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What cutting tool i need to use for a long ID chamfer?

ISOLVE

Plastic
Joined
Feb 1, 2024
Hello Everyone, Rookie here. I am trying to cut the 45 degree chamfer as in the attached pic in my tormach 15L pro cnc lathe machine. May I know what cutting tool I need to use? I used a straight cutting insert and i broke it. LOL. I am very new to the CNC machining. TIA.

EDIT: Or may i know how to cut the chamfer? my bar size is .375".
 

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Well you will need a boring bar that will be able to fit in the center hole. .250" looks like it would work.

Otherwise there's no reason the boring bar you have pictured couldn't cut the chamfer. Did you try to take it all in one pass? You will need to take roughing passes before you take a finish pass with the bar following the angle. It should look like stair steps.
 
Well you will need a boring bar that will be able to fit in the center hole. .250" looks like it would work.

Otherwise there's no reason the boring bar you have pictured couldn't cut the chamfer. Did you try to take it all in one pass? You will need to take roughing passes before you take a finish pass with the bar following the angle. It should look like stair steps.
Thank you for your reply. Unfortunately I don't have .250" Boring bar.
I tried to cut it in two ways:
1. ID cycle with depth cut but for that I need a boring bar which fits the hole .250". So I didn't try this method.
2. Chamfer method, where the cutting starts from the edge of the .250" hole. after a two cut my insert broke. (not the cutting tip but the opposite side of the cutting tip)
 
Just an id cycle with depth cuts, nothing special then 1 cut to finish it.
What does Tormach offer as far as conversation toolpaths go?
I tried that but my boring bar is bigger than .250" hole size.
 
If I was doing that on a manual lathe I might go in with a larger drill to clear the path only a safe depth, so my boring bar would fit.
and I would hold my boring bar to a similar hole size to see that my boring bar wouuld not bump the part below the cutting edge, hold it to a washer or something..

Perhaps hold the boring bar over the print if it was to scale(same size) to see the other aspects of the boring bar would not bump the part where it was nor suposed to, not bumping where it should not bump.

Perhaps make a quick sketch of the part and hold the boring bar over the sketch and mimic the cutting path I intend to take.
 
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If I was doing that on a manual lathe I might go in with a larger drill to clear the path so my boring bar would fit.
and I would hold my boring bar to a similar hole size to see that my boring bar wouuld not bump the part below the cutting edge, hold it to a washer or something..

Perhaps hold the boring bar over the print if it was to sale(same size) to see tae other aspects of the boring bar would bump the part where it was nor suposed to

Perhaps make a quick sketch of the part and hold the boring bar over the sketch and mimic the cutting path I intend to take.
You know what, that is a very good idea. I am gonna do that today itself, appreciate your help.
 
Boring is a whole new ball game. Sometimes you bore on the back side of the part. Very often the wrong boring bar will rub below the cutting edge..or the insert will not have enough clearance to miss the arc the hole size makes. From here it looks like your boring bar might bump the part's other (opposit) side.
 
A trick I used to use for sharpening or designing a boring bar was to draw the part 10x scale and then draw my tool so it would fit into the bore with the proper clearance angles,..and so not rub or catch chips in a wedge between the tool heal and the part...
 
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Taking your time you can do a one-up, few-up with a tool bit.
If a production part then buying a boring bar/ or making one should be justified.
You could grind off a broken HSS drill bit and make a boring bar out of it. Use a large drill bit and grind off the end at 60* and small at the end so it can fit a little into the .275 hole a little.
Grind off most of the flutes so it is stronger

Bench grinder needed.
 
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I'm amazed how many people treat machining like a game, if you don't know the basics you shouldn't be going anywhere near a CNC lathe, even if it isn't a real one.
 
The book How To Run a Lathe give some insight on boring that a CNC guy should know (10 bucks well spent)..Buying a book on boring woud be a asset to any new lathe guy/gal, CNC and manual machines..

Boring is so different that learnig by try and error will take so long with many bad surprises that to buy a book may be a quicker method to success.

This may be a good book to buy(?). $35.00
 
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I have no experience of programing or operating cnc, but lots in the manual field.
Could you not have the boring bar angled to 45 degrees and have it fed into the job at 45 degrees (like a conventional compound slide would do).
That way, the 0.375" boring bar will probably clear the 0.250" hole when it just finishes cutting the desired taper.
 








 
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