Threading thread

[gadget_lover]

The technique I've seen described most often (using your numbers):

1) Assuming you've turned the part to the major diameter and have cut the thread relief.

2) set the compound to 29 degrees.
3) set the tool so that the 60 degree tip is pointing at 90 degrees to the work.
4) move the tool so that it can not hit the work and using the crossslide move it in to the doc (Major plus doc .0379)
5) Zero the COMPOUND slide's dial. This is your final depth. Do not use the cross slide any more.
6) back out the compound to clear the work and start threading. Use only the compound to move the tool in. When the compound dial reaches zero you are at depth.

NOTE: when everything is adjusted right, the right side of your 60 degree tool will be parallel to the travel of the compound.


Daniel

 

[Mirage_Man]

The technique I've seen described most often (using your numbers):

1) Assuming you've turned the part to the major diameter and have cut the thread relief.

2) set the compound to 29 degrees.
3) set the tool so that the 60 degree tip is pointing at 90 degrees to the work.
4) move the tool so that it can not hit the work and using the crossslide move it in to the doc (Major plus doc .0379)
5) Zero the COMPOUND slide's dial. This is your final depth. Do not use the cross slide any more.
6) back out the compound to clear the work and start threading. Use only the compound to move the tool in. When the compound dial reaches zero you are at depth.

NOTE: when everything is adjusted right, the right side of your 60 degree tool will be parallel to the travel of the compound.


Daniel

Daniel,

That's a interesting way of doing it. I've never thought about doing it that way but will give it a try. The only thing I question is what about a final pass or two using the cross slide to clean up both sides of the thread? I always do this as the 29.5 method will leave one side of the thread a little jagged. Also I would think you'd want to zero your cross slide so you have a reference point for each pass. That is of course assuming you back out of the thread after each pass using the cross slide.

I would also suggest getting some sort of method to measure your threads. I use a thread mic. There are other methods such as thread wires and triangles but I've never used them...yet :).

 

[gadget_lover]

It's assumed that once you start threading, you will use only the compound, even for backing off for the next pass. It does not hurt to have a reference point on the crossslide too. It helps when you do like I do and accidentally bump the handle mid thread.

Many people advocate doing the last pass with the compound. This should only be a thousandth or so. I'd have to do the math, but the 'jaggies' should be pretty minuscule if properly set up.

Daniel

 

[Mirage_Man]

It's assumed that once you start threading, you will use only the compound, even for backing off for the next pass. It does not hurt to have a reference point on the crossslide too. It helps when you do like I do and accidentally bump the handle mid thread.

Many people advocate doing the last pass with the compound. This should only be a thousandth or so. I'd have to do the math, but the 'jaggies' should be pretty minuscule if properly set up.

Daniel

Just to clarify, you meant cross slide in the statement above right?

 

[gadget_lover]

LOL You got me. I meant to say "Many people advocate doing the last pass with the cross-slide"

That'll teach me to type quickly just before leaving for work!


Daniel

 

[StrikerDown]

I'm probably all screwed up here but I thought the 29 degrees on the compound instead of 30 (1 half of 60) was to take care of the jaggies?

 

[gadget_lover]

Nevermind. Move along to the next post please.
Daniel

 

[Mirage_Man]

I don't have the energy at the moment to give a full response but maybe this link and picture will explain what I cannot.

http://www.mmsonline.com/articles/threading-on-a-lathe.aspx

 

[gadget_lover]

Thanks! That was the diagram and article I was looking for, but could not find.

Daniel

 

[gadget_lover]

Thanks! That was the diagram and article I was looking for, but could not find.

Daniel

 

[saltytri]

Daniel, thanks for the suggestion on setting up to correctly cut with the compound. Here's a 20 tpi cut by the numbers in 12L14 (which cuts so nicely that it feels like cheating). The bevels at both ends were cut at 60 degrees. I've just seen some info that says to use 45 degrees, which I'll do next time.

I realized that for a given compound angle, you can just multiply the calculated DOC by a fixed factor to get the reading to cut to on the compound dial. For example, this is 1.13 for 29 1/2 degrees. This is by measurement of the tool travel not by trig, which I had over 40 years ago and probably wasn't any good at even then. :thinking:

Thanks again to everyone for the help and advice!

David

 

[Fred S]

As Barry suggested, I cut a thread to spec, not to fit. To make a 20 tpi Surefire 6P tail cap thread, the DOC comes out to .0379. Following advice to cut with the compound set at 29.5 degrees, it took .044 of compound dial movement to reach .0379 of depth perpendicular to the workpiece. It seems that a physical measurement of perpendicular DOC using a dial indicator is necessary to pre-determine how much movement of the compound dial is necessary to get the correct DOC. Am I on the right track? Is there a more convenient way to calculate the correct movement of the compound dial? It's all well and good to have a DRO on the cross slide but it doesn't do anything for me when cutting with the compound!

It should be

perpendicular depth of cut/sin(60)= compound travel

This and many other thread cutting calcs are in the Handbook

 

[saltytri]

Tonight I made interior/exterior matching threads in a piece of 2" 6061 tube. It all came out pretty well except for one minor point. I don't have a tool that does a decent job of cutting the relief groove at the back of the interior thread. Any recommendations, especially for doing lights with 17mm and 18mm bores?

 

[Mirage_Man]

Tonight I made interior/exterior matching threads in a piece of 2" 6061 tube. It all came out pretty well except for one minor point. I don't have a tool that does a decent job of cutting the relief groove at the back of the interior thread. Any recommendations, especially for doing lights with 17mm and 18mm bores?

I don't have one because I usually don't cut an internal thread relief anymore but these are designed specifically for what you want to do.

http://www.micro100.com/inch/ltr.html

.

 

[saltytri]

Thanks for the link to Micro 100, Brian.

To avoid needing a relief groove, do you thread from the inside toward the outside and gradually feed in depth at the beginning of each cut?

Here's the latest from Beginning Shop Class:

Maybe it's time to make something for real.

 

[Anglepoise]

Looks very nice.
One tip. Keep the run out groove width close to the common 'O' ring thicknesses.
When your building flashlights, most will have an 'O' ring for sealing and this just cuts down additional steps.

 

[Mirage_Man]

Thanks for the link to Micro 100, Brian.

To avoid needing a relief groove, do you thread from the inside toward the outside and gradually feed in depth at the beginning of each cut?

I don't recommend doing this unless you're very comfortable with your machine. I cut an internal thread relief for quite awhile before I attempted doing it this way. When I did I broke my share of inserts before I mastered it.

I thread toward the chuck but roll out of the thread at the same spot each pass based on a zero setting on my carriage dial (Not all machines have a dial on the carriage wheel). IOW I set the carriage dial at a zero point where I want the thread to end. As the carriage moves toward the chuck I watch the dial. When it reaches zero I disengage the half-nuts and roll out with the cross-slide at exactly the same time. the dis-advantage to doing it this way is if you roll out too late you risk breaking your insert or hitting a shoulder if you're threading toward one.

There seems to be many different ways that people thread on this forum. I think each has its merrits. I suggest finding what works best for you.

 

[gadget_lover]

I typically use my threading tool to do the relief groove. The groove is usually less than .050 deep and only a few threads wide.


Daniel

 

[saltytri]

I typically use my threading tool to do the relief groove. The groove is usually less than .050 deep and only a few threads wide.

I used a brazed carbide internal threading tool to do this and it pretty well buggered up the groove. Probably a case of operator error! At least there was a groove to work to.

I'm sure that Brian hit the nail on the head with his comment that the best thing to do is what works for each person. The great thing about a forum like this is that it can show a newbie what the various possibilities are - if you don't have experience and/or an experienced teacher at hand, it's hard to know what the different methods are that you should try to solve a given problem. Like with any highly skilled trade, there's an awful lot of lore that you won't find in books.

If anyone cares, MSC has a thread relief tool similar to the one he pointed out:

http://www1.mscdirect.com/CGI/NNSRI...id=13665Pstoreid=1040626Ppagenumber=842Pmode=

Since MSC is having a sale today, I ordered a couple along with one of these:

http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1785945&PMT4NO=66794381

I've bookmarked a couple of helpful posts on making cast iron adapter plates for these chucks, so some fun will start when the Brown Truck turns up in a few days.

 

[tino_ale]

Interresting... thread :naughty:

Does anyone has accurate major diameters of E-series compatable bodies and minor diameters of heads and tailcaps? I'm looking for the nominal dimensions.

Also E-series parts are 20TPI right?