Cutting metric threads

[rebekah andersonParticipant @rebekahanderson95322]

Yeah very fine. It allows me to turn bars automatically with a smooth finish.

so these are the ones to change. Am I right in saying its the last two: the driven one on the lead screw and the driver it's linked in to.

if so which ones. There are so many gears listed in each post i'm kinda lost which two gears to buy and insert. And which way round

[Roderick JenkinsParticipant @roderickjenkins93242]

Do you have any other gears apart from those on the lathe at present? If so, how many teeth does each one have?

[Sub MandrelParticipant @submandrel]

°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°

I'm forever blowing bubbles… thanks Bear!

Neil

[rebekah andersonParticipant @rebekahanderson95322]

I have no other apart from what's on the lathe.

As for bubbles, on ipad just press and hold 0 and you get °

[John Stevenson 1Participant @johnstevenson1]

Becky,

Slow down,

You are a member of the yahoo Myford group, go on there, get the manuals from the files section and take a read.

It's the last 4 gears you need to change but before that you need to get some gears.

[Brian WoodParticipant @brianwood45127]

Becky,

I don't want to interfere, but the Myford ML4 threading table I sent you by email gave you all the information you need for screwcutting in both Imperial and Metric. The gear set would have been 20×2, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 and one at 38 to give you 19TPI cutting for gas threads.

All these would be 14.5 degree Pressure Angle and 20DP. RDG sell suitable gears in their Myford shop

I don't have the booklet for ML2 but I'm willing to bet there was no change to those details with the later ML4.

It seems to me that you are short of most of those gears and just have the ones that give you a fine feed. Some more expense I'm afraid.

Brian

[rebekah andersonParticipant @rebekahanderson95322]

Ok i think i'm getting there.

Just one more thing.

Reading the chart, there is 1st and 2nd stud. If i logically worked backwards from the lead screw, i'd say the order of the gears would be the 2nd stud driving the lead screw and driven by the 1st stud. Which then is driven by the reverse selector gears which in turn is driven by the manderel gear.

If so, would the banjo be removed to fit a 60/65 set of gears?

[rebekah andersonParticipant @rebekahanderson95322]

This is the current set up.

 

Edited By rebekah anderson on 30/05/2013 12:31:06

[rebekah andersonParticipant @rebekahanderson95322]

No thats ok. I know i'm being mince. Just a lot of terms being used and not sure half the time what's what.

This is the chart I have. Just need to know which stud is which.

Edited By rebekah anderson on 30/05/2013 12:39:36

[Brian WoodParticipant @brianwood45127]

Hello Becky,

The stud logic is completely straight forward,

The lathe spindle gear is coupled through the tufnol tumbler reverse gears to drive an identically sized gear. on its own short shaft. These are probably 25 tooth gears. Linked to that by the short coupling wire is the one called Mandrel

Mandrel is the first gear in the chain. It then goes through 1st stud to 2nd stud and finally leadscrew.

You arrange gears as shown on your chart , idler gear being any size that fits the space, it has NO influence on the overall gear ratio, working as it does like a belt to take the drive. Compounded gears alter ratios.

I hope that helps you

Regards Brian.

[rebekah andersonParticipant @rebekahanderson95322]

So if we look at my drwing, the 12T needs to be changed to a 20T then the left 100T to a 50T and the 20T thats on the 100T remains the same. The lead screw changes from 100T to 55T

This would give me a pitch of 1.0

Edited By rebekah anderson on 30/05/2013 14:38:47

[JasonBModerator @jasonb]

Now I'm not a myford man so shoot me down if I am wrong but that table won't work on your ML2. As JS previously said you don't have two studs so this is basically what you have

[rebekah andersonParticipant @rebekahanderson95322]

Right so thats what i thought but every one was saying to reffer to the chart and saying about stud one and stud two along with listing a load of gears.

Now i don't have a clue any more what i need to do.

Can any one just use the drawing and annotate what gear i need to mount where.

Please please. I don't want to buy a load of gears only to use a couple. Rdg sells them induvidually so no problem there.

Will luv yah forever

[JasonBModerator @jasonb]

As you are going to have to buy some gears anyway why not buy a 127T as that can be used with your existing 20T and an idler to give your 0.5mm

 

On the mandrel change the existing 12T to a 20T. On the leadscrew fit a 127T and on the stud fit something to bridge the gap on stud No 1. This is refered to as a simple gear train as you don't have two gears on the same stud

Maths :

20/127 = 0.15748 of a turn of the leadscrew per turn of spindle

8tpi leadscrew gives 25.4 / 8 per turn or 3.175mm per turn

3.175 x 0.15748 = 0.4999999mm per rev of the lathe spindle

 

Do wait for someone else to confirm this before spending money on gears, I should think something like a 40T for the idler would be about right and by swapping the 20/40 positions you will be able to get 1.0mm pitch

 

Edited By JasonB on 30/05/2013 15:39:52

[Michael GilliganParticipant @michaelgilligan61133]

It actually depends which calculator you use

… We have trodden this path before.

The answer to Jason's calculation is really 0.5

MichaelG.

 

Edit: corrected typo

Edited By Michael Gilligan on 30/05/2013 15:21:06

[JasonBModerator @jasonb]

Yes its because I knocked off the last few digits of the 20/127 ratio

Edited By JasonB on 30/05/2013 15:22:46

[Brian WoodParticipant @brianwood45127]

Becky,

My apologies, I was quoting from the ML4 table which did have a 2nd stud. Jason is helping more than I am but his answer above gives a 0.5mm thread

If you run 40/127 it will give the ratio you want for M6 [1mm pitch]

Sorry for the confusion, Myford changed more than I expected between the ML2 and ML4 which was the lathe of my experience.

Just one small point, do you have room on the leadscrew without fouling the swarf tray for a gear of 127 teeth? It will be 6.35 inches diameter.

Regards Brian

[Anonymous]

It's easier to use integer arithmetic – no calculator needed.

Andrew

[JasonBModerator @jasonb]

Posted by Brian Wood on 30/05/2013 15:25:00:

If you run 40/127 it will give the ratio you want for M6 [1mm pitch]

Brian, Becky wants metric fine M6x0.5, see her opening post.

Becky if you can let me know the centre distance between the Mandrel and lead screw I should be able to work out the gap and what the minimum tooth gear needed would be.

J

[Brian WoodParticipant @brianwood45127]

I think it would be best if I just get back in my box!! A case of reading what one expects. Sorry to all

Gear size for 127 Teeth is still valid

Regards Brian

[rebekah andersonParticipant @rebekahanderson95322]

sorry brian, my fault.

I was using the chart as an example to confirm if I understood it all. It didn't have 0.5 on it so I went for the 1.0

also the 0.75 was more confusing to me with massive gears.

thank you guys. I think we are getting there. I will check to see if a 127 gear can fit in. I think it might.

cheers

[JasonBModerator @jasonb]

Looking at your lathe again it may be a bit tight to fit a 127T in which case the two 21T option JS suggested may be better

21T on the mandrel driving a 35 on the stud, also on the stud and keyed to the 35T fit another 21T to drive an 80T on the leadscrew.

Maths

21 / 35 = 0.6

21 / 80 = 0.2625

0.6 x 0.2625 = 0.1575

0.1575 x 3.175 = 0.50006mm pitch

[John Stevenson 1Participant @johnstevenson1]

127 has an OD of 6.45 but another problem i can see is that becky has the 12/30 fine feed gear which is a one piece gear.

You can't remove the 12T to replace with any other, she needs one of these.

[Ady1Participant @ady1]

Everything is TPI (threads per inch) even on the planet Zog TPI works

Once you "think you've set it up" use a digital caliper to confirm your setup

So for a 1mm thread you jam the caliper between the carriage and the headstock area and turn your headstock, by hand, 25.4 times

If the caliper reading for the carriage movement isn't an inch(or v close) then there's an error

If your using metric(ugh) then use the same caliper check system for those continental mm thingys

(If you have a DRO setup then it's a doddle)

Edited By Ady1 on 30/05/2013 17:59:22

Edited By Ady1 on 30/05/2013 18:25:39

[Ady1Participant @ady1]

There's a simple changewheels calculator I wrote here

This can be used on any standard Headstock->Banjo->Banjo->Leadscrew hobby lathe

 

 

Edited By Ady1 on 30/05/2013 18:20:38

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