Adding 3rd stud to drummond

[NobbyParticipant @nobby]

Hi

I wanted a slower feed on my drummond lathe so I added a 3rd stud and arm. I tryed work out the feed per rev. ? but with no luck .By hand its about 3&1/2 thou per rev.

[NobbyParticipant @nobby]

[adyParticipant @ady]

Give us the geartrain numbers and we’ll figure it out for ya nobby.

 

eg

spindle20

1st 50/20= 20/2.5= 8teeth c/f

2nd  60/30= 8/2= 4 teeth c/f

3rd  60t leadscrew for final calc 60/4= 15x8tpi= 120tpi

 

1000/120= about 8.5 thou

 

a 100 tooth on the leadscrew would crank things right down

been at ra pub again tonite so e&oe…*hic*

 

 

Edited By ady on 17/02/2011 00:13:20

[adyParticipant @ady]

Is that an extra wee one on the top? a 30/20?

 

gives 180tpi= about 5.5 thou

 

small problemo though, the leadscrew will go backy wards.

[NobbyParticipant @nobby]

Hi ady

Thanks mate . I have had a better look this morning On the spindle/ mandrel is a 20

1st stud 30-20 2nd stud 50-20 3rd stud added 55-20 Leadscrew 60.

The 8 t.p.i leadscrew rotates forward . Its a bit warmer in the workshop today.

Nobby

 

 

[mgjParticipant @mgj]

Do the Drummonds not have a tumbler reverse lever for the leadscrew? If so, that would get round the problem quite easily – what was forwards becomes reverse and vice versa.

 

But you are right, the new set up will reverse rotation, so one will have to introduce an idler of any size somewhere in the train.

[adyParticipant @ady]

20×0.66= 13.3c/f

13.33/2.5= 5.33c/f

5.33/2.75= 1.94

 

60/1.94 = 30.93x8tpi= 247.5tpi

 

so a midgies thumb over 4 thou from the looks of it

Edited By ady on 17/02/2011 12:34:04

[NobbyParticipant @nobby]

Hi mgj & ady

It has not got a tumbler gear like my super 7 mk 1 The slot were the belt tension arm is you can fit an idle gear. I willl have another go with the calculater and work out the t.p.i from that I can get the feed per Rev

Cheers Nobby

[EddieParticipant @eddie]

Hi Nobby

Avoid the calculator, and the teethcounting…

Set up a clock gauge and turn the chuck 10 revolutions.

Take the reading on the clock gauge/ 10 that will give you the Thou/rev

Eddie

[mgjParticipant @mgj]

Well 4 thou per rev is a pretty useful general purpose feed for a decent finish, so it looks as that bit of it is sorted.

 

Just the idler gear then. Anywhere in the train Nobby, any size: it doesn’t affect the ratio at all

[AndyBParticipant @andyb47186]

Hi Nobby,

 

The jaws on the headstock (the second photo shows the bottom jaw at the top) are for mounting idlers and tumbler reverse.

 

The Drummond site has plans for one (you will have to register but it is well worth it; tons of info from like-minded people) There are also various plans for fine feed arrangements.

 

http://finance.groups.yahoo.com/group/drummondlathe/files/tumbler/

 

The tumbler reverse is worth its weight in gold so well worth making one if you can’t get an original.

 

Andy

[NobbyParticipant @nobby]

Hi Guys

Thank you all for input on this . I tried eddies idea 4 thou easy . I will get on website as A.B . mentioned . Back to scewcutting this lathe is great as it does not double up when you engage lever similar to the X lathe. Yesterday I cut 20 tpi with no problems. as you may have seen I fitted a 125 Micrometer dail on the leadscrew.

[mgjParticipant @mgj]

It looks in lovely condition Nobby – a credit to you.

[NobbyParticipant @nobby]

Hi Ady

Cheers Mate

To avoid drilling the casting for the brass zero line to keep as original I made a steel clip that just clips over. I made and fitted a micrometer dail to my Drummond hand shaper.

I have just bought a small Drummond Little Gooiath but just the basic bed head and tailstock. Its noy here yet . More problems ?

Nobby

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