I'm pondering lathes ... I started out thinking about a new Warco
machine, but have now moved on to thinking about secondhand Super-7s.
Any Super7 I find is likely (I suspect) to be an imperial machine - how
well will this cut metric threads? I did find this comment on a webpage
"You really only need electrical reverse when screwcutting Metric
threads on an Imperial machine, or visa-versa, and have to leave the
leadscrew clasp nuts engaged"
Is electrical reverse a necessity or just something that makes the job
I expect to be cutting 0.75 mm pitch metric threads - is this within
the range offered by standard Super7 change-wheels? I've been surfing
for info on the threads it can cut, but no luck so far!
cutting a metric thread on an imp lathe you have to keep the clasp nu
engaged as theres no "next line" on the indicator dial to pick th
thread up from( so you electricly reverse the tool) . for a .75m
thread , its 45 t driver. ist stud 40 and a 45driven ,2nd stud is 5
and a 21 teeth driven and a 70 t on the leadscrew
You can cut metric pitch threads on a machine with an imperial pitch
leadscrew if you use a suitable train as 2 x 127 =254 and there are
25.4mm in an inch a 127 tooth changewheel makes life easier. I have
seem such a wheel on a Myford but don't think it is standard. I used
to cut lots of 1mm pitch LH thread on a Harrison L5 with imperial
4tpi leadscrew using such a train.
The electrical reverse issue is just that you must leave the half
nut engaged when cutting such an odd pitch (in the imperial world);
therefore you can't disengage, wind back and then re-engage using the
thread indicator. If you don't have electrical reverse then there you
just have to pull the belt by hand. I'm always somewhat cautious about
using electrical reverse on a machine with a screwed mandrel nose lest
the chuck decide to unscrew itself (especially when you apply the spindle
brake). But I'm sure there are others better qualified to advise on that
as bizarely a Myford is one lathe I have never used!
All Myfords whether they be imperial or metric will have an imperial
leadscrew, only the cross slide and top slide have different threads.
As Alan replied the electrical reverse is needed to wind back to the
start for the next cut.
The worry of unwinding a chuck at screwcutting speed is very slight.
I abused one commercially for a few years and only had it come loose a
couple of times and I 'do' try hard
Many people now are swapping the single phase motors over for three
phase but running off an invertor or VFD. This gives you smoother
running, instant reverse and controlled acceleration and braking.
These still run off a 13 amp plug.
Myfords come as standard with no screwcutting box, it's a specified
Without the screw cut box you have to manually swop the change wheels
at the end to the pitch you want from a table supplied.
With the exception of two 21T gears which are extras and needed for
metric you can cut the whole range of imperial and metric threads.
0.75 pitch is one of the standards.
If you get the much sought after screwcutting box model you will need
a quite expensive metric add on kit so if you do aim to make full use
of metric and imperial screwcutting the non box model is actually
easier to use.
Here's a link to an online Myford manual
the screwcutting box
The Myford use of 21 tooth gears isn't mathematically correct, only
the 127 wheel can do that but the errors of using the 21T wheels are
that low they are probably better than the leadscrew accuracy anyway.
One disadvantage of the 127 wheel is that it has to be run without the
end guard on as it's too large to fit.
21 tooth and 127 wheels are available on Ebay far cheaper than from
Myfords, if you can get them to answer the phone, from a delightful
seller called Marypoppinsbag, - Hiya Gert
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Sorry you have a typo here
It's 45T driver to 40/35 driven to 50/21 driven to 70 leadscrew
You have the first driven incorrect at 45, it should be 35.
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There are several published charts, from Myford as well as others,
that cover in detail the available metric screw pitches available. The
full metric conversion set is not really a requirement, as you simply
need to check the chart for the particular lathe (gearbox or not) and
aquire those few gears that you do not yet have. Looking at the chart
it appears the quadrant
would be required as well for the gearbox equipped lathe. If one were
inclined to be cheap, a quadrant or a reasonable facsimile thereof could
be cobbled together without too much fuss, though you might keep it out
of sight when the purists come visiting. For the change gear equipped
lathes it is less of a burden as you only have to add a few gears to the
collection that should be with the lathe already. 21t, and 63t come to
mind, though I don't have a chart in front of me.
If you know anyone with a pile of Model Engineer back issues, you have
better than average chances that the subject is covered in some detail
in there, as well as several different strategies for dealing with the
half nut issues. The booklet from the Workshop Practice Series of books
on screwcutting is good for the charts therein, though I was hoping for
more than that when I bought a copy. It still rates as a keeper.
Model Engineers Workshop (or perhaps it was ME) ran an article on a
metric coversion that entailed a rework of the gear drive train to
include a dog clutch. The benefit of that setup was that the clutch
could be disengaged and the carriage would back to the starting point of
the thread using the crank handle on the leadscrew, then re-engaged
without losing reference.
Brendan, as you know I'm quite a supporter of the imported machines
because of their terrific value for money but for someone who can
afford a little more and has the confidence and knowledge to buy
secondhand, a Myford S7 will rarely disappoint.
You can see from the comprehensive answers to your question one of the
major advantages of going the Myford route. Not only do you get a first
class machine but a wealth of knowledge and advice is instantly
available. The machine has been so widely used over the past 60 years
that if it can be done it has been done and by some very ingenious
My own machine is an imperial S7 with gearbox for which I have a metric
change gear set. As mentioned before the major difference is the
quadrant which has a longer slot to accommodate a wider range of gears.
I bought my set from RDG as at the time they were the cheapest, it
needed a little cleaning up but works fine. I see no reason why
something suitable couldn't be sorted out fairly easily. There are so
many gear charts about that produce extremely close approximations of
metric threads that it is not really an issue for the common metric
In my opinion the electrical reverse is necessary but is also not an
issue for a S7 fitted with a clutch (they all are), as the clunk
produced by single phase on start can be isolated by the use of the
clutch. This just disengages the motor from the drive system so has no
affect on the gear train. Once the motor is reversed the clutch can be
eased in to reverse the direction and return the tool for the next cut
without disengaging anything. Reversing the motor electrically is just
a switching issue and can be sorted easily without the expensive (but
very good) Myford switch. Change gears are available from a number of
sources and can be found quite cheaply.
D A G Brown wrote a series of articles in Model Engineer (4145, 4147,
4149 and 4151) about metric thread cutting on Myford lathes. It
included some fairly straight forward modifications and covered a
comprehensive set of threads including BA and Module. Unfortunately my
ME collection is incomplete and I can't help with copies but I'm sure
someone will have them.
You already have a comprehensive answer for non gearbox lathes but if
you are lucky enough to find a S7 with the standard gearbox the nearest
approximation for .75mm pitch is a 28 tooth driver with the gearbox set
at 40 TPI. This gives an actual pitch of 0.741mm which is an error of
1.2%. Unless you are cutting long precision threads this is fine for
most practical applications. In my opinion having the gearbox is well
worth the slight complication when it comes to cutting metric threads.
Brendan, I should have added that a chart of the possible metric/BA
threads available with a S7 and standard gearbox was published in MEW
No 42, in a letter from John Walford. It appears that the only common
pitch for which there is not a suitable solution is 0.5mm. all the
others seem to be covered and the 1.2% error on the .75mm thread is the
largest error. Of course if you are only cutting a limited range of
metric pitches then I'm sure that the additional of a couple of change
gears could reduce this error further. Since this chart was published
in 1997 the availability of reasonably priced change gears has improved
greatly, particularly the "conversion" 21, 63 or 127 gears. The D A G
Brown article explains how to calculate the necessary ratios.
I'm sure the error with standard wheels is finer than that on the 0.5
You can't get an exact match but 35 - 38/25 - 45/20 - 65 will give you
and 20 - 75/65 - 60/30 - 55 will give you 0.5003030
Using two 21's set as 21 - 30/21 - 70/45 - 60 will give 0.5000625
The most exact is a 20 driving a 127 with an idler in between, this
does give 0.5 exactly
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Thanks for all the useful info - it's been filed.
What's the feeling towards ML7s rather than Super7s? I did bid on
Super7 but was outbid (instantly, and I don't want to start offerin
more than I can afford in a frantic bidding war) ... ML7s seem that bi
cheaper! For a reason I guess, but ...
John thanks as always. In your examples there are more than enough
zeros before the error figure to keep me happy. This quest for exact
pitch always makes me smile when for typical use you only ever have a
few mm engaged at any time anyway.
Hope this post appears only once but I seem to be having a lot of
trouble with the Google servers today.
Same applies here, I have to smile when I see these sorts of figures
being quoted as gospel and I remember when I worked at Raglans the
lead screws came off the machine like a banana because of the relieved
I wonder if they mapped any errors after straightening on the fly
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You are in danger of closing the circle here, the challenge of finding
a good Myford for your money drives many into the hands of the likes of
Warco. There is nothing inherently wrong with the ML7 it is just an
earlier/simpler version of the later Super 7. In fact the
specifications cross over with the ML7R which is really an original S7.
Like anything that has been about for 60 years there are good, bad,
brilliant and terrible examples to be had. A well equipped and well
looked after ML7 will provide many years of enjoyable and productive
service. A "dog" (old or new), ML7 or S7 will be an expensive
lesson in machine re-building. The ML7 has evolved and improved with
the years. The headstock bearings are a good example of this evolution,
although all versions are good some are better than others. If you find
an old ML7 with whitemetal bearings that's in good condition it will
perform well for years. If you find one that is shot you will not get
spares from Myford but have to replace it with expensive bronze and a
new spindle. Later models like the ML7R have the same bronze/ball
bearing arrangement of the S7. However, many of the ML7/S7 assemblies
are inter-changeable as the bed changed very little up to the
introduction of the power cross feed model. Old machines can be worth
more as parts so many are broken and sold on E-bay. If you can do a bit
of hand fitting, scraping etc there is no reason why you can't
re-build one that suits you. Not necessarily the cheapest way of doing
it though. The top speed of an ML7 (except the ML7R) is lower than the
S7 and because fo the spindle bearing design it is not recommended that
you drive them at the 2000rpm of the S7 for long periods. This again
can be greatly affected by the condition of the particular machine, a
well looked after and well adjusted ML7 will certainly run faster than
standard but possibly not as fast as the S7.
Many complain about the cross-slide, top slide, index dials etc on the
ML7 being shorter/simpler than the S7 but they are solid reliable and
have served many successfully for a lifetime. The one part I would miss
on my S7 is the clutch which is not fitted to a standard ML7. However,
there are many articles on how to make one and with a modern 3 phase
motor and VFD system it's benefit is greatly reduced anyway.
In short, rather than worry about the name tag (ML/S7) you need to look
at the specific machine. Many have been modified and the differences
are distinctly blurred (G). I would much rather have a good ML7 than a
clapped out S7. I would not hesitate for a second if I found a good ML7
for a reasonable price. They don't have the bells and whistles but
they do have they Myford build and feel. Pay particular attention to
the bed as although a (Myford) re-grind will only set you back a couple
of hundred pounds it could indicate much more work is required (saddle
re-fit etc). All of this can be done but it demands patience, knowledge
and development of some hand skills if an accurate machine is to be
produced. Having said that, many beds are re-ground/replaced
needlessly. The physics of lathe design mean that accurate work can
still be produced with a fair bit of bed wear.
Brendan, I won't go on as there is plenty to read on the net about
the Myford. In my opinion the ML7 is a fine lathe and there are many
good ones about. But and it's a big BUT, the design has been so
successful there are thousands out there some of which have been worn
out/abused and neglected and of course a few have been cared for and
loved. Sellers will ask similar prices for both because "it's a
Myford". You will need to learn enough about recognizing the
differences even after they might have been hidden, or find someone you
trust, to ensure that the one you buy is a goodun. In may ways the ML7
is the "bargin" Myford, a very good and capable lathe that suffers in
the shadow of an outstanding brother. This is where many turn to a new
import as there are less (but still plenty) of unknowns.
I'm a case in point for much of what Keith said. I got an old-ish
(1967) but very well used and worn ML7. I got it for the price of a
drink and petrol money and have been slowly restoring it whilst still
It's probably about 90% finished now, and has cost me about £400 in
parts and services and a lot of my own time. However, it could very
well have cost me double this to restore it if I hadn't managed to get
a couple of under the counter deals or had no access to other machine
I had the bed re-ground by Myford but ground and scraped the saddle
and gibs myself, fitted a new hardended spindle and bearings
(definitely an under the counter purchase) and made a new leadscrew
from Acme stock with the loan of a NG members lathe. Made new pins and
bushes on the Myford and various other bits on the mill & surface
grinder. De-rusting, sandiing, & spray painting I did myself
The final step (for which I shall no doubt be pilloried for not
heeding earlier good advice on here..) will be replacing the single
phase motor with a 3-phase and VFD. This is primarily so that I can
get a higher top speed than available at present.
When it is finished I will have a very nice small lathe, in 'as new'
condition, albeit with limitiations (the cursed small spindle bore!)
in what I hope will be an accurate working condition.
For me it has been as much fun restoring and making parts for it as it
will be using it, and make no mistake, they are a very nice lathe to
use compared to some of the chinese ones.
But I have been lucky, and getting one cheap enough in the first place
was a big plus.
You pays yer money...
All of this is excellent advice with which, I fully agree. The only thing I
can add is that if you are buying at auction (especially eBay) it's good to
work out what you might have to pay for a lathe in excellent condition and
including all of the bells and whistles that you think you may need and then
set your price based on the possible need to totally rebuild and re-equip
the machine to achieve the required specification.
eBay items vary (like any market place) considerably from totally knackered
to loved and cherished but the prices don't vary much to compensate.
I bought a very well equipped Super 7B on eBay which turned out to be very
well worn but I paid what I considered reasonable price if I had to pay for
a bed/saddle regrind and refit so, as I got the lathe for perhaps £600 to
£800 less than a warranted good item, I was not out of pocket having fully
reground and restored the lathe (actually, I did the work myself so I was
not out of pocket at all but you get the idea).
One thing I learned the hard way was to beware of the incredibly well
equipped machine. Mine came with the lever-collet system and the lever
tailstock attachment as well as practically ever other accessory available
which at the time I thought was a bonus. In fact, quite obviously in
retrospect, the lathe had been used in a production environment and
therefore was 'tired' to say the least. A full regrind, total clean, strip
and paint, replacement of all bearings and the tailstock barrel (all
available from Myford), new chuck and way too many hours to think about,
plus the VFD, poly-V belt conversion and DRO has now given me a superb,
accurate and near silent machine. It hasn't fixed the small spindle bore
problem though :)
Overall, they are a superb machine for small work and are nice to use but
caveat emptor, as ever, is very applicable.
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Jusrt spotted a Warco BH600 on the homeworkshop site for £975 ono:
Warco BH600 Gap Bed Lathe (6" x 24")in excellent condition. Owned
since new in 2003 & has seen light use, complete with stand, 3 jaw & 4
jaw chucks, faceplate, fixed & travelling steadies, centres, drill
chuck, halogen light, T-slotted cross slide. Dual dials - imperial &
metric with imperial leadscrew. (I can load onto a pallet if required
for ease of collection).£975 o.n.o.