Turning hex or out of round material

[Ripcrow]

Do you turn hex in a lathe if so how do you do it without wrecking tools.I have seen on this forum machinists turning parts that are off centre .when I try this my cutting tools are broken or a blunt very quickly.Am I trying something that is impossible or is there a trick I don't know about

 

[compressor man]

Are you using carbide tipped tools? I believe that HSS tools are better able to stand interrupted cuts without breaking their tips off.

 

[va4ngo]

I only use self sharpened HSS tools and have not had issues. Other members will respond if you can be mire specific. Eg type of tool, material being cut, speeds feeds depth of cut etc
Phil in Melbourne

 

[Ripcrow]

Trying brass hex but have seen people turning mild steel off centre.my speed and feed is not known as I manually do it.. Is a high revolution speed with slow feed better

 

[stevehuckss396]

Trying brass hex but have seen people turning mild steel off centre.my speed and feed is not known as I manually do it.. Is a high revolution speed with slow feed better

I cut camshafts out of drill rod/silver steel using carbide insert tools. The V8 took 5 hours and never changed the tool. Slow speed and .005 cuts and no trouble other than a hot chip down the shirt once in a while.

 

[Tin Falcon]

Am I trying something that is impossible or is there a trick I don't know about

Doable certainly . Impossible certainly not.

Tricks ? Well more like basic understanding of machining practice.

First of all make sure you have a good understanding of speeds and feeds.

Remember the 2 1/2 rule. Avoid the tool and material sticking out more than 2 1/2 times its cross section . a 1/4 tool bit should not stick out more than 5/8 inch . 1 " stock should not extend more than 2 1/2 inches out of the chuck unsupported.

Insure the cross slide and compound gibs are properly adjusted. Adjust tool to center height just like you would for round material. And Avoid carbide tooling for interrupted cuts on steel. Carbide does not like interrupted cuts.
On Hex I take light cuts on hex until the points are gone. And I have made circles and fly wheels from flat plate rough cut on the saw and finished on the lathe.

So use good sound setup practice ,avoid carbide tooling and you shoud be fine. Hope this helps . Give it another try and get back to us with your results.
Tin

 

[jwcnc1911]

If your turning hex, you'll want to indicate your part to zero by finding the opposing high spots on the corners of the hex. Unless your using a 3 jaw chuck. For me, I prefer a little faster speed but I'm not afraid of the powerfeed. Having said that, I've broken my share of tools. Start with a moderate speed, cutting tool far enough away you can gently feed in until you clean up all the hex to make the part round. Then proceed as normal. I've personally always had good luck with carbide tipped tools, even inserted tools on interrupted cuts. Granted the majority of my experience is CNC but the process is the same. I'll make a video tomorrow evening if no one has by Monday. It should be very similar to "normal" turning but feed very slowly until you find where your tool makes first contact. Usually I'll roll the chuck by hand and feed in close, zero the handwheel so I know about where to expect contact. Feed in slow from there.

 

[Tin Falcon]

.my speed and feed is not known as I manually do it.

Not hard to figure out. One can purchase a digital non contact laser tachometer for IIRC about $20 . I imported mine from Hong Kong for IIRC $14. I am assuming a variable speed drive.
As far as feed measure the thickness of your chip .
also keep you depth of cut conservative until the points are gone.
Tin

 

[MachineTom]

When turning hex to round I make the first cut the to the depth of the round size plus .010. So the first pass removes all the hex, slow th feed a bit if you like, no need to baby your way through this material. If the material is like 12L14, You can take .100 with no trouble on most lathes.

 

[Sshire]

What Tom said.
I'm using indexable HSS (Arthur Warner). I set the cutter depth on a flat (as opposed to a point) + a few thou more. Pretty much correct SFM for 12L14 but brass and aluminum I crank it way up. Slow my carriage feed motor (it's not geared to the spindle) or hand feed. This way, no banging on the points of the hex. I suspect, since the interrupted cuts are eliminated, carbide could be used.
If that made no sense, I can do a quick video.

 

[Sshire]

I ran down to the shop and did a quick video. The carriage noise is not CNC. Just my carriage feed motor.

[ame]http://youtu.be/Mkh9QDiSB6w[/ame]

 

[Ripcrow]

Thanks for the video mine looks and sounds nothing like that.my tooling is 10 mm and my material has been sticking further out of the chuck so I will try things differently.my machining knowledge is limited so thanks for your responses,they are invaluable

 

[Forestgnome]

HSS tooling, Not too much bottom relief. You need good support under the tip. Plus plenty of radius, about .01-.03 would be good.

 

[Richard1]

Spent today turning 40mm square mild steel into 1 1/16" round.
HSS tooling, 3/8" depth of cut to just get rid of all the corners and leave it at 1 1/2" round.
162 RPM and somewhere about halfway up the power feeds.
Ran fine, didn't have to sharpen the tool, probably turned a couple of feet it.

Don't know if this is useful to you but maybe there is something useful there.

 

[Engineeringtech]

I cut hex bar stock all the time. Aluminum and steel. Use an HSS /cobalt bit, and feed slowly, until you knock off the "points". My DV-59 uses 5C lathe collets, so I buy hex collets from Hardinge. They are the only hex lathe collet I can find, which are made to insert stock from the FRONT. Other brands are sized to be used with bar feeders. (stock is forced in from the back side of the collet.

 

[Sshire]

Both Hardinge and Lyndex make good, front loading hex collets

http://www.shophardinge.com/productGrid.aspx?catID=6903

http://www.lyndexnikken.com/products-5C-Hex-Collet-c1230.htm

 

[Engineeringtech]

Both Hardinge and Lyndex make good, front loading hex collets

http://www.shophardinge.com/productGrid.aspx?catID=6903

http://www.lyndexnikken.com/products-5C-Hex-Collet-c1230.htm

Haven't always had as good a success with Lyndex as Hardinge. But they do front load. The others like Royal are made for rear loading and are too tight for front loading.

 

[Wizard69]

Trying brass hex but have seen people turning mild steel off centre.my speed and feed is not known as I manually do it.. Is a high revolution speed with slow feed better

What exactly are we talking about here as far as the brass alloy goes. It makes a huge difference because some brass or bronze alloys are extremely difficult to machine. Many see brass and think oh that is easy, I did this once myself when I was young and foolish. I was working machine maintenance at the time and a brass piece needed a couple of holes drilled into it. Seeing brass I told the engineer no problem and started back to the shop seeing a smirk on his face. He comes around latter to see how things where going and frankly they where not going anywhere. I later learned the brass was some super Ampco alloy specifically designed to be very wear resistant. Mind you all I had to do was drill some holes, very embarrassing for a kid new to the trades.

So you really need to know what you have alloy wise.

As far as turning stock, I've done cold rolled steel four inches square with carbide tooling and have come out all tight on a 9 x 20 lathe. That is probably pretty much as extreme as you can get with interrupted cuts. Carbide really doesn't like interrupted cuts either so it isn't impossible to get it to do the job if approached carefully.