How to complete this part??

[WesPete66]

I am in process of making a part & could use some pointers.. (Lathe is an Atlas QC54. Am using HSS tooling)
The part is a ring, 2.25 OD x .75 ID x 1.00" long/thick. On one side is a recess, or counterbore, of 1.625 dia x .875" deep. What would be your choice of HSS cutting tool and process to make this recess? I've looked at some youtube videos & haven't found much in common amongst them. Help please?
Thanks!

 

[kd4gij]

I would use a boring bar.

 

[pdentrem]

Lantern tool post or QCTP?
Pierre

 

[mikey]

I would use a boring bar.

I agree.

 

[Wreck™Wreck]

A counter bore is one of the most common operations that you will ever do in lathe work.
Face it and bore it with a boring bar that will fit into the hole that is extended just enough to clear the holder, having not mentioned the material no other parameters may be suggested. At 7/8" deep this far less then one diameter so hit it hard.

 

[WesPete66]

Sorry, yes on the QCTP, and the part is steel (CF from the local welding shop).
But how does one make a boring bar create a flat bottom recess? I'm picturing a boring bar with a .250 square tool bit in a hole, held in with a set screw.. Do you just extend that tool bit out long enough to cut to the full depth needed, while the end of the bar protrudes through the thru-hole?

 

[ddickey]

Are you wanting to grind your own tool?
If so this vid may help

 

[Wreck™Wreck]

Sorry, yes on the QCTP, and the part is steel (CF from the local welding shop).
But how does one make a boring bar create a flat bottom recess? I'm picturing a boring bar with a .250 square tool bit in a hole, held in with a set screw.. Do you just extend that tool bit out long enough to cut to the full depth needed, while the end of the bar protrudes through the thru-hole?

Having not used such a tool in 30+ years I now see why the question was asked. If you insist on HSS tooling buy a solid bar for such a small hole or a bar that holds square or round bits at an angle like so. Cumbersome for small holes however
https://i.ytimg.com/vi/chiJb7Xp2rk/maxresdefault.jpg

 

[Silverbullet]

Many of the older style boring bars have two ends one is straight a cross the bar the other end at 45 degrees to the bar. With that they make it easy to use high speed tools ground to perform the operation. For the bore your doing a self ground bit an extra long tool bit would do.

 

[mikey]

Sorry, yes on the QCTP, and the part is steel (CF from the local welding shop).
But how does one make a boring bar create a flat bottom recess? I'm picturing a boring bar with a .250 square tool bit in a hole, held in with a set screw.. Do you just extend that tool bit out long enough to cut to the full depth needed, while the end of the bar protrudes through the thru-hole?

Okay, I think I might have a simple solution involving a simple HSS tool you can grind quickly. Its called a knife tool and looks like this:



I am assuming you are familiar with tool grinding and will give you simple angles. If you need more info then please let me know so I can clarify. This tool has a side cutting edge angle of zero, side relief of about 15 degrees, an edge cutting edge angle of about 70 degrees with 15 degrees of end relief. It has a side rake angle of 15 degrees and a back rake angle of 10-12 degrees. The nose radius is less than 1/64"; small but it is there.

You already have a 0.75" ID hole, correct? If you mount this tool so that the shank of the tool parallels the ways, you can just touch off at the surface, move the tip into the center bore, dial in your desired depth of cut and feed out with your cross feed to cut outward. It will allow you to precisely size the counterbore very quickly.

Let me know if this is unclear. I could probably have cut the counterbore in the time it took to type this.