tapered bore

savarin

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I need to bore a narrow taper into an 8mm hole approx 25mm long.
I turned the taper that has to fit in it by setting the compound over.
I've kept that degree setting but now need to bore the internal taper.
What would be the easiest method when I do not have a boring bar that will fit in that hole.
 
Make a a boring bar from a HSS sq. blank that cuts on the back side of the hole and run the lathe in reverse. You will not have to change the settings that way and have a perfect fit. Go easy if you chuck threads on.

"Billy G" :))

You will need one that is opposite cutting of the one below.

bbb (700 x 525).jpg
 
Another option would be to make a half round reamer and cut your taper with that. Cut another taper like you did before out of drill rod and mill half of the tapered section away so you have a flat to the center line of the part. Then harden it, stone the flat until it's sharp and ream your tapered hole to depth using lots of cutting oil.

Tom
 
This is a timely topic for me as I'll shortly be boring my first internal taper, which will be the recess for an ER32 collet in the chuck I'm making.

Is it normal to bore in reverse, i.e. from the narrow back to the wider front of the taper, or should it be done in the 'normal' direction for boring, front to back.?

Unlike the OP I'll have plenty of room for a regular boring bar.

Thanks,


M
 
Your Taper should be cut in the normal manner because you did not cut the male. The reverse cut is done when you have made the male and need a perfect fit of the female. They can both be cut one after the other without moving the top slide. just move the cross slide in and reverse the lathe after you put in the new cutter.

I think you may be confused. The cut is the same (right to left) except you are cutting on the other side of the hole (from the back of the lathe) This is why you reverse the rotation of the chuck.

I have to leave for a short time. If you have more questions and they don't get answered I will get to them as soon as I get back.
"Billy G" :))
 
Bill, I think he may have been asking which direction to feed, not whether to cut on the front or the back of the bore. :confused:

You feed in the direction that your tool is ground. In other words if you want to cut on the front of an internal taper and feed right to left (normal as Bill called it), you'll need to grind a left hand tool. If you want to cut on the back side of an internal taper and feed right to left (reverse), you'll need to grind a right hand tool. You generally feed toward the headstock when turning or boring (right to left), especially if you are turning to a shoulder where you would feed to the carriage stop.

Tom

lathe_tools_std_shapes.jpg

lathe_tools_std_shapes.jpg
 
Yes, never having cut an internal taper before I don't know what's normal.
The taper will be 8 degrees, I assume I set that on the compound then use the carriage to feed?
How do I increase the depth for each pass? Should I use the cross-slide as I would for a parallel bore, or should I use the compound feed as I would when cutting a thread?

I'm assuming I start the cut on the side of the bore closest to the tool post and go from right to left towards the headstock.

Thanks,


M
 
You set the taper on the compound and use the compound crank to feed. If you have a taper attachment on your lathe, then that would be the better option. Either way, depth of cut is controlled by the cross slide dial.

Yes, feeding right to left is the way to go.

Tom
 
You set the taper on the compound and use the compound crank to feed. If you have a taper attachment on your lathe, then that would be the better option. Either way, depth of cut is controlled by the cross slide dial.

Yes, feeding right to left is the way to go.

Tom

Thanks, I think I've got it now. :))


No taper attachment on this lathe though, it's a small 7 x 12 Sieg.


M
 
Last edited:
Just got back. Thanx Tom for picking this one up. I owe you one. Mike you should be all set. Tom gave you good info.

"Billy G" :))
 
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