Facets in my 16 TPI Threads - Need some help!

[Bamban]

The speed for manual threading is way below the optimal speed for carbide. I suggest you try a sharp HSS tool. Grinding the tool is no big deal. Use the fish gauge as a template. Hone to a fine edge after grinding. Use a stone to create the flat at the tip of the tool.

I am not totally sold about the carbide issue on low speed manual threading. I use carbide laydown on my 90s vintage Jet 1024, and plunge it straight with the cross slide.

This barrel was threaded 3/4x16 to host an adapter to be turned and threaded for a 7/8x32 tuner. I cut the threads using the jog button, and that is slow. The stick out is quite long, the tuner requires 0.9 inch long thread, plus a shoulder.

I have Warner HSS threading bits and carbide special order ones from Thinbit, and a bunch of laydowns from my favorite supplier in China. I could not tell the difference on the thread quality using any of the three types.

The times when I am running 2 lathes I thread in the 1024 using the proximity sensor at higher rpm speeds with the laydown. I am not sure if I could tell the difference in the thread looks.

 

[davidpbest]

I am not totally sold about the carbide issue on low speed manual threading. I use carbide laydown on my 90s vintage Jet 1024, and plunge it straight with the cross slide.

I feel exactly the same. I have had few problems threading with carbide at slow speeds on most materials provided the specific insert is selected with care and knowledge of the cutting geometry, and the setup is rigid (solid tool post advertisement goes here). Granted I don't thread aluminum often, but I regularly thread 304. 316, brass and bronze with carbide without issue and plunging straight in. This 29.5° compound technique is very over rated IMO. The Laydown insert 16ER-AG60-BMC has a great range of suitable materials including aluminum and stainless.

 

[Aukai]

David what holder do you have for that insert?

 

[davidpbest]

I have these:
External: Carmex SER0500F16 which is 1/2" shank
External: Carmex 075-3EXRHTHL which is 3/4" shank
Internal: Dorian 881 which is a combination internal Laydown and External On-Edge style for BXA QCTP
Internal: Carmex SIR 0625 P16 which is a 5/8 x 3/4" shank
They all take the same 16 size inserts, although the internal and external are different inserts.

The Dorian came with a collection of tools with the QCTP, and unless you want that specific configuration with integrated QCTP mounting block and different external/internal inserts, I would stick with the Carmex. Hertel, Tool-Flo and Dorian also make square shanked external toolholders similar to the Carmex. Iscar makes internal shanked toolholders similar to the Carmex internal.

 

[Janderso]

https://www.mscdirect.com/product/details/60873023?orderedAs=SER+0625+H16&pxno=13296405&refnum=13296405&rd=k&tg=Recommendations&tpp=false&searchAhead=true&searchAheadTerm=ser%200625&typahddsp=SER%200625%20H16&hdrsrh=true

https://www.mscdirect.com/product/details/85108983?fromRR=Y

Here's the tool I'm using.

I didn't know they made negative threading holders/inserts.

 

[davidpbest]

I didn't know they made negative threading holders/inserts.

The toolholder mounts the insert at negative rake for clearance. The insert geometry reverses that to plus 3°. Discussed/presented here.

 

[Aukai]

MSC is not recognizing BMC?

 

[davidpbest]

Carmex BMA is the original equivalent. I have both and the BMA's are Carmex, the BMC's I have are clones.

Here's the insert from MSC.

 

[Aukai]

Thank you sir....

 

[TX COWDOC]

UPDATE:
I got the lathe back into position, leveled and tried threading with some barrel drops that Bamban gave me. Overall, vastly improved. I tried threading with just the cross-slide and a new AR Warner HSS tool / bit. 16 TPI at 65 RPM. I fed at 0.003 for 2 passes then 0.002 for 11 passes then 0.001 with a spring pass for 10 passes. Still feel some coarseness in the threading. Close inspection of the result reveals some surface irregularity that I can't figure out.