Adam. This is my favorite type of content. I love being invited into your ‘problem solving brain’. This was a truly elegant solution to an initial oversight. The sound of that precisely machined tool seating in its indexed position is just so satisfying. The whole project had been a treat to watch. Thank you.
As I was watching you drill those holes I was thinking he knows what he is doing. It would be a bitch to drill those from the other side but those don’t look like through holes. That kept bugging me until you fessed up. Damned nice to see we are all human. Beautiful work.
stumbling around the internet, and there's Adam. It doesn't matter whatever he's working on. The man's just amazing to watch. If you're interested in metal working, learn from this man. He is the Best, of the BEST !
You could put another set of holes on the other half in 15degree increments to give you your 30 and 60 degree indexed locations, plus all the 15s in between, then just flip it over if you need them.
Excellent idea. Two years from now, you'll create a washer that will allow you to bypass the pin and allow you to set it an any angle . You still be the bom!
Do the other half of the bolt hole circle with a 12 hole bolt hole circle, then you can index every 30° if you flip the boring bar upside down and reverse the tool in the holder.
Although my hobby work operates at about 10 percent in size of your work, your work is so clear and visible , excellent in your explanation and precision. I learn a lot - many thanks.
Hi from England Adam... What you have done here was common sense... Back in the early 1900s such a dowel arrangement was referred to as a "feather"... a lot of British trucks (Albion, Thornycroft, Dennis) vehicles used feathers on many of the shafts, links & shackles etc...to prevent inadvertent unscrewing etc during use... This was common practice until well after WW1....(all the subsidy scheme commercials used feathers on pins & fixings)... I can imagine it not really lending itself to high production...
Nice job, beautiful work. If it were me, I would have used the other half of the circle to do 30 and 60 degree holes. Your tool can extend either side of the bar (i think) so it would be just as useful to have 0-30-60 on the other half of the flange. I'm not a machinist so I may be talking nonsense. I do love your channel Adam, I find myself calling on some ABOM torque when I am wrenching on my own car.
You might consider drilling all the way around, but change the spacing on the other half so you can get more angles with the same bar. Then maybe mark the holes on the back-side with little punches to remember which holes are what angle. Though, I can't really imagine you'll have too many times when you gotta cut an internal on the shaper at 30 degrees... Fun build as always, Adam.
On the other half, offset the holes by a few degrees and you can get in between the holes on top. Or tool grinding could do that. Well done, elegant solution!! Food for the brain!!!
Nicely done Adam. Now I understand why you replied to my comment on the other video, #4 in the series I think, that there was "more to come on that". Honestly the index pin was my first thought, but you mentioned cutting flats on the sides on the bar to help tighten it, which is another decent way to go about doing it. I am an industrial controls technician/electrician by trade but love watching these machining videos by you and a lot of the other youtube machinists. This is just great content. Keep them coming because I am learning new things almost on a daily basis.
I think the only suggestion I'd make for these indexing holes is you've got one side drilled in 22.5 degrees so I'd probably drill the other half of the bar in 30 degree increments to give you +/- 30 & 60 degree options The geometry of the bar means it'd work either way up.
You can add flexibility to it by adding more holes for the pin in the clapper, at offsets from 12 o clock. A 2.5, 5 and 7.5 degree hole on either side would make it possible to do pretty much any angle you'd want. Just reset the dowel in a position that would add up to or subtract to your target angle. Great video as always.
I was thinking the same thing, but do you think the pin's diameter is small enough so that the holes will be sufficiently offset at 2.5 so that there isn't a breach?
He could have put 8 pin holes in the clapper equally spaced half way around and that would have given a vernier type of adjustment pattern to the holes but in reality when does one ever need a boring bar on a shaper set to exactly that angle? It adds complication and now you have to remove a 1/8 pin from a blind hole while the clapper is dissassembled. The holes he has should be good enough for almost anything in reality. Its only a side project.
@@jtgoodling Given how much he loves the shaper and the work he's put in, I reckon Adam would try as many things as he can on it. You could cut inside splines for example.
i nodded off watching this video (just late, not a lack of interest) and still had eyes closed but started to come to right when you said "how many of you guys fell asleep at the wheel while i was drilling those holes?" actually beemed right awake and thought you somehow knew for a split second, lol. wierd. Abom machining the subconscious. Melbourne native and fellow machinist sub!
When drilling hole for the dowel pin I would have went all the way through with a smaller diameter drill. This way when or if the pin breaks you could drive the broke piece out with a punch from the opposite side. Just a suggestion. I know this from experience......lol. Great work Adam!!
Old Shaker dictum. Don’t make something unless it is both necessary and useful; but if it is both necessary and useful, don’t hesitate to make it beautiful. The shakers were woodworkers, but it is equally fitting for metal working. Well done.
Was wondering about the hole depth. Thought that through magic of editing did not get to see the drill punch through. Only shows that Super Abom is a human! Love all you do, Adam!
Adam, it is a pleasure to watch your efforts. While I'm excited about the smaller stuff I am learning to do, it does make me yearn to work with some of that larger equipment. I appreciate your attention to detail.
You might think about NOT gluing the pin in the clapper. Instead drill a couple more holes in the clapper to correspond with 12:00 when you rotate the clapper pivot off of dead horizontal. Maybe a pin hole at 5 degrees either side of the "straight up" hole? 10 degrees too? Nice project, and you'll get a ton of use out of it.
Nice, practical project. I miss the DRO I had at my last job. The little screen would give a graphical view of what you are doing which was so convenient.
That's a very elegant and effective solution you've come up with there. You've also left yourself the option to drill differently spaced holes in the other half of the semicircle if you want other tool angles (e.g. 30 and 60 degrees).
Adam, as always- beautiful workmanship. I would suggest perhaps adding a thin bronze washer under your large nuts as that will give you a bit better torquing ability without scoring up the nut and clapper.
Facepalmed when Adam first drilled those indexing holes … good to see Adam keep that to show how we all make mistakes but can recover if we keep our heads. Indexing for "12" holes will add flexibility on the other half to do 30°, etc. Could be useful to mark the bar on the thread side so that it's easy to tell which range is being indexed and its respective zero without having to look underneath the clapper.
Adam, since you spaced your holes at every 22.5 degrees along half of the circumference of the flange, why not drill another set of holes on the other half of the flange with 15 degree spacing? This will give you 30 and 60 degree positions.
Adam, a very nice job. Looking forward to seeing chips fly on the next part. But I have to ask.... what's with the wonky hand wheel on the mill we see while you're zeroing in the square tool bit prior to the drilling? Someone run into that sucker with a forklift? You get mad at it one day? Someone got the machine drunk?
Did you consider going all the way around the circle? I thought that you might be able to use that for two-sided tools such that you have a roughing tool on one side and a finishing tool on the other, just need to flip the bar over rather than going to the trouble to reinstall the tool and make sure that everything is centered again. Ingenious solution to the problem though, and I'm still impressed at your willingness to remove metal from your expensive new machine without any real reticence.
That's awesome. And u can always drill 15 degree ( or whatever degree) divisions on the other side of the bars if needed. Great simple and very effective fix to the problem.
15:20 FINALLY! I caught a mistake... only after watching hours and hours of Abom. I'm always amazing about machining and how you can just modify your existing or make new tools. I wish this type of stuff was offered in school. I would definitely be on a different career path.
The diameter he's dealing with is 2.5", so the circumference would by 3.14 x 2.5 = 7.85 inches. At 5 degrees he would need 72 equal arcs (or 36 for the semicircle), which corresponds to an arc length of 7.85/72 = 0.109 inches. But he's drilling 0.25" diameter holes so that's not going to work (the holes would 'join up', as it were). Even 10 degrees is too tight, but he could do 15, 30, 45, etc.
Awesome stuff as always, Adam. When you took the bar out of the vice I had to rewind and see if the holes were through or stopped. I even did an "uh oh" out loud. Haha! nice work
Great idea to be able to index the bars ! It is a bit of a tricky couple setups but I have faith bud. What a sweet job fella. I am sure this will serve you well my friend. This opens up many possibilities for the shaper for sure.
Interesting issue, when I watched you assembly of the tool in the last video I was wondering how you were going to ensure the tool would be perpendicular to the part. This modification should fix that.
I thought he'd insert a piece of tool steel into the bar and clamp it in the correct orientation or put it against a stop. Then tightening the nut should be possible as well.
We have extrusion and drawing tooling, that gets indexed like this for some operations. It's all tapered, and as soon as you slide it in, it's stuck, even before you put the spanner nut on.
Nice! Did you think about maybe doing half of the circle at 22.5° and the other half in 30° increments? That could come in handy, just rotate the bar 180° and now you can index different angles
Curious how you were planning to ensure it was indexed properly w/o the pegs? You'd have to probably loosen/tighten up the big nut each time after indicating it. Seems like this was a needed thing regardless of the nut not tightening. Was thinking the same as others too regarding using 15deg points instead of 22.5. But yeah - you can still drill the holes on the opposite half as others said.
Hello Adam greetings from France Did you consider making a Automatic tool lifter for your shaper (clapper box) possibly air actuated. That would be amazing. Thanks for the video.
did not read all 492 comments could have been said .. if you drill the other 8 holes and drill 2nd hole and pin on other part double pin across twice the hold . if you have problem with just 1 pin .. love the shows please keep them going ..
nice fix adam, a ball bearing with half the hole in the base and the other half in the tool holder at various angles would also work. With a through pin hole the pin could work loose and come out( although very dificult)
I'd like to see you fabricate a large spanner for that large nut. Or are you using one or your larger adjustable wrenchs. You could have it hanging near your shaper.
I was thinking this, too - just do every 15 degrees and he'd have a setting for the most common occasions. I'd imagine most of the slotting done with this tool will be at 0 degrees, though.
Adam. This is my favorite type of content. I love being invited into your ‘problem solving brain’. This was a truly elegant solution to an initial oversight. The sound of that precisely machined tool seating in its indexed position is just so satisfying. The whole project had been a treat to watch. Thank you.
Simple solutions to problems are often the most elegant.....once you figure them out. Well done Adam
I like the solid sound that the bar makes against the clapper when pin lines up with the index hole. Well done Adam!
As I was watching you drill those holes I was thinking he knows what he is doing. It would be a bitch to drill those from the other side but those don’t look like through holes. That kept bugging me until you fessed up. Damned nice to see we are all human. Beautiful work.
I'm also stunned at how many people want you to half index the opposite side of that pattern. You've got a lot of smart people here!
stumbling around the internet, and there's Adam. It doesn't matter whatever he's working on. The man's just amazing to watch. If you're interested in metal working, learn from this man. He is the Best, of the BEST !
Hi Adam: nice video. You never bore me "turning the handles." I always learn something from watching you work.
Very nice solution Adam. Like Roy Reynolds suggested, adding holes every 10 or 15 degrees on the other half of the bar would add to the versatility.
The precision fitment you always seem to achieve is inspiring to an amateur like me👍
I'm glad you showed us this issue and your solution to it. Very nice job as always
the way you get that job centered in the mill was just amazing. The speed and accuracy of you using that Starret was just magic!
Now you need to use the shaper to make a wrench to turn the nut.......
You could put another set of holes on the other half in 15degree increments to give you your 30 and 60 degree indexed locations, plus all the 15s in between, then just flip it over if you need them.
i was thinking the same thing till adam made the mistake.
Excellent idea. Two years from now, you'll create a washer that will allow you to bypass the pin and allow you to set it an any angle . You still be the bom!
This was a great video Adam! Thank you for including more of the process of setting up unique jobs on the mill.
Do the other half of the bolt hole circle with a 12 hole bolt hole circle, then you can index every 30° if you flip the boring bar upside down and reverse the tool in the holder.
That's double clever.
Although my hobby work operates at about 10 percent in size of your work, your work is so clear and visible , excellent in your explanation and precision. I learn a lot - many thanks.
Hi from England Adam...
What you have done here was common sense...
Back in the early 1900s such a dowel arrangement was referred to as a "feather"...
a lot of British trucks
(Albion, Thornycroft, Dennis) vehicles used feathers on many of the shafts, links & shackles etc...to prevent inadvertent unscrewing etc during use...
This was common practice until well after WW1....(all the subsidy scheme commercials used feathers on pins & fixings)...
I can imagine it not really lending itself to high production...
Nice job, beautiful work. If it were me, I would have used the other half of the circle to do 30 and 60 degree holes. Your tool can extend either side of the bar (i think) so it would be just as useful to have 0-30-60 on the other half of the flange. I'm not a machinist so I may be talking nonsense. I do love your channel Adam, I find myself calling on some ABOM torque when I am wrenching on my own car.
You might consider drilling all the way around, but change the spacing on the other half so you can get more angles with the same bar. Then maybe mark the holes on the back-side with little punches to remember which holes are what angle.
Though, I can't really imagine you'll have too many times when you gotta cut an internal on the shaper at 30 degrees...
Fun build as always, Adam.
Holes every 15º would add the capability of 15º, 30º, 60º and 75º. With your bars, you could then cut internal splines.
That's an ingenious way of dealing with bar. Saves set up time. Your attention to detail is impressive. I love watching your channel
On the other half, offset the holes by a few degrees and you can get in between the holes on top. Or tool grinding could do that. Well done, elegant solution!! Food for the brain!!!
Nicely done Adam. Now I understand why you replied to my comment on the other video, #4 in the series I think, that there was "more to come on that". Honestly the index pin was my first thought, but you mentioned cutting flats on the sides on the bar to help tighten it, which is another decent way to go about doing it. I am an industrial controls technician/electrician by trade but love watching these machining videos by you and a lot of the other youtube machinists. This is just great content. Keep them coming because I am learning new things almost on a daily basis.
I'm a novice. Have learned a lot on using dial indicators and general setup. Great videos. Thanks
I think the only suggestion I'd make for these indexing holes is you've got one side drilled in 22.5 degrees so I'd probably drill the other half of the bar in 30 degree increments to give you +/- 30 & 60 degree options The geometry of the bar means it'd work either way up.
I was thinking the same, except I'd do 10 degree increments.
The other side could be indexed at 15 degree increments. Common angles for dove tails.
You can add flexibility to it by adding more holes for the pin in the clapper, at offsets from 12 o clock. A 2.5, 5 and 7.5 degree hole on either side would make it possible to do pretty much any angle you'd want. Just reset the dowel in a position that would add up to or subtract to your target angle. Great video as always.
I was thinking the same thing, but do you think the pin's diameter is small enough so that the holes will be sufficiently offset at 2.5 so that there isn't a breach?
@@reina4969 I think so, most pins are hardened and it's only for locating. The nut will handle most of the actual load.
He could have put 8 pin holes in the clapper equally spaced half way around and that would have given a vernier type of adjustment pattern to the holes but in reality when does one ever need a boring bar on a shaper set to exactly that angle? It adds complication and now you have to remove a 1/8 pin from a blind hole while the clapper is dissassembled. The holes he has should be good enough for almost anything in reality. Its only a side project.
@@jtgoodling Given how much he loves the shaper and the work he's put in, I reckon Adam would try as many things as he can on it. You could cut inside splines for example.
i nodded off watching this video (just late, not a lack of interest) and still had eyes closed but started to come to right when you said "how many of you guys fell asleep at the wheel while i was drilling those holes?" actually beemed right awake and thought you somehow knew for a split second, lol. wierd. Abom machining the subconscious. Melbourne native and fellow machinist sub!
Like the simplicity of this indexed improvement, the solid snap on sound to boost.
Adam: You make thing I would find hopeless.... EASY. You are truely a master AND you film it too all on your own. You sir: I salute.
When drilling hole for the dowel pin I would have went all the way through with a smaller diameter drill. This way when or if the pin breaks you could drive the broke piece out with a punch from the opposite side. Just a suggestion. I know this from experience......lol. Great work Adam!!
Old Shaker dictum. Don’t make something unless it is both necessary and useful; but if it is both necessary and useful, don’t hesitate to make it beautiful. The shakers were woodworkers, but it is equally fitting for metal working. Well done.
Was wondering about the hole depth. Thought that through magic of editing did not get to see the drill punch through. Only shows that Super Abom is a human! Love all you do, Adam!
Adam, it is a pleasure to watch your efforts. While I'm excited about the smaller stuff I am learning to do, it does make me yearn to work with some of that larger equipment. I appreciate your attention to detail.
A tool maker's dream. Very little mod to the machine, with a simple but effective tool solution.
That DRO function is sick! I didn’t know they could do that.
Great video as usual, Adam. Also, it is good to know that I am not the only person who makes mistakes in the shop.
Super simple idea that needs a bucket full of smarts to do, great job there.
You might think about NOT gluing the pin in the clapper. Instead drill a couple more holes in the clapper to correspond with 12:00 when you rotate the clapper pivot off of dead horizontal. Maybe a pin hole at 5 degrees either side of the "straight up" hole? 10 degrees too?
Nice project, and you'll get a ton of use out of it.
Really nice work. It is relaxing to watch someone who knows what they are doing. I appreciate your videos.
very elegant solution, much better than just some flats on the bar
Simple solution? Maybe, but imo its an /elegant/ solution! I think that just nudges the bar to a whole new level, very professional... Well done!! 😊
I thought about this when the earlier part came out, I wish I’d said something now 😊 great solution - very well thought out
Nice, practical project. I miss the DRO I had at my last job. The little screen would give a graphical view of what you are doing which was so convenient.
Really elegant solution that makes those bars even more versitile.
SunuvaB...simple solution to the problem, well done Adam. It's things like this that gets you the viewers, honest work.
That's a very elegant and effective solution you've come up with there. You've also left yourself the option to drill differently spaced holes in the other half of the semicircle if you want other tool angles (e.g. 30 and 60 degrees).
That was my thought too.
Adam, as always- beautiful workmanship. I would suggest perhaps adding a thin bronze washer under your large nuts as that will give you a bit better torquing ability without scoring up the nut and clapper.
Wow that setup is just amazing! Well done mate, continue like this!
Facepalmed when Adam first drilled those indexing holes … good to see Adam keep that to show how we all make mistakes but can recover if we keep our heads.
Indexing for "12" holes will add flexibility on the other half to do 30°, etc.
Could be useful to mark the bar on the thread side so that it's easy to tell which range is being indexed and its respective zero without having to look underneath the clapper.
Awesome. I too assumed that the pressure would keep that bar stationary. Great fix!
Abom79 Why not do one-half in stepped increments (0, 30, 60...), and the other half in between (15, 45, 75...) giving just that many more angles?
Nice to see thing go together nicely. Really nice work as usual 👍🏻
Adam you never cease to amaze me. Good Job
YOU ARE GOOD AT WHAT YOU DO. GREAT JOB. WISH I COULD USE MY DRO THAT GOOD.
Adam, since you spaced your holes at every 22.5 degrees along half of the circumference of the flange, why not drill another set of holes on the other half of the flange with 15 degree spacing?
This will give you 30 and 60 degree positions.
Oh man, you've got your thinking cap on!
15 degrees might be a tad tight. Back of the napkin calc says only 100 thou between hole edges. 30 degree spacing might work better.
Absolutely awesome! You're a genius Abom! Your workmanship is amazing!
Elegant solution. I caught the through hole problem. Thanks as always.
Adam, a very nice job. Looking forward to seeing chips fly on the next part. But I have to ask.... what's with the wonky hand wheel on the mill we see while you're zeroing in the square tool bit prior to the drilling? Someone run into that sucker with a forklift? You get mad at it one day? Someone got the machine drunk?
Excellent solution Adam. I would add a flat washer to prevent the nut marring your nice clapper.
I’m glad you drilled all the way through. I saw the mistake when you began knocking the edges off of the holes! Great job buddy!
Damn Adam that is good thinking! Simple, but effective. Good job! Your experience is showing through!
Did you consider going all the way around the circle? I thought that you might be able to use that for two-sided tools such that you have a roughing tool on one side and a finishing tool on the other, just need to flip the bar over rather than going to the trouble to reinstall the tool and make sure that everything is centered again.
Ingenious solution to the problem though, and I'm still impressed at your willingness to remove metal from your expensive new machine without any real reticence.
Nice work Adam. Thanks for taking the time to show us.
That's awesome. And u can always drill 15 degree ( or whatever degree) divisions on the other side of the bars if needed. Great simple and very effective fix to the problem.
Just what I was thinking
Or put another pin in the clapper to subdivide the 22-1/2 degrees into 11-1/4. One hole vs many.
Turned out really nice Adam!
ATB, Robin
LOL. 😜
But I was impressed with the ingenuity of indicating the tool bit to angle the bar precicely. 👍
15:20 FINALLY! I caught a mistake... only after watching hours and hours of Abom. I'm always amazing about machining and how you can just modify your existing or make new tools. I wish this type of stuff was offered in school. I would definitely be on a different career path.
You could drill the other half of the bar at 5 or 10 degree increments
The diameter he's dealing with is 2.5", so the circumference would by 3.14 x 2.5 = 7.85 inches. At 5 degrees he would need 72 equal arcs (or 36 for the semicircle), which corresponds to an arc length of 7.85/72 = 0.109 inches. But he's drilling 0.25" diameter holes so that's not going to work (the holes would 'join up', as it were). Even 10 degrees is too tight, but he could do 15, 30, 45, etc.
aporiac Yip every 15 degree should be good
I was thinking keyway. When you said indexing pin, so simple, easy, and very useful. Thank you.
Its a perfect fix Adam. Make it easy for sighting and repairing tool wear as well, because the tool will always be in an exact place.
that is such a satisfyingly positive click when if goes home on the pin
Awesome stuff as always, Adam. When you took the bar out of the vice I had to rewind and see if the holes were through or stopped. I even did an "uh oh" out loud. Haha! nice work
Awesome solution to the problem Adam, looking forward to seeing this in action for your future projects..
Great idea to be able to index the bars ! It is a bit of a tricky couple setups but I have faith bud. What a sweet job fella. I am sure this will serve you well my friend. This opens up many possibilities for the shaper for sure.
Beautiful work. A simple, elegant and perfectly implemented solution.
Interesting issue, when I watched you assembly of the tool in the last video I was wondering how you were going to ensure the tool would be perpendicular to the part. This modification should fix that.
I thought he'd insert a piece of tool steel into the bar and clamp it in the correct orientation or put it against a stop. Then tightening the nut should be possible as well.
Excellent engineering and implementation Adam.
You really do some beautiful work Adam.
Great project. I thought a good idea would be doing 15 degree increments on the other side, and sure enough I wasn't the only one.
I too thought this, there seemed to be plenty of room. Can always add extra holes in the future if required.
Just be sure to keep the Abom torque in reserve so it doesn't try to shear that little pin, 1/8 isn't a lot. :-)
Nice ideia. Now index the other half with different number of holes to get different angles heheh, Go all in even if unnecessary :D
good simple idea
We have extrusion and drawing tooling, that gets indexed like this for some operations. It's all tapered, and as soon as you slide it in, it's stuck, even before you put the spanner nut on.
Nice! Did you think about maybe doing half of the circle at 22.5° and the other half in 30° increments? That could come in handy, just rotate the bar 180° and now you can index different angles
you can do the other half with different angles, maybe with 15 degrees increments
Curious how you were planning to ensure it was indexed properly w/o the pegs? You'd have to probably loosen/tighten up the big nut each time after indicating it. Seems like this was a needed thing regardless of the nut not tightening. Was thinking the same as others too regarding using 15deg points instead of 22.5. But yeah - you can still drill the holes on the opposite half as others said.
Brian Ullmark yes few more deviations could have been better but it depends on what he needs, still the way he’s done it I think it’s a great idea
This project is really shaping up
Add a scribe line to the clapper and several on the bar to help identify the angles
Hello Adam greetings from France
Did you consider making a Automatic tool lifter for your shaper (clapper box) possibly air actuated.
That would be amazing.
Thanks for the video.
Thats a slick solution to the problem for sure! another awesome machining video, watching and learning over here
did not read all 492 comments could have been said .. if you drill the other 8 holes and drill 2nd hole and pin on other part double pin across twice the hold . if you have problem with just 1 pin .. love the shows please keep them going ..
Your excellent machining and drill prep skills show when your 1/8" drill didn't wander and "move" the far side hole (the hole that mattered).
A very elegant solution.
Well done.
Thanks.
Absolutely phenomenal precision work man. Love it.
An Elegant Solution !!! There's A Reason Why You Are The Most Watched Machinist !!!!
nice fix adam, a ball bearing with half the hole in the base and the other half in the tool holder at various angles would also work. With a through pin hole the pin could work loose and come out( although very dificult)
I'd like to see you fabricate a large spanner for that large nut. Or are you using one or your larger adjustable wrenchs. You could have it hanging near your shaper.
Maybe do a different set of angles on the other half like 15, 30 and 60?
I was thinking this, too - just do every 15 degrees and he'd have a setting for the most common occasions. I'd imagine most of the slotting done with this tool will be at 0 degrees, though.
As others have already be saying, you can do 15 degree or 30 degree increments on the other side of the circles...
You could also add indicator marks on the opposite side of the bar, 180 degrees from each hole, to tell you which hole you are in...
Perhaps you could put another set of indexing holes on the other side of the bar to give you 30 degree increments for dovetails etc. Just a thought.