Threading on a lathe when you cannot set up 29.5 degree compound

[koenbro]

I am learning how to make (external) threads on my lathe. Although I can rotate the compound to any arbitrary angle, once at 29.5 degree (or 60.5) orientation advancing the crosslide and/or compound will not result in the desired movement. My compound and toolpost can only be setup at 90 degree rotation.










So I need to keep the tool perpendicular to the z axis and advance in both z and axes with each pass s- let's say -10 thou in z and 17.3 thou in x.

Anyone has the same problem?

 

[WobblyHand]

Remove the two pins? Worth a try if you want to use the 29.5 angle. Sometimes the pins are spring loaded, so they may go down. Just remove the tee nut and press the pins out - you really don't need them.

You could simply go straight in, as well, if your lathe is rigid enough. Plenty of folks do that with no ill effect. Really don't need the z offset, save to reduce cutting force. Just take less deep cuts. Try both ways and see which you prefer.

 

[GrifterGuru]

I would say remove the pins.

I run an OXA size TP of the same design and that can be bolted rigid to the compund on my 7x with no need for pins and still cuts deep without the TP rotating.

There is an old trick of using a thin, fine, metal mesh between the TP and the compound slide to aid in stopping rotation if you are worried about it. Think I saw a reference to metal screen door mesh somewhere once?

 

[Smithdoor]

I am learning how to make (external) threads on my lathe. Although I can rotate the compound to any arbitrary angle, once at 29.5 degree (or 60.5) orientation advancing the crosslide and/or compound will not result in the desired movement. My compound and toolpost can only be setup at 90 degree rotation.
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So I need to keep the tool perpendicular to the z axis and advance in both z and axes with each pass s- let's say -10 thou in z and 17.3 thou in x.

Anyone has the same problem?

Most my threading I only use the cross slide for feed.

If can not use compound it is not problem.

FYI Turret lathes don't have a compound and some have threading.

Dave

 

[koenbro]

Great tips. Considering that thread cutting is so common, has anyone drilled new pin holes at 29.5 degrees in the TP’s t-nut?


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[woodchucker]

I would say remove the pins.

I run an OXA size TP of the same design and that can be bolted rigid to the compund on my 7x with no need for pins and still cuts deep without the TP rotating.

There is an old trick of using a thin, fine, metal mesh between the TP and the compound slide to aid in stopping rotation if you are worried about it. Think I saw a reference to metal screen door mesh somewhere once?

Just paper will do it. It prevents slick metal to metal.

 

[WobblyHand]

Great tips. Considering that thread cutting is so common, has anyone drilled new pin holes at 29.5 degrees in the TP’s t-nut?


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Not I. Since I'm always moving the cutter around, pins would be in the way. I just don't see the pins as necessary nor a big time saver.

 

[DavidR8]

I would pull those pins.
Personally I can't imagine not being able to swivel my toolpost.

 

[RJSakowski]

I would make a new t nut for the QCTP san the two pins. You will then be able to rotate the QCTP to any angle but you will still have the the original should you feel that you need the extra security afforded by the pins.

 

[GrifterGuru]

Just paper will do it. It prevents slick metal to metal.

TBF, I have used folded over 600 grit W 'n' D before and that worked very well. It was just after I got the post and wnated to ensure it did not swivel under load. Few days later, I pulled the post off to clean after working some cast iron (dirty filthy stufff that it is), forgot the paper when I refitted the post, locked it down and never noticed any difference.

Mind, I suppose that is more a function of how I lock it down with the spanner than anything else.