Thoughts on my threading...

[Varmint56]

Dave, set your compound at 59 to 60 Deg. Use the compound to feed in till you are within .002 to.003 of final pitch dia. & then feed the last couple of passes with the crossfeed. Without a rigid set up & especially with stainless, thread quality will look ripply! They don't really look to bad. As long as the
form & diameter are correct they will be fine! Ron

 

[hogpatrol]

Many of the above plus tool bit issues, i.e. below center, above center, dull, insufficient clearance, improper rake, too heavy a cut, too slow, too fast, etc.

 

[ShaunBrady]

It was fed in by the compound.
Lathe is Grizzly 0706 and running on single phase.
I try to keep tool as close to holder as possible and try to thread as close to chuck as possible.

I couldn't find the 0706 Lathe on the Grizzly site. I have the 4003G which is about as light and entry level as it gets. I also straight plunge the cutter.

You see that wavyness in many internet seemythreads pictures, so you're not alone.

The things that eliminated it when I was starting were higher turning speeds, sharper cutting tools, and good lubrication.

I got the turning speed up by flipping the cutting tool and running the machine in reverse. This should only be done with camlock spindles, it is dangerous with threaded on chucks. It eliminates the worry of crashing into the shoulder or chuck. I thread at 270 rpm. Leave the feed direction the same on the gearbox.

I went to the Warner 3/4" two sided turning tool (kit #31). I only use an edge of the 3 sided insert for 2 sets of threads. It'll do more, but that eliminates problems. That works out to ~$2.50 per tenon, which doesn't buy a lot of my time for sharpening tools. HSS tooling cuts better than carbide at low speeds.

I'm using Vipers Venom for cutting oil. I'm not sure how much that oil helps, but lubrication definitely does.

Straight plunging the tool requires light cuts. I do 10-10-5-5-3-3-3-3-2-.... That's 10 thou to 20 deep, 3 thou to 42 deep, 2 thou to final depth. Plunging is hard on the tip of the tool, so keep an eye on it. When it starts going, the rest of it doesn't cut nearly as well.

 

[ridgeway]

I converted my Grizzly a couple years ago to 3ph and VFD. One of the best things that I have done. That and high pressure oil flush system for chambering...

 

[Dave in WI]

Corrected my post to show lathe is G0776.
Here is the threading setup I used this time, would have it closer to chuck on important one:

Here are the feet on this lathe:

Did a quick cut today with the 29.5° feed off compound, looks better:

But still have waves as usual:

 

[Dusty Stevens]

Very perceptive there Dusty on my single phase machine at home I am able to eliminate that wavyness in a couple ways I thread between centers for one and I grind my own threading tools.

You would think with the friends i have i could get a nice hand ground threading tool and a nice hss crowning cutter. Since i sold my surface grinder im stuck using inserts

 

[Roeder]

I spotted the single phase right off the bat. What kind of feet is your machine sitting on?

A friend of my has that machine. He removed the motor and re mounted it with rubber washers between the motor base and mount. Other makers of similar machines assemble them this way. Not a perfect solution but much better surface finish on threads.

 

[Dusty Stevens]

A friend of my has that machine. He removed the motor and re mounted it with rubber washers between the motor base and mount. Other makers of similar machines assemble them this way. Not a perfect solution but much better surface finish on threads.

Thats a good idea. I had a jet lathe years ago and got a good baldor motor on it and that solved that issue. The motor shop said the taiwanese motors are originally made to run on 50hz of course and they just happen to work on 60.

 

[10XSHOOTER]

Geared head or belt driven? looks like chatter From a geared head machine. lighter cuts faster speed.

 

[Stan Taylor]

You would think with the friends i have i could get a nice hand ground threading tool and a nice hss crowning cutter. Since i sold my surface grinder im stuck using inserts

I will make you one of each an ship them with that barrel I am working on for it's up to you to touch them up LOL the OPs problem I think is primarily rigidity at this point to much hanging out of that 4 jaw if I were him I would run a live center of of tail stock an lightly touch his breech face it would probably help eliminate most of the waves.

 

[Danny1788]

I use the same threading tool as your using, but I use iscar 908 carbide inserts.

These are the ones I use
https://www.mscdirect.com/product/details/40211476

 

[ridgeway]

Tuck that part in closer to chuck. Just stick out what you need...

 

[eww1350]

"A friend of my has that machine. He removed the motor and re mounted it with rubber washers between the motor base and mount. Other makers of similar machines assemble them this way. Not a perfect solution but much better surface finish on threads"

Dave, the quote above is spot on..correct..I have 2 Grizzly Lathes, G4003G, and the G0709.
I had the exact same issues while threading... I bought some 3/8" anti-vibration rubber material and isolated the single phase motor.. It will solve your problem, but it is a pain to do alone you will need a second person to help...


Eddie in Texas

 

[hogpatrol]

I use the compound and like my thread chips to roll off like a curly fry.

 

[msalm]

That side profile of your threads still looks like one side of your thread is longer than the other... Looks like you don’t have the ‘V’ squared up at a perfect 90 degrees to the work piece.

 

[Spotshooter]

Remember some compounds are marked backwards so you may have to set it at 59.5 degrees... vs. 29.5 degrees.

 

[riflewoman]

A couple of things.

When threading I used carbide insert “laydown” cutters for the correct threadform and pitch. I practiced at 300 rpm until I could safely make a full thread without tool damage or shoulder damage. I’d make the first pass as a “tickle” cut to make sure the pitch is correct. The next pass was a “heavy” cut where the compound was moved in the largest amount in the operation. After advancing the second time on the compound, I’d make a pass without advancing the tool. Then the next pass was done with the cross slide in .001 or .002. I would then alternate advancing using the compound and cross slide until the last 2 passes which were cros slide only. On most passes, I’d add drag on the apron hand wheel with my hand rubbing to keep the machine honest. 98% of the time my threads were 3A grade with good surface finish.

 

[MS72]

Chatter is a rigidity issue. Usually on a less than ideal setup, you want to slow the RPM down. You could try a live center to support while threading. May need to run a center drill in bore to give the center a good contact point.

 

[tobnpr]

Have you ruled out headstock problems? I'm thinking spindle...but could be compound or carriage.
"Rigidity" is a term that gets thrown around a hell of a lot.
That machine is certainly substantial enough that surface finish shouldn't be an issue. Hell, I've got 9A SB that's less than half the mass of my Sheldon and it turns impeccable threads... with carbide, too.

What's the surface finish like when doing simple turning operations?
Put a tenths indicator on the front corner of your compound and push sideways to see if youve got too much slop in the gib,perhaps. Check spindle for play- axial and radial- confirm within tolerances.

 

[ridgeway]

For manual work, those laydown full profile inserts are not ideal, IMO. They are made to run fast on a CNC and feed directly in. Single point is the best way to go IMO.