Threading With the Compound vs. Crossfeed

Here's my take on the age old debate between threading with the compound or the crossfeed. I cut four threads in total, two each with the compound and crossfeed, with and without cutting oil, to see if there was any difference at all.

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[StuartdeHaro]

If I could briefly say a few words about Disco Inferno, a fire 100 stories high is going to leave a mark on history. People would have died. We have solid historical records of fires that are much older. Rome in 64AD. London 1666. We know who owned the cow that burned down Chicago in 1871, yet there are no other contemporary accounts of this supposed musical conflagration that just happened in 1976. It just seems a little suspicious to me. Also, The Trammps seem a little too enthusiastic about fire. They keep saying”burn baby burn, ” and “burn that mother down.” Are we sure they’re not arsonists?

[graemewhite]

As an apprentice, I was taught to use the half included angle via the top slide and we only had hand ground HSS tooling.
The Old Boy turner in the repair shop showed me how to put the cut on with the cross slide, but to advance the top slide (set parallel to the work) a couple of thousandths every cut, to mimic the angled infeed cut and reduce the load on the tool and that's how I've cut all my simple threads since the 70's.

[jeffanderson]

I like your new energy, the quality of your videos has improved and the content is spot on.
A long time viewer appreciates the effort!

[ypaulbrown]

Outstanding content and production value on the video, cheers from an old guy in Florida, Paul

[greggroos]

When a machining video makes me LOL and detour into 1976 video...

[tates]

The third and just as common method is where the depth is fed with the cross slide. Also on every pass the compound set parallel to the spindle is advanced by half the depth of cut. This keeps the pressure on the leading edge and reduces tool load. This method almost exactly reproduces the compound set at 29 degrees.

[badmojamma]

Great video. Comparative analysis is always enlightening, and the titanic battle between crossfeed and compound as a threading method is informative and useful for hobby machinist dorks like myself. Dark Side of the Moon as a background prop works beautifully, too - Kudos, Stu!

[jameslezak]

Great video! I've always threaded with compound in feed, mostly because of speed in a production environment. When I began running NC lathes the programming had different in feed angles to control the flow of the shavings. I started using 10° with excellent results. I still do it that way. I usually had better tool life than the 29.5° in feed angle. Thanks for your time and sharing. 👍

[robertmoore]

Great videos. Thank you for sharing your knowledge with us.
I use the compound because that was the way I was taught.

[howder]

Well done, I find both methods to be comparable, even with an indexable tool. Enjoyed the discussion, cheers!

[phillhuddleston]

With using the compound you zero out the compound then just touch the tool to the work od and zero out the cross slide. When cutting you just need to take the cross slide to zero every time and move the cross side in a bit at a time. After the final pass write down the number on the cross slide for multiple parts and it is just as easy for production as using the cross slide only. Example, if the cross slide is set to .045 on the last pass you should be able to take your next part to .045 and get the same thread pitch diameter as the first part assuming the od's were the same as each other if not you have to compensate for that.

[tsstsstsstsstsstss]

Good as always! Remember us early adopters when this channel blows up!

[aceroadholder]

Good video. I would make several suggestions that might help machinists doing threading for the first time. The first is don't start threading on nominal sized stock. Look in the threading section of your machinist reference book. You will notice that for a 1"-8tpi thread the stock major diameter is not 1" (same-same for mm threads). The major diameter is some thousands of an inch under the nominal size. Note in the video the threads have a sharp crest whereas a correctly cut 60 degree V thread will have a crest flat equal to 1/8th the thread pitch. If you thread nominal sized stock and are using thread go/no-go gauges to check your work in process by the time you get the go gauge to go on to the work the thread will be under size. As an aside if you are using a threading die the work is noticeably easier to thread if the work has the correct o.d. for that particular thread.
There is a trick to be able to cut threads at a much higher rpm on a manual lathe besides threading outwards. While threading outwards with the lathe in reverse is a viable method it won't work when no thread relief is allowed. This will require feeding from the compound. Run the threading tool in close to the work and stop the cross feed hand wheel so the handle is at about the 10-11 o'clock position and set the cross feed dial to zero. Bring the threading tool up to the work with the compound feed and set it to zero. Up to 1/2" (13mm) threads I run the lathe at about 220rpm. Engage the half-nut and when the tool reaches the point you wish the thread to end snap the cross feed out and open the half nut at the same time. Do it a few times and you'll get surprisingly good at it.
If you are cutting metric threads follow the directions above except that after pulling the threading tool back and opening the half nut cut the power and let the spindle stop. You will notice that the thread indicator dial hasn't moved very far from where it was opened. Put the lathe into reverse and when the thread dial mark you were using comes back up, re-engage the half nut and back the carriage up to the initial start position. Once in position set the compound feed for the next pass and turn the cross feed to it's "zero" and make the next pass.

[seanwolfe]

Thanks Stu, I’ve always wondered what the difference would be to use the CF. As I learned the “correct” way, I have honestly never tried.

[SB-hinj]

It'll be interesting to see the effect of RPMs (or surface feet per min) on surface finish when single point threading. Don't see much mentioned on this specific area.

[jeffanderson]

I should add, I always use the compound as it is easier to keep track of the feed in depth. No DRO on my lathe.

[rickpalechuk]

Love this type of comparison content, would be neat to see fine thread (32) hard material (4140) with high speed and insert tooling. Now, as for the lazy factor.... hard to measure :)
As always, thanks for sharing
Cheers

[howtorepairpendulumclocks]

Great vid!!! Beginning with a whiteboard / chalkboard explanation of the theory would have helped. Also you may consider a negative tool top rake? Thanks!!!!

[billshiff]

The cross slide method has the disadvantage that you have to remember exactly what your last pass was on every pass.

[brucewilliams]

Maybe you could try using Joe Pyzynski's reverse threading method where you cut away from the chuck which allows you to cut the threads faster. Thank you for the content.