# Making a center height gage to set lathe tooling



## precisionworks (Jul 25, 2010)

There are as many ways to set lathes tools to center height as there are machinists. I sometimes use the Circle Machine Company tool shown below, and it works well in those situations where it physically can be used.





There are lots of other times that there's no room for the Circle Machine gage ... so I built (another) simple center height gage. As shown below, only three parts are needed - two pieces of ground flat stock & one piece of round stock. The round stock is cut slightly long and a sharp live center point is used to mark center height.













The round stock is faced off so that the scratch mark is still intact. The parts are laid one on top of another & center height is checked. At this point, the flat surface should be too high, leaving room for final machining.






The round stock is center drilled, tap drilled, & countersunk:






With the spindle set to the lowest rpm, a Balax Thredfloer forming tap is held by the Jacobs Super Chuck in the tailstock. TapMagic is squirted into the hole & flooded over the tap, the spindle is started & the *unlocked* tailstock is pushed forward until the tap engages. I keep a foot firmly on the foot brake & step on the brake as soon as the tap rotates in the drill chuck. Balax tap shanks are quite smooth & hard as glass, and the Jacobs chuck allows the tap to turn no matter how tight the chuck is. If you use an Albrecht keyless in the tailstock, don't expect it to let the tap slip  Some people will stop power threading after the tap has engaged three or four full turns & finish with a tap handle ... probably the best approach.






The three parts are put together with a pair of flat head allen screws. The reference edges are brought to a sharp 90 degrees on the surface grinder.






The top surface is ground down until it is .010" higher than lathe center - this flat is used to set ID tooling (boring bars, etc.) The other end is ground down an additional .010" until it's at dead center (see the step at the front of this photo). The "step" is used to set OD tooling:






Using the tool is simple, bring the point of an insert next to the reference flat & use a small straightedge to sweep the top. 






Finished gage in use.


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## Energie (Jul 25, 2010)

Hi Barry,

a very usefull tool, and a really solid construction. 


I´ve made a small one for my mini-lathe:







Another version with an usb-microscop-camera.

*0,15 mm too deep:*







*Ok:*


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## precisionworks (Jul 25, 2010)

> Another version with an usb-microscop-camera.


That is kewel :twothumbs

That's the first optical tool presetter I've seen that was shop built ... most cost a few grand:

http://www.fvfowler.com/opreset.html


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## wquiles (Jul 26, 2010)

precisionworks said:


> That is kewel :twothumbs



+1

Very cool indeed :twothumbs


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## PhotonFanatic (Jul 26, 2010)

I'm curious as to how precise using a straightedge, checked optically by the human eye with a machinist's square, between the cutting edge of the tool and the piece turns out to be. Anyone seen some numbers on that technique?


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## precisionworks (Jul 26, 2010)

> how precise using a straightedge, checked optically by the human eye with a machinist's square, between the cutting edge of the tool and the piece turns out to be.


The eyes can be closed, as the straightedge is swept back & forth while raising the toolholder block while feeling for contact. The Aloris & Dorian holders use a 24 pitch screw, so each complete turn of the adjuster nut moves the tool .042", or roughly .010" per quarter turn.

It's pretty easy to move the tool point up about .001" at a time as the tool point gets close to center height. One time the straight edge sweeps across the flat & contacts nothing, then the nut is turned slightly & the straightedge makes contact that can be barely felt ... I'm pretty confident that the point can be brought to center +/- .001", but that depends on a delicate touch.

If a person gets in a hurry, center could easily be missed by a couple of thousandths either way.

If you have just a few toolholders, this may not be the biggest problem you encounter. I currently have 24 Aloris or Dorian blocks, each loaded with a tool, and the center height gage surely makes life less stressful :thumbsup:


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## gadget_lover (Jul 26, 2010)

I would suspect that the straight-edge method is fairly accurate, especially when used with a sharp tipped tool. When combined with a machinist square, you can get it pretty close. 

I use that technique and more often than not the tool will face without leaving a nub.

For things that are not cylindrical, the height setting tool would be quite handy.

Daniel


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## precisionworks (Jul 27, 2010)

> For things that are not cylindrical, the height setting tool would be quite handy.


It's funny how certain events motivate a person to spend a couple of hours making a gage or fixture ... in this case, the Aloris #20 tool holder is the the culprit (see https://www.candlepowerforums.com/threads/277766 )

The #20 is one of the most used tools in the box, but it has one drawback - since the insert face is usually tipped in the direction of travel, the height of the point varies as the point is rotated from that one setting. The brain dead solution is to set the tool at the "middle" setting mark, meaning that the rake angle is wrong 100% of the time but the point height stays constant. Instead, I made the gage & will likely use it more often on the #20 than most other tools.

Boring bars are the other tool that needs frequent recentering. Every time the bar is lengthened or shortened from its current setting, the point has to be reset. If the same bar is always kept in the same block, the height adjuster nut will stay locked in place and the bar is rotated to bring the tip on center +.010" higher. If you ever try to bore with a bar that's even slightly below center, causing either the bottom of the insert to rub or the bottom of the bar to rub, you'll quickly find that it's no fun. Same thing if the point is too high, as the angle of attack between the tool point & the work changes greatly when the tool is much more than .010" above center.


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## PhotonFanatic (Aug 5, 2010)

For only $22, this tool setter might be nice to have on hand. Would be better if it had a digital readout. :devil:


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## precisionworks (Aug 6, 2010)

That's a neat idea :thumbsup:

American made, which is always surprising, at a low selling price. Looks like he turns those out on a Haas Mini Mill, which is perfect for smaller production jobs like the tooling he makes:

http://www.haascnc.com/details.asp?ID=MINIMILL&webid=VMC_MINIVMC#VMCTreeModel

IMO, the only thing missing from his centering tool is the "double step" that the Circle Machine gage has ... which allows either setting either on center or setting .010" above center.


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## Energie (Aug 15, 2010)

Hi Fred,

thanks for the link.
After some hours in the shop:





















Made of brass and stainless steel.
Quite accurate, +-3/100 mm.


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## PEU (Aug 15, 2010)

Very nice craftmanship!


Pablo


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## PhotonFanatic (Aug 15, 2010)

Energie said:


> Hi Fred,
> 
> thanks for the link.
> After some hours in the shop:
> ...



How do you set the level to be parallel with the SS rod that contacts the tool tip?

That is some nice work, BTW. How much did all the materials cost?


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## Energie (Aug 16, 2010)

PhotonFanatic said:


> How do you set the level to be parallel with the SS rod that contacts the tool tip?


 
A short clip: Link


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## wquiles (Aug 16, 2010)

PEU said:


> Very nice craftmanship!
> 
> 
> Pablo



+1

:twothumbs


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## PhotonFanatic (Aug 16, 2010)

Energie said:


> A short clip: Link



I understand how to adjust the tool holder, as shown in the video, but in constructing the device, what ensures the parallelism between the level and the tube that contacts the tool bit?

It looks as though there is a set screw on the level to clamp it to the main body--but before tightening that, I presume that the two pieces need to be aligned, no?

Nice MultiFix tool holder. :thumbsup:


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## wquiles (Aug 16, 2010)

PhotonFanatic said:


> For only $22, this tool setter might be nice to have on hand. Would be better if it had a digital readout. :devil:



By the way, I did order one of these today. I will report back in a few days (next week?) when it arrives


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## Energie (Aug 16, 2010)

PhotonFanatic said:


> I understand how to adjust the tool holder, as shown in the video, but in constructing the device, what ensures the parallelism between the level and the tube that contacts the tool bit?


 
There is no parallelism needed between the level and the tube, that contacts the tool bit.

First time adjustment:
- use a tool bit with the exact heigh
- set the level to zero and fix the scew
Without this adjustment, the device works not correct, if the lathe does not stand even.


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## unterhausen (Aug 17, 2010)

ordered one of the edge tools. $25 shipped is not worth the time it would take for me to order a level vial.


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## wquiles (Aug 17, 2010)

unterhausen said:


> ordered one of the edge tools. $25 shipped is not worth the time it would take for me to order a level vial.



+1

That is exactly why I ordered mine - my time is worth more than the $25 for the finished/proven product :twothumbs


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## unterhausen (Aug 18, 2010)

plus if I made something, my height would turn out wrong


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## precisionworks (Aug 18, 2010)

My height gage is one of the most used tools in the shop. It probably wouldn't be, but each of my 20+ holders gets checked whenever it goes on the machine. Saves a lot of headaches.


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## gt40 (Aug 19, 2010)

PhotonFanatic said:


> For only $22, this tool setter might be nice to have on hand. Would be better if it had a digital readout. :devil:


 
I went ahead and ordered one too. I am rapidly accumulating tool holders


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## 350xfire (Aug 19, 2010)

Damn precision.. That came out nice... This is why you are considered a "machinist" while I am just a hobbyist!!! Very nice work.


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## PEU (Aug 20, 2010)

Made one for myself, modeled it in SW>CAM and to the CNC mill I went 

Used a different way of adjusting the center before 1st use, instead of the method Energie used, I put a Stainless steel hex bolt (head flattened with the lathe) Its finished, I just need some threadlocking loctite to fix the screw in place. 
Really handy tool, thanks for the ideas, and thanks to the OEM for the inspiration 






































The bearings are pressed in place and so is the 1045 bar.
The level tube hole was kind of difficult to make, because it was the last operation, its offcenter a little, but it does not affect the device at all.
Its a little long for my lathe, forgot to check this when I modeled it, not a big deal since my cnc lathe is almost sold, next one will be CNCed by me, and of course will be bigger 


Pablo


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## precisionworks (Aug 20, 2010)

Nice work Energie & PEU 

Only one small mod that will add lots of value to your tools - mill a small step at the end of the contact arm, perhaps 2mm wide & only .010" deep (I like to mix Metric & English). The step allows setting ID tooling like boring bars .010" above center, where they work much better (and have less chance of rubbing the bottom of the tool). The tool I made has this step, as does the Circle Machine tool shown in the first post.


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## PEU (Aug 24, 2010)

Using an height gage and a couple of precision rectangular gages to have the same height as the center of the bar I centered the bubble, then applied loctite 271 and let it rest for an hour, now the device is calibrated and ready to be used.







Pablo


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## Energie (Aug 24, 2010)

Hi Pablo,

Nice device.
Perhaps it would have been better, to adjust it on your lathe.
Hopefully your lathe stands exact even.


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## PEU (Aug 24, 2010)

Energie said:


> Hi Pablo,
> 
> Nice device.
> Perhaps it would have been better, to adjust it on your lathe.
> Hopefully your lathe stands exact even.



You know I also tought about this, but then I went this route because I tought its the best way, why it would be better to do the leveling on the lathe? Thanks!


Pablo


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## gt40 (Aug 24, 2010)

PEU said:


> Made one for myself, modeled it in SW>CAM and to the CNC mill I went
> 
> Used a different way of adjusting the center before 1st use, instead of the method Energie used, I put a Stainless steel hex bolt (head flattened with the lathe) Its finished, I just need some threadlocking loctite to fix the screw in place.
> Really handy tool, thanks for the ideas, and thanks to the OEM for the inspiration
> ...


 
Nice design. I may have to make something like this. I received the edge gauge people here have posted about and the pin is too small to fit in my bison 6 jaw. I guess I could machine a sleeve for it or use a collet but it will end up annoying me everytime I use it. 

Your design looks good...


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## precisionworks (Aug 24, 2010)

The Circle Machine setup gage does include an angle adjustable vial ... this allows using it (primarily) on slant bed CNC lathes.


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## unterhausen (Aug 24, 2010)

The rod in the Edge tool is fairly small. Before I opened the package I was thinking it couldn't possibly fit in that little box if they included the rod. Then I opened it and realized that the whole thing is quite a bit smaller than I thought it was. If it didn't fit in my 6 jaw, I would just put the rod in a drill chuck in the tailstock. I may do that anyway, seems like it would be easier.


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## wquiles (Aug 25, 2010)

unterhausen said:


> The rod in the Edge tool is fairly small. Before I opened the package I was thinking it couldn't possibly fit in that little box if they included the rod. Then I opened it and realized that the whole thing is quite a bit smaller than I thought it was. If it didn't fit in my 6 jaw, I would just put the rod in a drill chuck in the tailstock. I may do that anyway, seems like it would be easier.



I received mine and found exactly the same thing. The OD of the steel rod is just "barely" smaller than the smallest diameter I can chuck with my Bison 6-jaw :mecry:

I like your idea of using the tailstock, but I also though about making a slightly larger steel "sleeve" so that I can hold it on the chuck


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## PEU (Aug 25, 2010)

whats the diameter of the rod they provide? I made mine with 12mm rod (~1/2")

sleeve the *******! 


Pablo


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## precisionworks (Aug 25, 2010)

> The OD of the steel rod is just "barely" smaller than the smallest diameter I can chuck with my Bison 6-jaw :mecry:



Wow, my 8" Set-Tru grips down to 0.157" (4 mm) ... you must have the cheapo model:nana::lolsign:

Or maybe it's because mine is a 3-jaw instead of a 6-jaw ...


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## saltytri (Aug 25, 2010)

First you guys talk me into buying an expensive 6-jaw chuck and then you make fun of it. Sheesh, it's tough to catch a break around here. :laughing:


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## wquiles (Aug 25, 2010)

precisionworks said:


> Wow, my 8" Set-Tru grips down to 0.157" (4 mm) ... you must have the cheapo model:nana::lolsign:
> 
> Or maybe it's because mine is a 3-jaw instead of a 6-jaw ...


Well, as my machining mentor, you can make fun of me any time you want 

But yes, the limitation on small diameters comes from the 6 jaws. Fortunately for the type of work that I do I very rarely hit this small OD limitation.




saltytri said:


> First you guys talk me into buying an expensive 6-jaw chuck and then you make fun of it. Sheesh, it's tough to catch a break around here. :laughing:


I still would not change mine to a 4-jaw or 3-jaw - I love my set-tru 6-jaw chuck :devil:


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## wquiles (Aug 25, 2010)

PEU said:


> whats the diameter of the rod they provide? I made mine with 12mm rod (~1/2")
> 
> sleeve the *******!
> 
> ...



The steel rod is 0.25" dia. I have some W-1 drill rod, so I will be making a sleeve for it


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## precisionworks (Aug 26, 2010)

> I have some W-1 drill rod, so I will be making a sleeve for it


That will work well, as long as you keep the drilling speed under 100 sfpm & use a "peck drilling" approach. 

Because the drill is buried in the part, the AccuLube unit does very little to reduce the friction caused by the drill flutes contacting walls of the hole *unless* the drill is frequently withdrawn so the lubricant can be reapplied to the flutes. Try advancing the drill one revolution of the tailstock feed wheel, withdraw, then advance 2 turns, withdraw, 3 turns, withdraw, etc. W-1 is almost as unforgiving as stainless if the tool is allowed to get too hot.


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## wquiles (Aug 26, 2010)

precisionworks said:


> That will work well, as long as you keep the drilling speed under 100 sfpm & use a "peck drilling" approach.
> 
> Because the drill is buried in the part, the AccuLube unit does very little to reduce the friction caused by the drill flutes contacting walls of the hole *unless* the drill is frequently withdrawn so the lubricant can be reapplied to the flutes. Try advancing the drill one revolution of the tailstock feed wheel, withdraw, then advance 2 turns, withdraw, 3 turns, withdraw, etc. W-1 is almost as unforgiving as stainless if the tool is allowed to get too hot.



Well, you brought back bad memories from drilling W-1, so I kept looking and found from 12L steel :devil:

The good thing about the sleeve is that I can still use the other side to hold the tool by a chuck on the tailstock as well. Here I for the sleeve almost completed (I still used the "pecking" method!):






Test fit - a slight press fit:






Finished sleeve:











After T4 "bluing":











In use:






I centered a few tools - I will try cutting some Al pieces tomorrow to see how "well" the centering works


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## wquiles (Sep 1, 2010)

Well, as it turns out, although I still consider it a great buy, the gage I got is "not" giving me proper center when the bubble is in the middle (target). The way I know? Do a facing operation. Only when the cutting edge is truly on center, you will get a flat face with no "nub". When I tried it using the target position, it ended up being a tad below center, and I of course ended up with a nub. I just adjusted the cutting bit until it got me a perfect facing operation, and then used this "true center" position to "calibrate" the center gauge. Now I know that I need the bubble in between "target" and the outermost line - so from now on re-centering tools will be easy and quick 

Piece of Al I used to do the test:







Even here where the bubble is a tad off-center, it still was a tad too low:






Will


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## Mick (Sep 2, 2010)

If you are using an insert with a large positive rake and a large tip radius you will measure the tip but actually be cutting at a lower point on the insert and get a nub.


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## wquiles (Sep 2, 2010)

On positive or negative inserts, the first part of the edge to touch metal starts the cut (really a shear action), and depending on the depth of the cut, the amount of edge engaged in the cutting/shear varies for each type of insert - that is part of the design of any insert.

With the inserts that I am using, the topmost edge "does" start the cut in turning/facing operations, and even in the lightest of cuts it would leave no nib, but only when perfectly on center. So I still stand by my earlier comment, in that when I set the gage to that leading edge, the gage is not properly giving me a "center" reading - it is off center.

Will


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## precisionworks (Sep 2, 2010)

> an insert with a large positive rake and a large tip radius you will measure the tip but actually be cutting at a lower point on the insert and get a nub.


All inserts start the cut at the pointy edge, but more of the edge beside or behind the point is engaged as both the DOC and the feed are increased. Inserts are always brought to center using the tip, whether that tip points up (pos. rake), down (neg. rake), or straight (neutral rake).



> I still stand by my earlier comment, in that when I set the gage to that leading edge, the gage is not properly giving me a "center" reading - it is off center.


You are correct :thumbsup:


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## Mick (Sep 2, 2010)

On Korloy CCGT32.52 inserts the rake of the tip extends through the nose radius. This insert will not cut on the highest point of the tip until the insert is engaged ~.015 into the work. If you make a .005 finishing cut you will leave a small nub if the tip is on perfect center. I just looked very carefully at the insert and the nose radius is not flat, it is sloped to the rear.

If you look closely at Will's photos of his TMX inserts you can see they are made the same way as the Korloy.

https://www.candlepowerforums.com/threads/246303


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## precisionworks (Sep 2, 2010)

The insert above is Korloy CCGT 32.51 Hi Carb (Travers Item #22-286-702). I realize that the .51 nose radius is smaller (sharper) than the .52, but the photo surely makes it appear that the pointed tip is the first part of the insert to contact the work, as the side of the insert is curved inward starting just below the tip.



> If you make a .005 finishing cut you will leave a small nub if the tip is on perfect center.


How do you determine when the tip is on center? Of the dozen or so different inserts that I run on a regular basis, each one leaves no nub when set on the lower step of my center height gage. The boring bars are all set .010" above center, but don't get used for facing or O.D. turning.


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## wquiles (Sep 2, 2010)

precisionworks said:


> (snip pic)
> The insert above is Korloy CCGT 32.51 Hi Carb (Travers Item #22-286-702). I realize that the .51 nose radius is smaller (sharper) than the .52, but the photo surely makes it appear that the pointed tip is the first part of the insert to contact the work, as the side of the insert is curved inward starting just below the tip.



+1

All of my positive inserts are the same way. The highest point "does" contact the work first.

I must admit that I still can't quite "see" an insert that has an edge "higher" than the rest of the insert that would not cut/touch/shear the work first.


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## Mick (Sep 2, 2010)

If you set your tool post at 90 degrees so you can take advantage of the 80 degree diamond insert's ability to turn and face without rotating the tool then these inserts will contact on the side below the tip. The situation is worst for a larger radius but I suspect the 1/16 radius inserts will leave a nub also.

The highest point on the insert will contact first if you set your tool at 45 degrees.


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## wquiles (Sep 2, 2010)

That is exactly how I set my 80 deg inserts, and my tool post is always at 90 deg (Mirage_Man will joke that mine is welded at 90Deg as I even thread straight-in!), and I don't have my insert contact the work below the tip, so I guess we will have to agree to disagree on this one.


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## Mick (Sep 2, 2010)

Take a very light face cut and watch the chip come off the insert.

Better yet, blue the insert and look at the contact point.


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## precisionworks (Sep 3, 2010)

> If you set your tool post at 90 degrees


AFAIK all insert tooling is designed so that the insert holder is set 90 degrees to the work, as each insert shape has a designed "lead angle" (usually from 0 degrees to 45 degrees). Setting the tool at any angle other than 90 can be done for special situations, like getting the point into a corner, but normal set up for inserts puts the holder at 90 degrees to the work.

Some info from Lindsay: http://www.lindsaycuttingtools.com/pdf-sections/tech.pdf


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