Gunsmithing who does NOT use a compound for cutting threads?

[JJones75]

Got into a discussion today about thread and seems like people have different ways of cutting threads.
Seems that several only use the cross slide and feed the tool strait in when using carbide others set the compound at between 5-30 deg so the cutter is only using one edge.
Just wondering how some of the folks here do it and why

 

[Tac284]

I use 29.5 and feed with the compound then finish the last few thou by going straight in with the cross slide.

 

[bohem]

I've done both, depends on the material and the cutter being used.

For full form cutters I just run them straight in and it works fine. I have never had to try them with the cross-slide but I use them sparingly and so it's minimal time that I'm talking from.

For partial form inserts I setup the feed on the compound and see which it happens to like better for something that I've never cut before. Not on final sizing, but on initial passes.

Barrel stainless with a partial form carbide insert like a 16ER hasn't given me any trouble finishing cleanly on a straight plunge.

 

[sjett]

Using full profile cutter 60deg threads I use the compound for better depth control and cut at an angle not plunge cutting


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[bohem]

OK, I'll try that next time I break them out. I had good results and just ran with it, but I'm certainly open to giving it a whirl, thanks for the advice.

 

[wtopace]

Here's a picture I found online about 3 years ago that was really helpful when I was starting out. It made the threading compound angles a lot easier to understand. I use pretty much exclusively the compound for threading unless I am picking up an existing thread. The biggest reason for me being that I never can seem to remember the cross slide setting after backing it out for every pass. Worst thing to think while machining, "Was I at 0.008 or 0.010?", keeping the cross slide at 0 and cutting with the compound removes any uncertainty for me.

 

[JJones75]

I use the compound at 29.5 deg as well. I always set up a dial to read off the back of my tool post to help keep track of everything accurately.
Get threading too set upand run cross slide in to touch off on part then set dial to zero. Adjust cross slide in .010" and make pass after disengagement of the half nut I back the cross slide out well past zero and return to start. Run cross slide back to the initial cutting point (.090" on mine) then adjust the compound in .005" and make cut back out cross out past zero return to start point. Adjust cross slide in to last starting point (.085") and adjust compound in .005" and repeat until depth is reached.
I also set up a dial that the carriage will feed into so that I can disengage the half nut even the same time , I also only use the same number to drop in on the entire threading processes , I have found that it does help some on some machines

 

[Tac284]

Some days threading is the last thing I want to think about!

Some threading from the last few days

 

[selfbowhunter]

I use 29.5 and feed with the compound then finish the last few thou by going straight in with the cross slide.

I do the same but use 30*.

chuck

 

[mcfred]

I never can seem to remember the cross slide setting after backing it out for every pass. Worst thing to think while machining, "Was I at 0.008 or 0.010?"

I use 30 deg and periodically write the last feed on the cross with a sharpie. It wipes right off with a bit of acetone.

I've heard from machinists that using 30 deg on old manual lathes helps to keep the backlash consistent in the lathe pushing against the gears, etc. but on modern CNC they just cut straight in.

 

[glbreil]

I turn the tool upside down run the lathe in reverse and cut away from the shoulder at 255 rpms and cut straight. Higher rpm with inserts seems to give a nicer finish for me. I am not good enough to cut toward the shoulder with any speed.

Gary

 

[ugsly]

I use the compound at 29.5 degrees, Ive tried plunging straight in and it does the job but the threads dont come at nearly as nice for me. Plus the compound I can really get down to taking a fine cut. There is nothing fast about cutting good threads on a manual lathe.

Kc

 

[wtopace]

... There is nothing fast about a manual lathe.

There, I fixed it for you! I find it relaxing while machining, but my current project (built 3 rifles in the last week and I'm only a part-time gunbuilder on vacation from the real job) is a turner's cube. If you haven't tried one, I would recommend the tedious headache, only once though. I have definitely gotten very good at boring holes to a very precise diameter and depth, but there is absolutely nothing fast about any manual machining. It's about an hour per side of the cube for me with 4 nested cubes.

 

[skeetlee]

whats a turners cube? Pics man pics!! Lee

 

[LRI]

I use 30 deg and periodically write the last feed on the cross with a sharpie. It wipes right off with a bit of acetone.

I've heard from machinists that using 30 deg on old manual lathes helps to keep the backlash consistent in the lathe pushing against the gears, etc. but on modern CNC they just cut straight in.

Not exactly bud. See below:

Fanuc G76 Threading Cycle

N5 G76 P010060 Q100 R0.05
N6 G76 X30 Z-20 P1024 Q200 F2
Controlling Thread Infeed Angle with Fanuc Threading Cycle G76
Controlling Thread Infeed Angle with Fanuc Threading Cycle G76
G76 : Threading Cycle Parameter P P actually consists of multiple values which control the thread behavior,

01 : Number of spring cuts, you can change it at your will.
00 : Thread run out at 45 degree
60 : Thread Infeed Angle / Flank angle
All the parameters of Fanuc threading cycle G76 are fully explained here. The values with P are actually 03 pairs of values, the last pair is to control the thread infeed angle of each pass for threading, You can see the bold line above with value 60.

G76 Threading Cycle with 60 Degrees Infeed Angle for 60 Degree Threads (Compound Infeed/ Flank Infeed)

If you put 60 for the infeed angle, this will put most of the load on the front edge of the threading insert.

G76 Threading Cycle with 55 Degrees Infeed Angle for 60 Degree Threads

If you put 55 for the infeed angle for the standard 60 degree threads, this will put most of the load on the front edge or leading edge of the threading insert and will also put a small load on the back edge of the threading insert.

G76 Threading Cycle with 0 Degrees Infeed Angle ( Radial Infeed)

If you put 0 for the infeed angle, this will put the load on the full profile of the threading insert.

Square thread always need a straight radial infeed (plunge infeed ).

G76 Threading Cycle Recommended Infeed Angles

The following indeef angles should be used as infeed angles with G76 fanuc threading cycle. 80, 60, 55, 30, 29, 00




An explanations as to why:

One would think that with big/robust automated equipment topics like tool deflection, chatter, and poor surface finish become a thing of the past.

If it only it were that easy. On a conventional Imperial thread form (60 degree) it can induce quite a bit of loading on the insert. A 1-1/16th OD thread is relatively easy on tooling. Going to something big like a 4 or 5 pitch thread means the insert gets real big real quick. The more tool in contact with the part, the more potential for poor surface finish due to chatter, etc.

Having the ability to program a compound entry angle on a turning center helps to mitigate this.

Next challenge: Multiple start threading. Very, very aggressive pitch rates means a great deal of side loading on the insert. Again, reducing the contact patch helps reduce the risk of poor finish.

Last, material condition. Mild, free machining steels, not so hard to do. Getting into things like D2, 6AL-4V, Invar, Inconel, Waspaloy, etc. means you better have your poop in a group. You can work harden this stuff to where its unmachinable without annealing it again.

Hope this helps.

C.

 

[selfbowhunter]

chad,

how do you suggest cutting threads on a manual machine? I use 30* set the cross slide and compound at zero. cut with the compound for most of the thread and finish up a couple thou feeding straight in with the cross slide. I never move the compound back out after taking a cut but run the cross slide out and then back to zero to start a new cut. so the cross slide always stays at zero until the last cut. don't know if that makes any sense but you never lose your place that way. a friend who is a real machinist at the company I work for showed me this a few years ago. I trusted him even though he wasn't a gun builder.

chuck

 

[LRI]

I set the comp to 29 and go. Cross slide to 0. Incremental feeds on the comp. Use the CS to get out.

 

[sortafast]

I don't thread on the lathe a ton as my lathe is too small to do anything other than pistol barrels . But when i do, i run 29.5° on the compound for most threads. I actually can't think of a time when I ran threads going strait in. Like was said above, when you are loading both sides of a 60° threading tool you get chatter, chip breaking and evacuation becomes an issue and its just a bit harder to control than a 29.5° infeed. The reason to run less than 30° escapes me right now, but I think it has something to do with having a relief on the back of the thread so that you only cut on one side of the V, not both. Not sure though. I did a lot of reading when I was teaching myself how to thread and this was one of those things that was discussed and it made sense. And I figured that there were a bunch of people that knew a lot more than me on the subject and they were probably right so I should listen.

 

[Red_SC]

whats a turners cube? Pics man pics!! Lee

The first type is the common one, but it's only limited by your imagination. Typically nested boxes, usually connected together but sometimes cut so the inner boxes are loose inside the outer box but too large to get out.

From what I hear, new hires in machine shops were sometimes handed one and told to duplicate it without any instructions how to do it.

 

[skeetlee]

piece of cake! LOL!!!!! I wouldn't know were to start! Lee

 

[x ring accuracy]

I set the comp to 29 and go. Cross slide to 0. Incremental feeds on the comp. Use the CS to get out.

Simple and to the point.

 

[MDM]

What is you guys' approach to chasing threads? For example, say I have a Savage small shank and want to set the barrel back .5". What's your method to pick up the existing thread and continue it on or .5" or so?