A curious comparison between me (the beginner) and you (the pros)

M

Maplehead

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Hi All
So pictured below you see to mild steel blocks. The one on the left is cut from my bar stock without anything else done to it. The one on the right is a "finished" blank. Later it will be milled into my guitar bridge.
Stock block
L 2.92"
W 1.668"
H .986"
Finished blank
L 2.79"
W 1.625"
H .955"
My comparison here is a question. How long would it take you pros to turn the block on the left into the finished blank on the right?
I have added into the pic the tool I use to do the above. I get nervous about heavy cuts with these little circular blades on the tool so I only make at most .010" cuts.
I run the tool at 1000 RPM's. (I usually start with .005" cuts until the patina is off then I go to .010" cuts, and I use my x axis powerfeed running slowly.)
When I get within .010" of my final dimension I then go to a .005" pass, then a .003" pass, then .002" pass and finally two .001" passes at double the speed.
My goal with the small cuts is to minimize the depth of the swirls because I do the real finish with hand sanding.
I'll share with you later how long it all takes me. For now I'm curious and I would love to know how long it takes you pros to make the finished blank.
 

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Not a pro, just an amateur with a token amount of experience.

Depth of the swirl pattern from the cut is mostly a matter of how much feed per tooth, not the depth of cut, unless you go so deep you get chatter. If your mill is capable, generally it is better to take a fairly deep initial cut to get the mill scale off the rough part, as that scale will wear the cutter down more than the internal steel. I wouldn't hesitate to take .020 - .030" depth of cut, as long as your machine can handle it without chatter. And play with the depth on the finish pass You may find it gives a better finish if you make the finish pass at around .010 or more depth of cut. A lot depends on your insert geometry, look at the specs that came with it. Typically there is a range of DoC, including a minimum. Below that, the insert tends to slide/scrape across the surface rather than truly cutting.

Feed per tooth: You have 4 cutters (teeth), so at 1000 RPM, thats 4000 teeth per minute. If you're feeding at 5" per minute, thats 5"/4000 = 0.00125" per tooth, which is a pretty shallow cut per tooth. Again, the box your inserts came in should have a feed per tooth spec. You probably don't want to go for the maximum of that spec, but near the min is pretty good, especially for finishing.

These are things you may want to clamp up a piece of random stock and try before working a part to target dimensions.

How long? Would depend on how close to those finished blank sizes I'd need to hit. I'd probably give a wild *ss guess of about 1.5 hours to get set up, do the cutting, and token clean up afterwards. That's assuming the vice is on the mill and the mill tram is known to be OK. But it's not a race. I do this for fun. I walk into the shop and start working on something. If it takes longer than it takes, it just does. I don't get caught up on estimating time. That's for guys that do it for $$$, I'm playing.
 
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Taking very shallow cuts with carbide inserts has never worked well for me. I can get excellent finishes with HSS and if really needed I can take fairly thin cuts. Sneaking up on size will likely result in too thin of final passes. At some point a carbide insert quits cutting and starts burnishing, rubbing, rather than cutting. When you get to .025+- to go, measure and take half of the remainder. Measure again adjust if needed and take the final pass. The tool will be lifting the chip and not burnishing. Obviously your holding system has to be ridged or you will have problems. People have gotten by W/O DROs for a long time. But they sure are nice because they show you where things are in real time, not where you hope they are. As extra insurance lock any axis not moving for the final pass.
 
Not a clue. Oh wait..I'm not a pro. But on a good day, with the wind blowing in the right direction, at low tide, facing a rising sun, with a coffee on the bench, and both my good eyes....
Nope. I still don't know.
 
Looks like a 3” face mill. Let’s say’s 2-3 passes per side. Shouldn’t take to long a hour tops. Ive never used a circular insert but I’d think they’ed give a mirror finish with proper speeds and feeds.
 
Cadillac said:
Looks like a 3” face mill. Let’s say’s 2-3 passes per side. Shouldn’t take to long a hour tops. Ive never used a circular insert but I’d think they’ed give a mirror finish with proper speeds and feeds.
Click to expand...
I'd love to know how to get a mirror finish from that mill.
 
Not more than 10 hrs...


J/k... maybe an hour if I had to tram the vise in...

-Bear
 
I’d imagine a pro would use CNC for the whole thing.
 
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