Threading with carbide inserts

[jmarkwolf]

I've heard that carbide inserts like deep cuts and fast feeds, and have experienced much the same with what little turning I've done with carbide inserts.

How does this reconcile with threading with carbide inserts, since it is neither deep nor fast?

I've got a project coming up where I want to cut some 7/8-20 OD threads close to a shoulder. I'm seriously considering purchasing a right-handed ID threading tool, running the spindle and threading screw in reverse, and threading on the back side of the work, away from the shoulder to avoid crashing. But many such tools are indexable.

What to do?

 

[macardoso]

I do almost all my threading with carbide (and turning too!). There is not really a minimum speed limit for carbide, the big difference is the maximum speed you can cut. There are exceptions for super hard materials because you are aiming to generate enough heat to soften the metal locally in front of the cutting edge, but this doesn't apply to most of the cutting in the home shop.

If you find carbide is not working well for a particular application, you may want to look for a sharper insert with a ground edge (edge sharpness is also the reason why many move to HSS). These are often advertised as being for aluminum but they work very well on soft steels and stainless as well. I see it is easy to find the 16ER threading insert with this edge geometry, although I haven't tried them personally yet. I usually thread at 100rpm but might go down to 50 if I am feeling nervous.

The selection of the insert to your application really makes all the difference in the world.

What material are you cutting?

 

[jmarkwolf]

Hi Macardoso

I'm threading 1045 steel.

 

[mksj]

I use almost all carbide inserts for my lathe. With threading I have had good success with using the Carmex BMA lay down inserts, I typically take passes at 0.01" until close to target, then 0.005" and maybe a 0.002" and a single spring pass. Varies based on material, that is also a direct depth cut with the cross slide. I do thread at higher speeds in the 250-450 RPM range, but the inserts did OK at around 120-150. They are strong but brittle, so inching along or slow threading speeds is not a good approach. The Carmex inserts last a long time, I broke the tip dropping the holder before I wore out the first cutting point of 3. They are also sharp enough that you can take lighter cuts and they will still take off material. If you do not have a stop system, threading away from the shoulder/chuck is more optimal for most people. Best prices on Carmex seems to be buying direct.

Precision Tools � Carbide Cutting Tools

Carmex Precision Tools specialize in threading tools for turning and milling - Thread Turning Inserts and Tool Holders, Thread Mills and Swiss Lathe Tooling.

carmexusa.com

Carmex Precision Tools, LLC. - LAYDOWN

This is a 7/8-14 thread in bronze, 2nd is a M16-2.0 in O1 rod. The finish is that of the cutter , buy good inserts and a decent holder.

 

[Janderso]

CARMEX CTTK-23 - Multi-Piece Lay Down Threading Set with Inserts, 3/4

Includes(1) SER0750 K16 (3/4" External Holder) (1) SIR0750 P16 (3/4" Internal Holder) (5) 16 ER AG60 C5 (Uncoated Insert - External Partial Profile) (5) 16 IR AG60 C5 (Uncoated Insert - Internal Partial Profile) (3) 16 ER G60 C5 (Uncoated Insert - External Partial Profile) (3) 16 IR G60 C5...

www.travers.com

I have this set. I like it very much. The inserts are very sharp and leave a nice finish at lower speeds.

 

[Liljoebrshooter]

I use carbide inserts almost every time threading. I have better results with a positive rake tool. I use a Kennametal NTP2R for almost everything I do because that's what I have. I have some neutral rake inserts and you can easily see the difference when cutting the same material.

Joe Hynes

 

[Bamban]

My experience mirrors Mark's.

Laydown carbide inserts work well even at rpm below 40. This was done with ChiCom inserts, no dressing up, just brushed off the chips.

No thread relief, stop close to target, turn chuck by hand, release ha!f nuts and turn spindle back on, retract....

Have not broken a tip yet stopping while cutter is engaged.

 

[AGCB97]

I seldom use HSS for anything. I especially like not having to grind treading bits except for an occasional acme. And because they are at the proper angle when the QCTP is sqaure to the work, no fishtail gauges either.
Just my opinion and practice.
Aaron

 

[Lonnie]

I remembered this thread so today I tried threading at 75 rpm with a carbide insert. I believe the stainless rod is 303 but not 100% sure.
Here's the result right after I test fit a nut. Threads are 5/8" x 11tpi.

 

[Lo-Fi]

Got to be happy with that result!