¿ªÔÆÌåÓý

Hi, Roy. That is a good point. I had thought of recommending Helicoils, but the expense of the special taps and insertion tools seemed somewhat prohibitive at our level. Used many a Helicoil myself to get a million dollar light bulb-making machine going again. Not as impressive as saving a 10 million dollar jet fighter, but they do work great, if you have enough depth to use them. I have cut them off to use in shallower holes, but I was getting paid to do that, not playing on my own time. They are a wonderful tool to have in reserve when just nothing else will work.
Rance, don't be afraid of using steel for making things; it machines nicely, and is pretty darn common in junk and salvage yards. Don't be seduced by stainless steel for making parts, unless really needed. It sounds superior, but for a novice it can be a nightmare, mainly because of it's "stringy" toughness when machining. Wait a bit until you see how other materials cut, then practice on some stainless to see the difference. All part of the learning curve, Babe!
BTW, remember to use coarser threads in soft materials, and finer threads for harder ones. For example, 1/4-20 for aluminum, 1/4-28 for mild steel. That's why the different thread sizes are there, not just for marketing purposes, as it sometimes seems.
Which brings up another point: when did hardware store like Sears stop selling fine thread fasteners? It seems like everything is now the coarse thread (NC as opposed to NF). At least thats the way it is at my local Sears.
Ron.
---- roylowenthal <roylowenthal@...> wrote:

G'day Jim.

Have you found that the fuse protects the FETs or SCRs if there is a
short circuit on the motor side?

In my experince on large drives I found that the energy let through
of a standard fuse is higher then the fusing energy of the silicon
junction. By the time the fuse blows the SRC etc has already had it.
Special fuses for protecting SCRs etc can be obtained but they become
a very weak link in the chain, they have to melt (fuse) at about 1/6
of the energy of the junction to be able to clear before the junction
is over stressed.
External factors like circuit inductance can help the fuse protect
the SCRs etc but it has to be designed in, in fact when it is, the
fuses are often eliminated altogether.

A number of people report blowing a fuse when they stall the lathe,
doesn't the current feedback loop prevent this? I have stalled my
lathe many times and haven't taken out a fuse yet, I wouldn't expect
to. I would value your comments.

One good turn deserves another.
Regards
Ian

G'day John.
You've given me an idea how to machine the tool holder and the packer.
I need to think about what radius is required and whether the lathe
could cut it. If the concavity in the tool holder can be cut by
mounting it on the face plate and so can the convex surface on the
packer/s. The standard tool holder with the tol mounted on the
outside could cut the radius.

I will explore the idea of using a commercial rounded section, I am
sure I have seen something like it in brass; used for trimming
comings on boats and for carpet edging.

In that the Micro Mark rocking tool holder costs USD26.20 and a
standard tool holder costs USD10.95 it may not be worth the time and
effort to just to save USD15.25.
It must be remembered that the rocking holder does not totally
obviate the need for shimming but it makes it much less critical.
Ellis's comments about increasing the clearance should be noted.

I am sure I have seen a tool post with the rocking packer straight on
the flat floor of the tool holder slot.

One good turn deserves another.
Regards,
Ian

Garry, check that you didn't trap a wire somewhere when you screwed the casings etc back together, cutting through its insulation and creating a short circuit. I speak from personal experience!
Andy

graysubs56 <graysubs@...> wrote:
Hi all,
I have the 7x14 Mini Lathe with the digital readout. I had cause to
change over to the metal gears and put new bearings in as well. My big
question is now that I have it all back together the machine keeps
blowing the fuse when I turn on the power. The gear box is not stiff,
the motor and box turn over by hand and I color coded all the wires
before I pulled them out so I could make sure they went back in the
right place. The yellow light still comes on, even when the fuse is
blown. Have I inadvertedly blown some of the electronics in the board?
Regards,
Garry






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--- In 7x12minilathe@..., Victoria Welch <wrlabs@...> wrote:

On Saturday 31 March 2007, steam4ian wrote:

Thanks Vikki.
Good sleuthing. In that it fits the 7x14 it should fit the 7x12.

I'm not 100% sure that post fits the 7x stuff, but it seems a safe
assumption, I think :-).

That
tool post is really good because the bottom of the tool slot is
cupped to match the curved packer, the tool and packer is supported
over the full length of the packer. Somewhere I have seen a standard
tool post used with just the packer curved, the problem is that there
is only a thin line of contact with the bottom of the slot, not much
friction.

Does not sound good to me, I'd avoid anything like that unless I was
just doing balsa :).

At the price the Micro mark tool post could be hard to justify
against getting a QCTP, but it is worth thinking about.

I think that would be more rigid than the QCTP and if it were somewhat
less expensive having a few of them around might be worth it.

Take care, Vikki.
--
Victoria Welch, WV9K/7
?€?Anyone who describes Islam as a religion as intolerant encourages
violence,?€? --Turkish Foreign Ministry spokeswoman Tasnim Aslam

I use one of these, every day. Works great! It's cheap, effective and
only sometimes requires re-grinding relief. It is much stiffer than
the "cheap" QCTP's .There's no problem with the tool shifting, after
you learn to tighten the set screws really snug.

Bob

Ian wrote.......Has anybody made, bought or used a rocking shim in the tool post?.......

I have used them in the past. The main problem is you need to allow for the 'rock' when grinding the tool angles. Especially clearance. A tool will cut without rake, but not without clearance.
HTH
Ellis

Hi Vikki,

That rocker post you linked looks like something you could make out
of your old stock toolpost. Just whack it on the faceplate and cut
those rocker depressions in the lower tool ledge using your QCTP.
Make the radius match some off-the-shelf bar and you will have
minimal machining to make the rockers.

Sound feasible?

John



--- In 7x12minilathe@..., Victoria Welch <wrlabs@...>
wrote:

On Saturday 31 March 2007, steam4ian wrote:

G'day all.
Not wanting to rain on Rance's parade I have started a new topic.
Has anybody made, bought or used a rocking shim in the tool post?
The idea is that the bottom of the shim has a slight convexity

and

the tool tip height can be finely adjusted by differential

tightening

of the front and back screws. This replicates the adjustment

provided

by the cup washer and half moon shim in the old lantern style

tool

posts. Tip height adjustment does alter the tool rake but not

enough

to be a problem

The one I was considering (still am :) is this one:

MerchantID=RET01229&Action=Catalog&Type=Product&ID=82689

Seems like it should be solid enough. I like my QCTP, but it does

flex

sometimes.

My experience was with the a single rocker post that held one bit

on a

bigger machine, I liked it and it was easy to adjust.

I am concerned about the lateral tool rigidity, that is, the
likelyhood of the tool swinging back under load. Any comments.

Before I pick up some 50mm x 3mm flat and attack it with a file

it

would be good to hear from others.

Can't speak from experience on that one I linked to, but it

*looks*

good :). I need to ask them if that is for the 7x variety, at 5/8

max

for a bit, I am not sure.

Hope this helps!

Take care, Vikki (no connection to Micro-Mark).
--
Victoria Welch, WV9K/7
"I'm anti-war! Trouble is, the enemy isn't." -- Unknown

Hi Ian,

Just a thought. Might not be what you want to hear. If only one
resistor is burnt out and they are in parallel as a 0.33 ohm for
current sensing then the machine should run, but overload sense at
half load. So either BOTH resistors have failed or there is
something else failed too.

John


--- In 7x12minilathe@..., Ian Fletcher
<ian.fletcher@...> wrote:

Thanks for advice, resistors ordered at cost of ??1 so if that is

all that is wrong I shall have saved ??84 !! Thanks for your
interest and support. Ian

-----Original Message-----

From: born4something <ajs@...>
Date: Fri Mar 30 08:07:03 GMT 2007
To: 7x12minilathe@...
Subject: [7x12minilathe] Re: circuit board diagram

Hi Ian,
66 ohms sounds a bit high. You may have tricked people with that
space between the R and 66. Electronics types often use the

prefix

as a decimal point (like 1k2 means 1.2k-ohms) and when there is

no

prefix they just insert the base symbol, R. So R66 is likely

0.66

ohms. It's a convenient notation and avoids using those little

dots

that don't print clearly and are often multiplied when

photocopying

stuff!
Check the other resistor. If it is 0.66 ohms I'd expect quite a
reasonable reading in circuit without even unsoldering it as the
surrounding components are unlikely to be anywhere near as low

as

that. If they are, it's likely a failed FET or triac, depending

on

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

Looks as though it might be: 5W = 5 watts, R66 = 66 ohm. Not

sure

about the J, though - could represent a tolerance (as in plus or
minus a certain percentage from the marked resistance value).
However, 66 ohms isn't a standard "preffered" value - 68 ohms

is,

though. Can you unsolder its twin, if it has identical markings,

and

check it? If it is 66 ohms, you may have to use a couple of 33

ohm

ones, and connect them in series (though if you use 68 ohms,

it's

probably close enough).

As to wattage, if you can't get 5 watts from Maplin or

somewhere, get the next size up.

I wonder what made it burn out, though? Hopefully, it was

something simple like a short circuit caused by swarf.

Andy
ftr1d <ian.fletcher@> wrote:
Hi, I have just purchased a 240 volt Clarke 300m

with a

dead circuit

board. A new board will cost ??85 so I am looking to repair

it. The

only

fault I can see is a blown ceramic block, one of a pair, which

is

marked 5WR 66J and is in R1 position on the board. I assume it

is

a

creamic resistor? Does anyone have a circuit diagram or can

give

me the

specification of the part. Thanks Ian






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[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

You have either misconnected something on the board, or cause a short. the most common cause of blowing fuses is either the bridge rectifier or the pot shorting out on the fuse-holder.

Check the connections and check for swarf on the board.

Begin there and let me know what you find - give me a yell if I can help.

Rabid
Uncle Rabid ( )
We Repair Electronic Speed Controllers
For Asian Mini Lathes and Mini Mills
"Just Crazy Enough To Get the Job Done"

Hi,
I just picked up a Cummins mini lathe and was wondering if there is
any resource out there that can tell me what speeds to run for diff
materials....I mostly play with Stainless Steel and not sure what speed
I should run my lathe at....Can anyone help??....Thanks, Kevin

On Saturday 31 March 2007, steam4ian wrote:

Thanks Vikki.
Good sleuthing. In that it fits the 7x14 it should fit the 7x12.

I'm not 100% sure that post fits the 7x stuff, but it seems a safe
assumption, I think :-).

That
tool post is really good because the bottom of the tool slot is
cupped to match the curved packer, the tool and packer is supported
over the full length of the packer. Somewhere I have seen a standard
tool post used with just the packer curved, the problem is that there
is only a thin line of contact with the bottom of the slot, not much
friction.

Does not sound good to me, I'd avoid anything like that unless I was
just doing balsa :).

At the price the Micro mark tool post could be hard to justify
against getting a QCTP, but it is worth thinking about.

I think that would be more rigid than the QCTP and if it were somewhat
less expensive having a few of them around might be worth it.

Take care, Vikki.
--
Victoria Welch, WV9K/7
¡°Anyone who describes Islam as a religion as intolerant encourages
violence,¡± --Turkish Foreign Ministry spokeswoman Tasnim Aslam

Thanks Vikki.
Good sleuthing. In that it fits the 7x14 it should fit the 7x12. That
tool post is really good because the bottom of the tool slot is cupped
to match the curved packer, the tool and packer is supported over the
full length of the packer. Somewhere I have seen a standard tool post
used with just the packer curved, the problem is that there is only a
thin line of contact with the bottom of the slot, not much friction.

At the price the Micro mark tool post could be hard to justify against
getting a QCTP, but it is worth thinking about.

One good turn deserves another.
Regards,
Ian

On Saturday 31 March 2007, steam4ian wrote:

G'day all.
Not wanting to rain on Rance's parade I have started a new topic.
Has anybody made, bought or used a rocking shim in the tool post?
The idea is that the bottom of the shim has a slight convexity and
the tool tip height can be finely adjusted by differential tightening
of the front and back screws. This replicates the adjustment provided
by the cup washer and half moon shim in the old lantern style tool
posts. Tip height adjustment does alter the tool rake but not enough
to be a problem

The one I was considering (still am :) is this one:



Seems like it should be solid enough. I like my QCTP, but it does flex
sometimes.

My experience was with the a single rocker post that held one bit on a
bigger machine, I liked it and it was easy to adjust.

I am concerned about the lateral tool rigidity, that is, the
likelyhood of the tool swinging back under load. Any comments.

Before I pick up some 50mm x 3mm flat and attack it with a file it
would be good to hear from others.

Can't speak from experience on that one I linked to, but it *looks*
good :). I need to ask them if that is for the 7x variety, at 5/8 max
for a bit, I am not sure.

Hope this helps!

Take care, Vikki (no connection to Micro-Mark).
--
Victoria Welch, WV9K/7
"I'm anti-war! Trouble is, the enemy isn't." -- Unknown

G'day all.
Not wanting to rain on Rance's parade I have started a new topic.
Has anybody made, bought or used a rocking shim in the tool post?
The idea is that the bottom of the shim has a slight convexity and the
tool tip height can be finely adjusted by differential tightening of
the front and back screws. This replicates the adjustment provided by
the cup washer and half moon shim in the old lantern style tool posts.
Tip height adjustment does alter the tool rake but not enough to be a
problem

I am concerned about the lateral tool rigidity, that is, the likelyhood
of the tool swinging back under load. Any comments.

Before I pick up some 50mm x 3mm flat and attack it with a file it
would be good to hear from others.

One good turn deserves another.
Regards,
Ian

The other day I put a dial indicator in a spare toolholder for my
QCTP, set it on centreline of my lathe, and left it on the shelf.

Tonight I had to do some stuff using the 4 jaw chuck, the job was
helped immensely by having the gauge set up already. (although it was
slowed by me not having the correct key for the chuck :{)

Stu G

A common method of making strong threaded holes in aluminum is with
Helicoils. If you're not familiar with them, they're spring looking
objects, wound from trapezoidal wire, usually stainless steel. In
practice, the hole is tapped oversize with a special "STI" (Screw
Thread Insert) tap, the insert is screwed in, its driving tang is
broken off & the job is done. In addition to being common in the
aviation industry they're also widely used to repair damaged threaded
holes.



Roy

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

Thanks Ron. So how about using threaded inserts in an aluminum

block?

First downside I see with an insert it creates an additional place
for possible lost rigidity. I've seen Pem Nuts for 6-32 screws in
1/16" alum. pate. Has anyone seen similar for 3/16 or 1/4 inch

bolts?

T-Nuts come to mind, but those are for wood. If the threads are the
only forseeable problem, then I'd prefer to use alum.

As for rigidity, my toolpost is 2 3/4 square and 1 5/8 high. Top

lip

is a bit over 1/2, the middle slot is about 3/4, the bottom lip is

a

bit over 1/4. The middle slot is about 1/2 in from the outer edge.
With that, the shortest threaded insert would be for the bottom
(1/4").

Good point about shimming the sides. I have some ideas on that but
I'll wait before introducing those.

Anyone know of sources for threaded steel inserts? Thanks.

Rance


--- In 7x12minilathe@..., <trainguy_347@> wrote:

Hi, Rance. Aluminum (aluminium) is strong, but it has been my

experience that threaded holes are easily stripped or deformed with
twisting motions. Steel would probably be best. As for the

stability,

try using a shimming block against the inside vertical surface of

the

tool, between it and the tool post. Good luck, Ron.

---- rancerupp <rupps@> wrote:

Thanks Ron, and to Clint for posting the pics.

Ron, others, would you think that al. would be sufficient for

this or

does it have to be steel? The toolpost that comes with the 8x12

seems

huge. I would think that an alum. one of the same dimensions

would be

fine.

Also Ron, did you have any problems with the mounted tool bit
twisting while using your set screw configuration? Clint had
expressed concern of rigidity.

Rance


--- In 7x12minilathe@..., "Ronald Durbin"
<trainguy_347@> wrote:

I have done this with a smaller post, except that
I used set screws (or grub screws, as our British brothers

and

sisters

call them) comming up from the bottom. To adjust, just undo

the

retaining nut on top, lift up the post, back off the top

screw

slightly, engage (run further in) the bottom screw tightly,

and

replace the post as per normal. This sometimes take a few

tries,

but

once the height is achieved, all is well. Great drawings, by

the

way!.

Ron.

Rance, as a machinist, even a hobby machinist, you do start to look at things differently. It sometimes is a curse. When my eyesight was better, I saw every crooked picture on a wall, and noticed every miter joint that didn't line up. With age, I don't notice as much, but still like to believe that I can think out problems and come up with creative solutions. Today, I tried my hand at making a miniature cannon, with plans as a guideline, but not using them for accurate machining. I just wanted to get my skills back, and it was fun figuing out how to replace a section that I accidently cut off! Good luck, Ron.
Keep makin' chips!!


---- rancerupp <rupps@...> wrote:

Well dooooooooh! 8) I have a lathe now. What was I thinking. I'm
gonna have to change my mindset. I could easily make my own steel
inserts now, right? :D That's one of the reasons I got this thing, so
I could make bits here and there when I need one and not have to run
to the h/w store or across town.


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

Thanks Ron. So how about using threaded inserts in an aluminum

block?

First downside I see with an insert it creates an additional place
for possible lost rigidity. I've seen Pem Nuts for 6-32 screws in
1/16" alum. pate. Has anyone seen similar for 3/16 or 1/4 inch

bolts?

T-Nuts come to mind, but those are for wood. If the threads are the
only forseeable problem, then I'd prefer to use alum.

As for rigidity, my toolpost is 2 3/4 square and 1 5/8 high. Top

lip

is a bit over 1/2, the middle slot is about 3/4, the bottom lip is

a

bit over 1/4. The middle slot is about 1/2 in from the outer edge.
With that, the shortest threaded insert would be for the bottom
(1/4").

Good point about shimming the sides. I have some ideas on that but
I'll wait before introducing those.

Anyone know of sources for threaded steel inserts? Thanks.

Rance


--- In 7x12minilathe@..., <trainguy_347@> wrote:

Hi, Rance. Aluminum (aluminium) is strong, but it has been my

experience that threaded holes are easily stripped or deformed with
twisting motions. Steel would probably be best. As for the

stability,

try using a shimming block against the inside vertical surface of

the

tool, between it and the tool post. Good luck, Ron.

---- rancerupp <rupps@> wrote:

Thanks Ron, and to Clint for posting the pics.

Ron, others, would you think that al. would be sufficient for

this or

does it have to be steel? The toolpost that comes with the 8x12

seems

huge. I would think that an alum. one of the same dimensions

would be

fine.

Also Ron, did you have any problems with the mounted tool bit
twisting while using your set screw configuration? Clint had
expressed concern of rigidity.

Rance


--- In 7x12minilathe@..., "Ronald Durbin"
<trainguy_347@> wrote:

I have done this with a smaller post, except that
I used set screws (or grub screws, as our British brothers

and

sisters

call them) comming up from the bottom. To adjust, just undo

the

retaining nut on top, lift up the post, back off the top

screw

slightly, engage (run further in) the bottom screw tightly,

and

replace the post as per normal. This sometimes take a few

tries,

but

once the height is achieved, all is well. Great drawings, by

the

way!.

Ron.

--- In 7x12minilathe@..., Michael Taglieri
<miket--nyc@...> wrote:

Another way I got the same result was to replace the clamping screw
that's there with a slightly longer one and modify the screw so I could
turn it from the threaded end to lock and unlock the tailstock. I filed
the end of the screw to a square and made a little wrench with a square
hole that I use to tighten and loosen the screw. Initially I was
wondering if that little square nubbin on the end would be strong enough
to torque the clamping screw down with, but I case-hardened it and it's
held up fine.

Mike Taglieri miket--nyc@...

Everyone has his reasons.
- Jean Renoir "The Rules of the Game"


On Wed, 28 Feb 2007 01:48:21 -0800 (PST) Malcolm Parker-Lisberg
<mparkerlisberg@...> writes:

To save all the trouble of all that machining, remove
the 5mm cap head screw that holds the tailstock bottom
plate to the top half that is used when adjusting the
offset. Drill 5mm through the top half, removing the
thread for the screw and make a sliding captive 5mm
threaded plate to take a 30 mm m5 cap head screw from
the inside of the top of the tailstock. Raise the
clamping nut with two 10mm washers so your tailstock
clamping spanner clears the new 5mm caphead offset
clamping screw. You can now adjust the position of the
tailstock without having to turn it over to adjust the
offset clamping screw.

Exactly what I've done ,the nut was made by milling two flats on steel
round bar drilling and threading and then slicing, the nut fits nicely
in the slot ,however as I have made a cam lock to the little machine
shop design ,the cap head does not interfere with any thing.

Geoff UK

Thanks Ron. So how about using threaded inserts in an aluminum block?
First downside I see with an insert it creates an additional place
for possible lost rigidity. I've seen Pem Nuts for 6-32 screws in
1/16" alum. pate. Has anyone seen similar for 3/16 or 1/4 inch bolts?
T-Nuts come to mind, but those are for wood. If the threads are the
only forseeable problem, then I'd prefer to use alum.

As for rigidity, my toolpost is 2 3/4 square and 1 5/8 high. Top lip
is a bit over 1/2, the middle slot is about 3/4, the bottom lip is a
bit over 1/4. The middle slot is about 1/2 in from the outer edge.
With that, the shortest threaded insert would be for the bottom
(1/4").

Good point about shimming the sides. I have some ideas on that but
I'll wait before introducing those.

Anyone know of sources for threaded steel inserts? Thanks.

Rance


--- In 7x12minilathe@..., <trainguy_347@...> wrote:

Hi, Rance. Aluminum (aluminium) is strong, but it has been my

experience that threaded holes are easily stripped or deformed with
twisting motions. Steel would probably be best. As for the stability,
try using a shimming block against the inside vertical surface of the
tool, between it and the tool post. Good luck, Ron.

---- rancerupp <rupps@...> wrote:

Thanks Ron, and to Clint for posting the pics.

Ron, others, would you think that al. would be sufficient for

this or

does it have to be steel? The toolpost that comes with the 8x12

seems

huge. I would think that an alum. one of the same dimensions

would be

fine.

Also Ron, did you have any problems with the mounted tool bit
twisting while using your set screw configuration? Clint had
expressed concern of rigidity.

Rance


--- In 7x12minilathe@..., "Ronald Durbin"
<trainguy_347@> wrote:

I have done this with a smaller post, except that
I used set screws (or grub screws, as our British brothers and

sisters

call them) comming up from the bottom. To adjust, just undo the
retaining nut on top, lift up the post, back off the top screw
slightly, engage (run further in) the bottom screw tightly, and
replace the post as per normal. This sometimes take a few

tries,

but

once the height is achieved, all is well. Great drawings, by

the

way!.

Ron.