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Learning to lathe [things]

PhotonFanatic

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The past two days have been spent working a fair bit on my lathe, trying to learn how to knurl.

I have purchased a set of cutting knurls and their toolholder, that allow me to cut a 45-degree diamond pattern.

When you haven't even seen one of these in action, it is hard to know if you've set the tool up properly, but suffice it to say that my first few attempts fell dismally short of being satisfactory. So off to the Practical Machinist website, where I asked for advice. The replies led me to another website, from a competing manufacturer to my tooling, where there was some very instructive material posted. See this.

Armed with a little more knowledge than I had before, I managed to get something resembling what I was looking for, although it still isn't perfect. Of course, that will just mean a bit more lathe time.
biggrin.gif


Two shots, both of the same piece, just one is darker than the other to cut down on the reflections:

Knurl_Cut2.jpg

Knurl_Cut3.jpg
 
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Anglepoise

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Re: Learning to lathe

Knurling is an art. Also luck is involved.
Cut knurling is very popular in Europe
but it think it is now gaining popularity here.

With soft materials like aluminium, you need to
be able to get rid of the excess metal from being re ground into the pattern. Cut knurling is meant to alleviate this problem.

Some people hate parting off. I hate knurling and am always on the look out for tips to improve.

You seem to be on the right track.
 

Mirage_Man

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Re: Learning to lathe

Guys how does this differ from other types of knurling? I have a knurling tool that came with my Phase II set. It has the two wheels that you push up against the work and give it a slow RPM and feed. With lots of lube of course.

Just wondering what other options are out there as I hate to put that much pressure on my poor old 10L.

I saw the post where Scott is using a "clamp" type knurling tool. Is that a better way to go?

MM
 

will

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Re: Learning to lathe

knurling is just pushing the metal in, and letting the peaks form. the knurling tool that is like a clamp only puts pressure on the work and the clamp itself. The other method puts pressure on the tool, pressure on the work, AND pressure on the bearings in the lathe.
 

TranquillityBase

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Re: Learning to lathe

A much better way to knurl, and it's easier on the lathe too.

TB
 

Anglepoise

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Re: Learning to lathe

For the sort of work we do, and the fact that most of our machines are on the 'light' side, the straddle/sissor style of knurling tool works well and is affordable.

PhotonFanatic's new knurler does not squeeze the metal but rather cuts it. There is a little strain on the work piece,spindle bearings and cross slide nut and screw, and they say that the quality and consistency of the knurl produced is far better than any other.

In my experience, Aluminium is the hardest metal to get a good knurl.

Even the pros can set up their CNC machines for a 500 part run and get good knurl results.

Repeat the same set up tomorrow and the knurl is wrong and they have to spend time tweaking things.
 
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TranquillityBase

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Re: Learning to lathe

I have two of the Eagle Rock/ Knurlcraft K1-201's, and they aren't inexpensive...I paid $250 each from McMaster, but it looks like they don't carry this knurling tool anymore. I've only been able to consistantly knurl stock that's .995" dead, and I only knurl solid stock.

This method makes it much harder to produce a finished part, but it's all I've been able to do with good results.

If the scissor pressure applied is too great, the knurler will move my tool post, everytime...and I'm sure you'ld cringe watching me tighten the tool post pre-knurling.

TB
 
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PhotonFanatic

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Re: Learning to lathe

One night's work--meager as it was:

Night-on-the-lathe-I-017.jpg


Really spent most of the time switching tool holders and inserts to see how the new stuff from Sandvik worked.
 

PhotonFanatic

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Re: Learning to lathe

Tonight's experiment: I have a tube of 6AL4V Titanium that I wanted to play with--turn it down and cut it off into less than 2" lengths for future anodizing experiments.

Now I don't have any inserts or tools specifically for Ti, but taking Anglepoise's suggestions to heart, I decided to give it a try using what I do have.

I used some Sandvik inserts designed for Al. They are brand new, and therefore very sharp. Cranked down the RPMs and went to work. This is after some sanding and polishing, but nothing close to what the Kenster can do. I'll poll him for his techniques later.
biggrin.gif



Ti-2.jpg


Overall, I was pleased with how easy it was to machine, but then again, I haven't tried knurling it, nor have I tried to thread it yet.
 

wquiles

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Re: Learning to lathe

Good going Fred!. You are already more brave than I am by using Ti. I am sticking to Al for now, even if TranquillityBase is hounding me to try Ti already ;)

Will
 

Anglepoise

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Re: Learning to lathe

Fred,
You should not have any problems threading Ti. Knurling.....well that's another matter<g>.

As far as getting the best finish on Ti. This is the one time you can ramp up the speed safely. I am still learning Ti secrets, but found that the best surface finish was with a round nose tool, .002>.005 thou cut at approx 780 rpm, (200sfpm)

This was the only time I was able to get away with some speed and I was delighted with the finish.

Just carry on experimenting and it will all drop into place.
 

KC2IXE

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Re: Learning to lathe

you know, with the right inserts, Ti can be cut at around 1400 sfm - crank up the speed for surface finish
 

PhotonFanatic

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Re: Learning to lathe

you know, with the right inserts, Ti can be cut at around 1400 sfm - crank up the speed for surface finish


I'm all eyes and ears! What would your insert material recommendation be, please?
 

Anglepoise

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Re: Learning to lathe

KC2IXE said:
you know, with the right inserts, Ti can be cut at around 1400 sfm - crank up the speed for surface finish

Is that a typo? Do you mean 1400sfm or rpm?

I have never seen any recommendation any where near that high figure ( 1400 sfm translates to approx 6000rpm on an 1" diameter) and would like to have more info even though my poor lathe can not get past 1000 rpm and thats on a good day.
 

KC2IXE

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Re: Learning to lathe

Anglepoise said:
Is that a typo? Do you mean 1400sfm or rpm?

I have never seen any recommendation any where near that high figure ( 1400 sfm translates to approx 6000rpm on an 1" diameter) and would like to have more info even though my poor lathe can not get past 1000 rpm and thats on a good day.

Nope guys - NOT a typo!!! 1400 sfm!!

Go to the Sandvik site

Go to the insert guide
I picked (at semi random)
Turning, External - Longitudinal, C-shape insert 80° - Lead angle -5°, T-MAX M, screw and top clamp, Square shank

ISO Area "S" insert grades
S= Heat resistant and titanium all,

- enter the material ASTM B348 (one of the specs for 6al4v)


and the one I grabbed this AM came out to 1400sfm - the one I JUST picked came out a bit over 900 -

CNMG 09 03 04-PF 1525
CNMG 321-PF 1525

ap = 0.4 mm ( 0.25-1.5 )
0.016 in ( 0.01-0.059 )
fn = 0.15 mm/r ( 0.07-0.3 )
0.006 in/r ( 0.003-0.012 )
Vc = 280 m/min ( 350-215 )
925 sfm ( 1150-705 )

(wish I had written down the one from this AM)

When I figures a .005 DOC and the like - came out to 1400sfm.

CNC in industry - the speeds can get CRAZY if you have the HP and rigidity

A couple of years back, I got some high end inserts - I found I can wind my Craftsman 12 out most of the time, and it's got a 2K+ spindle speed
 

KC2IXE

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Re: Learning to lathe

forgot to mention - boy was I scared the first time I turned a piece of 3.5" diameter 6061 at 2K RPM - but BOY it came out like a mirror
 

Anglepoise

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Re: Learning to lathe

Well something is wrong because on page A82 of the Sanvik 'Metal cutting
Technical Guide' they recommend a high of 670 sfm using there H10 carbide insert at a .004 feed and that is for Ti low grade( Commercially pure soft stuff)
The rating for ASTM B, Grade 5: Ti-6AL-4V drops the SFM down to 260.

And that rating is full flood coolant with their recommended for Ti, H10 insert
and a 15 minute life expectancy of the cutting edge.

So who knows. All I know for sure is that my little lathe can just hit 1000rpm with the bearings warmed up.
 

KC2IXE

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Re: Learning to lathe

Anglepoise said:
Well something is wrong because on page A82 of the Sanvik 'Metal cutting
Technical Guide' they recommend a high of 670 sfm using there H10 carbide insert at a .004 feed and that is for Ti low grade...snip...

Yeah - I have not checked all the various grades, but I know there can be HUGE differences in speeds between grades

Believe it or not, I HAD/HAVE flood cooling on my little Atlas. Makes a mess, but when you need it, you need it. I say had/have because I hvae not NEEDED it since I moved 5 years ago!! Recently, I've been working mostly in brass, and I'm actually speed limited by a counterboring operation, so turning and the like have not needed flood cooling

I hope my one paying client doesn't get TOO shocked at the price jump next time he orders. Hvae you looked at the price of brass lately? GASP
 
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