screwcutting from a shoulder

[jacques maurelParticipant @jacquesmaurel42310]

watch the video: http://youtu.be/VPd-0ZH7E3c

J Maurel

[jacques maurelParticipant @jacquesmaurel42310]

screwcutting from left to right.

[Steve WithnellParticipant @stevewithnell34426]

Why?

[adyParticipant @ady]

Because it shows screwcutting from a shoulder

[JasonBModerator @jasonb]

Not a method to try if you have a screw on chuck and no method of locking it

[Speedy Builder5Participant @speedybuilder5]

Interesting, not setting the topslide to half the included angle ?

[Clive HartlandParticipant @clivehartland94829]

It was EN1 steel and appeared butter soft when cutting.

The thread cutting appeared to be’ interupted’ visually on the video to speed things up a bit.

 

Clive

[Steve WithnellParticipant @stevewithnell34426]

I’ve never “finished” a thread with a single point tool, always taken the last cut with a die to get the profile right. I am just being pedantic? My application is usually a model engine of some form or other.

 

To cut the piece on the video, I’d have used a parting off tool at the shoulder to create a concentric groove, then cut the thread conventionally left to right (then run a die down it…). I don’t see the benefit of the set up in the video. I expected the trick to be getting a good thread right upto the shoulder, which is something I haven’t worked out how to do.

 

 

[Steve WithnellParticipant @stevewithnell34426]

Oops should have written “right to left”!

 

[JasonBModerator @jasonb]

The main reason for doing it is to save that panic moment when you try to disengage the feed at the end of the cut before you run the tool into the sholder. Handy if you have a lathe with a fast slowest speed and a coarse pitch thread.

 

J

[Phil PParticipant @philp]

I must admit to having a bit of a smug snigger when I watched the video.

 

Now I have the Graham Meek single tooth dog clutch fitted, “panic moments” are a thing of the past, cutting threads up to shoulders is a breeze.

 

Just for reference I have clocked mine and it trips the feed and stops the cut within 0.005″ every time.

 

Phil

[jacques maurelParticipant @jacquesmaurel42310]

This method is I think the simplest one for screwcutting near a shoulder with a standard lathe, you need only a thread dial indicator, a carriage stop and a left hand tool. This method is described in the book: “screwcutting in the lathe” (by Martin Cleeve) p 80 (special application of the leadscrew indicator) of my 2003 reprint.

By far the best method for screwcutting near a shoulder is to use the « single tooth dog clutch » as described in the thread : « screwcutting simplified ». But making this attachment is a complex job and it must be customized for each lathe.

Other method: the “high speed screw cutting attachment” described in MEW N°168 uses an automatic quick opening of the half nuts, of course this is valuable only when the half nuts can be opened without losing the pitch. This attachment must also be customized for each lathe.

An universal attachment (requiring no customization) being able to stop the tool near the shoulder and even to retract it would be a good thing, does it exist?…..

[Hugh GilhespieParticipant @hughgilhespie56163]

An universal attachment (requiring no customization) being able to stop the tool near the shoulder and even to retract it would be a good thing, does it exist?…..

Think it’s called CNC

[John Stevenson 1Participant @johnstevenson1]

 

 

 

The speed at which one can screwcut on a manual lathe up to a shoulder, is directly proportional to the size of the operators sphincter muscle.

John S.

[chris stephensParticipant @chrisstephens63393]

Hi Robert,

“Interesting, not setting the topslide to half the included angle ?”

 

Why is it interesting, who in their right mind would bother to set the top slide over?

Despite the fact that a lot of “time served” were taught to do it, it really makes little or no difference to the end result.

I suppose I should add a caveat, if you are properly set up for screw cutting it makes little or no difference.

chriStephens

[Steve WithnellParticipant @stevewithnell34426]

So if I understand this correctly, if your sphincter isn’t twitching like a rabbit’s nose, then the feed rate isn’t high enough?

 

 

[jacques maurelParticipant @jacquesmaurel42310]

Some answers:

To Mr withnell: you can make a thread right upto a shoulder with this method like with a single tooth dog clutch, but the tool is starting from the shoulder.

To Mr Gilhespie: This attachment is for a standard lathe but yes the result is the same as with a CNC , the tool being retracted always at the same place!

To Mr Humphrey: the top slide is not moved but the tool is special with 15° rake angle and set at the helix angle (3° for a standard coarse iso thread). So it was possible to have a good result on FCMS with no lubricant (the video is clearer with no lubricant).

[Steve WithnellParticipant @stevewithnell34426]

M. maurel, la dernière personne à m’appeler Monsieur Withnell était mon proviseur quand j’étais dans le pétrin!

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