Myford Super 7 -59 metrification?

[PekkaNFParticipant @pekkanf]

Converting imperial lathe to metric

[PekkaNFParticipant @pekkanf]

Hello,

 

There is one relatively local Myford Super 7 lathe that has about right price and condition for sale. It’s without gear box and power cross feed.

 

I’m completely metric, completely dystolexic with imperial units.

 

Problem that it is a genuine imperial machine. I just know that I won’t cope with imperial cross feed and graduations.

 

How feasible it would be to convert an old lathe to metric: Thread making, graduations and all.

 

DRO and metric conversion gear for screw cutting?

 

PekkaNF

[KWILParticipant @kwil]

Pekka,

 

Yes, you can obtain metric leadscrews, nuts and dials from Myford. There is a metric conversion set for screwcutting as well.

 

You can also fit a DRO as I have done, in addition I have the Imperial gearbox but have an additional quadrant fitted (ME Article by D.A.G Brown) so I have the best of both worlds.

 

K

[John Stevenson 1Participant @johnstevenson1]

You will just need to change the cross slide screw and nut, same for the top slide if you want to be bothered.

Dials are the same.

 

As regards leadscrew I’m almost sure they only did an imperial screw and metric conversion gears.

I have never seen a metric gearbox or a chart relating to a metric screw.

 

I stand to be corrected and probably will be.

 

John S.

[Martin WParticipant @martinw]

Hi

 

Another way may be to fit a DRO set to overcome the problem. No idea of the feasibility of fitting nor as to the availability of suitable suppliers or the cost in relation to buying the Myford bits.

 

Cheers

 

Martin

[Richard ParsonsParticipant @richardparsons61721]

PekkaNF

I have the same problems over here in Hungary. Most of the stuff is metric except for the old Russian Army type equipment where the threads are UNC or UNF (SAE). The spanners they used are Metric A/F, -but not always. Sometimes the heads are the old Whitworth sizes. 

There is no need to be dyslexic in inch units. All you need is a number box (a calculator – well it is a box full of numbers)

Metric to inch – there are more metric numbers in a size than inch- (1” is 25.4mm). Multiply the inch size by 25.4 to get metric. To get inch from metric divide the metric by 25.4.

To convert threads per inch (TPI) to metric is a little trickier. Divide 1 (one) by the TPI and multiply by 25.4. To convert Metric pitch to inch TPI just divide the metric pitch by 25.4 and divide 1 by the answer.

Inch numbers like 23/64ths or 9/16ths just divide the top (23 or 9) by the bottom (64 or 16) and you have the inch sizes in decimals.

To do the business and cut metric threads on an inch lead screw (8TPI) you will need to get metric conversion set from Myford. This will depend on the type of change wheel set the lathe comes with.
If it is the manual change type check what is there in the lathe’s inventory as it may have them. It is also a good idea to check with Myford about the ‘Extras’ you need
If it is of the “Quick Change” type you will need these and a special ‘Banjo’ –change quadrant:-

Change wheel
 No Needed
 
63 T
 1
 
60T
 2
 
55T
 1
 
50 T
 2
 
45T
 2
 
40T
 1
 
35T
 1

 

Edited By David Clark 1 on 01/12/2010 13:17:22

[John HaineParticipant @johnhaine32865]

Even a “native metric” S7 (I bought a new one a few years ago, with the large bore mandrel) only has a 1/8″ pitch leadscrew, so you do still need metric conversion gears if

you are doing long screws.  However for most applications the approximate metric gearing that Myford give in the handbook is quite good enough at least for fixings.

 

Fitting DROs has been covered in at least one MEW article – problem solved I would think?

 

Or do a CNC conversion and let the PC take care of it….

 

What’s gone wrong with the web formatting on this site?

[TerrydParticipant @terryd72465]

Looks like the table in the previous post has stretched the table o the page

It needs editing out.  HELP David, I’d quite like to read this one

Terry

Edited By Terryd on 01/12/2010 11:19:14

[TerrydParticipant @terryd72465]

Hi All,

 

I have emailed Richard and David for a fix.

The ‘Home’ button is at the bottom of the page

 

Terry

[KWILParticipant @kwil]

Pekka,

 

Go to photo 9 in my Album and you can see how neatly a DRO can be fitted to a Super 7

 

K

[PekkaNFParticipant @pekkanf]

Thanks

 

I probably could still get it, but this imperial unit thing is giving me shakes.

 

KWIL: I saw the picture of your (or a spitting image) “Myford S7 Topslide w/ Integrated DRO” somewhere. That looks freaking great. But you need taxidermist to put it all together? That would be way to do it.

 

Once I almost set my mind to buy bigbore S7 and my understanding was that the lead screw was not metric and it needeed a transpose gear to cut metric threads.

 

I saw the table earlier as a table, now it looks like a list.

 

I can convert (with a calculator) metric/imperials, but it’s the numbers and their represantion that throws me of the balance, specially the fractionals, they look to me like 13/15 or chiken-foot-pounds-per-mikey-mouse-digits. I understand completely if someone feels the same way metric. If it looks strange, it’s not nice to work with.

 

Another thing is how much you get with a one turn of crank. It doesn’t sound much, but try to crank like 12 rounds and then think some divisions…Some very mathematically talented can keep the perfect mental record, I can (and I have) would hash it up  even with metric. I hate on SOB lathe thas has one crank “illogical”, it moves wrong way….like someone would switch brake and gas pedal on a one paricular model car.

 

Cold-feet-chiken

PekkaNF

[KWILParticipant @kwil]

Pekka,

 

Yes that is my Myford Topslide.  I was tempted by the Big Bore S7 when they first came out, but did not like the colour, much to the Myford man’s displeasure !

 

I decided in the end to buy a Harrison M300 with an even larger spindle bore, that machine is all metric but is fitted with my usual DRO system as well.

[NJHParticipant @njh]

Hi Pekka

 

I had just the opposite problem to you!

Over some 30 years of occasional Model Engineering  I have used Imperial measurements and accumulated a large array of “useful bits” , measuring equipment and machinery  – all Imperial. ( That is except for a set of 1- 5mm x 0.1 drills )

Having settled into retirement I was looking for a new lathe and came across a Myford S7 in excellent condition – but metric !  Oh no – but I’ve Imperial measuring equipment.

I bought it anyway. A little thought though made me realise that metric measuring equipment is relatively cheap and digital micrometers, calipers  and height gauges do both. All that I needed to convert was my brain! So I made a quick and simple wholly metric project  and that helped a lot. 

I’m now on the way to a brain that is able to operate in both – just like the digital equipment! I must say though that I fitted digital scales to my ( Imperial) mill and that has been one of the best mods I’ve ever made. 

 

Good Luck

 

Norman 

[Ramon WilsonParticipant @ramonwilson3]

Hi Pekka,

As mentioned on another thread I have recently purchased metric feed screws to convert my imperial S7. A bit pricy but usual Myford quality and no real problems were experienced in fitting them – I actually got round to it yesterday – and have been using it today. Finally I’m glad to say I’m ‘all metric’  – well except the leadscrew of course but I very rarely use that as a means to measure saddle movement. As stated previously above Myfords metric lathes apparently still have imperial leadscrews with a metric ‘equivalent’ dial/handwheel.

 

The dial for the cross slide is straight forward enough 0.05 divs and engraved with mm progression and I much prefer the ‘x on the dial’ is ‘x off the diameter of the work’ too.  I found the topslide dial a bit confusing though as this is marked off in .025 divs and engraved with number of .025 divs ie 5-10-15-20 etc. I think I shall make a sleeve to fit over the dial and engrave it with progressive mm. Apart from that I’m dead happy – just wish I had thought of doing it years ago.

 

Hope you get yourself sorted out too

 

Regards – Ramon

 

 

[Ian S CParticipant @iansc]

my Taiwanese lathe has an imperial lead screw, the other screws are metric, and the micrometer dials on all except the tailstock are dual metric/ imperial measurements, the tailstock ic just metric but it has both engraved on the actual barrel. For thread cutting the metric / imperial gears are mounted together, so thatyou just unbolt, turn over and do it up again. Ian S C

[Anthony RhodesParticipant @anthonyrhodes37318]

I do not have a Myford. I do not have a metric lathe. Ther has been a lot of discussion in various media about how Myford owners and would be owners would like to have a proper metric lathe.

 

What are the requirements for a metric lathe? The important ones are metric feed screws on the cross slide, the compound slide, and the tailstock and a metric leadscrew. It would also be convenient to have a metric thread on the spindle if the chucks are thread mounted.

 

It’s my understanding that it’s possible to buy a “metric Myford” with the cross and compound feed screws metric, don’t know about the tailstock feed screw, but that no 7-Series Myford has ever been offered from the factory with a metric leadscrew.

 

So why doesn’t somebody retrofit their Myford with a metric leadscrew???

 

It must be possible to purchase metric Acme screw stock of a suitable diameter and pitch (well actually it wouldn’t be “Acme”, it would be Trapezoidal Metric Thread, 15 degree pressure angle in place of the 14-1/2 of Acme). You would also need split nuts to fit. These can be made from scratch or can be retrofitted from Myford Imperial split nuts.

 

The above concepts are fairly straight forward and their are articles and/or discussions of the general ideas in magazines or on the internet. The biggest issue is deciding what pitch to choose for the leadscrew. The most likely options would appear to be 3 mm, 2.5 mm, 2 mm, or 4 mm, I’ve seen references which would support any of these pitches. The decision should not be made on the basis of 3 mm being closest to 8 TPI, rather it should be on convenience of calculating gear trains for cutting various pitches from the primary pitch of the leadscrew.

Another approach would be to build a true inch – metric QC gearbox to use with the inch leadscrew or even design a QC gearbox which would drive seperat inch and metric leadscrew (two leadscrews on the same lathe). An inch – metric gearbox, with either one or two leadscrews, isn’t so much more difficult than a gearbox for only one measuring system and it doesn;t require a double set of gears. The gears that determine the pitch, often arranged as a graduated cone selected via a tumbler lever which is disengaged from one gear, the slid laterally to be engaged with a different gear in the cone, can be used either as driven gears for TPI or as drivers for metric pitch. You do need to make the selector shaft on which the tumbler lever rides and the cone shaft accessible on both sides of the gearbox. I doubt that the standard Myford gearbox could be adapted in this way because it was designed to fit on the lathe without consideration for these kinds of issues but the selector shaft, the tumbler lever, the cone shaft, and the 3-range selector shaft could brobably be fitted to a special gearbox casting. To be done properly you might want a few additional gears in the cone for easier metric gearing but it’s still pretty straight forward.

 

So the question is, is the project so difficult or do people just not understand the concepts?

 

Anthony

Edited By David Clark 1 on 12/07/2011 15:05:40

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