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Old 08-06-2011, 05:12 PM   #1 (permalink)
 
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Default Why *I* Use a Cutting Lubricant/Coolant

I ran a little test to see the differences between drilling with a lubricant and without.
Note: This was done out of curiosity, not to call anyone out on their process.

The picture below consists of 3 pieces of 1/2" diameter, extruded acrylic rod that I drilled an 8mm hole through. All were drilled at the same speed (1650 RPM) and approximately the same feed (3/8" per plunge).

Now, this being extruded acrylic, these results are (or at least should be) exaggerated when compared to cast acrylic. If anyone has some clear cast acrylic around that they'd be willing to experiment with, I'd be interested in seeing those results.

I started with the piece on the right. No fluid was used in drilling this piece.

The middle piece was drilled right after the first using a small squirt of water after each plunge.

The piece on the left was then drilled using "PAM Spray for Grilling". As before, a small amount was sprayed into the hole after each plunge.

Finally, I set another piece of acrylic in the vise and drilled it. This was done to see if the cumulative heat build up had an effect on the pieces. Other than the residual spray on the bit, no fluid was used. About three quarters of the way through, this piece actually melted in half on my drill bit and is not shown.
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acryliclubecomp.jpg  
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Last edited by HeathRiley; 08-06-2011 at 07:51 PM. Reason: add emphasis to exaggerated result
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Old 08-06-2011, 05:29 PM   #2 (permalink)
 
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heath, Im trying to understand why you feel you need to lube the drill hole(so to speak)? Sorry about the "out of context", if you drill using a lower rate of speed and your plunge rate is also slow using 1/4" increments, you should be ok. A sharp bit also helps! Sometimes i hold my shop vac up to the blank vise to suck the shavings out as its drilling and my thinking on this is that those are also heating up, so i get them out of there, and at the same time the suction that is coming from the vac is drawing air across the bit in hopes that it actually helps to cool the blank. hope this helps.
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Old 08-06-2011, 05:33 PM   #3 (permalink)
 
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Very interesting results.
Its always fun to experiment.
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Old 08-06-2011, 05:45 PM   #4 (permalink)
 
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Heath - depend on the objectives and outcomes -

Drilling lucite, extra care and measures to keep drill marks from happening has value because I want them polished out. My observation is that use of high quality drill bits that are very very sharp, I am not getting much for marks. Personally I am having best results with premium bits such as Colt and Norseman. That goes as far as having the few bits I use in clear/translucent sent to the tool grinding guy and paying a few bucks for a premium grind.

As I remember from Ed Davidson (Yo-Yo Spin) in one of his DVDs -- extruded is not the good stuff for turners -- cast is the stuff to get. The reason that Ed gave is that the extruded melts easily in turning.

Last point -- If you are getting so much heat that the media is melting onto the bit, you are doing something wrong. I have done that with with work hardening while drilling Stainless (how to trash a tungsten steel bit in a hurry) and just changed bits at the first sign of losing the ability to cut below the workhardening.

The materials you are using (water - pam etc) are for cooling and for transporting swarf. You are getting a lot of friction if you are melting acrylics onto the bit. That suggests you are not cutting clean -- as in the workhardening of stainless and easily could be a less than sharp bit.

There is nothing wrong with using coolants with maching operations -- but they do add cleaning steps and the possiblity of contamination as well as a level of mess. Dishwashing detergent in water and mineral spirits (or kerosene or stoddard solvent or similar) can be used. WD 40 (which is mostly mineral spirits has been used a lot) --

So --

What kind of bit are you using. Drilling on the lathe or drill press. What kind of vise to hold the blank. How fast is your feed rate -- what is the runout on your drilling rig?? How are you cleaning your work up before going to the next step to assure you will not have contaminats on the blank.

I think I saw an earlier thread where you were struggling with paint on the inside of blanks.


(heat is a function of friction and you should not be seeing much friction in a good boring operation)
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Last edited by KenV; 08-06-2011 at 05:52 PM.
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Old 08-06-2011, 08:27 PM   #5 (permalink)
 
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My purpose for posting this was to show how much heat build up there is between using coolant/lubricant and not. When I drill, I do it in batches. I prefer to minimize the amount of down time. Less heat build up equates to less time spent waiting for bits to cool off. I've never had an actual pen blank melt on me while drilling.

I guess it isn't common knowledge that extruded is a less desirable form of acrylic for machining. I've edited the original post to emphasize my point of the exaggerated results (extruded vs. cast acrylic).

I am using Norseman bits with factory grinds on them. Ken, when I need to sending these out for sharpening, is a there a specific type of "premium" grind I would ask for?

These were drilled on a Rigid DP15000 drill press. I'm not sure what the runout is on this. An inexpensive self centering vise was used for work holding. Feed rate...about 2 seconds per plunge at 3/8" per plunge...so 3/16" per second.

I have used the lathe when I have a blank small enough to fit in one of my collet chucks.

As far as cleaning up contaminants: I have a bucket of soapy water that I toss the blanks into after drilling and let them soak for a bit. I then take a bottle brush and scrub the holes, and rinse. When the water stops beading up, I call them clean enough.
However, someone has recently recommended acetone, so I'm going to give that a go.

If there are any recommendations on a cutting fluid that is safe for acrylics and water soluble, please let me know.
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Old 08-06-2011, 09:48 PM   #6 (permalink)
 
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Heath -

As with stainless, I would slow down the drill press a bunch -- The materials you are cutting are not hard and the feed rate should not be much differrent, but the heat produced at a few hundred RPMs will be much much less. Slower speed will be less sloppy with swarf and coolants too. Smaller swarf pan can work.

Norseman is a good quality bit!!! Have a someone with fine diamond grit tool and die gear and skills do the grind. The local saw sharpening shop here will do drill bits and he uses a drill doctor (fair to good for general purpose uses, but not for really a premium sharpening for good cutting). You need someone with good gear and good skills to get a premium sharpening. In Portland you should not have a problem finding a tool grinding shop with decent gear. (I spent 8 month there on a temp duty assignment a couple years back -- neat City!!!!)

Water with a drop or two of dishwashing detergent is probably most adequate for a cutting fluid. If you are doing lots of drilling - a mist coolant spray on the bit otherwise a drip system will do. That will be a lot less mess than milk - the recommended coolant for drilling copper.

Get a bronze brush as used for gun cleaning and run it through to get the swarf out or run them through a dishwasher stuck on the pins with a rubber band on top for restraint.

P.S. It was Ed Davidson's DVD on one piece yo-yos that discussed the difference in cast vs extruded acrylics.

Ken in Juneau
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Old 08-07-2011, 01:29 AM   #7 (permalink)
 
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Thanks for the feedback, Ken. I'll take your advice into consideration, do more extensive testing when time allows, and post my results.
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Old 08-10-2011, 03:19 PM   #8 (permalink)
 
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Heath, looks to me like you have a good system. I would keep using it. I don't have a problem with the drilling speeds ans some lubricant. Like the picture shows, it works to make a better hole. Those not using a lubricant, i would deffinately slow the rpm down a bit. Thanks for the tests results.
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Old 08-10-2011, 03:27 PM   #9 (permalink)
 
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I haven't done any extensive research on lubricants for drilling, EXCEPT that the only way I can drill Bakelite is with a brand new bit and Pam. Otherwise, about 1 1/2 inches into the hole and I hear that dreaded crackle. Look up the side of the Bakelite and there will be a perfectly straight crack line from the very top to the very bottom of the blank.

This is drilling on the lathe at 500 rpms and begin very gentle with the TS screw.
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Old 08-10-2011, 03:57 PM   #10 (permalink)
 
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LOL here is a test and photographic evidence that what we have been taught since metal shop in junior high is in fact correct, a cool bit drills a better hole. That holds for any speed folks! Only question is does using lubricant provide a significantly better hole to warrant using it?

Get a huge kick out of those who have to say "but your picture is wrong and here is why......" I even learn a bit, think I'll do some testing of my own and slow the drill press down a bit more.
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