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Help with Insert Feed/Speed chart

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Splat

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#1
I have my first boring job to undertake. I need to bore a 0.787" hole 1.75" deep in 1.25" diameter 1045 steel bar. I'm using a CG5 CPHB21205 insert in a Circle/Widia 3/8" carbide bar. I'm trying to figure the SFM to deduce the RPM needed. I'm looking at the Widia/Circle catalog (here) and I don't understand the speed and feed chart found on page 62. What's the "ap [inch]" or "f [inch]" column mean? I've looked all over the catalog but can't find what that is. Is that a hardness rating of the work? :confusion:If I knew what that was I think the rest would hopefully fall into place. Really appreciate help here. Thanks.
 

mikey

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#2
Splat, I am attaching the Tech catalog from Circle Machine, which is far easier to understand than the Widia publication. Look at page 16 under medium carbon steel and see if this answers your question. Note that SFM varies with grade, while depth of cut varies with the insert geometry.
 

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Splat

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#3
God bless ya, Mike! I'm gonna take a look at that attachment. I'll let ya know. Thanks buddy!
 

mksj

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#4
There is a difference between boring and milling as far as the legends. ap [mm] and f [mm/rev] are milling characteristics, I would think that cutting speed m/min would be relevant to boring. You can use the equations below to calculate the drilling parameters. Each metal may have unique properties, 1045 is considered medium carbon steel or P2. I assume you are boring with your lathe as opposed to a boring head, I would suggest drilling out most of the material with sequential drills to 3/4" and then do something like a .765 cut wit the boring bar to check the hole sizing and then do a final dimensional cut. I often find that I need to calibrate the DRO to the bored hole size (cut dimensions).

Seems no way to get the resolution up in the pictures posted anymore so attached a PDF.
Wadia Insert Steel Milling and Boring.jpg
 

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Last edited:

george wilson

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#5
Your chips should be brown hot. Assuming you are using HSS or carbide. Regular carbon steel cutters(which I make all the time to turn special moldings) won't take the heat. But work just fine at slower speeds.
 

Splat

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#6
Thanks guys. The attachment Mikey sent is easier to read than the chart I was referencing. MKSJ, that's more good info there and that definitely helps. Gonna try my first boring attempt tomorrow morning. I'll let you know how it goes.
 
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