How would this lathe tool be used?

I often run a die down my coarser machine cut threads - unless the thread is one that I don’t have a die or chaser nut. Saves having to get that final cut at the right depth and with a good finish, while the thread will be dead straight aligned without worrying about a crooked start. Easier on the arms, as well as the die, for the larger diameter threads I deal with.

Neil Wyatt:

Thank you for taking the trouble to upgrade my link (Japanese fountain pen making); would you please remind me how this is done?

Good to know that it has been of interest, and not just on the chasing point.

When I first learned about single point thread cutting in the lathe, it was Whitworth threads, round root and crest, and a hand chaser was used to finish the thread.

In later years I have read of early thread cutting on the lathe using a hand held thread chaser to form the complete thread without the assistance of a lead screw(internal and external threads), I think I first saw this in the first volume of Model Engineer 1898.

Ian S C

On youtube click share and then embed.

You can ignore the various settings and use the defaults.

Copy the code and then in your posting click the 'YouTube' icon.

Paste the code in the box and then click OK, an 'iframe' box will appear in your post.

Once you have made your posting the video will be embedded.

The blue icon with <> on it to the right of the YouTube one can be used to embed other things like tweets etc. taht give you html 'embed' code when you click share.

I'm not entirely convinced that the two buttons do different things...

Neil

Neil Wyatt:

Thank you.

I think I have noticed in the past that after viewing an embedded video other, unwanted, videos are offered; is there a way to avoid this?

Hi a bit more info here on an older post relating to threads and truncating, mainly used on Whit form when cut by single point where the crest is truncated in place of the radius when a full form tool isn't available.

**LINK**

In particular look at the link by Jon Gibbs on his second post and page 34 in the BS84 standards relating to thread truncation.

Truncated threads were the norm in the aircraft industry in the 60's when many threads on difficult parts were all screwcut rather than with a die box etc. done many hundred's of them.

However as Robert says if the part is subject to high stress its best not to compromise on the root profile !

John

True, but better still to roll the thread rather than cut it at all, if that's the case.

One of my first engineering jobs was in a Nottingham factory that made jacking screw legs for articulated lorry trailers. The ones I was doing were inch-and-three-eighths 2-start Acme left hand. The thread rollers were fed 10 foot lengths of bar-turned steel, so quite large threads could be handled in this way.

I was quite surprised to note, when I added a Myford (Norton) gear box and new leadscrew to my ML7, that the leadscrew was thread rolled. That was in about '65.

Sam

Simple knurling is a less obvious use for thread chasers.

Allowing for the helix angle, grip the chaser sideways in the tool post. As here.

Rotate the work in 60° steps, each time shaving grooves across/along the workpiece.

If you don’t have a chaser, you can make one up using half of a screw thread as here.

The piece (half of a screw) could be glued in place or brazed. In this instance, a steel screw suitable hardened would last longer, but brazing would interfere with the degree of hardening.

In this photograph is one I prepared earlier - about twenty five years earlier.

Knurling the brass knob by the above method took only a couple of minutes. The red and the black knobs were commercial mouldings intended to be pressed onto Alan screw heads.

Regards,

Sam

Thanks replies and interesting digressions. I had assumed this was a hand made tool because of the engraving - but following up Bob Stevenson's suggestion I found a reference to Thomas Chatwin in Grace's Guide **LINK**. Is that the firm you were thinking of Bob? I couldn't find the distinctive Chatwin sig.

Anyhow, I now have a better idea of what the tool is meant for, and shall bung it back in the box, pending the need to cut a full form 22 TPI Whit thread. Which will happen in the next week or so if I see it as a useful lump of HSS and regrind it, but probably never if I leave it alone.

Robin

I thought the point of a chaser was to create a full profile thread?

One thing most of us can manage is running a hand chaser gently over a cut thread to tidy it up.

Neil

http://www.lathes.co.uk/chasescrewcutting/

MichaelG.

.

P.S. This, from Grace's Guide, looks promising:

https://www.gracesguide.co.uk/images/1/19/Im192001AE-Chat.jpg

... except, of course, that its inclusion of a 'pitch error compensating device' would presume the use of a single-point tool. 

Edited By Michael Gilligan on 21/10/2018 08:33:51

Well, I'd've thought that was the right way to do it - accurate, strong and wear-resistant.

Could be useful if you get an early Drummond as the cross-slide screw is 22 tpi. The awkward number not being considered a problem by the manufacturer as they didn't provide a dial, nor list 22tpi in the screwcutting chart although achievable with the gears provided.

A chaser is very useful for rounding BSW crests . If measuring the O.D. or "try to fit" BSW threads with sharp crests at nominal O.D. the result will be very loose fitting threads. Better to have the recommended alternative flat crest than sharp crests.

I think it's in the settings when you generate the embed code.

You will generally be offered things relevant to what you have seen before ... if you have cookies enabled.

Neil

... Posted By Mick B1

... Well, I'd've thought that was the right way to do it - accurate, strong and wear-resistant.

Yes Mick!

Another plus for Myford.

‘You'll See It When You Believe It’ - Wayne W. Dyer.

Regards,

Sam

Edited By Sam Stones on 21/10/2018 19:33:46

Really? Doesn't everyone do 'em that way? Quicker and cheaper as well as better, if you can justify the capital cost.

I have to smile at you fellows in the Myford Squad

There was a recent thread about a cracked Myford gear cover and owners were queuing up to say how they had repaired theirs. No one suggested the gear covers might not be 'fit for purpose'

Neil