# the 1 st  tool bit



## jam (Feb 1, 2014)

the 1 st tool bit that I sharpen by hand  this is how it cut a 1 1/2 rod
	

		
			
		

		
	




	

		
			
		

		
	
 not the best but a start


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## Brain Coral (Feb 1, 2014)

Good morning Jam,

That finish looks great from here...  :thumbzup:  You must have had a smile of satisfaction on your face after your first tool bit grind worked out so well. 

Cheers.... 

Brian


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## Ray C (Feb 1, 2014)

Very good...  Keep practicing.  For extra credit, make-up a target diameter and see if you can turn down precisely to that value -regardless of what the finish looks like.  And for extra-extra credit, practice turning it down to a known diameter with different finish types.


Good work... Be Safe, Have Fun.


Ray


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## righto88 (Feb 1, 2014)

Looks good, Let's see a photo of what your tool bit looks like!


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## chuckorlando (Feb 1, 2014)

Nice work my man. 

Ray, would you mind talking a bit about how to get different finishes?





Ray C said:


> Very good...  Keep practicing.  For extra credit, make-up a target diameter and see if you can turn down precisely to that value -regardless of what the finish looks like.  And for extra-extra credit, practice turning it down to a known diameter with different finish types.
> 
> 
> Good work... Be Safe, Have Fun.
> ...


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## Ray C (Feb 1, 2014)

chuckorlando said:


> Nice work my man.
> 
> Ray, would you mind talking a bit about how to get different finishes?



OK, I can start the discussion now but, I have errands today.  Also, I want others to write in and share their experiences as we can all learn...


I want to reiterate that it's more important at first to attain the ability to turn to a specific diameter regardless of the finish.  There are different things to learn and if you take it step-by-step like this, you will not encounter evolving, simultaneous problems.  Also, I'm not an expert on using high-speed-steel bits.  I do indeed use them for specific purposes but not for general purpose cutting; as such, my bag of tricks is limited.

Keep in mind that as you turn a piece of unknown metal, several things are going on.  Since the metal is unknown, it may have layers of hardness that impact finish.  Harder metal cuts with a cleaner finish (up to a point -but then gets ragged for really hard metal) and as you cut into it, the piece evolves as you reach the softer core.  Also, as the diameter decreases, you need to adjust your RPMs to attain the proper SFM cutting rate.  This adds a layer of variability if you have a machine with few speed steps or don't have a variable speed lathe.

Keep the above things in mind as you progress.

In general rougher finishes are done with a pointier bit and a slightly faster feed rate.  Smoother finishes are the opposite... slightly rounded point with moderate to slower feed rates.  On smooth finishes, the vibration in your lathe setup makes all the difference in the world -so that's a area to watch out for.

The real battles to overcome in either case, is knowing what feed/speed to use and depth of cut.  When I come back, I'll cover some examples.  Later today, I was planning on setting-up some HSS bit holders because, in the last couple weeks, they've gotten out of whack.  I'll take some pics...  In the mean time, others are encouraged to share their thoughts....


Ray


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## GK1918 (Feb 1, 2014)

Good job, your off to a running start.  Its only gonna get better.


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## chuckorlando (Feb 1, 2014)

Hitting the marks never been an issue for me. Most anything I have turned has come out in the .0001 range. If it dont, I was simply not paying attention good enough I figure. Feeds and speeds on the other hand is something I need to work on.

Now you mention slowing the feed gives a better finish. Would one need to slow the spindle speed as you slow the feed? Or simply just slow the feed rate? 

You can look at a cross section of our class projects and clearly see a range of finishes. All perfectly acceptible for our level and what we are making, but clearly some better then others. Some with more tooling marks, some with more shine.

Thanks for taking the time. If need be I can start a thread on it if the op dont want us OT in his thread


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## righto88 (Feb 1, 2014)

chuckorlando said:


> You can look at a cross section of our class projects and clearly see a range of finishes.  Some with more tooling marks, some with more shine.



If your fellow students are taking notes and will share with others I believe you will find some answers. Also your instructor should be 
able to help. It would be nice to compare notes and ask questions such as "what were the settings, feed, speed, tool shape, ect,"


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## hvontres (Feb 1, 2014)

chuckorlando said:


> Hitting the marks never been an issue for me. Most anything I have turned has come out in the .0001 range. If it dont, I was simply not paying attention good enough I figure. Feeds and speeds on the other hand is something I need to work on.
> 
> Now you mention slowing the feed gives a better finish. Would one need to slow the spindle speed as you slow the feed? Or simply just slow the feed rate?
> 
> ...



Unless you own a Hardinge HLV-H or something similar, the feed on you lathe is set in "/Rev. In essence, you are always cutting threads on a lathe, just most of the time the pitch is so fine that you can't see it. So when you reduce the feed on a lathe to get a better finish you are reducing the "pitch" of your thread to the point where it no longer matters.


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## Ray C (Feb 1, 2014)

Ok, here are two basic HSS bits that I use frequently.  These are all right cutters but, I have them in left side too.  The first has a slightly rounded point.  These are not good for cutting up against a tight shoulder but, they give a nice smooth finish in most cases.  These are not fancy grinds and they are easy to make.






In all these test cuts, we're working on A36 Hot roll.  The outer hard skin and scale was cut off with a carbide bit.  Always use a sacrificial bit or junky piece of carbide to cut that outer scale off as it will eat-up a fresh piece of HSS.   Since we're using A36, you will always get a dull gray finish.  It's not really possible to get that mirror glossy look with A36 -so don't even try. 

The first thing to do is measure the diameter so you can calculate RPMs.

RPMs = 4 x SFM / Diameter.  SFM for A36 is about 125 and the Diameter is 2".  4 x 125 / 2 = 250.

I'm leaving the RPMs at 250 and am taking cuts of 0.008".

[EDIT:  BTW, I'm adjusting the overhead lighting so that every line and imperfection shows up.  This is to help demonstrate what the finish looks like].

With IPR (Inches Per Revolution) at 0.004, it's a very smooth matte finish.  If you wipe it with a towel, it will not get snagged or leave lint behind.  This is a finished piece of metal that needs no touching up.  You could polish it with emery cloth if you wanted too.




With IPR at 0.006 it's still a smooth finish but, will snag a towel lightly but not leave a lot of lint behind.




With IPR at 0.012", still smooth to the touch but, will snag a towel and leave lint stuck in the finish.





Now comes the spear-point.  I use these to get right up against a shoulder and make a clean edge.





Same RPMs (250) with IPR at 0.008".  Keep in mind, all DoCs are 0.008" and that not enough to significantly change the diameter so, I'm leaving the RPMs at 250.   Anyhow, at IPR 0.008, to the touch, this is a very noticeable ridged finish that will snag a cloth.




IPR at 0.004".  This is much smoother and refined; still snags a cloth but not as badly.




There's more to discuss about what to use, when, where and why.  All kinds of factors also come into play if you're working with low, medium or high carbon metal but there's a similar theme across the board when using these two common HSS cutting bits.  For now, I just wanted to get some photos up so you can see that once RPM is set properly, feed-rate and bit configuration are what control surface finish.

Ray


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## chuckorlando (Feb 1, 2014)

Thanks guys. So it seems slower feed is a better finish all things considered? To a point I am sure. If so, thats the exact opposite of what I was trying to do. ahahaha. I never thought about using old tool to take the scale. That would likely explain why the face mill inserts did not seem to last as long as I thought they should on my last tool.

The teacher just got us our speeds and feeds paper work last week. Unfortunately the school dont have as much interest in our needs as him. So almost all the paper work we get are copies of from his apprenticeship or copies from his personal books and notes. 

Our instructor told us to start at about 50% of what is in the machinist hand book and work up till we think it's proper. Logic being all machines are not equal and your better safe then screwed.


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## Ray C (Feb 1, 2014)

chuckorlando said:


> Thanks guys. So it seems slower feed is a better finish all things considered? To a point I am sure. If so, thats the exact opposite of what I was trying to do. ahahaha. I never thought about using old tool to take the scale. That would likely explain why the face mill inserts did not seem to last as long as I thought they should on my last tool.
> 
> The teacher just got us our speeds and feeds paper work last week. Unfortunately the school dont have as much interest in our needs as him. So almost all the paper work we get are copies of from his apprenticeship or copies from his personal books and notes.
> 
> Our instructor told us to start at about 50% of what is in the machinist hand book and work up till we think it's proper. Logic being all machines are not equal and your better safe then screwed.



For HSS, yes...  Slower feed usually gives smoother finish.  

It's very important to have the proper SFM charts available so you can calculate the proper RPMs.  Here is a good chart:  http://www.southbaymachine.com/setups/cuttingspeeds.htm

Equally important is knowing how to set the lathe for different Feed Rates.  Some lathes have a couple levers and some you need to change gears.  Some are hybrid (like mine) in that there are only a couple feed-rate gear combinations and each one supports quite a few different feed rates which are selectable with a dial setting.

Also for HSS cutting bits, your feed rates will almost always be between 0.003 IPR to 0.015 IPR.  Anything slower than 0.003 and you'll fall asleep before the cut finishes and anything faster than 0.015 will be too coarse and wear-out the bit too fast.  (The same speeds are true for carbide but, for different reasons).

And finally, high RPM rates will break, wear out or burn-up HSS real fast.  The typical chart that I showed you above is a very good starting point that, depending on the batch of material, will only need to be tweaked about 5-15% up or down to find the sweet spot.  Most of the time, unless you have a variable speed lathe, you can't get it perfect anyhow.

Go ahead.  Experiment but, I urge you to practice on particular finish style and focus on nailing a given diameter within say, +/- 0.001".  Once you can do that, switch to a different finish style and practice again nailing a particular diameter.  Guess what?  Sometimes the techniques of nailing a diameter are different given the type of finish you're after. 


Ray


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## Ray C (Feb 1, 2014)

Something to keep in mind...  If you have a machine with a lot of vibration, slower feed rates (regardless of RPM) will kill your surface finish.  If the machine is shaking like a leaf while taking it's graceful time to make the cut, that gives plenty of time for the vibration to show-up in the surface finish.

I've written much about how to stabilize a lathe but, if it needs to be reviewed, please ask the question by starting another thread.


Ray


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## chuckorlando (Feb 1, 2014)

Thanks for the link. I see I have been using to much spindle speed on the face mill. Lesson learned. On the bright side it gave me a chance to practice my lapping.

Thanks


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## jam (Feb 1, 2014)

Brain Coral said:


> Good morning Jam,
> 
> That finish looks great from here...  :thumbzup:  You must have had a smile of satisfaction on your face after your first tool bit grind worked out so well.
> 
> ...




thanks man yes I do


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## jam (Feb 1, 2014)

Ray C said:


> Very good...  Keep practicing.  For extra credit, make-up a target diameter and see if you can turn down precisely to that value -regardless of what the finish looks like.  And for extra-extra credit, practice turning it down to a known diameter with different finish types.
> 
> 
> Good work... Be Safe, Have Fun.
> ...


 


I can do a target diameter   I need all the extra credit I can get what finish type do I need to do I have 1 EXTRA CREDIT  I need 2  
 no bs I *Need All the Advice I Can Get*... 
:LOL::help:


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## Ray C (Feb 1, 2014)

OK, see if you can make a spear-point bit like the one I showed.  -Not the rounded edge (soft point) one, the spear point.  Do that then, make a couple cuts at different feeds and show us the results.  Take nice close-up pictures like you did last time.  Keep your DoC (Depth of Cut) at 0.008".  Tell us what diameter stock and what RPM you'll use...

Start there and we'll play it out...

Ray





jam said:


> I can do a target diameter   I need all the extra credit I can get what finish type do I need to do I have 1 EXTRA CREDIT  I need 2
> no bs I *Need All the Advice I Can Get*...
> :LOL::help:


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