#### Single Point Left Hand Threading

Al Costich

My copy of HTRAL says, "In cutting  left hand threads the lathe is set up exactly as for
cutting right hand threads, except that the lathe must be arranged to feed from left to
right  when the spindle is revolving forward."
I found a sketch in my copy that shows the compound swung 29 degrees toward the tail stock.
That seems contrary to having the compound swung 29 to the head stock.
However, it seem more logical in that the feed in the compound  would then be correct.

So what's correct?

Thanks.

Alan

Ted

As you advance feed on the compound you want to move the tool into the side of the thread that is getting the bulk of the cut. So, towards the tail stock for left hand thread and towards the head stock for right hand thread.

Ted

Guenther Paul

You can through that book away American and metric thread is 60 degree not 58 you set the compound on 30 degree.
The British withworth thread is 55 degree

GP

On Sunday, March 7, 2021, 07:45:28 AM EST, Al Costich <alcostich@...> wrote:

My copy of HTRAL says, "In cutting  left hand threads the lathe is set up exactly as for
cutting right hand threads, except that the lathe must be arranged to feed from left to
right  when the spindle is revolving forward."
I found a sketch in my copy that shows the compound swung 29 degrees toward the tail stock.
That seems contrary to having the compound swung 29 to the head stock.
However, it seem more logical in that the feed in the compound  would then be correct.

So what's correct?

Thanks.

Alan

m. allan noah

On Sun, Mar 7, 2021 at 8:24 AM Guenther Paul <paulguenter@att.net> wrote:

You can through that book away American and metric thread is 60 degree not 58 you set the compound on 30 degree.
The British withworth thread is 55 degree

Sigh. Think about it. The angle of the compound in-feed does not set
the angle of the thread- the shape of the tool does. The 29 degree
thing is so you always cut a little on the back side, leaving a clean
flank, but do the bulk of the cutting in a direction that keeps the
backlash taken up in the compound. So, the angle does not matter at
all. I thread with the cross feed going straight in, and don't touch
the compound at all, regardless of handedness. I certainly don't make
a 0 degree thread :)

allan

--
"well, I stand up next to a mountain- and I chop it down with the edge
of my hand"

Steve Wells

Saving subject posts for the FTE webpage...:)

Correct, the SBL automatic feed screw machine threads
at 0 degrees, straight in, in both directions, reversing the
spindle and leadscrew direction on front and rear tool bit passes.
Another little strange fact, at the minor flat of the acme thread,
the SBL print has a 0.010 depth square clearance cut. This is cut
by the front "rougher bit" flank minor, which has this square flank extension profile.

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of m. allan noah
Sent: Sunday, March 7, 2021 9:06 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

On Sun, Mar 7, 2021 at 8:24 AM Guenther Paul <paulguenter@att.net> wrote:

You can through that book away American and metric thread is 60 degree not 58 you set the compound on 30 degree.
The British withworth thread is 55 degree

Sigh. Think about it. The angle of the compound in-feed does not set the angle of the thread- the shape of the tool does. The 29 degree thing is so you always cut a little on the back side, leaving a clean flank, but do the bulk of the cutting in a direction that keeps the backlash taken up in the compound. So, the angle does not matter at all. I thread with the cross feed going straight in, and don't touch the compound at all, regardless of handedness. I certainly don't make a 0 degree thread :)

allan

--
"well, I stand up next to a mountain- and I chop it down with the edge of my hand"

Steve Wells

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of Steve Wells
Sent: Sunday, March 7, 2021 9:45 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

Saving subject posts for the FTE webpage...:)

Correct, the SBL automatic feed screw machine threads at 0 degrees, straight in, in both directions, reversing the spindle and leadscrew direction on front and rear tool bit passes.
Another little strange fact, at the minor flat of the acme thread, the SBL print has a 0.010 depth square clearance cut. This is cut by the front "rougher bit" flank minor, which has this square flank extension profile.

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of m. allan noah
Sent: Sunday, March 7, 2021 9:06 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

On Sun, Mar 7, 2021 at 8:24 AM Guenther Paul <paulguenter@att.net> wrote:

You can through that book away American and metric thread is 60 degree not 58 you set the compound on 30 degree.
The British withworth thread is 55 degree

Sigh. Think about it. The angle of the compound in-feed does not set the angle of the thread- the shape of the tool does. The 29 degree thing is so you always cut a little on the back side, leaving a clean flank, but do the bulk of the cutting in a direction that keeps the backlash taken up in the compound. So, the angle does not matter at all. I thread with the cross feed going straight in, and don't touch the compound at all, regardless of handedness. I certainly don't make a 0 degree thread :)

allan

--
"well, I stand up next to a mountain- and I chop it down with the edge of my hand"

ww_big_al

Marc (That Lazy Machinist) put up a good video explaining compound rest threading angles. He was an industrial arts instructor at a Canadian college.
Al

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of Steve Wells
Sent: Sunday, March 7, 2021 9:50 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

https://youtu.be/9P-Qqc0uGyM

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of Steve Wells
Sent: Sunday, March 7, 2021 9:45 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

Saving subject posts for the FTE webpage...:)

Correct, the SBL automatic feed screw machine threads at 0 degrees, straight in, in both directions, reversing the spindle and leadscrew direction on front and rear tool bit passes.
Another little strange fact, at the minor flat of the acme thread, the SBL print has a 0.010 depth square clearance cut. This is cut by the front "rougher bit" flank minor, which has this square flank extension profile.

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of m. allan noah
Sent: Sunday, March 7, 2021 9:06 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

On Sun, Mar 7, 2021 at 8:24 AM Guenther Paul <paulguenter@att.net> wrote:

You can through that book away American and metric thread is 60 degree not 58 you set the compound on 30 degree.
The British withworth thread is 55 degree

Sigh. Think about it. The angle of the compound in-feed does not set the angle of the thread- the shape of the tool does. The 29 degree thing is so you always cut a little on the back side, leaving a clean flank, but do the bulk of the cutting in a direction that keeps the backlash taken up in the compound. So, the angle does not matter at all. I thread with the cross feed going straight in, and don't touch the compound at all, regardless of handedness. I certainly don't make a 0 degree thread :)

allan

--
"well, I stand up next to a mountain- and I chop it down with the edge of my hand"

Steven H

https://youtu.be/FRa5An0i_sM

This is MrPete222 You Tube video link for cutting EXTERNAL left hand thread. You can find other videos on You Tube. Are you cutting and external or internal thread?

On Mar 7, 2021, at 9:06 AM, m. allan noah <kitno455@...> wrote:

﻿On Sun, Mar 7, 2021 at 8:24 AM Guenther Paul <paulguenter@...> wrote:

You can through that book away American and metric thread is 60 degree not 58 you set the compound on 30 degree.
The British withworth thread is 55 degree

Sigh. Think about it. The angle of the compound in-feed does not set
the angle of the thread- the shape of the tool does. The 29 degree
thing is so you always cut a little on the back side, leaving a clean
flank, but do the bulk of the cutting in a direction that keeps the
backlash taken up in the compound. So, the angle does not matter at
all. I thread with the cross feed going straight in, and don't touch
the compound at all, regardless of handedness. I certainly don't make
a 0 degree thread :)

allan

--
"well, I stand up next to a mountain- and I chop it down with the edge
of my hand"

sblatheman

Steve,
FYI: there were only 2 special crossfeed screw machines at the SBL plant.
There were 3 or 4 of a similar design for leadscrews.

Ted

On Mar 7, 2021, at 9:50 AM, Steve Wells <wswells@earthlink.net> wrote:

﻿https://youtu.be/9P-Qqc0uGyM

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of Steve Wells
Sent: Sunday, March 7, 2021 9:45 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

Saving subject posts for the FTE webpage...:)

Correct, the SBL automatic feed screw machine threads at 0 degrees, straight in, in both directions, reversing the spindle and leadscrew direction on front and rear tool bit passes.
Another little strange fact, at the minor flat of the acme thread, the SBL print has a 0.010 depth square clearance cut. This is cut by the front "rougher bit" flank minor, which has this square flank extension profile.

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of m. allan noah
Sent: Sunday, March 7, 2021 9:06 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

On Sun, Mar 7, 2021 at 8:24 AM Guenther Paul <paulguenter@att.net> wrote:

You can through that book away American and metric thread is 60 degree not 58 you set the compound on 30 degree.
The British withworth thread is 55 degree

Sigh. Think about it. The angle of the compound in-feed does not set the angle of the thread- the shape of the tool does. The 29 degree thing is so you always cut a little on the back side, leaving a clean flank, but do the bulk of the cutting in a direction that keeps the backlash taken up in the compound. So, the angle does not matter at all. I thread with the cross feed going straight in, and don't touch the compound at all, regardless of handedness. I certainly don't make a 0 degree thread :)

allan

--
"well, I stand up next to a mountain- and I chop it down with the edge of my hand"

Steve Wells

Thanks Ted, I'll correct that.
That means it is the only one left, and I have the saddle off the other one.
I keep breaking the old style finisher bit, my fault, not the machine, but
I might have to switch over to the carbide tool holders as you suggested.
I found the print for them in the big book.
On a different note, are you about out of felt yet?
I am close, so I'll probably submit an order this month.
Also ECL (Roy Dean) spec'ed for me, an upgraded replacement grease
for DE-112, SBL-CE1625. can you remember those Roy Dean tubes?
Were they 2 oz? I'm trying to nail down what the fill quantity is.
I'll send you some of the new grease to try when it arrives.

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of sblatheman via groups.io
Sent: Sunday, March 7, 2021 10:25 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

Steve,
FYI: there were only 2 special crossfeed screw machines at the SBL plant.
There were 3 or 4 of a similar design for leadscrews.

Ted

On Mar 7, 2021, at 9:50 AM, Steve Wells <wswells@earthlink.net> wrote:

﻿https://youtu.be/9P-Qqc0uGyM

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of Steve Wells
Sent: Sunday, March 7, 2021 9:45 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

Saving subject posts for the FTE webpage...:)

Correct, the SBL automatic feed screw machine threads at 0 degrees, straight in, in both directions, reversing the spindle and leadscrew direction on front and rear tool bit passes.
Another little strange fact, at the minor flat of the acme thread, the SBL print has a 0.010 depth square clearance cut. This is cut by the front "rougher bit" flank minor, which has this square flank extension profile.

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of m. allan noah
Sent: Sunday, March 7, 2021 9:06 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

On Sun, Mar 7, 2021 at 8:24 AM Guenther Paul <paulguenter@att.net> wrote:

You can through that book away American and metric thread is 60 degree not 58 you set the compound on 30 degree.
The British withworth thread is 55 degree

Sigh. Think about it. The angle of the compound in-feed does not set the angle of the thread- the shape of the tool does. The 29 degree thing is so you always cut a little on the back side, leaving a clean flank, but do the bulk of the cutting in a direction that keeps the backlash taken up in the compound. So, the angle does not matter at all. I thread with the cross feed going straight in, and don't touch the compound at all, regardless of handedness. I certainly don't make a 0 degree thread :)

allan

--
"well, I stand up next to a mountain- and I chop it down with the edge of my hand"

Ondrej Krejci

Greetings,

The idea of feeding the threading bit one degree less than the smallest half angle towards the direction of cutting:  29° for 60°, 26.5° for 55°, 0.5° or 14° for most butress types; is that the tensioned side will be rougher, slightly scraped by the back side of the bit and have a lower tendency to loosen.
Otherwise, one can feed in with the cross slide with an undersized tool, almost sharp tipped in case of V-type threads, then, having the compound set parallel to the ways, take side to side passes to achieve size and make both flanks shiny.

Enjoy,

OK

On Sunday, March 7, 2021, 11:05:15 AM EST, Steve Wells <wswells@...> wrote:

Thanks Ted, I'll correct that.
That means it is the only one left, and I have the saddle off the other one.
I keep breaking the old style finisher bit, my fault, not the machine, but
I might have to switch over to the carbide tool holders as you suggested.
I found the print for them in the big book.
On a different note, are you about out of felt yet?
I am close, so I'll probably submit an order this month.
Also ECL (Roy Dean) spec'ed for me, an upgraded replacement grease
for DE-112, SBL-CE1625. can you remember those Roy Dean tubes?
Were they 2 oz? I'm trying to nail down what the fill quantity is.
I'll send you some of the new grease to try when it arrives.

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of sblatheman via groups.io
Sent: Sunday, March 7, 2021 10:25 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

Steve,
FYI:  there were only 2 special crossfeed screw machines at the SBL plant.
There were 3 or 4 of a similar design for leadscrews.

Ted

> On Mar 7, 2021, at 9:50 AM, Steve Wells <wswells@...> wrote:
>
> ﻿https://youtu.be/9P-Qqc0uGyM
>
> Steve
>
>
> -----Original Message-----
> From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of Steve Wells
> Sent: Sunday, March 7, 2021 9:45 AM
> To: SouthBendLathe@groups.io
> Subject: Re: [SouthBendLathe] Single Point Left Hand Threading
>
> Saving subject posts for the FTE webpage...:)
>
> Correct, the SBL automatic feed screw machine threads at 0 degrees, straight in, in both directions, reversing the spindle and leadscrew direction on front and rear tool bit passes.
> Another little strange fact, at the minor flat of the acme thread, the SBL print has a 0.010 depth square clearance cut. This is cut by the front "rougher bit" flank minor, which has this square flank extension profile.
>
> Steve
>
>
> -----Original Message-----
> From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of m. allan noah
> Sent: Sunday, March 7, 2021 9:06 AM
> To: SouthBendLathe@groups.io
> Subject: Re: [SouthBendLathe] Single Point Left Hand Threading
>
>> On Sun, Mar 7, 2021 at 8:24 AM Guenther Paul <paulguenter@...> wrote:
>>
>> You can through that book away American and metric thread is 60 degree not 58 you set the compound on 30 degree.
>> The British withworth thread is 55 degree
>>
>
>
> Sigh. Think about it. The angle of the compound in-feed does not set the angle of the thread- the shape of the tool does. The 29 degree thing is so you always cut a little on the back side, leaving a clean flank, but do the bulk of the cutting in a direction that keeps the backlash taken up in the compound. So, the angle does not matter at all. I thread with the cross feed going straight in, and don't touch the compound at all, regardless of handedness. I certainly don't make a 0 degree thread :)
>
> allan
>
> --
> "well, I stand up next to a mountain- and I chop it down with the edge of my hand"
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>

sblatheman

Steve,
The tubes were 1 1/2 oz. (see picture from my 1967 catalog)
I will send you an email later today.

Ted

On Mar 7, 2021, at 11:05 AM, Steve Wells <wswells@earthlink.net> wrote:

﻿Thanks Ted, I'll correct that.
That means it is the only one left, and I have the saddle off the other one.
I keep breaking the old style finisher bit, my fault, not the machine, but
I might have to switch over to the carbide tool holders as you suggested.
I found the print for them in the big book.
On a different note, are you about out of felt yet?
I am close, so I'll probably submit an order this month.
Also ECL (Roy Dean) spec'ed for me, an upgraded replacement grease
for DE-112, SBL-CE1625. can you remember those Roy Dean tubes?
Were they 2 oz? I'm trying to nail down what the fill quantity is.
I'll send you some of the new grease to try when it arrives.

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of sblatheman via groups.io
Sent: Sunday, March 7, 2021 10:25 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

Steve,
FYI: there were only 2 special crossfeed screw machines at the SBL plant.
There were 3 or 4 of a similar design for leadscrews.

Ted

On Mar 7, 2021, at 9:50 AM, Steve Wells <wswells@earthlink.net> wrote:

﻿https://youtu.be/9P-Qqc0uGyM

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of Steve Wells
Sent: Sunday, March 7, 2021 9:45 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

Saving subject posts for the FTE webpage...:)

Correct, the SBL automatic feed screw machine threads at 0 degrees, straight in, in both directions, reversing the spindle and leadscrew direction on front and rear tool bit passes.
Another little strange fact, at the minor flat of the acme thread, the SBL print has a 0.010 depth square clearance cut. This is cut by the front "rougher bit" flank minor, which has this square flank extension profile.

Steve

-----Original Message-----
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of m. allan noah
Sent: Sunday, March 7, 2021 9:06 AM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Single Point Left Hand Threading

On Sun, Mar 7, 2021 at 8:24 AM Guenther Paul <paulguenter@att.net> wrote:
You can through that book away American and metric thread is 60 degree not 58 you set the compound on 30 degree.
The British withworth thread is 55 degree

Sigh. Think about it. The angle of the compound in-feed does not set the angle of the thread- the shape of the tool does. The 29 degree thing is so you always cut a little on the back side, leaving a clean flank, but do the bulk of the cutting in a direction that keeps the backlash taken up in the compound. So, the angle does not matter at all. I thread with the cross feed going straight in, and don't touch the compound at all, regardless of handedness. I certainly don't make a 0 degree thread :)

allan

--
"well, I stand up next to a mountain- and I chop it down with the edge of my hand"

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