Right/Left boring bars - newbie help needed!

[cazclocker]

I'm somewhat new to machining, and still always learning new tricks on my little watchmaker's lathe (pictures elsewhere on this forum). In looking at boring bars on MSC's website, I see Left and Right boring bars. I'm assuming the Left/Right designation refers to the cutting action taking place depending on which way the headstock is turning. Of course, my motor is reversible, so I can turn material either way. For normal turning (not boring operations), I prefer to operate with the headstock on my left with the headstock rotating clockwise as viewed from the headstock to the tailstock. But for boring operations I like to turn the other direction because it makes it easier to see what's happening inside the hole being bored.

So how do the "right" and "left" designations line up with the two turning directions of my headstock? Knowing that would make ordering a pre-made one so much easier...so far all I have is one little homemade one.

Thanks in advance...

 

[kd4gij]

Left hand boring bars are for running in reverse. tool on the back side of the hole. What lathe do you have. How does the chuck mount? Reson I ask is if the chuck threads on the spindle, It is not recamended to cut in reverse. That said I do bore in reverse just have to take lighter cuts and be verry caefull as the chuck could spin off.:yikes: not a good thing.:nono:

 

[cazclocker]

Thanks. My lathe is a Rivett, it's just a WW-styled watchmaker's lathe. And yes, my 3-jaw and 4-jaw chucks both seat into the spindle but are secured with a drawtube. When running in reverse, I check for tightness often.

I still don't know if I should order a right bar or a left bar, though. Does it make a difference?

 

[kd4gij]

With a Right hand BB running in forward cutting the front side closes to you. Left hand running in reverse cutting the back side. It boils down to your prefrence. You can take heaver cuts with a right hand bar. I have bouth. I have a craftsman Atlas lathe with a thread chuck just have to take it easy and be verry carfull when I am running in reverse.

 

[Kevin45]

I'm somewhat new to machining, and still always learning new tricks on my little watchmaker's lathe (pictures elsewhere on this forum). In looking at boring bars on MSC's website, I see Left and Right boring bars. I'm assuming the Left/Right designation refers to the cutting action taking place depending on which way the headstock is turning. Of course, my motor is reversible, so I can turn material either way. For normal turning (not boring operations), I prefer to operate with the headstock on my left with the headstock rotating clockwise as viewed from the headstock to the tailstock. But for boring operations I like to turn the other direction because it makes it easier to see what's happening inside the hole being bored.

So how do the "right" and "left" designations line up with the two turning directions of my headstock? Knowing that would make ordering a pre-made one so much easier...so far all I have is one little homemade one.

Thanks in advance...

With your lathe chuck running in the CCW direction as looking at it from the tailstock. the R.H. designation and the L.H. designation of a cutting tool spells out what side of the part you are cutting from.

For instance, standing in front of the lathe, a R.H. tool will be cutting from the R.H. side of the part, tailstock to head direction.

A L.H. tool will cut from the L.H. side of the part. Head to tailstock direction.

As far as boring bars, a R.H. boring bar will cut from the R.H. side and on your side of the part. Tailstock to head direction

A L.H. boring bar, will cut from the R.H. side of the piece, tailstock to head direction, BUT you need to run the head in reverse and the boring bar will be in the direction of the backside of the lathe.

One little bit of advice, be careful and pay real close attention when using a L.H. boring bar and running your head in reverse. It's uncommon to run it that way when you are used to almost everything being run and cut with R.H. tools. So what comes natural will get most into trouble without paying REAL CLOSE ATTENTION.

And there is nothing wrong with writing yourself a note and posting it on your machine when running parts. Post-it Notes and I get along real well. I always have a pad of them on my machine to jot a note down when making parts.

 

[cazclocker]

Thanks guys. Kevin, your explanation was just what I needed. Also, you guys have convinced me to do my boring operations with the headstock turning the same direction as when I'm turning - CCW, as seen from the the tailstock toward the headstock. If nothing else, it will be safer. With that in mind, it sounds like what I'm after is a right-handed boring bar to keep the cutting on the right-hand wall of the hole.

Here are a couple of pictures of my homemade boring bar - my sliderest only takes 3/16"-diameter shank (remember, it's a small but well-made watchmaker's lathe) for any cutting bits. This boring bar is just made from HSS.

 

[mikey]

Circle Machine makes a really good inserted tip Carbide bar if you need to go deep: model CCBI-180/187-4-5R. It has a minimum hole diameter of 0.208" but can go nearly 2" deep and hold very good tolerances when used correctly. This bar has a 5 degree positive lead, which makes it better for cleaning up the bottom of a bore. The inserts have an 11 degree clearance angle so you are less likely to rub in smaller bores. The inserts also have positive radial rake to aid in chip clearance. Most importantly, the inserts come with nose radii as small as 0.002" so you can take reasonable roughing and finishing cuts at speeds and feed rates you can manage on your smaller lathe.

For small holes, this is one of the best and most accurate boring bars I have ever seen. I have CDCD, CM1, CG6 and TN7 inserts for this bar and all work well for most materials. If you are cutting tools steels or semi-hardened steels then the CM1 works very well on those and most other materials.

As I'm sure you know, the nose radius on an inserted tip boring bar is the most important factor that governs your cutting conditions - feed, speed and depth of cut. The bar above will allow you to use a small enough nose radius that your lathe can handle. Take a good look at it and watch ebay - they come up from time to time for ridiculous prices.

Oh, and I agree that using a RH bar is probably best from a "use what you are used to" point of view but if your chuck is not threaded on then a LH boring bar, when used in a good solid holder, will push the carriage downward and result in a much more rigid set up. The cutting forces will produce the same results on the lathe that a rear-mounted parting tool does - it makes a small lathe more rigid. You do have to pay attention to your habits and make sure you turn your wheels in the right direction but there are distinct advantages to cutting from the rear.

Hope this helps.

 

[mikey]

I forgot to mention that the CCBI-180/187-4-5R is a 3/16" carbide boring bar. If you make a good tool holder, meaning a nicely finished bore for the bar that clamps around the bar (no set screws bearing on the bar) then this bar will surprise you with its performance.

 

[cazclocker]

Mikey, many thanks to you for your input. MSC's website reports that Circle has been replaced by Kennametal. However, plugging in the model number you gave turns up a result - I assume the model number was retained in spite of the maker's name being changed.

I was NOT aware of nose radius - I'm afraid I'm not even familiar with the term. I'll consult my references, but from the context it sounds as if "nose radius" refers to the sharpness of the corners of the triangle-shaped insert.

Nearly $200 for a boring bar is pricey, but not out of reach for me. So far the deepest I've had to bore has been 5/8", but it might be nice to have that bar around just for it's capacity in case I ever need to go that deep. I wonder if there's an identical model in a shorter length...???

For reference, I'm attaching pictures of the toolholding capability of my lathe's compound sliderest, which only holds cutters with a shank diameter of 3/16". The lathe and sliderest are around 128 years old!

 

[Bill Gruby]

My friend, that lathe is to die for. It is absolutely beautiful. ------ "Billy G"