Diy Internal Threading Tool - Lathe.

[6literZ]

Last night and this morning I spent a little time messing around on my 4003G lathe and decided to have a go at the DIY internal threading tool I've seen posted here.

My goal is to have a tool small enough to make and thread barrel thread protectors for as small as 1/2-28 threads. I didn't have any plans and just kind of winged it, in fact I didn't even go inside to get my caliper so all measurements are just eyed up. I also started with 1-1/8" O1 drill rod, so it took a long long time to remove all that extra material. I should order some more appropriate sized material for future use.

After making it look like the other pictures I've seen I used my soup can forge and heated the cutting area to red hot and quenched it in iso32 oil. It seems very sharp, although I'm unsure how it could be sharpened or touched up so I'll only use it on aluminum. I may have to grind off one end to fit inside a half inch ID.

I also found it difficult when adjusting my compound slide to cut the angle which required the compound to be off the scale, I used a small protractor as best I could, the angle seems okay. I bought a cheap combination protractor from harbor freight to see if that would help setting the compound angle.

 

[T Bredehoft]

Nice tool. I'd suggest a 'fishtail' threading tool gauge, you hold the gauge against the work and fit the tool to it. No numbers needed.

 

[6literZ]

So the compound slide had to be adjusted to actually cut the angles on the cutting surfaces, so 30* to cut one side of the single point cutter, and then the next angle was no longer able to measure off the scale on the compound, which probably isn't accurate anyway.

I've seen people use sine bars, but I don't have those.

 

[Big Bore Builder]

Read up on threading: The old South Bend book "How To Run A Lathe" is very valuable.

Set the compound to 29 degrees.

The homework assignment is:

1. Why 29 degrees? Simple answer.

2. Which way do you set it? Makes a big difference.

Now for that "Fishtail" gauge: Old timers call it a Thread Gauge. Sometimes called an "Arrowhead" tool. Used as a grinding gauge for the tool bit and a setting gauge in the lathe.

Here they are:



Note the angles: One is 60 degrees and one is 55 degrees.

Standard threads are 60 degrees. Whitworth threads are 55 degrees.

Most american threading and metric, use the 60 degree gauge.

Threading and chambering barrels? Mausers are 55 degree Whitworth,so grind the tool bits accordingly.

Remington, M70, most everything else is 60 degrees.

The numbers and scales on the gauges are for checking thread pitch, not for measuring!!

 

[Big Bore Builder]

So the compound slide had to be adjusted to actually cut the angles on the cutting surfaces, so 30* to cut one side of the single point cutter, and then the next angle was no longer able to measure off the scale on the compound, which probably isn't accurate anyway.

I've seen people use sine bars, but I don't have those.View attachment 117534

So the compound slide had to be adjusted to actually cut the angles on the cutting surfaces, so 30* to cut one side of the single point cutter, and then the next angle was no longer able to measure off the scale on the compound, which probably isn't accurate anyway.

I've seen people use sine bars, but I don't have those.View attachment 117534

Common problem on import lathes.

Set the compound at 29 degrees with a good angle gauge, protractor, or what ever you have, then stamp a set of witness marks for easy resetting.

 

[epanzella]

I needed a small boring bar and internal threading tool for a smokeless muzzle loader project so I also made them based on posts I saw on this site. To make it easy get zero rake I made them from 0-1 drill rod that was 5/8" square. I removed the unused point to get into a smaller bore. I used a torch for heat treating with no tempering. They work great and stay sharp. BTW, I don't use the compound at all for threading. I mounted my QCTP on a large block of steel that's bolted to the xslide. Threading is just as good and parting is awesome. With my compound freed up I used it for the Z axis in a milling attachment.

 

[Mark_f]

I have heard a lot of argument about using the compound for threading and was taught that way forty some odd years ago. I have experimented threading with the cross slide and found it works just as good. ( if there is a difference in thread quality , I can't see it and the fit seems just as good)

 

[Cobra]

I agree Mark. I just need to be careful with the feed but I use the DRO and it seems to work fine.

 

[Mark_f]

I agree Mark. I just need to be careful with the feed but I use the DRO and it seems to work fine.

I have used the dial with good results but I have an indicator set up on my cross slide and it works good.

 

[epanzella]

I was never good at using the dials. I just keep forgetting where I was. I do have indicators on my Lfeed & Xfeed and they work well for me.