Indexible Boring Bar Advice Needed

[BCRider]

If using endmills as boring bars is a common occurrence, a holder for the endmill wouldn’t be a bad idea in the QCTP holder (or a square 4 way).

I would make it out of square stock though, set the endmill once and you can rotate the holder around when you need a fresh flute.

Again, a nice and handy idea for for those with a QCTP. Or since most QCTP's come as part of a set which includes a boring bar holder perhaps make up an adapter bar similar to the one I did in the picture? The one on the left with the off center end mill just happened to fit perfectly with mill scale and all into the boring bar holder that is seen in the picture.

In my case the end mills I'm using as boring bars are those which were badly dulled or chipped from use in the mill. I've got no way to sharpen them for further use as end mills. So regrinding them to serves now as single tooth end mills means that they can't be flipped over any longer either. But for those that might use a new end mill for boring the square holder is a pretty nice idea.

But perhaps not so easy for many of the 4 way posts found on the mid and smaller size lathes. Here's why....

4way posts have fixed height slots where the center height of the lathe axis is above the center of the slot so it can line up with the intended square shank cutting tools. In my case (I just checked) the 11/16 (.69") has roughly .16" between my tool height setting spacer and the top of the slot of my old 4way. So in my case I'd be limited to use of an end mill with only a 1/4" shank installed in a holding block with a very high position off center hole. Anything larger would not allow me to have the cutting edge at the center height of my lathe.

This issue with the 4way, which was all I had at the time, is what led to making the shop made boring bar tool post and adapter bars seen in that previous post.

[oxford]

Oxford, if I'd had a QCTP at the time that's what I'd have done too. It really is the easy and obvious option.
.

If using endmills as boring bars is a common occurrence, a holder for the endmill wouldn’t be a bad idea in the QCTP holder (or a square 4 way).

I would make it out of square stock though, set the endmill once and you can rotate the holder around when you need a fresh flute.

[Spindle]

I did buy it, just need to make a shank. Can't find a 5/8-18 R8.
I had high hopes for reaming & got perfect .9375 ID on the 3 reaming attempts, but the surface was ruined on all of them. 1 slow pass, only in 1 direction, oil flood, new Grizzly reamer. Once on the lathe, twice on the mill. No floating holder though. That reaming situation probably deserves a separate thread.

[Bented]

I see what that one does, very nice. The one I asked about had a very small dial @ 2-3 inches up the bar from the cutter. Of course I can't find a picture of that right now.

Don't think I'll ever have one of those, but this was on the shelf next to the Bridgeport head, thought It might be fun to try. Ericson Tenthset.

Buy it, your quest for repeatable <.001" diameters will require such a tool for boring.
You have a small part, as mentioned above, drill then ream this will very likely get you within the desired dimensions

[Spindle]

Oh, the grinding wheels. I think you'll find that 120 is pretty fine. Wheel grits cut a lot more smoothly than sandpaper grits. I bought a 120 originally to use for my wood working chisels. But for grinding wheels 120 is almost super fine. So I found that for touch ups to edges it's fine. But for actual hogging new shapes out of tool blanks it's slow and the pressure seems to polish the working face and I have to freshen it with one of the diamond bars frequently. I wish I'd gotten an 80 grit instead if I were to have only one wheel. For a two wheel setup I'd go 60 for rough hogging and a 100 or 120 for the touchups to edges on existing tools.

For stoning the edges on HSS tools for the ones used for the fine cuts or for the shear cut tool I did for my shaper I use a fine india stone. I've no idea what the equivalent grit number would be. But the fine india is still pretty coarse compared to the "hard arkansa" stones or the white ceramic Lansky stones I use for finer work. For lathe and shaper work I found that the fine india was dandy. The mirror like edges from a few more licks with the white ceramic didn't make the edge cut any smoother or last any longer but took about 4 times as long to make it look good.

Again, hope that helps.

The gray wheels on my tool bit grinder are labeled "medium" & "coarse". Coarse is good for initial shaping but I want to replace the medium one with a 100 or 120 fine for final finish, then use this india stone for touch up.

[Spindle]

Boring head for small holes like so.

https://www.ebay.com/itm/254376510932?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=254376510932&targetid=1262749490862&device=c&mktype=&googleloc=9003784&poi=&campaignid=14859008593&mkgroupid=130497710760&rlsatarget=pla-1262749490862&abcId=9300678&merchantid=119011253&gclid=CjwKCAiAqIKNBhAIEiwAu_ZLDkTzSI7A62oSqqCz2yuVQIUw69JrBOGpziwO8vntW8jQ-iiC9n8AkxoCI2UQAvD_BwE

I am not suggesting that you buy such a tool, this is merely the first picture that appeared during a web search that answers your question.

I see what that one does, very nice. The one I asked about had a very small dial @ 2-3 inches up the bar from the cutter. Of course I can't find a picture of that right now.

Don't think I'll ever have one of those, but this was on the shelf next to the Bridgeport head, thought It might be fun to try. Ericson Tenthset.

[BCRider]

Oxford, if I'd had a QCTP at the time that's what I'd have done too. It really is the easy and obvious option.

But the boring bar holder and how I held all my boring bars from that point on since it was automatically at the proper center height (made directly in the lathe BTW) was born back when I was still putzing around with the 4 way tool post. Things sure are a LOT easier now that I finally broke down a year or so back and bought a QCTP.

[oxford]

I have used an endmill for a boring bar in the lathe like pictured above.

Instead of a holder I just put the endmill directly clamped in the quick change tool holder and “index” it so one flute is cutting. I then just clock the tool post slightly give the endmill some side clearance so it doesn’t rub.

[BCRider]

Oh, the grinding wheels. I think you'll find that 120 is pretty fine. Wheel grits cut a lot more smoothly than sandpaper grits. I bought a 120 originally to use for my wood working chisels. But for grinding wheels 120 is almost super fine. So I found that for touch ups to edges it's fine. But for actual hogging new shapes out of tool blanks it's slow and the pressure seems to polish the working face and I have to freshen it with one of the diamond bars frequently. I wish I'd gotten an 80 grit instead if I were to have only one wheel. For a two wheel setup I'd go 60 for rough hogging and a 100 or 120 for the touchups to edges on existing tools.

For stoning the edges on HSS tools for the ones used for the fine cuts or for the shear cut tool I did for my shaper I use a fine india stone. I've no idea what the equivalent grit number would be. But the fine india is still pretty coarse compared to the "hard arkansa" stones or the white ceramic Lansky stones I use for finer work. For lathe and shaper work I found that the fine india was dandy. The mirror like edges from a few more licks with the white ceramic didn't make the edge cut any smoother or last any longer but took about 4 times as long to make it look good.

Again, hope that helps.

[BCRider]

BCRider,

Thanks for the advice confirming my preference to stay with HSS which I'm already comfortable with. I intend to get a white 120 wheel and 220 and 600 bench stones to improve my HSS tooling. If those grits are wrong let me know. Can you post a picture of one of your endmills converted to boring tool?

I'm still working on the idea but here's what I've done so far.



The two bars in the shop made bar holder on the right are a 1/4" end mill in a 5/8" holder and a 1/2" end mill in a 1" holder. The other end of the 1" bar is also set up similarly with the nose taper and set screws to hold a 3/8" end mill.

These are the proof of concept bars i did originally about 7 years ago and which have done fine for boring where the depth of the bore does not exceed the reach of the end mill. Perhaps due to the high top rake provided by the helix shape these cut super clean and without any screeching sounds indicating chatter.

Because these two are totally axial I generally angle the cutting tip towards me by just a visual whisker. Although the geometry of the helix SHOULD be fine if they were dead on the axis of the spindle. The slight angle towards myself is just to avoid getting it wrong.

A while back I did the bar on the left to offset the end mill so I could use it for deeper cuts. But I didn't think it through very well. It was one of those jobs that suddenly gets launched when one gets tired of cleaning up and finds a piece of metal just after putting away the boring bars and just wants to make some chips.

The hole is angled so the tip cuts and the mill scale on the holding bar "just" misses the side of the bore by about .01. But of course I didn't allow for repeated sharpening of the end mill and eventually the support bar would rub. But it's the style I want to use for the next "proper" design that uses an endmill as the cutting insert.

For smoothness of cuts these end mill boring bars work a lot better than the brazed carbide bars or the other home made bars with small pieces of HSS ground to look like lathe tools. The generous top rake provided by the helix seems to shear the metal with much less risk of chatter or "singing". These are currently my "go to" tools provided the depth of the bore is suitable for their use. So much so that I felt pretty safe when I suggested using a worn or chipped 1/2" or 5/8" end mill (which ever fits the boring head) for boring the bushings or other boring jobs in a mill.

For the odd time I run into metal that is harder or that is super abrasive on the edges I'd like to have a carbide option though. The brazed carbide bar set fills this role currently but they are hellishly prone to "singing" at a high pitched chatter unless almost ridiculously light cuts are used. So I'm following this thread with interest.

I hope this side track post away from carbide insert bars is helpful.

[Bented]

I did see some bars with dials, what do they do?

Boring head for small holes like so.

https://www.ebay.com/itm/254376510932?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=254376510932&targetid=1262749490862&device=c&mktype=&googleloc=9003784&poi=&campaignid=14859008593&mkgroupid=130497710760&rlsatarget=pla-1262749490862&abcId=9300678&merchantid=119011253&gclid=CjwKCAiAqIKNBhAIEiwAu_ZLDkTzSI7A62oSqqCz2yuVQIUw69JrBOGpziwO8vntW8jQ-iiC9n8AkxoCI2UQAvD_BwE

I am not suggesting that you buy such a tool, this is merely the first picture that appeared during a web search that answers your question.

[Spindle]

BCRider,

Thanks for the advice confirming my preference to stay with HSS which I'm already comfortable with. I intend to get a white 120 wheel and 220 and 600 bench stones to improve my HSS tooling. If those grits are wrong let me know. Can you post a picture of one of your endmills converted to boring tool?

[BCRider]

I've dabbled on and off with both brazed and insert carbide and found that I keep using it wrong and edges crumble. So I've got mixed feelings about it. But to be fair since I'm a hobby only sort I don't pay the big bucks for the better brand names.

Years ago I bought a cheap set of indexable lathe tools that use the TCMT inserts. The inserts that came with the tools were terrible. They'd crumble the tips just looking at them sideways. The tools sat in the cutter drawer for about 15 years during which I'd try it now and then on a tough job to see if they were right for that work. They never were.

Recently I risked a $20 bill on a pack of 10 TCMT inserts. And I gotta say that so far these are working out not too badly. They still crumble when I tried to use them on the mystery steel that loves to work harden when cut too fast. But used at more like HSS speeds it's working OK on the tough mystery steel and doing nicely at a higher speed on the regular mild steel. So I'm feeling more kindly to them at this point. But I'm still more a fan of HSS than carbide.

Frankly for the bronze bushings I think your better bet is still a piece of HSS ground with a neutral top rake and given a honed finish with a nice smooth nose radius to get the nicest cut. This is a classic option for bronze and brass and has never let me down.

[Spindle]

I did see some bars with dials, what do they do?

I wasn't interested in getting into inserts until the shop I took this job to said they use insert tooling almost exclusively and that got me curious. Then I discovered how complex it is and came here for a bit of advice and wasn't disappointed.

[JRouche]

Just received a like new Bridgeport #2 boring head w/accessories in original box and would like a recommendation for a good indexable boring bar set. You guys probably know those that work well and those to be avoided.

Bronze bushes, McMaster-Carr.


Index-able boring bar has a dial on it. You mean that kind? Goy one right here.

Kidding. A regular bar will suffice, lemme say JR