# Internal threading away from the chuck



## Armourer (Jan 7, 2018)

Hey all, I have a project I am doing were I need to internal thread into a blind hole. I was thinking about trying to thread it away from the chuck, but my chuck is threaded on and I am worried about it spinning off. Is this a bad idea to try and do? Anyone have any other way of threading it? Thanks all for your help!


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## HBilly1022 (Jan 7, 2018)

I did that on my 10 x 22 lathe and it has a threaded chuck, BUT it also has locking clips that prevent the chuck from unthreading. I got away with it but I only took light cuts. One time the chuck did try to come off but thankfully the locks stopped it. I would not try it unless your lathe has some kind of chuck locking device.

I'm relatively new to this stuff and others with more experience will likely chime in with a solution for you.


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## Terrywerm (Jan 7, 2018)

Here is what I do when possible:

Machine the bore just a bit deeper than it needs to be - .125" to .250" - This dimension depends on the size of your project.
Cut a relief channel about .125" wide and just a bit deeper than the major diameter of the thread. It should be located at a depth that allows the length of thread that you desire.
Machine your thread as normal. The relief channel gives you a 'safe zone' in which to stop the travel of the carriage without crashing the tool into the bottom of the bore.
Here is a cutaway view of a sample part:


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## jlsmithseven (Jan 7, 2018)

I've done it already on a Le Blonde lathe. I wasn't taking heavy cuts....I think the important thing is to take light cuts and see if anything changes. When you go slow and take deep cuts, that's when it wants to un-thread.


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## Bob Korves (Jan 7, 2018)

terrywerm said:


> Here is what I do when possible:
> 
> Machine the bore just a bit deeper than it needs to be - .125" to .250" - This dimension depends on the size of your project.
> Cut a relief channel about .125" wide and just a bit deeper than the major diameter of the thread. It should be located at a depth that allows the length of thread that you desire.
> ...


In addition to what Terry said, you can move the tool to the bottom of the hole and then wrap the boring bar with masking tape even with the end of the hole.  That lets you see very clearly how far you are away from crashing.  You can also cheat and have a foot brake like I do, which stops the spindle in less than one revolution.  Still, lately I have been threading internal holes outward instead of inward.  Much safer, less stress.


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## middle.road (Jan 7, 2018)

Bob Korves said:


> In addition to what Terry said, you can move the tool to the bottom of the hole and then wrap the boring bar with masking tape even with the end of the hole.  That lets you see very clearly how far you are away from crashing.  You can also cheat and have a foot brake like I do, which stops the spindle in less than one revolution.  Still, lately I have been threading internal holes outward instead of inward.  Much safer, less stress.


Oh, what I wouldn't give to have a brake on my 1440 after my half-nut mechanism malfunction.
I'm attempting to do everything left to right in order to reduce the stress and you mention.


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## Armourer (Jan 7, 2018)

Thanks for the replies! I think I will try and thread into the chuck, I was worried about not seeing were to stop the cutter but I just finished boring the hole out and I will see no problem. Now my next problem, figuring out to make the relief cut at the bottom of the hole....


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## Bob Korves (Jan 7, 2018)

Armourer said:


> Thanks for the replies! I think I will try and thread into the chuck, I was worried about not seeing were to stop the cutter but I just finished boring the hole out and I will see no problem. Now my next problem, figuring out to make the relief cut at the bottom of the hole....


Make something like this from HSS, or buy one:
http://internaltool.com/products/lathe/79/thread-relief-tools


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## mikey (Jan 8, 2018)

Bob Korves said:


> Make something like this from HSS, or buy one:
> http://internaltool.com/products/lathe/79/thread-relief-tools
> 
> View attachment 253346



As Bob said, I use these on most blind internal holes and thread toward the chuck. Micro 100 sells these in solid carbide and you can often find them for good prices on ebay. To be fair, my lathe has a clutch on the drive shaft and I also use a carriage stop, just in case, so I don't hesitate to thread toward the chuck.


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## epanzella (Jan 8, 2018)

I made a carriage stop/dial indicator holder for my Grizzly G4003G. When boring or threading a hole to specific depth I kill the power .050" from the shoulder and turn the chuck with a piece of 3/8 key stock right to the shoulder. The lathe will coast to about 20 thou of the shoulder before it stops. I use a 2" DI on the long feed and a 1" on the cross.


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## Armourer (Jan 13, 2018)

Well, thought I would post an update, I managed to get it threaded and I appreciate all the help from everyone here. I thought I could look in and watch my threading tool and stop when required but it was a real pain to do that. So instead I could hear the tool cutting and once you couldnt hear it cut I disengaged the half nuts. It worked like a charm this time, but in the future will rig up a dial indicator to do it properly! Also found a piece of HSS that was in my junk drawer that someone had ground already to make the relief cut to finish the threads into.


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## Bob Korves (Jan 13, 2018)

I recently posted this on a different thread.  Run your tool into the hole all the way with the spindle stopped until it bottoms out.  Sight across the work and mark the depth on the boring bar with some masking or other tape, or with a Sharpie marker.  Now you do not need to look inside the bore.  Simply stop the tool before the mark enters the hole.  My lathe has a foot brake that stops the spindle basically instantly, so it is possible to get very close to the depth of the bore before stopping the spindle or disengaging the half nuts or feed handle.  Goodbye alibi.    It is also quite possible to cut or thread out from the hole rather than into the hole.  Lots less exciting.  YMMV.


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## magicniner (Feb 3, 2018)

If your chuck screws on then look at how you tighten it, if you don't have a tool or tool set which you use to tighten it adequately then it's likely to come off. 
My chucks screw on, they accommodate holes for a C-Spanner and the spindle lock allows me to tighten them adequately whilst still being able to remove them with ease. If you can't use a C-Spanner you could make something to hold in the chuck which allows suitable torque to be applied.


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## Wreck™Wreck (Feb 3, 2018)

The best way to internal thread from left to right is to start on the left side, this may be self evident but one never knows.


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