Can I finish a Metric Thread after Disengaging Half Nuts Without Threading Dial?

[Rhee]

Guys,

I'm new to the machining hobby and have a HF mini lathe and mill.

While in the middle of cutting a internal metric thread, a bearing on the lathe froze up and I disengaged the half nuts in order to fix it. My lead screw is Imperial and there's no threading dial on the machine. Can I finish the threading operation? If so how?

Thanks,

Rhee

 

[janvanruth]

external possibly, internal small diameter i wouldn't even try

 

[jrmach]

Go git em Digger

JSYK,,you need to (pick up) your thread
Might try You Tube,,don't know where to start with a pos machine

 

[James H Clark]

With the compound set at 29 1/2 degrees as usual, re-engage the desired thread and start the operation with the tool backed out from the cut. After the machine has started turning, slowly and carefully re-introduce the cutting tool into the unfinished thread, carefully adjusting whichever dial is needed, whether it be crossfeed or compound until the tool is starting the cut. You will make small adjustments as necessary. Takes longer to describe than to do it. There may be a u-tube vid showing this. When you get to the desired positon on the crossfeed, re-set the zero on dial. Good luck.

JH

 

[jrmach]

With the compound set at 29 1/2 degrees as usual, re-engage the desired thread and start the operation with the tool backed out from the cut. After the machine has started turning, slowly and carefully re-introduce the cutting tool into the unfinished thread, carefully adjusting whichever dial is needed, whether it be crossfeed or compound until the tool is starting the cut. You will make small adjustments as necessary. Takes longer to describe than to do it. There may be a u-tube vid showing this. When you get to the desired positon on the crossfeed, re-set the zero on dial. Good luck.

JH

no,no,no,,,,,,,,,,,,,,,,with machine running slow,you engage the half nut with the tool backed out,then the tool is clearly above previous thread cut,,,""shut the machine off""then use your dials to zero in so the tool fits nice and cozy in previous cut.Then re-0 dials,,,back tool out,start machine again,and immediately shut off again,,dial in and make sure shit is good,now put in reverse and start machine again and your back in business.No need to worry about 29 degree or any degree for internal threads

just make sure yur 60 degree tool is centered

 

[Peter from Holland]

How far finished is the tread
If a piece of threaded rod goes in a ful turn or so you can align on the threaded rod Easier to see

Peter

 

[Mcgyver]

no,no,no,,,,,,,,,,,,,,,,with machine running slow,you engage the half nut with the tool backed out,then the tool is clearly above previous thread cut,,,""shut the machine off""then use your dials to zero in so the tool fits nice and cozy in previous cut.Then re-0 dials,,,back tool out,start machine again,and immediately shut off again,,dial in and make sure shit is good,now put in reverse and start machine again and your back in business.No need to worry about 29 degree or any degree for internal threads

just make sure yur 60 degree tool is centered

this, plus a loupe and sheet of white paper underneath make it easy to pick it quite accurate

 

[jrmach]

this, plus a loupe and sheet of white paper underneath make it easy to pick it quite accurate

Yup,and very bright light

 

[Gordon B. Clarke]

this, plus a loupe and sheet of white paper underneath make it easy to pick it quite accurate

On an internal thread?

To the OP. What diameter is the thread?

 

[nihilistic]

Sure, use a tap

 

[michiganbuck]

internal would be tougher than external..You could sacrifice a bolt/screw of that same thread/pitch with grinding it a little more than half away so it would fit into the ID thread start you have made. Slip in a wedge along side so it becomes tight and straight. shave of wood might be good for a wedge.
Now put your lathe in gear and run forward a little to make it all lead screw tight in the direction you will be threading.
Next take a loop(magnifying glass)and with adjusting the compound and cross hand wheels bring your tool bit to center of the thread on the home made screw gauge. Remove the tread gauge and you are back to proper place.

Likely you can get .002 close with good eyeball through a loop and that should be plenty close to make the thread.

Yes in some cases you might find a smaller screw with the same pitch so not needing to make a gauge at all.

Yes finding double that pitch you can loop to the top of the thread not the root.

and last, you will have to figure your finish depth because your dial number won' tell where to stop .

As James H Clark mentioned with the compound at 291/2 or about you can easily adjust the center line back to good.
If both the compound and cross were straight a line up adjustment would be more difficult.

For a hobby part you can use a higher class screw/bolt from a hardware store for a gauge.

The Id burr may make it seem tight when it is actually loose.

 

[Mark Rand]

Loosen the threading tool in the toolpost/tool-holder. Advance the carriage until the tool would be in the existing thread. Engage the half nuts. Now pull the tool into the nearest thread groove by hand, adjust the cross slide to get the tool aligned with the axis of the lathe, while keeping the tip in the thread and tighten the toolpost/tool holder. Now back off the tool, retract it and carry on making cuts. Works every time!

 

[Rhee]

Thanks,guys!

I got it done. The thread is M27-1.5, so it is pretty big. I was threading with the lathe in reverse so I could view the bit from the operator side of the the lathe going into the thread. I engaged the half nuts with the bit close to the grove and then used the cross slide and compound slide to get the tip centered in the grove the best I could. I did wear a loop.

Thanks again, big time! I didn't have to start over!

Rhee

 

[James H Clark]

You're welcome.

JH

 

[EPAIII]

This looks like something that needs a video. Anyone want to do one?

Whoops, looks like someone or two or two dozen already has:

YouTube