Okay, total newbie, got a question for all you machinists

[Clark]

Tark,
"Most of us are tinkers, some of us tailors" - Brian Eno 1974 The True Wheel

 

[tark]

Thanks Clark. Now the pic is right side up!.

 

[MachIVshooter]

Another problem is they are constantly having to be adjusted and or tightened up. I would tighten up the side to side play in the table and ten minutes later it was back. I think that is why it broke carbide cutters.

Definitely. Carbide is quite brittle for it's extreme hardness, and any sudden shock loading will absolutely chip or break cutters.

I don't keep much in the way of HSS under 1" diameter, and you certainly can run carbide at lower speeds. I do it all the time in, especially with softer, gummier aluminums like 5052 and 6061 that will clog the flutes if you build too much heat. But your machine and set up has to be rigid.

As an aside, it is impressive that you turned out those guns on a combo machine! I find them incredibly aggravating to use, much moreso than two separate machines of similar size.

 

[tark]

I find them incredibly aggravating to use, much moreso than two separate machines of similar size

They are that, for sure. But I knew nothing about machining before I went to work for Les. I still know very little. I couldn't machine a part to spec from a blueprint if my life depended on it. I just made it up as I went along.

 

[Mauser lover]

Okay, so carbide is a no-go on the smaller machines as a general rule?

Beautiful guns though...right side up or upside down...

What is HSS?

 

[MachIVshooter]

Okay, so carbide is a no-go on the smaller machines as a general rule?

What is HSS?

HSS is high speed steel. Most rotary tooling will be HSS, cobalt or carbide. Cobalt is basically in between the others for hardness, toughness and heat tolerance. HSS will lose an edge pretty quickly if the tool gets very hot, while carbide can maintain an edge at temperatures that have HSS turning colors. Cobalt is a bit harder than HSS and will hold an edge at higher temperatures, while also being cheaper than carbide and a bit tougher in terms of shock loading and flexing. Conversely, it's not as tough as HSS and nowhere near as hard, rigid or tolerant of heat as carbide.

It's not that you can't use carbide on small machines, but they need to be tight, and you will be limited on the size of carbide cutter you can run due to the lack of rigidity. I used 1/16 to 1/4" carbide all the time on the mini, but anything larger, the chatter due to the larger flutes and lower RPM shock loads the edges and chips or breaks them. You will have a lot better luck running carbide on the 8520, 21-100 or G0795 than on a Seig X2 size machine.

The reason to go for carbide when you can is cutter life and rigidity. HSS tooling deflects a lot more than carbide, and won't hold an edge nearly as well in harder alloys, even if kept cool. The only downsides to carbide are the brittleness and cost; carbide is typically about 3 times the price, and you get very little visual warning in deflection before they snap if your tool pressure is too high.

 

[Mauser lover]

Thanks... I was actually laying awake in bed last night and could have beat my head against my nightstand when I thought "oh duh you numbskull, high speed steel!"

Thanks for the explanation though, it was good to know all that extra stuff too!

 

[Clark]

My youngest brother had this book as text in getting a 2 year machinist and welding degree from Highline College.
http://www.ebay.com/itm/Machining-Fundamentals-by-Walker-John-R-/112467653230

In 1978 Boeing was paying me $7/hour to design and develop new aircraft electronics while my baby brother made more than twice that much making parts piecemeal for a quality clearinghouse that sold them to Boeing.
To this day his gunsmithing looks like jewelry, while mine looks like branding cattle. And we both have the same book.

The most important time I use that book is when my inside threads turn out to be left hand threads.

 

[MachIVshooter]

The most important time I use that book is when my inside threads turn out to be left hand threads.

Hahahaha! We've all done that! Just remember to think of your threading tool as a screw or tap; If it's going in toward the headstock when the spindle is running forward (clockwise from the back of the spindle for the uninitiated), it's cutting RH threads.