Author Topic: Zee Needs Popcorn  (Read 57470 times)

Offline Art K

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Re: Zee Needs Popcorn
« Reply #120 on: July 19, 2018, 03:07:20 AM »
Zee,
Thought I'd let you know that I am following along. I've been on vacations for the past two weekends, yes an extra long 4th. Sorry to hear about the trireme, is that just a matter of reprinting the associated parts? The boring bar meeting the chuck, been there done that, just with less a shower of sparks than you. :mischief: I have a set of boring bars that I got with my Criterion boring bar set, carbide I might add. But it came with a set of 9 bars all 1/2" shank. Basically 3 diameter sizes & 3 lengths. Having said that when I built the Upshur single I needed to bore the cam gear 3/16". So I bought a very small one from Travers Tool, I then used it on VAL. You had mentioned having trouble drilling larger drills, was that related to the off centered tail stock and would it drill fine now that you have it centered? The final result on the cylinder looks good, any chance you can face it to length? I really was way behind... :facepalm2:
Art
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Offline crueby

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Re: Zee Needs Popcorn
« Reply #121 on: July 19, 2018, 03:08:54 AM »
Going all in one go should work, though you might get chatter as it starts, till it gets the whole drill diameter in the metal. When step drilling, I usually go every other fractional size. If you have some offcut brass, good time to run a couple of tests to work out sizes and speeds.

Offline zeeprogrammer

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Re: Zee Needs Popcorn
« Reply #122 on: July 19, 2018, 04:04:56 AM »
Hi Art. Regarding the trouble with drilling larger drills. I mainly have issues with brass. Not really surprising. When drilling in the mill, I often have issues just as the bit breaks through to the other side. I've read in places that drilling brass may require a different set/type of drill. I'm not sure. I know when turning brass, the shape of the cutter is different than for other metals (i.e. flat).

I'd be interested in knowing if there's a method of drilling to reduce that problem. As in...as one gets close to breaking through, do you do something different?
For that matter...I need to learn more about rotational speed of the drill bit.

Cylinder is already faced to length and because of the step in the bore, it's a loss...other than it was useful to practice milling the curve.

@Chris...when you say 'every other fractional size'...that tells me every 1/32. No?

As for when chatter begins...(this has happened to me before)...think about the shape of a center drill. 60 degree angle and then to a straight, short, little bit. The problem seems to occur when the drill reaches the end of the angle and the straight bit begins. I'm not sure.

Good idea to run some tests. I have bits of brass that are too short to make anything out of but big enough to drill.

Ah. I see it's after 5 again.  :cheers:
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Offline zeeprogrammer

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Re: Zee Needs Popcorn
« Reply #123 on: July 19, 2018, 04:07:26 AM »
Does anyone have a favorite chart showing drill bit size versus rotational speed versus material type?
Or is there a general rule to go by?

Thanks.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Offline crueby

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Re: Zee Needs Popcorn
« Reply #124 on: July 19, 2018, 04:27:25 AM »
Yes, 32nds, in general. When breaking through I will slow the feed to keep it from grabbing. Even in the middle, feeding too fast can make it grab and stall. On narrow and/or deep holes, need to back out if chips are nit clearing. If you hear or feel it binding, could be a chip jam near the tip, which can overheat and stall things.

Online Kim

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Re: Zee Needs Popcorn
« Reply #125 on: July 19, 2018, 05:23:38 AM »
Yes, 32nds, in general. When breaking through I will slow the feed to keep it from grabbing. Even in the middle, feeding too fast can make it grab and stall. On narrow and/or deep holes, need to back out if chips are nit clearing. If you hear or feel it binding, could be a chip jam near the tip, which can overheat and stall things.
This is an interesting sub thread, Zee.

I've always done 1/16" steps or even 1/8" steps in drill sizes (in brass or otherwise).  I don't know if this is right or not, but I have used speeds something like:

190 RMP for 1/2" or larger
300 RPM for 1/4"-3/8"
480 RMP for <1/4"
800 RMP for 1/16"
1500 RMP for really tiny stuff

Not exactly that, but something like this.  I've not done a lot of tiny trilling on the lathe. That's mostly mill. And most big stuff tends to be on my lathe - before boring.

Do these speeds seem reasonable to all you experienced machinists?  I'm just doing what I feel I've heard (slower for bigger, faster for smaller) and what has worked for me in the past.

Kim

Offline 10KPete

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Re: Zee Needs Popcorn
« Reply #126 on: July 19, 2018, 05:26:21 AM »
Would someone please find a pic or description of how to flat the cutting edges on a drill to make it suitable for brass, acrylic, etc.???

I can't find the pic I thought I had and I can't seem to come up with the right words...

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Offline Stuart

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Re: Zee Needs Popcorn
« Reply #127 on: July 19, 2018, 06:16:47 AM »
Zee
Did you back off the dril for brass ie rub the cutting edge with a slip stone to take off the sharp edge.

I have two sets one ground for brass /gunmetal. And another for everything else
My aim is for a accurate part with a good finish

Offline Jasonb

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Re: Zee Needs Popcorn
« Reply #128 on: July 19, 2018, 07:28:55 AM »
Zee if you think you may be drilling something that is going to snatch in the mill don't use the quill levers but instead use the fine feed. If the drill grabs it will pull itself down when hand feeding but the fine feed helps to prevent this.

Another option is to use a milling cutter to open up the hole, the higher helix angle is less likely to snatch.

I've never stoned a drill and don't seem to get many snatches.

Offline b.lindsey

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Re: Zee Needs Popcorn
« Reply #129 on: July 19, 2018, 01:33:57 PM »

Offline zeeprogrammer

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Re: Zee Needs Popcorn
« Reply #130 on: July 19, 2018, 02:10:36 PM »
Thanks everyone.

@Kim...well that tells me I've been running at way too high of RPM.
@Stuart...I didn't modify my drill bits. Along with Bill's post of that helpful video, I'll have to try it.

@Jason...you remind me of something I noticed yesterday when I was squaring up the brass using an end mill. Using the built-in DRO, I would change the quill setting and make a pass. I noticed the DRO would change by 3-4 thou as cutting began. Both the quill and Z axis were locked down.

BTW: When using the fine feed on the quill, I have to make two turns of the fine feed knob before the DRO starts changing. Unusual?
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline Ye-Ole Steam Dude

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Re: Zee Needs Popcorn
« Reply #131 on: July 19, 2018, 02:12:08 PM »
Thanks Bill for that great tip.

Have a great day,
Thomas
Thomas

Offline Jasonb

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Re: Zee Needs Popcorn
« Reply #132 on: July 19, 2018, 02:53:53 PM »
Something not right there Zee the DRO should change almost straight away, slight delay possible going from one direction to the other is to be expected due to backlash.

Offline mklotz

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Re: Zee Needs Popcorn
« Reply #133 on: July 19, 2018, 03:03:18 PM »
1)  You shouldn't be using a center drill; it's the wrong angle for a twist drill.  Use a spotting drill with an included angle near that of a twist drill, typically 118 degrees.

2) For brass, grind small 90 deg flats on the drill cutting edges so it scrapes. Ideally, you should have a whole set of "brass drills" ground this way.

3) Pilot drill the size of the drill core, the central part that doesn't cut because it has no clearance.

4) Below about 5/8 hole size, drill final size.  Drilling in tiny increasing increments is a recipe for chatter.
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Offline b.lindsey

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Re: Zee Needs Popcorn
« Reply #134 on: July 19, 2018, 03:54:07 PM »
Zee, I suspect you have some backlash in the quill and once the cutting starts it pulls the quill down by this amount. Shouldn't happen if the quill is locked so you may want to check that...maybe it isn't locking properly.

Bill

 

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