Internal threading question

I've never cut an internal thread, I have taps up to M14, now I need an M16x2 thread 35mm deep (open ended). If I buy this 10mm internal threading tool will I be able to cut an M16 thread, or is that going to be too tight? I'm guessing it will be.

The tool can do it if you can. You need the thread diameter less double depth for comfort 16-2-2=12mm so you have 2+mm clearance up the hole (actual minor diameter is 13.84mm). The only thing to check is that they do a 2mm insert for that holder.

You could buy quite a few taps for the cost of it mind.

Edited By Pete Rimmer on 21/05/2020 06:24:59

If you look at the bottom of that link, there is a tab to be the first to ask a question about the tool. You could use that for a definitive answer from the suppliers?

Glanze give a minimum hole size of 13mm for that holder though only for 26mm length, with just 1mm between height and OD you should be OK.

I'll first admit that the only internal thread I've cut was a 1" thread as practice following Toms Techniques Youtube vids when I started playing and using a hand ground cutter. A smaller internal hole with a tight tool and I think i'd cut it away from the chuck with inverted tool to make it easier to check clearances and place the tool before each run.

pgk

The price of the insert is the highest I have seen. Check out APT.

Won't that cut a left hand thread ?

To cut a right hand thread the tool needs to be the right way up and the lathe spindle running in reverse with the feed away from the chuck. I have to cut a thread into a back plate for a new chuck.

Probably misunderstood what you mean, but I don't see how the tool can cut if it's the right way up and the spindle is in reverse?

Rob

You would need a L/H internal holder and insert which puts the form on the opposite side of the triangle to cut outwards with tool right way up.

Upside down and machine in the right spindle direction but feed reversed should work with conventional tool if you want to cut from chuck end  

This is how you can do external threads by using an internal tool on the far side of the job and run in reverse, the business end is on the correct side of the tool

Edited By JasonB on 21/05/2020 20:34:22

Check the size of insert used and confirm it is capable of the 2mm pitch.

Rob this link to the Sandvik site has a diagram on page 25 of the pdf catalogue showing what Jason is saying about left hand tools and inserts for right hand internal threads being cut with the tool moving away from the head stock.

Sandvik threading insert guide.

Martin C

Last time I needed an internal M16 thread to fit a screwcut external thread I just drilled and tapped, although I did already have the taps.

Andrew

From experience definitely give APT a look

Tony

Thank you all for your responses, the link that Jason posted shows that although the diameter would be ok I'm going to have trouble with the 35mm depth and I don't fancy my chances of going in from both ends and meeting up in the middle. Thanks also for the APT recommendations, their inserts are certainly more reasonably priced than the Glanze, but I have a question - how is it that Glanze sell only a single insert for their internal threading tool, yet APT have a different insert for every thread pitch?

Thanks, Peter

Edited By pgk pgk on 22/05/2020 07:01:47

Edited By pgk pgk on 22/05/2020 07:04:24

As I said there is only a 1mm increase in tool diameter from the 9mm x 26mm end to the 10mm shank so you will have clearance into the hole but as it is a fairly coarse thread you may come a croper. Can't remember if my tool is 10 or 12 mm will see if I have a chance to measure it later.

The Glanze insert is a "partial form" eg it has 60 deg angle but will not cut the exact crest and valley form, it will cut a range of pitches which you would need to check. The other are known a s"full form" and have the pitch in the description and will cut correct crests and valleys for that pitch only. So you can gave one all rounder.

Thanks for the link, Martin. Confusion due to my interpretation of "right way up"

Rob

Rob, sometime words just don't work and that's when the old saying kicks in, a picture is worth a thousand words.

Martin C

For non critical work, you could use a metric insert to produce a unified thread and vise versa. They are both 60 degree form and the other differences are relatively minor. You could also get away with Whitworth and BSP threads.

I did have a measure of my 10mm one but it has the 10mm shank all the way and I only have a partial form 0.5-1.5 insert so could not really give an exact answer but it did fit into a M16 nut with plenty of room to spare.