Single point threading in reverse

[birdiemc]

Joe Pieczynski has a video about threading in reverse with the tool mounted upside down in the tool holder. I tried it today with a hss tool I ground and snapped off the tip like I've never done before. In his video he's using carbide and plunging straight in, no 30degree on the compound. After snapping my tip I got to thinking about it and I cant decide which way is up now.
With the carriage running left to right, but the compound swung ~29.5° like normal it seems to me the tool is still only loaded on the one edge thus reducing the tool load, in the same way it would were the tool inverted threading toward the headstock the way it's been done since the dawn of time.
Am I thinking about this correctly?

 

[asa]

Joe Pieczynski has a video about threading in reverse with the tool mounted upside down in the tool holder. I tried it today with a hss tool I ground and snapped off the tip like I've never done before. In his video he's using carbide and plunging straight in, no 30degree on the compound. After snapping my tip I got to thinking about it and I cant decide which way is up now.
With the carriage running left to right, but the compound swung ~29.5° like normal it seems to me the tool is still only loaded on the one edge thus reducing the tool load, in the same way it would were the tool inverted threading toward the headstock the way it's been done since the dawn of time.
Am I thinking about this correctly?

Did you have your spindle running in reverse?

 

[J E Custom]

When you run the tool upside down, it tends to lift the carriage and can cause the tool to rise and grab, sometimes breaking it. if you thread on the inside and start on the close side, it applies down force to the lathe carriage and produces normal loads on the lathe tool and carriage.

The main difference is that the cross feed and compound work differently (Backwards) than outside thread cutting and can get confusing sometimes.

J E CUSTOM

 

[Chevytruckman]

I also watched his video and do threading just like he does(away from the carriage). As seen in his videos, I also find it much less stressful and have not had any issues with breaking carbide. I do however have a fairly tight lathe and use 29.5 degrees on the compound to infeed.

 

[birdiemc]

Didnt specify, sorry, this was threading external threads with the tool upside down and spindle running in reverse, moving carriage left to right.

That's a link to the video I watched that inspired me to try.

 

[birdiemc]

I also watched his video and do threading just like he does(away from the carriage). As seen in his videos, I also find it much less stressful and have not had any issues with breaking carbide. I do however have a fairly tight lathe and use 29.5 degrees on the compound to infeed.

So, normal infeed with the compound not cross slide to minimize tool loading, right? I didnt have a good chamfer on the end of my work, so when I drove it back in fwd, with cross slide backed out a little it must have grabbed. I heard it snap, and figured that's all it was, but wanted to check anyway.

 

[ar10ar15man]

i use this method, small cuts, no issues
how deep was the cut, how short is the tool
i use 5/8 square and 3/4 square with inserts
straight in

 

[Chevytruckman]

Yea, normal infeed with the compound. I have had more luck keeping tool chatter down by keeping the tools cutting load down. If your setup was rigid enough I'm sure using the cross-slide straight in would also work fine.

 

[RoyB]

If you have a threaded spindle for your chuck, and you run the lathe backwards, you run the risk of unscrewing your chuck with disastrous results.

 

[nvbowhunter]

Birdiemc,
I too thread just has Joe instructs in his video. I use this method for both external and internal threads. When cutting threads on a barrel tenon I use my compound to make a plunge in initially to my targeted pitch diameter. Pitch diameter can be verified using just 2 wires as you're measuring a single groove. Once this relief cut is made and pitch diameter target # confirmed you're good to go as in normal threading (but with chuck running in reverse). I use a 5/8 RH threading bar that is for external threads on one end and internal on the opposite. You have to swap the carbide inserts from the opposite end so you're carbide insert is upside down. This system really is awesome and greatly improves the visibility issues that we have when truing action threads. With this system the tool is running against the far side of the action threads and can be viewed more readily by the lathe operator. A bonus to this method is it allows you to thread at a much faster spindle speed so the carbide performs better. Practice this method on scraps and you'll soon wonder why any of us w/o thread on chucks ever cut threads any other way.

 

[birdiemc]

The 2 wire method is brilliant. I just got a set of wires last week and have been going nuts trying to hold all 3 wires, hold the mic, and turn the spindle on it. First stab at it I dropped one in my chips....quickly learned the hard way to clean the space below before using wires.

 

[KyCarl]

Lay a rag across the ways or a little dab of grease helps. I wasn't allowed to clean out chips that was someone else's job?
I have a print out of thread depths feeding straight in. I ran a L&S copymatic that
didn't have a compound you had to feed straight in. I just used a fishtail to line it up.

 

[KyCarl]

It looks like most barrel journals are in the 1"-2" range?
Why not get a set of thread mics with the correct anvils and
you won't need wires. I have 0-1 and 1-2 because I did a lot in those sizes.
If you had the holder and insert upside down the lathe would be in reverse
Wouldn't it try to lift everything rather than pushing down on the ways?

 

[birdiemc]

Another good idea. Think a Shars would be good enough for that or need to shell out the big bucks for a starret? Every time I turn around I'm spending just another couple hundred on this dang hobby...between lathe tooling and loading equipment I'm gonna go broke. And to make matters worse I hate my little grizzly and want to get a real lathe, so that requires adding on to the shop...it never ends