Need threading, boring bar recommendations | The Hobby-Machinist

I'm looking for a recommendation on the above. I would like it to be able to do both bore and thread.

I would like it to be somewhere between .5 and .750 in diameter.

I' also like it to be 8-12 or so inches long. As long as i could get so that the diam would not become a hinderence with it becoming to weak (flexing).


Something that will not break the bank. I have to save for everything i buy.

So what are your thoughts folks. Here are my big boring bars. It uses 1/4 and 1/8 HSS bits. One end is angled at about 45* which allows it to cut to the bottom of a hole. The other end is straight. You can grind bits to whatever shape you need. 60* for threading. A left hand type bit for boring. These boring bars are relatively easy to make. Mr Pete has a video on how to machine a square hole. Lots of other videos on how to make these.



I use this for internal threading most of the time.

What would you think bout 5/8 by 10" long

I do t think you’d have much success with a 5/8” bar sticking out of its holder 10”. My experience is consistent with what one can read, and that is that pst 4:1 starts to get iffy. That means an extension of 2.5-3” for your 5/8” bar. You can get a little more in certain materials etc.

There are some quite inexpensive carbide bars if you are willing to buy direct from China (e.g. AliExpress). Carbide bar gets you more like 8:1 extension.

Hi AES,

Yushi contains other products and information you need, so please check it out.

It seems you have a strange problem here. Would you mind to disclose the type of lathe you have? I cannot understand that a floppy thread can give the results you describe. As soon as the nut is tightened, the stud is under tension, and all floppyness should disappear I think.

But resting the toolpost on a nut is definitely a no-no!

Boring the 19.5 mm hole – yes you should not use a drill; btw drills in this size usually have a Morse 2 shaft. But this ‘cut’ of  less than a thou makes me again think that something is fundamentally wrong. Even ten times as much is not a heavy cut.

For more information, please visit Round Bar Threading Machine.

But it is difficult to make a diagnosis without seeing the setup.

Material suppliers in Switzerland – well ‘it depends’. Pestalozzi in Dietikon sells also really small quantities, but you should fetch it yourself in their warehouse. They deliver only by truck, and that’s expensive. Now if you happen to live in Geneva then this is not a good idea I admit. The only other way I can suggest is to find a nearby mechanical shop and ask politely…

Ah, and the thread form tool? You don’t have the chip inserts in mind, do you? In a lifelong time of hobby tinkering and 10 years of semi-professional machining I never felt the urge to use them. And on a ‘floppy’ lathe–I would know better means to burn money.  Most of my threading is done with tools made from these ubiquitous ‘broken center drills’ (used in a GHT retracting holder, worth its weight in gold).

Greetings, Hansrudolf  (from central Switzerland)

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