First Try at Metric Threading

[mikey]

The (single, see photo) bolt was tight, and it is horizontal.

I’m glad you told me that about the thread relief (safety groove). I have been making it the minor diameter.

Okay, the helix angle of your cutter can be adjusted with the set screws on the side. The Aloris blade has no relief angle under the cutting edge. It relies on the 12 degree angle it is held at for relief; this may not be enough. If this is really the issue on the torn trailing edge and flank then advancing the top set screw a fraction of a turn and retracting the lower one will tip the blade towards the chuck. That may clean up that trailing edge.

One advantage of the deeper thread relief is that it cleans up the tail of the last thread for a very clean finish. This is good workmanship, Erik.

 

[benmychree]

I think that introducing a back rake to a threading tool will change the thread flank angle, not a good idea. The reason that we disengage the half nuts is to save time in running back to the right hand end to start a new pass, whether or not this saves time depends on the length of the thread, for short threads, it may make sense to leave the half nuts engaged in running back to the starting point, for long threads, decidedly not.

 

[mattthemuppet2]

I think that introducing a back rake to a threading tool will change the thread flank angle, not a good idea.

only if you don't take that into account when creating the angle of the tool to cut the thread. Maybe hard to do by hand (why I didn't do it) but presumably straight forward when creating carbide inserts, otherwise all those mass produced parts created using laydown threading inserts would have incorrect thread geometry, right?

 

[erikmannie]

Thanks for all the feedback. I am sure looking forward to 7 days of nothing but metric threading.

The past year, I have picked up 4 or 5 HSS preground 60° tool bits made from 3/8” and 1/2” import HSS. I also have import as well as Aloris laydown carbide inserts on threading bars which are best suited to interior threading.

For those who leave their half nuts engaged throughout the whole process and set their compound angle at 30°, please tell me that nobody is plowing through their threads backwards (i.e. not backing off the cross slide) on their way back to the tailstock end (and calling it a spring pass). Just because you can doesn’t mean you should.

 

[Ischgl99]

For smaller threads, you don’t need to use the compound and can feed straight in if you wanted to give that a try. I’ve done that up to 1.5mm so far and it worked well. Since you are doing this for fun, that might be something to see how you like it compared to the traditional method.

Some people have built flip up threading tool holders so that you don’t need to retract the cross slide when running the carriage backwards to the start position. When you reverse the spindle direction, the tool holder lifts up and rides the thread back without doing any cutting. I have one partially built that I will get around to one of these days to give it a try.

 

[SLK001]

For those who leave their half nuts engaged throughout the whole process and set their compound angle at 30°, please tell me that nobody is plowing through their threads backwards (i.e. not backing off the cross slide) on their way back to the tailstock end (and calling it a spring pass). Just because you can doesn’t mean you should.

That's a terrible idea. There is enough slack in the gearing to completely throw off the alignment when you shift it in reverse like that. You can actually damage the threads you just cut when you do this.

 

[erikmannie]

This morning I am doing an M10-1.25. My thread relief is 8.168 mm & the chart says “minimum Minor Diameter of 8.315 mm”, so there will be no cutting in the thread relief.

I turned the hex steel down to 9.94 mm & the chart says “Major Diameter between 9.760 mm and 9.972 mm”.

The tip on the threading blade is no longer new (see photo).



I recentered the tool (it required lowering the tip about .007”!).

 

[erikmannie]

Scratch pass shows 1.25 mm pitch and no taper:

 

[erikmannie]

What it looks like after 4-5 passes (dialing in the compound .004” each pass) and a spring pass. Hardware store bolt next to it.

 

[erikmannie]

The pitch diameter of the hardware store bolt is 9.072 mm. The chart says that the pitch diameter range is 9.042 to 9.160 mm.

I just measured the pitch diameter of the one that I am cutting and I got 9.464 mm, so I have more passes to make.

I need to go in at least another .30 mm (about .012”). I will dial in .002” on the compound, do a spring pass and remeasure.

External Metric Thread Table Chart and Fastener Sizes M1.6 - M18

Standard metric external thread size M1.6 to M18 per. ANSI/ASME B1.13M-1995

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