More CCMT lathe tools

Some more CCMT lathe tools, now I think I have the entire 5/8″ shank “collection” – left hand, neutral, chamfer and boring bar (3/4″). I have commercial right hand tools and 1/2″ boring bar.

ccmt tools

boring bar 34    neutral     champferTool

It was bugging me that I couldn’t figure out how to make these without clamping more than once. Then I got the idea that I could use the insert corner relief as a reference point and if I drilled it all the way through, a mounting and reference point. So I made the set to test the idea and it worked great.

 

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Making tool post tool holders

finished tool holders

Everything here was shop made (even the nuts), except square head bolts and insert & insert screw

Tool holders (for the lathe) gotta be the metal equivalent of wood working clamps: you can’t have enough and when you do have enough, it still isn’t.
I wanted to make a holder for 3/4″ boring bars as the one I have (bought) is 1″ with a reducer sleeve (sorta ick but works well) and doesn’t index bars with a flat. While digging through the stock piles, I found a plate that would make several regular holders.
cutting dovetailsThe first order of business (after squaring the stock – see the previous posts on the fly cutters) was to cut the dovetails. This involves cutting a slot, to depth, then plowing a groove down the center to provide a relief for the dovetail cutter as it really doesn’t like center cutting. I cut this 15 to 20 thou deeper. Ideally I would use a keyway cutter to waste out most of the dovetail but I don’t have one so I went measureing dovetailstraight to the dovetail cutter. The regular posts were cut as one (and sawn apart after). I think this dovetail cutter isn’t ideal and needs some radial and axial rake, it makes quite a racket and gave me a headache even though I was wearing hearing protection. Notice the different colored chips (and shapes); dark blue and curly when I was really hogging out the slot, silver slivers from the dovetail cutter.
To measure dovetail width, it is best to use dowels/pins in the dovetails and measure between them. Here, I’m using an adjustable parallel to do that (1.080″ with 1/4″ pins for my BXA tool post).

tool holders partly finishedMy existing holders are all metric, mine will be all imperial – 3/8″-16 and 3/8″-24. I didn’t have any 3/8″-24 nuts so I just made some (from hex rod) as that was quicker than making a store run. The discs were cut from some rod I knurled.
Next up was the threaded holes. 24 tpi (NF) for height adjustment, 16 tpi (NC) for the set screwspower tapping. One of the holes is blind and some didn’t have much run out room so I used a spiral flute bottoming tap. These taps eject the chip back (spiral point eject the chip forward) and I was able to power tap everything (started the blind hole under power and then finished with a tap handle).

drilled and tappedThe bolts in the photo are interesting; I single pointed them from hex stock. Notice the thread goes pretty close to the shoulder and there isn’t a thread relief groove. I did this by running the lathe in reverse so the threading tool moves left to right, allowing me to position it close to the shoulder without worrying about a crash. I used an internal threading bar on the outer back side of the stock.

I threaded some stainless steel rod cut offs for the posts and locktited them in place.

Here is one of the tool holders with a shop made left hand cutter:

lh tool in holder

And the boring bar holder:
boring bar holder

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Positive vs negative rake: surface finish

pos vs neg

I’m happy with both finishes but the finish left by the negative rake fly cutter is fabulous, almost mirror like, the positive rake fly cutter left a more matte finish. I think the lines are visible because the insert has a small radius (ie more pointy).
Not at all a apples-to-apples comparison, I’m prepping some steel (both unknown alloys) for a project and used best sized fly cutter on each.

Here is the 5″ fly cutter in action (the 2.5″ fly cutter video is in the previous post):

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Fly cutter 2.5 video

I’m enjoying this tool! Makes short work of squaring up stock.

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Fly cutter 2.5

fly-cutter-2.5Since the previous two insert cutters I made turned out so well, I decided to try another, a smallish fly cutter.
I have a Suburban Tools fly cutter and it is a monster by my standards. I got the smallest bar they make (5″, ~$125), cheaped out and made my own adapter (vs buying theirs for ~$200). It is nice but kinda big for my mill and shows that my mill has some kind of funky resonance centered around 1,000 rpm. Pretty annoying shake but everywhere else it is smooth (I’ve run the cutter up to 3,000 rpm). If you look at the picture below, you’ll see why I call it the whirling dervish of flayed flesh. The extra wings are counter balances I added to see if I could tame the resonance. Nope.

whirling dervish of flayed fleshSo, this project. One interesting thing about the Suburban tool is that it has a negative rake, ie it “drags”. A plane blade or chisel has positive rake, a scraper [usually] has negative rake. If you stand a chisel on its nose, tilt the handle towards you and pull, you are using negative rake. Leaves a nice finish but [as I understand it] requires more power and rigidity than positive rake.  As the inserts I bought have built in rake, I decided to make life simple and mount the insert at 90° (zero) and let the insert provide positive rake (11° for this TPGB 321 insert).

fly-cutter-face-faceI wanted to use a disk to keep things as balanced as possible and have the face of the insert on the center line. I had a left over R8 threaded mount (7/8″-20) so I decided to used that for extra rigidity. The disk is ½” mild steel (3″ wide, which ended up giving me a 2.5″ radius cut) with a [vertical] slot cut in it. I machined a rectangular insert mount, also from ½” steel and and proceeded to weld it into the slot backwards. Which really, really steamed my dumplings. Lucky me, I had been anal enough to make everything nice and square so I had reference surfaces I could indicate. Back to the mill and cut a new insert seat.

fly-cutter-butt-faceIt works well. The surface is matte, not shiny like the Suburban tool leaves but still nice and smooth.
I played around with speeds and feeds and the surface shown here (which is ½” hot rolled (black) mild steel) was a skim cut at 2,600 rpm, 11 ipm and 0.001″ DOC, two passes to get full coverage.
And that renounce at 1,000 rpm is still detectable. Damn. But, thankfully, not a big deal.

fly cut

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The wheels fall off

chopped

When I got my quick change tool post set, it included this combo knurl tool & facing holder. Kinda useless as I hate push knurlers. So I decided to make it useful by sawing off the knurler, extending the slot and punching a couple of threaded holes (M10x1). It is made of hardened steel, but it ain’t all that hard (easy to cut with a sharp file) so it didn’t put up any fight, didn’t even notice any difficulties power tapping.

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Dovetail fly cutter

A Randy Richard's dovetail cutter

I got the plan for this dovetail cutter from a Randy Richard video using a screen grab (he’ll email you a copy but it was easy to just grab it). It’s a sweet design using common TPGB321 inserts ($7.25 from Enco). I got these when I ordered the parts for making the champfer tool and made the bozo assumption that all 3/8″ IC inserts used the same screw. Well, no, the fourth letter (“B”) describes the hole (and counter sink) and chip breaker. And B is a 70-90° double countersink vs the 40-60° double countersink of T (CCMT). So the special screws I bought will have to wait for another project. But, at 82°, common flat head screws seem to fit well, in this case a #4-40.

dovetailflycutterI didn’t have any dovetails to cut so I did a test using it as a fly cutter. It did really well on this semi hardened steel, very smooth, I was a bit worried that large flat part of the cutter would chatter.
The cardboard is a cardboard box blast shield to try and keep the chips somewhat contained (and out of my shirt/hair). The unfortunate side effect is that it acts like a popcorn popper with the lid off.

 

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