Bridgeport question

[Fritz Maurer]

When using a fly cutter to bore a small hole, how to measure the protrusion of the tool bit with a micrometer When the center line of the tool holder is not accessible? In other words, measuring from the tip of the tool bit to the far side of the tool holder is not the same diameter as the hole in the workpiece.

Or should I have set it up differently before I began cutting.

 

[Lumbersawyer]

Is the fly cutter body round? If it is, the diameter divided by 2 = the radius, plus the length of your cutter will be the diameter of the cut.

 

[Janicholson]

When using a fly cutter to bore a small hole, how to measure the protrusion of the tool bit with a micrometer When the center line of the tool holder is not accessible? In other words, measuring from the tip of the tool bit to the far side of the tool holder is not the same diameter as the hole in the workpiece.

Or should I have set it up differently before I began cutting.

Easiest is to make a trial cut to then measure the actual cut. this compensates for radial runout of the tool holder and spindle, as well as the tip radius. It also reduces the number of calculations and rounding error. Setup for a chunk of wood should be straight forward. Jim

 

[DoubleO7]

Easiest is to make a trial cut to then measure the actual cut. this compensates for radial runout of the tool holder and spindle, as well as the tip radius. It also reduces the number of calculations and rounding error. Setup for a chunk of wood should be straight forward. Jim

I use a $2 HDMW white cutting board from WM or Dollar General for test cuts. It is like a slab of thick milk jug and cuts like hard butter.

 

[Fritz Maurer]

Is the fly cutter body round? If it is, the diameter divided by 2 = the radius, plus the length of your cutter will be the diameter of the cut.

Yes, I made it from a 1/2 " bolt and turned the head round and made a 3/16 square hole. Your formula sounds good I'll try that in the future.

 

[Fritz Maurer]

Thanks guys the test bore is a good idea I will try that. Unfortunately I had to press ahead with this setup using trial and error to get the hole right, this job HAS to leave tonight ( boring a welded driveshaft yoke ). Thanks boys

 

[Butch(OH)]

I understand cheap because I am cheap but sometimes too cheap is just plain not the way to go about things. This doesn't answer your question or get the job out of the shop tonight but you own a Bridgeport, buy a boring head and learn the many things it will do. A new one is $50 on eBay with a set of boring bars and used ones are often cheaper. One screwed up part due to a rigged up bar and it's paid for.

 

[farmersamm]

For the future, you might consider double end boring bars.

The expensive! ones https://www.ebay.com/itm/3163065452...ms/HtShjcUyRzQA9/LmiI3rlU=|tkp:Bk9SR67Fofy7ZQ

Or the cheap ones that you won't feel bad cutting down to fit the Bridgeport. https://www.ebay.com/itm/3336477448...kULA69Y9Bz8ijhTqcZDjdykmoI|tkp:Bk9SR-TZqfy7ZQ

I have a set of the cheap ones, and I love them for internal threading on the lathe. I prefer a HSS bit for all my threading.

 

[farmersamm]

Boring head is the best choice. Bars are available down to 7/16 minimum bore.

If you're forced to use a cobbled together fly cutter. You can set the bit with a dial gauge. Mount the gauge in your Noga, run it up against the bit while it's mounted in the spindle, zero it, then adjust your bit length using the dial gauge.......which hasn't moved since you zeroed it.

 

[used red MN]

Mount the gauge in your Noga

Apparently this would be a Noga.
“Noga” by brand only

 

[Fritz Maurer]

Embarrassingly, I have all of the stuff pictured... never occurred to me to take the boring bar out of the tool holder, even while I was robbing the bits out of it! But, as it were, the bar was way longer than I needed and rigidity might have been a problem, and not really interested in cutting up an Armstrong bar.

The dial indicator is another good idea... l didn't know what a Noga was until URMN cleared that up. I have that unit as well. Thanks for all the good information. Been a profitable 12 hours here!

 

[drsportster]

You're trying to do a boring bar job with a flycutter which is a surface facing tool

 

[Brokengun]

First May i ask what size of hole and in what type of material are you wanting to bore a hole ?

If your hole is in steel and you need presission; I would suggest you find a boring head that fits your mill to Bore a hole. A fly cutter is not made for boring.

Here is an example of a low cost version of a Boring head with an R8 shank for a Bridgeport Milling Machine

HFS(R) 9Pc Set 2" Boring Head R8 Shank 1/2" Carbide Bar Set Bridgeport Milling | eBay

The alloy steel shanks are hardened and ground to withstand rigorous use while maintaining accuracy. Whether you're processing inner hole surfaces, boring outer circles, or cutting grooves, this set is equipped to handle the task with precision and ease.

www.ebay.com

 

[Fritz Maurer]

First May i ask what size of hole and in what type of material are you wanting to bore a hole ?

If your hole is in steel and you need presission; I would suggest you find a boring head that fits your mill to Bore a hole. A fly cutter is not made for boring.

Here is an example of a low cost version of a Boring head with an R8 shank for a Bridgeport Milling Machine

HFS(R) 9Pc Set 2" Boring Head R8 Shank 1/2" Carbide Bar Set Bridgeport Milling | eBay

The alloy steel shanks are hardened and ground to withstand rigorous use while maintaining accuracy. Whether you're processing inner hole surfaces, boring outer circles, or cutting grooves, this set is equipped to handle the task with precision and ease.

www.ebay.com

Bad terminology. I erroneously thought a rotating single point was a fly cutter. Boring bar really does make more sense. I thought they were boring bars when they were stationary. The hole was a steel forging built up with weld to be bored to 1.187".

 

[Brokengun]

Bad terminology. I erroneously thought a rotating single point was a fly cutter. Boring bar really does make more sense. I thought they were boring bars when they were stationary. The hole was a steel forging built up with weld to be bored to 1.187".

Thank You for your reply and the additional information. I personally am a master at Bad terminology, so please that is not an issue with me.

If you don't mind I will try to answer your original Question.

* I will approach this project as if I am doing this for myself.

The diameter of the hole is 1.187 in diameter. I have a homemade boring tool, made using a 1/2" bolt with the head turned Round, with a 3/16th square hole to accommodate a cutting tool.

First I would divide the 1.187 by 2 = .5935. to determine the radius of the hole.

I will then take the diameter of the Head of the cutting tool (turned down bolt.) I will assume its close to .750 and divide it by 2 = .375

The maximum length the cutter should extend from the cutting head is .2185 (.5935 minus .375 = .2185 )

I would use a 1/2" R8 collet or holder to secure the cutter; I would not use a drill chuck to hold the cutter (bolt)

I would "not" start at the maximum length of the cutter and I would also use a low RPM and verify my measurements, first, before using a higher RPM.
Most homemade holders and cutting tools may not have a good relief angle to actually cut and instead scrap the hole.

Please be careful; hope this information helps

 

[Duey C]

First May i ask what size of hole and in what type of material are you wanting to bore a hole ?

If your hole is in steel and you need presission; I would suggest you find a boring head that fits your mill to Bore a hole. A fly cutter is not made for boring.

Here is an example of a low cost version of a Boring head with an R8 shank for a Bridgeport Milling Machine

HFS(R) 9Pc Set 2" Boring Head R8 Shank 1/2" Carbide Bar Set Bridgeport Milling | eBay

The alloy steel shanks are hardened and ground to withstand rigorous use while maintaining accuracy. Whether you're processing inner hole surfaces, boring outer circles, or cutting grooves, this set is equipped to handle the task with precision and ease.

www.ebay.com

@Brokengun: Bought that one just now. Been waiting for a good deal and at 67 bucks, it was A-OK. Thank you!

A flycutter works just fine boring a hole if one has nothing else. A magneto driving disk of aluminium didn't mind.
Boring a hole sure let me know how loose the gibs are in my crappy little mill! Wiggle, wiggle.
Very interesting thread sir! And a fair question. Main Babbitt bearing, single point cutters are adjusted the same.

As Dave Gingery told a friend and I in Wyandotte, MI many yrs ago at a model engine show,
If it works, that's the right way to do it!
(Dave was the grab your neighbors old screen door, melt it down and cast/make your own machine tools guy)

 

[Duey C]

Oops. Double post

 

[Brokengun]

@Brokengun: Bought that one just now. Been waiting for a good deal and at 67 bucks, it was A-OK. Thank you!

A flycutter works just fine boring a hole if one has nothing else. A magneto driving disk of aluminium didn't mind.
Boring a hole sure let me know how loose the gibs are in my crappy little mill! Wiggle, wiggle.
Very interesting thread sir! And a fair question. Main Babbitt bearing, single point cutters are adjusted the same.

As Dave Gingery told a friend and I in Wyandotte, MI many yrs ago at a model engine show,
If it works, that's the right way to do it!
(Dave was the grab your neighbors old screen door, melt it down and cast/make your own machine tools guy)

I am glad the link to the Boring Head, Helped. Its always a good feeling when your efforts can be helpful.

I originally came to this site because I needed some advise/information; and YES, I received the HELP that I needed.
I am always appreciative to those willing to share their knowledge, skills and even opinions.

Thank You

You are right about using what ever works. I do take caution however on encouraging something that I know could be dangerous.