Threading trouble

[Douglas JohnstonParticipant @douglasjohnston98463]

A hand crank is a real asset when threading. I nearly always do it that way, it is much more relaxing than doing it under power. A bit of a pain for long threads, but they can often be done under power. Carbide thread cutting inserts don't seem to mind the slow cutting speed.

Doug

[John PParticipant @johnp77052]

Hi

In MEW 149 an article by Richard Bartlett on
page 36 through to 40 describes a method
for metric screw cutting using a non reversing
motor and dis- engaging the lead screw.

John

[GreensandsParticipant @greensands]

I have just discovered the design for a swing up tool holder for threading as illustrated on the Mikesworkshop website and would like to have a go at making one up. Mike illustrates his design by a series of photos together with some indication of the sizes involved but is anyone aware of a fully dimensioned set of drawings suitable for use with the Myford 7 series lathe?

[SillyOldDufferModerator @sillyoldduffer]

See also Journeyman's Website.

[GreensandsParticipant @greensands]

Dave – Thanks for the link. It looks interesting.

[Andy StopfordParticipant @andystopford50521]

+1 for zero-to-zero, not quite as foolproof as a swing-up toolholder (I imagine, I've never used one), but close, and the angled feed helps on difficult materials.

Hand Cranking

I made a hand spindle crank for my mini-lathe because I had a some internal 1/2" NP threads to make in stainless steel a while back, and it seemed like a good idea. I have to say, it did not work well.

To avoid work-hardening the steel required a reasonably deep cut, but I found as the thread deepened, there was a tendency for the tool to dig in. Nothing immediately terrible happened of course, but I was then left with a burr in the thread which was extremely difficult/impossible to get rid of before threading could recommence.

After a while I gave up and completed the rest of the job under power with no problems. I guess that with such a small lathe, there is insufficient inertia to overcome a slight dig-in when turning slowly by hand. A more aggressive approach might help, but then I'd probably be concentrating so much on cranking, that the tool would collide with the end of the bored hole.

[John BaronParticipant @johnbaron31275]

Hi Andy,

Even with a lathe handle I never thread a blind hole into the hole, if I can't use a tap then I thread from the bottom of the hole out wards ! No crashing into the bottom and you can do it under power with confidence.

Just one point, I use carbide threading inserts ! I stopped trying to grind HSS threading tools quite some time ago. You get nice threads even with a lathe handle. Most people seem to run into trouble by cutting too deep at one go.

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