, I do not need an industrail
machine. I am simply wondering what INEXPENSIVE lathe can

perform

the task and HOW to perform the threading task ( what gear set up

ect ).

Harbor freight has 2 7x10 lathes listed that look

identical,

there is a $10 price diferance...... which is better? what is

the

diferance? Will either do the required task?

hi all-

we've been working on getting the 8x12/14 cnc'd lately and posted some
comments and pictures on its progress. so far, we're just a few steps away
from having the carriage being driven. we've opted to maintain manual
functionality so threading, feeding, etc. aren't tampered with. it could
have been a much simpler build if we machined the brackets manually but
instead wanted to take advantage of making these via cnc for nice rounded
contours.

<>

thanks for listening!
david


MetalWorkingFAQ.NET - Over 50 content sites! <>
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Hi John,

Yes, it's probably wise to be aware of that. It's not that common if
you don't work with the stuff much but as you say, people may not
make the connection. Same goes for lots of things we work with once
we stray from metal.

John


--- In 7x12minilathe@..., "John" <John@...> wrote:

Turning epoxy resin and/or using it as a handle can cause a problem
for some people because they have, or develop, contact sensitivity

to

the resin. This may result in an allergic reaction, anything from

red

skin and/or itching to swelling to difficulty breathing. The

allergic

reaction is generally not immediate, it can take 12 hours or more

for

symptoms to develop so it is easy to miss the connection between
exposure and symptoms. The allergy is mainly to un-reacted hardner

so

chances of a reaction diminish over time and also if the epoxy

cure is

accelerated by raising the temperature.

Be alert for any of the above, especially if you turn this

material on

your lathe since the resulting additional surface area brings
additional risk of a reaction.

John



--- In 7x12minilathe@..., "rancerupp" <rupps@> wrote:

John,

I think I understand most of what you are saying. Between your

first

two paragraphs are you talking bout two different procedures?

Overall, are you basically saying "Cast a rod of fiberglassing

resin

using pvc. Then turn it off and turn the resin rod into whatever

you

wnat."? It seems like an appropriate sized cardboard tube(capped

on

one end) could be used for casting the resin. Then just soak the
cardboard tube off after it hardens.

What's all this about axial and rotational keying? :) Thanks.

Rance


--- In 7x12minilathe@..., "born4something" <ajs@>
wrote:

Hi,

Just a suggestion.

For making plastic handles on shafts I turn a few grooves (for

axial

keying), grind a couple of flats (for rotational keying) and

then

cast the handle with fibre glassing resin from the hardware

store.

Use oversized PVC conduit as the former so centre isn't

critical.

Glue a piece to some scrap with silicone, etc. Then spray the

inside

lightly with WD40 as a release agent. Support the shaft by

clamping

from above and pour the resin in. Next day, stick the shaft in

the

chuck and turn off the PVC. If the WD40 has worked well you

won't

need to machine much before it slips off anyway. Discard that

and

continue turning the resin to shape. Fine cuts go smoothly and
produce mountains of fine stringy swarf. Don't let them build

up or

the job will eventually grab the whole pile and wrap it up!

Finish

with emery or wet & dry if you want a nice polish.

Place where I once worked used to cast blocks of that stuff

for

making items from. They always saved the offcuts in a bin for
smaller jobs. Turns beautifully.

John