Topics

Need help internal threading 13" SB lathe 1 7/8" spindle

Rolland Sicard
 

Need DETAILED advice on working with backlash on the compound and cross-slide when cutting internal threads on a backplate for 3 jaw chuck.  Need something step by step to by.  Please advise.  Thanks.

Newbie to cutting threads on 13" SB lathe.

Steven H
 

Do you have a copy of the South Bend book “How to Run a Lathe” or Atlas Press Company’s “Manual of Lathe Operation”? Both of those books will show you how to set up for internal threading. These books are available online , eBay, Amazon. Regarding backlash, depending on which way you are moving the respective slide (cross slide or compound) you need to move well past past zero (say half a turn) and then turn the handle the opposite direction to come back to zero to remove the backlash. I always like to have the compound gib snug unless I am using the compound to turn a taper. Also, if you haven’t tried threading before, try doing some practice threading first before tackling a critical project such as the internal thread on your chuck backplate. Also check You Tube for ‘internal threading on a lathe’ videos. One good You Tube instructor is MrPete222, he is a retired shop teacher. Good luck.

Steve Haskell

On Jan 26, 2019, at 5:14 PM, Rolland Sicard via Groups.Io <rolland.sicard@...> wrote:

Need DETAILED advice on working with backlash on the compound and cross-slide when cutting internal threads on a backplate for 3 jaw chuck.  Need something step by step to by.  Please advise.  Thanks.

Newbie to cutting threads on 13" SB lathe.

Flash Gordon
 

I am sure there are detailed videos on You-tube.

EdS

On 1/26/2019 5:14 PM, Rolland Sicard via Groups.Io wrote:
Need DETAILED advice on working with backlash on the compound and cross-slide when cutting internal threads on a backplate for 3 jaw chuck.  Need something step by step to by.  Please advise.  Thanks.

Newbie to cutting threads on 13" SB lathe.

Guenther Paul
 

Have you cut out side threads ?  What is the size of the thread ? Do you know the thread depth ? I will help you

GP


On Saturday, January 26, 2019, 7:48:27 PM EST, Flash Gordon <eschwerkolt@...> wrote:


I am sure there are detailed videos on You-tube.

EdS

On 1/26/2019 5:14 PM, Rolland Sicard via Groups.Io wrote:
Need DETAILED advice on working with backlash on the compound and cross-slide when cutting internal threads on a backplate for 3 jaw chuck.  Need something step by step to by.  Please advise.  Thanks.

Newbie to cutting threads on 13" SB lathe.

Jim_B
 

I am going to assume that you are not too familiar with ID threading.

It’s a bit different than OD and you need to prepare the work.

You said 1-7/8 spindle. I assume, from my data that its an 8-tpi thread.

The pitch of that thread is 0.125”. The Double Depth is 0.160”  The diameter you want to bore for the threads is 1.740 to 1.754.

You will need a step, for thread relief, of 1.875 on the input to the threads and, if its not a through hole a step one the end of the threads. I would make the exit step at least two turns, for your 8tpi thread that’s 0.250” I would make the input step the same if you have room.

 

 

Here is a picture of an input relief for a 2-1/4 8 thread. If you look carefully you can see both the input and output relief.  It’s better if the input step has an angle.

Now you have three backlashes to worry about. The compound, the cross feed and the leadscrew.

I assume you have turned the workpiece and it is true to the spindle.

You need an ID threading tool. Could be a threading tool mounted on a boring bar or one like in the second picture. Boring bar makes it nice and ridged.

If you are threading to a step, you will also need some way to measure the threading tool depth as you are threading.

I like to use a way mounted DI.

 

The compound should be set at 60 degrees.

Making sure the compound is fully engaged on the ways and roughly centered in the opening, turn the compound dial two or three turns clockwise, then two or three turns COUNTER CLOCKWISE.

Set the scale to zero. From this point NEVER turn the compound clockwise until the thread is cut.  (This removes backlash in the compound.)

 

Next bring the saddle toward the work. Center the tool, at the beginning in the thread area. (It helps to coat the thread area with dye. )

Adjust your DI or however you will measure the depth so you know when to stop threading.

With the lathe running, on the slowest speed, no feed and SLOWLEY turning the cross feed COUNTER clockwise watch for the tool to JUST touch the thread area. (By starting in  the middle, or at least 1 full turn of the dial away from the surface, you have removed cross feed lash. ) Stop the lathe and set the dial on the cross feed to ZERO. Rotate the cross feed CLOCKWISE ONE turn.

Back the saddle away from the work ¼”. (This allows room to remove backlash in the leadscrew.)

Rotate the cross feed COUNTERCLOCKWISE to zero.

Rotate the compound COUNTERCLOCKWISE to 0.0025”

Start the lathe, wait for the thread dial to come to a number.

Engage feed and take your first pass.

STOP  the feed when you reach your depth.

Turn the cross feed one full turn CLOCKWISE.

Back the saddle away from the work so there is ¼” of travel between the work and the tool.

 

Now is a good time to check the thread pitch with a scale to insure you set the feed up properly.)

 

Return the cross feed dial COUNTERCLOCKWISE to zero.

Advance the compound COUNTERCLOCKWISE to 0.005”

Start the lathe and when you Thread dial comes around to your number or line engage the feed.

STOP when your tool has cleared the thread area. Stop the lathe.

Back the tool out of the thread by turning the cross feed 1 full turn CLOCKWISE.

Move the saddle back so the tool clears the work by ¼”

At this point  I take a free pass. DONOT  advance the compound.

Return the cross feed to zero by turning COUNTERCLOCKWISE.

Start the lathe. When you thread dial comes around to your number/line engage feed.

Stop at the end of the cut. Stop the lathe Back out the cross feed 1 full turn.  Move the saddle out leaving ¼” gap to the work.

Repeat the above 9 more times. ( this will give you a thread depth of 0.020”. You need a depth around 0.080”

 

Because you are moving at 60 degrees it’s really 0.080/.866 = 0.092” indicated on the compound dial.

 

You should now advance at a slower rate,  0.0015/0.0015/0, for 10 more times and then 0.001/0.001/0 until you have  a depth on your compound of 0.080.

You now need a test fit.

If its tight try a few more “Free” passes. Still tight advance in steps of 0.0005 with several free passes.

Should look like this.

 

 

That picture shows a shop made ID threading tool

 

This is an ER-40 collet chuck for the Heavy 10.

 

If you screw up the first time Its OK. Been there, Done that.

 

Best to try on a blank of any kind.

 

Jim B.

 

From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of Rolland Sicard via Groups.Io
Sent: Saturday, January 26, 2019 5:15 PM
To: SouthBendLathe@groups.io
Subject: [SouthBendLathe] Need help internal threading 13" SB lathe 1 7/8" spindle

 

Need DETAILED advice on working with backlash on the compound and cross-slide when cutting internal threads on a backplate for 3 jaw chuck.  Need something step by step to by.  Please advise.  Thanks.

 

Newbie to cutting threads on 13" SB lathe.


Virus-free. www.avast.com

--
Jim B

Steven H
 

Excellent write-up on internal threading technique Jim B.

Steve Haskell

Jim_B
 

Thanks Steve

Sent from my iPhone-8
Jim B,

On Jan 26, 2019, at 9:17 PM, Steven H via Groups.Io <stevesmachining=aol.com@groups.io> wrote:

Excellent write-up on internal threading technique Jim B.

Steve Haskell


--
Jim B

druid_noibn
 

Hi Jim,

Well Done - good details and picts - Many thanks.

Kind regards,
DBN aka John

Jim_B
 

Thanks John. 
It is a tedious process and requires a lot of concentration but once you get into the swing it goes fast. 

-8
Jim B,

On Jan 26, 2019, at 9:49 PM, druid_noibn via Groups.Io <druid_noibn@...> wrote:

Hi Jim,

Well Done - good details and picts - Many thanks.

Kind regards,
DBN aka John

--
Jim B

Guenther Paul
 

On Saturday, January 26, 2019, 9:54:33 PM EST, Jim_B <jim@...> wrote:


Thanks John. 
It is a tedious process and requires a lot of concentration but once you get into the swing it goes fast. 

-8
Jim B,

On Jan 26, 2019, at 9:49 PM, druid_noibn via Groups.Io <druid_noibn@...> wrote:

Hi Jim,

Well Done - good details and picts - Many thanks.

Kind regards,
DBN aka John

--
Jim B

Jim_B
 

Oops I said “Set compound at 60 degrees”

Incorrect

SET COMPOUND AT 30 degrees.


Sent from my iPhone-8
Jim B,


--
Jim B

Jim_B
 

I was thinking of the 60 degree V on UNC and Metric threads.
My Bad

Sent from my iPhone-8
Jim B,

On Jan 26, 2019, at 10:29 PM, Jim_B <@Jim_B> wrote:

Oops I said “Set compound at 60 degrees”

Incorrect

SET COMPOUND AT 30 degrees.


Sent from my iPhone-8
Jim B,


--
Jim B


--
Jim B

Bill Libecap
 

Thanks for such a detailed explanation

carbure2003
 

THis video is one of the best on youtube on internal threading ......explanatoins are simple.
 
when threading, compound feed motion has to be in direction of the feed. It is why the compound is oriented this way.  
 
When I do internal threading, I keep the compound in the same position as for external threading.  My variant is that I put the threading tool upside down ( rotation 180 degree of the boring bar)
Instead of touching the materiel on the side seen in the video, I touch on the far side, visible section of the work piece for the operator. The advantage is that you can see a portion of what you are doing. The other advantage is that if you are mastering external threading, you don’t have to change your sequence of motion..... direction of advance on compound, and retraction direction on the cross slide. It also keeps the compound away from the chuck. In some cases it can be close, when working on small stuff. If you re install a threaded piece for re work it is easier to catch back the thread position.
 
smallest I have done internal threading is 1/4-40,  limited to the size of my small threading tool.
 
I have seen a video on youtube of a guy threading something of the size of M4 thread.
 
 
 
Guy Cadrin

---------- Original Message ----------
From: "Guenther Paul" <paulguenter@...>
To: <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] Need help internal threading 13" SB lathe 1 7/8" spindle
Date: Sun, 27 Jan 2019 03:22:57 +0000 (UTC)

Jim
Here is a you-tube I dont like his presentation watch it and we can go from there
 
 
 
 
GP
 
 
On Saturday, January 26, 2019, 9:54:33 PM EST, Jim_B <jim@...> wrote:
 
 
Thanks John. 
It is a tedious process and requires a lot of concentration but once you get into the swing it goes fast. 

-8
Jim B,

On Jan 26, 2019, at 9:49 PM, druid_noibn via Groups.Io <druid_noibn@...> wrote:

Hi Jim,
 
Well Done - good details and picts - Many thanks.
 
Kind regards,
DBN aka John

--
Jim B


____________________________________________________________
What Popcorn Really Does To Your Memory
clearstateofmind.com
http://thirdpartyoffers.netzero.net/TGL3242/5c4dad202114c2d1f0a0ast02vuc
SponsoredBy Content.Ad

ww_big_al
 

[ARK] Here is another very good YouTube video by Joe Pi that demonstrates Guy’s method below. Joe  has several good threading videos. Just search his channel with the word threading.

 (

Joe Pieczynski

 

https://www.youtube.com/watch?v=k1DHKjMtdQw

 

That Lazy Machinist also has good explanations. He is a retired French Canadian teacher and his web site has both French & English version. Here is his web site. About half way down is threading. He also posts his videos on YouTube.

http://www.thatlazymachinist.com/free-training.html

Al Knack

 

 

 

THis video is one of the best on youtube on internal threading ......explanatoins are simple.

 

when threading, compound feed motion has to be in direction of the feed. It is why the compound is oriented this way.  

 

When I do internal threading, I keep the compound in the same position as for external threading.  My variant is that I put the threading tool upside down ( rotation 180 degree of the boring bar)

Instead of touching the materiel on the side seen in the video, I touch on the far side, visible section of the work piece for the operator. The advantage is that you can see a portion of what you are doing. The other advantage is that if you are mastering external threading, you don’t have to change your sequence of motion..... direction of advance on compound, and retraction direction on the cross slide. It also keeps the compound away from the chuck. In some cases it can be close, when working on small stuff. If you re install a threaded piece for re work it is easier to catch back the thread position.

 

smallest I have done internal threading is 1/4-40,  limited to the size of my small threading tool.

 

I have seen a video on youtube of a guy threading something of the size of M4 thread.

 

 

 

Guy Cadrin



carbure2003
 


Joe is cutting with the tip of the tool up, lathe revolving in reverse.
 
I have the tip of the tool facing down with spindle running in forward direction.  
 
Running lathe in reverse direction can be dangerous as chucks may become loose on threaded spindles like SB lathes.
 
Joe’s method allows faster cutting speeds.
 
Guy
Please note: message attached

From: "ww_big_al" <arknack@...>
To: <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] Need help internal threading 13" SB lathe 1 7/8" spindle
Date: Sun, 27 Jan 2019 08:29:21 -0500



____________________________________________________________
What Popcorn Really Does To Your Memory
clearstateofmind.com
http://thirdpartyoffers.netzero.net/TGL3242/5c4dc6e31fc0b46e220d5st04vuc
SponsoredBy Content.Ad

Steven Schlegel
 

Yes, thanks for the details! Great description. I've read it through three times and still picking up details.

Steven


From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of Bill Libecap <blibecap@...>
Sent: Saturday, January 26, 2019 10:48:18 PM
To: SouthBendLathe@groups.io
Subject: Re: [SouthBendLathe] Need help internal threading 13" SB lathe 1 7/8" spindle
 
Thanks for such a detailed explanation

Rolland Sicard
 


Many thanks to all that commented.  It was really helpful.

On Sunday, January 27, 2019, 7:58:51 AM MST, carbure2003 <guycad@...> wrote:



Joe is cutting with the tip of the tool up, lathe revolving in reverse.
 
I have the tip of the tool facing down with spindle running in forward direction.  
 
Running lathe in reverse direction can be dangerous as chucks may become loose on threaded spindles like SB lathes.
 
Joe’s method allows faster cutting speeds.
 
Guy
Please note: message attached

From: "ww_big_al" <arknack@...>
To: <SouthBendLathe@groups.io>
Subject: Re: [SouthBendLathe] Need help internal threading 13" SB lathe 1 7/8" spindle
Date: Sun, 27 Jan 2019 08:29:21 -0500



____________________________________________________________
What Popcorn Really Does To Your Memory
clearstateofmind.com
http://thirdpartyoffers.netzero.net/TGL3242/5c4dc6e31fc0b46e220d5st04vuc
SponsoredBy Content.Ad

Jim_B
 

One point I forget.
When your test fitting starts to fit well but still binds, take, what should be your last one or two passes, by feeding out, COUNTERCLOCKWISE, on the cross feed. Note that if you need more than one pass you will not be returning to zero on the cross feed dial.
Since. In threading at 30 degrees on the compound, you only cut on one side of the tool the off side, of the thread, is jagged. Feeding at the end straight out cleans up the off side.

Sent from my iPhone-8
Jim B,

On Jan 27, 2019, at 10:14 AM,
--
Jim B

David Beierl
 

 In threading at 30 degrees on the compound, you only cut on one side of the tool the off side, of the thread, is jagged.

That's why you feed at 29 degrees instead of 30, so that it cuts just enough on that flank to keep it clean.

Yrs,