# just when you think something should be invented...



## PeterT (May 7, 2020)

...you discover it already has been! lol

Personally I think his example of 'expanded flycutting' was kind of a strange way to demonstrate what I think is the main design intent of the tool. But it gets the point across. You can accurately open up to a bore size on the fly vs. a conventional boring head which requires repeatably stopping the mill, unlock the gib screw, dial in a new radial DOC, re-lock, re-power the machine.... etc. Yes, there are automatic boring heads which can be pre-set to extend out to a predetermined stop. But this tool offers kind of unique control. Trouble is as he says, gobbles up a lot of vertical head room real estate & is a hefty boy to get into position.


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## Janger (May 7, 2020)

Do people bore holes with a rotary table and chuck? Eg center your hole part on the rotary under an end mill. Plunge in to depth or drill first maybe. Then move the table to one side say 0.1*end mill diameter. Rotate part on rotary table. Vacuum chips. Repeat... until hole is to size. If you didn’t own a lathe maybe this would make sense?


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## PeterT (May 7, 2020)

Yes I think that could be done, John. Its equivalent to how a CNC is driving an endmill. As usual, pros & cons. Now you have a 4-6" invasion of privacy from below (via the RT plus any clamping fixtures). You are also kind of limited by the cutting length of the EM & the resolution of your mill lead screw. 0.001" of table displacement = 0.002" of hole enlargement. And EM is cutting accross its entire surface vs. a point tool traversing like a boring cutter. 

I suspect the BoreMate is one of those niche tools that might be better suited to certain operations or parts without getting put on & off too many times. Its interesting though.

Another kind of downside to boring heads is the graduation dial is a tiny thing & the screw can only be so fine. Even a 0.001 division is just a teeny bit of adjustment movement. You can get precision boring heads but they are spendy. I would be curious to know what the BoreMate dial increments are. I'm guessing there has to be a set of gears in there so maybe some ratios are possible where a more precision can be achieved on the dial? He didn't really discuss that. I've seen some boring heads with indicator dials integrated right into the body so they measure absolute. There is another gadget that that you can clamp on & dial fage shows absolute displacement of the head. Mr. Pete has an episode on that. But I digress...


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## RobinHood (May 7, 2020)

Janger said:


> Do people bore holes with a rotary table and chuck? Eg center your hole part on the rotary under an end mill. Plunge in to depth or drill first maybe. Then move the table to one side say 0.1*end mill diameter. Rotate part on rotary table. Vacuum chips. Repeat... until hole is to size. If you didn’t own a lathe maybe this would make sense?



Yup, if your lathe is too small to hold a chunk of 316SS (10" OD, 3" thick") and you don't have a trepanning tool that could reach 3" deep, and you don't want to waste all that SS in the core because you need to have a hole of 8" to make a ring out of it....




 


 




and the finished ring with both threaded holes and clearance holes (front and back view)


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## PeterT (May 7, 2020)

Perfect example! That is a healthy chunk of SS Rudy. Must be a part for the food/booze industry or in sour gas service! lol

I saw a Stefan video (I think it was him) where he ground a reduced diameter neck on an EM to net some extra cutting depth so the shank portion wasn't rubbing & interfering. I guess there are limits to how far you could take this but a good trick.


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## RobinHood (May 7, 2020)

Yes, it is for a milk separator used in a dairy plant.

i learnt a huge lesson on tool deflection during that operation... that was a 2” cutting length EM. Had to flip the part around to get through the other 1”...

you are right, I think it was Stefan who modified the EM for the extra reach


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## John Conroy (May 8, 2020)

I did a similar operation when I made the table for my super spacer from a 12" brake rotor. I wanted the ID of the mounting flange on the rotor to be a snug fit over the register on the face of the super spacer. I could have done it on the lathe but I didn't want to hàve to catch 20 lbs of cast iron when it seperated from the center of the rotor. I mounted the rotor in the chuck of the super space and gradually plunged through the flange of the rotor while turning the super spacer. I made the hole slightly undersize on the plunge then made one more circle to finish it to the final size. I got a very nice zero clearance fit.

This is the register face of the super spacer without the chuck.






Plunging through with a 3/8" carbide end mill.






The rotor is held with the chuck.
















Then drilling the mounting holes to match the chuck mounting holes.






Then flip the rotor over and mill clearance for the fastener heads.











Finished product.


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