Member postings for jacques maurel

Some answers:

Big pain 1: 2mm lead is standard from the gear box.

Big pain 2: I use the thread dial indicator after each infeed so the delay for starting the cutting pass. From the infeed increasing you can see that there are not 6 videos sellotaped, only the 2 last (slow speed) are such.

Big pain 3: The tool is stopped and withdrawn (this is the purpose of this attachment) on a standard lathe. The result is like CNC.

This attachment was (is?) commercially available, called "Snap Tap" from a Swedish company (now Seco tool I think).

This link will work :**LINK**

Sorry I've made a mistake for the video link (while this attachment is of some interest)

Here is the good link: **LINK**

Do you know this threading attachment ? The tool is stopped and withdrawn just before the shoulder. This attachment is almost completely contained on a toolholder set in the toolpost. It’s not as efficient as the “single tooth dog clutch” but far easier to make and few costumization is necessary, whichever lathe you use. The result is like the one obtained on a CNC lathe, the tool is withdrawn always at the same place, no circular groove is made!
Video:

**LINK**

With the universal threading attachment (and the others variable lead attachments) it’s possible to use the “Thread dial indicator”, so it’s possible to open and close the “Half nuts”,(as you are using a standard thread from the gear box). This makes thread machining far easier!
It’s possible to work against a shoulder from left to right as described in this video:

**LINK**

The calculation is BC = 30/(p'/p-1) mm, p' being the lead to obtain and p the standard one.
Ex for p' = 20 TPI (1.27mm) and p = 1mm, BC = 111 mm (position 2).
The charts and graduations are here to help when setting the lathe for standard leads (imperial and module for a metric lead screw, metric and diametral pitch of an imperial one).
Almost any lead can be obtained within the range of the lathe gear box.

My attachment is quickly set up (contained on a toolhoder). Because for me the time for removing and resetting the top slide, is the same as the time for setting and resetting the banjo arm.

Ex : chart for machining module leads from a metric lead screw:

There are numbers stamped on the lever and charts are given so it's easy to cut any lead. On the photo (metric lead screw) one side of the groove is graduated for imperial leads, the other for module leads (for cutting single start worms). No change gear is needed, all cutting is from the standard gear box but the thread must be short (50 mm) read the article for details.

This was in ME issue 4270 (march april 2006) general view:

I've published a "universal threading attachment" almost completely contained on a toolholder, based on Thales theorema, point E being fixed and BC being adjustable:

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?.....

Edited By David Clark 1 on 17/08/2010 17:10:33