Myford tread cutting

[ron grimshawParticipant @rongrimshaw76129]

[ron grimshawParticipant @rongrimshaw76129]

Hi all, I have a myford S7 with gearbox, which I used to cut imp theards what I would like to do is metric theards, could someone enlighten me on how to do this, do I need complete gear change or is there a single gear that would change the way the gearbox worked and if so how would would I know what pitch I was turning without having to cut test runs. By the way I am new to the world of lathes.

Ron

[John CParticipant @johnc47954]

Hi Ron,

John Stevenson does a pair of gears that will let you cut most metric threads with your gearbox. He sells them here: **LINK** but it appears they are out of stock at present. The gears come with a chart to tell you what pitch you are cutting.

John

[JohnFParticipant @johnf59703]

Have a look at this thread it give some info.

**LINK**

Myford used to do a full conversion kit with a different quadrant and some extra changewheels, I will have a look at mine later and PM you

John

[Rufus RoughcutParticipant @rufusroughcut]

Hi Ron

Got this off the web ages ago for use without a gearbox and may be some of the other mewmbers could liken the 63 tooth gear convert position to you with a box, I'm led to belive it would be the biggest toothed gear you could fit within the gear covers without problems

I currently use an ML10 for screw cutting and fit a 127 tooth gear without the guards in place so no conversion Probs

I hope this helps

Barry

[Norman LortonParticipant @normanlorton75928]

Rufus, Ron mentions that he has a gearbox so he does not want to go changing the wheels driving that box.

Ron, the JohnF link above points to a thread that I started when I had the same question. All you need to do is have few different idler gears, for example sizes 20,21, 24, 25, 30, 33 and 34. The idler gear is fixed by screw to the one that meshes with the Tufnol gears for forward/reverse feed.

The 33 and 34 gears are unusual sizes and you can (usually) buy them from John Corden's link above. The other sizes are available from several Myford parts suppliers. John Stevenson should also suppy a chart detailing which idler gear works with what gearbox setting to obtain a close approximation to the BA or metric pitch desired. If you send a 'Message member' directly to me, quoting your email address, I will happily supply a copy of a spreadsheet (chart) that I worked out for the various settings and errors.

Norm.

[Rufus RoughcutParticipant @rufusroughcut]

Hi Ron

Sorry must have mis-interpreted your dilemma

Hi Norm

Thanks for that, but I'm a bit confused, isn't swapping idler gears the same sort of senario.

Rufus

[JohnFParticipant @johnf59703]

Ron, All above is correct but one thing you will also need is a slotted quadrant to accomodate the variouse change wheels.

The one in use with the gearbox has fixed centers for the gears used and you cannot use any other gears on this unit.

Regards John

[Norman LortonParticipant @normanlorton75928]

The issues of the best/easiest way to cut metric/BA have been discussed many times in this forum, but when I was asking the same questions as Ron a short while ago many people kindly answered, and so I am happy to repeat the perceived understanding on the topic in my own words. Incidentally, it is difficult to find threads of interest using the search window at the top of this page. I find it much better to go to Google and use a few choice words. The view that I feel most experienced users will express is as follows:-

1. If you do not have a gearbox then you have the fun of changing endless gears to obtain mostly any thread pitch you like and to reasonable precisions. You can use tiny 127 tooth gears, or bigger 63 tooth ones, or the Myford ingredient of mixing in 21 tooth gears. But you also have the fun of changing all these gears again every time you want a fine feed!

2. The delight of a gearbox is quickly selecting any imperial thread and being able to swap to a whole range of fine feeds in ten seconds. But without something else you cannot select metric/BA pitches.

3. To obtain metric/BA pitches, on a gearbox fitted lathe, Myford advised using the Metric Quadrant (that has slots) and a whole new range of loose gears. Once you have spent a lot of money obtaining these (if you can find a quadrant) you are back to all the fun of adding and removing gears every time, and you have lost the fine feed facility when the metric gear set is fitted. Some users estimate a 20-30 minute swap time! The benefit, however, is very precise metric pitches.

4.The easy way, on a gearbox fitted Myford, to get a good approximation to the metric/BA pitches is to swap the idler gear (normally 24T) for either a 20, 21, 25, 30, 33 or 34 gear. The last two have to be purchased specially and the the others are readily available. You then select the gearbox setting that gives the nearest approximation to your desired pitch, by looking it up in a table that someone has worked out. Typical pitch errors are 0.05 to 0.5% with the worst being 0.86%, but perfectly useable if up to ten threads are being engaged. The big benefit is that you can still instantly swap to fine feed, and the idler gear swap takes around 30 seconds.

Norm.

[Swarf, Mostly!Participant @swarfmostly]

Hi there, Norm,

Did you mean 'idler' or did you mean 'tumbler'?

Best regards,

Swarf, Mostly!

[Norman LortonParticipant @normanlorton75928]

Mmm, tumbler. Must have had idle thoughts.

[John Stevenson 1Participant @johnstevenson1]

Posted by John Corden on 15/04/2013 10:50:40:

Hi Ron,

John Stevenson does a pair of gears that will let you cut most metric threads with your gearbox. He sells them here: **LINK** but it appears they are out of stock at present. The gears come with a chart to tell you what pitch you are cutting.

John

Back in stock now lads.

[Author]

Posts