# Boring heads..



## Pcmaker (Aug 28, 2018)

I have a few questions about boring heads for mills.

I have a Precision Matthews PM-25MV mill and I was wondering what type of boring head to get? Is there a specific one I should get for my mill or anything with an R8 shank will do?

I'm countersinking block of steel for an allen shoulder bolt. The diameter I  need to drill is something like 13.13mm

I don't want to keep buying odd sized drill bits, so I'm thinking of getting a boring head so I can just adjust for the size hole I need by the thousandths. 

I used a 1/2" drill bit to drill the hold and I need to make it slightly bigger. Will a boring head do the job?

Does the boring head also cut the bottom of the work piece all the way to the center or does it just cut the side of the hole?


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## BaronJ (Aug 28, 2018)

Hi PcMaker,

Yes a boring head will do everything that you are wanting, and more.  There are a couple of caveats though, the mill must be properly trammed, or you won't get a true hole with vertical sides, and the tool that you use needs to be properly ground.  Often the tool bits that are supplied with boring heads are not shaped properly.  Last don't buy a boring head that is too big for your machine.  My mill is similar to yours and a 65 mm head is about as big as you need to go.


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## Pcmaker (Aug 28, 2018)

What diameter hole is the smallest a boring head can start working on?

I'm still working on better tramming the mill. I'm at about .003 thou off on the X axis and about .002 thou off the Y axis. Having a hard time getting better than these numbers.


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## Norseman C.B. (Aug 28, 2018)

Why not get a metric counter bore set  ?? Much less hassle


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## RJSakowski (Aug 28, 2018)

Pcmaker said:


> What diameter hole is the smallest a boring head can start working on?


It depends on the size of the tool.  My boring head is adjustable through center so the boring tool determines the minumum size. Aside from the cutting surface itself, the heel of the cutter needs clearance. but micro- boring is possible with the right tool.

A boring tool will face the bottom of the hole if properly ground.  It ius not a good practice to cut through to center as you will have the tool rubbing on the back side.  I will usually drill a pilot hole, even if the hole is blind.  If I need a flat bottom with no pilot hole, I drill the pilot to just short of bottom and finish with a boring tool that can cut to the center.


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## BaronJ (Aug 28, 2018)

Hi PcMaker,

You are going to have to do better than that !  I can tram within 1/2 thou along the table.  The problem across the table, is down to how much the mill head nods.  I've shimmed mine to just under a thou, but don't seem to be able to get any better than that.

As far as hole size is concerned you can drill holes if you really wanted to, but I think it is easier to drill and ream if you want precise hole sizes.  Its only when you need larger holes that a boring head becomes really useful.  I used to use mine for surfacing as well as counter boring and counter sinking.


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## T Bredehoft (Aug 28, 2018)

I've been using a 1/8 endmill as a small boring bar in my PM25, I can bore any hole over 1/8 in (3mm) in diameter. Bottoms are kinda touchy, go a tiny bit too far and my may break your boring bar. 
PS, I rigged a handle on my downfeed knob, so I can crank  it down smoothly. It's 2mm per rev.


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## whimsnag (Aug 28, 2018)

Pcmaker said:


> I have a few questions about boring heads for mills.
> 
> I have a Precision Matthews PM-25MV mill and I was wondering what type of boring head to get? Is there a specific one I should get for my mill or anything with an R8 shank will do?
> 
> ...



I have the same mill, but heard (I don't remember where -- maybe a Stefan Gotteswinter video?) that boring heads required power feed in the z-axis, in order feed the boring head at a steady rate.

Otherwise, making holes with diam > 1" would come in very handy.


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## Pcmaker (Aug 28, 2018)

Just bought a metric counterbore set from Amazon. Still want to hear more about boring heads before I make my decision about buying one. Especially about the Z-axis power feed requirement.


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## Pcmaker (Aug 28, 2018)

Just trammed my X axis to a hair under .001

The problem is the Y axis. Just checked it and it's off by about .006

Gotta check the manual, but I think I'll have to do some shimming, which I ididn't wanna do.


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## P. Waller (Aug 28, 2018)

Pcmaker said:


> I have a few questions about boring heads for mills.
> 
> I have a Precision Matthews PM-25MV mill and I was wondering what type of boring head to get? Is there a specific one I should get for my mill or anything with an R8 shank will do?
> 
> ...


Buying 100 drill bits will be cheaper and more efficient then using a boring head in a mill for such work.
Use a boring tool for boring accurate diameter holes only.
If you insist Criterion makes excellent tools. Choose your tool.
https://www.mscdirect.com/industrialtools/criterion-boring-heads.html


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## mikey (Aug 28, 2018)

Pcmaker said:


> Just bought a metric counterbore set from Amazon. Still want to hear more about boring heads before I make my decision about buying one. Especially about the Z-axis power feed requirement.



The largest boring head you can realistically use on your mill is a 2" head. Mr. Waller suggested Criterion, which many of us own and like. There are clones galore; look at the Criterion DBL-202 and either get a genuine one or a clone if you prefer.

Depending on which bar you use, a DBL 202 head can bore from 0.050" out to over 6.5" so a 2" head ain't bad. You can buy a head that takes either 3/8" or 1/2" shanked boring bars; the 3/8" bars are obviously lighter, will reduce vibration and are cheaper to buy. The 1/2" bars are more common. Do yourself a favor; buy cobalt boring bars and forget inserted carbide. Cobalt will cut well for you at the speeds your mill can run at and will do so with less deflection.

Power downfeed is nice to have but machinists have been using boring heads on manual milling machines for many decades and I wouldn't let not having power feed stop me from owning this essential tool. I can produce a mirror finish with my heads using manual downfeed. More importantly, I can hit the bore on size within reasonable limits. 

Just an aside. The hole you need to accommodate a socket head cap screw is called a counterbore. Counterbore cutting tools are sized to pass both the shank of the screw and accommodate the head with the appropriate washer for that screw. They work well, are used at low speeds to avoid chatter and are NOT precision cutting tools. They make nice countersunk holes, though. If you need precision fits, a boring head is the way to go.


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## Sandia (Aug 28, 2018)

If you decide to go with the boring head, I would recommend instead of the R8 shank, I would find a 1/2" or 5/8" shank boring head and use the collet. It is a lot easier to change out because of room on the Z axis.


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## 9t8z28 (Aug 30, 2018)

How do you use an end mill in a boring head?  Never heard of this.  2 flute or 4 flute?  Are you modifying the end mill?


T Bredehoft said:


> I've been using a 1/8 endmill as a small boring bar in my PM25, I can bore any hole over 1/8 in (3mm) in diameter. Bottoms are kinda touchy, go a tiny bit too far and my may break your boring bar.
> PS, I rigged a handle on my downfeed knob, so I can crank  it down smoothly. It's 2mm per rev.


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## T Bredehoft (Aug 30, 2018)

I made a split collet to hold the end mill. I use a two flute endmill without any modification. Just make sure the one cutter edge is in position to cut. For what it's worth, I'm boring holes in .093 aluminum to ,4375 (7/16).


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## BaronJ (Aug 30, 2018)

Hi PcMaker,

The column on mine is secured by four quite substantial bolts.  I just loosened them and used brass shim stock between the bolts and going about halfway down.  That head is quite heavy and the last thing you want is the column falling on you.

I used a piece of one thou shim folded in half in mine.


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## P. Waller (Sep 3, 2018)

9t8z28 said:


> How do you use an end mill in a boring head?  Never heard of this.  2 flute or 4 flute?  Are you modifying the end mill?


Drill mill tooling, not the fastest method but they work. http://www.iscar.com/Ecatalog/products.aspx?app=125&mapp=ML&GFSTYP=M&lang=EN
I often use 2 flute center cutting endmills in CNC lathes for roughing and boring small shallow holes less the 1" diameter and 1/2" depth.
Place the endmill in a toolpost holder with the flutes horizontal and plunge to depth at X .000, retract it and offset the X axis as if it were a boring bar. I grind the the cutting edges of the endmills behind the end for clearance as they will drag on the bore.

I would only recommend this for shallow bores less then 3 diameters deep in free machining materials.
Saves a tool change which can save a good deal of time if hundreds of parts are required.


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## 9t8z28 (Sep 4, 2018)

I was asking how to use an end mill in a boring head on the mill, not the lathe or CNC lathe but good info on how to do it.    You state that it saves you time by not having to do a tool change but how are you using the modified end mill to do other operations other than boring shallow holes ?   It would seem to me that you could only use this modified end mill to do the shallow boring so why not just use a boring bar?   I guess maybe you would have to drill a hole first and then use the boring bar so using a modified end mill only requires 1 tool ?


P. Waller said:


> Drill mill tooling, not the fastest method but they work. http://www.iscar.com/Ecatalog/products.aspx?app=125&mapp=ML&GFSTYP=M&lang=EN
> I often use 2 flute center cutting endmills in CNC lathes for roughing and boring small shallow holes less the 1" diameter and 1/2" depth.
> Place the endmill in a toolpost holder with the flutes horizontal and plunge to depth at X .000, retract it and offset the X axis as if it were a boring bar. I grind the the cutting edges of the endmills behind the end for clearance as they will drag on the bore.
> 
> ...


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## BaronJ (Sep 4, 2018)

Hi 9t8z28,

Put the slot drill in the boring head, center it, plunge to depth.  This will drill a hole the size of your slot drill.  Then enlarge the hole you just made by traversing the boring head slide.


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## P. Waller (Sep 4, 2018)

9t8z28 said:


> I was asking how to use an end mill in a boring head on the mill, not the lathe or CNC lathe but good info on how to do it.    You state that it saves you time by not having to do a tool change but how are you using the modified end mill to do other operations other than boring shallow holes ?   It would seem to me that you could only use this modified end mill to do the shallow boring so why not just use a boring bar?   I guess maybe you would have to drill a hole first and then use the boring bar so using a modified end mill only requires 1 tool ?


In order to use a traditional boring bar one must first drill a hole, using a center cutting end mill to plunge a hole then using it as a boring bar eliminates the drill tool change. Boring in a mill and boring in a lathe are the same with the exception that the part rotates in the lathe and the tool rotates in the mill. It also does not matter if CNC or manual as the operation is the same, all that a controller does is move the tool for you, it is not magic, the only reason that you can not easily mill a radius on a corner using the hand wheels is that your hands are not capable making the small variable moves required.

A drill/mill tool is essentially a boring bar that will plunge cut a smaller hole first then act as a boring bar when moved off center. The problem with using a standard solid end mill is that they are not as rigid as a boring bar thus the shallow hole, shallow being 3 X Diameter or so.

You may put an end mill in a boring head set on center and plunge then move it until reaching the finished hole diameter, the flutes must be oriented correctly however.


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## 9t8z28 (Sep 7, 2018)

Good info.  Thats what I figured


P. Waller said:


> In order to use a traditional boring bar one must first drill a hole, using a center cutting end mill to plunge a hole then using it as a boring bar eliminates the drill tool change. Boring in a mill and boring in a lathe are the same with the exception that the part rotates in the lathe and the tool rotates in the mill. It also does not matter if CNC or manual as the operation is the same, all that a controller does is move the tool for you, it is not magic, the only reason that you can not easily mill a radius on a corner using the hand wheels is that your hands are not capable making the small variable moves required.
> 
> A drill/mill tool is essentially a boring bar that will plunge cut a smaller hole first then act as a boring bar when moved off center. The problem with using a standard solid end mill is that they are not as rigid as a boring bar thus the shallow hole, shallow being 3 X Diameter or so.
> 
> You may put an end mill in a boring head set on center and plunge then move it until reaching the finished hole diameter, the flutes must be oriented correctly however.


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## BaronJ (Sep 8, 2018)

Hi Guys,



BaronJ said:


> Hi 9t8z28,
> 
> Put the slot drill in the boring head, center it, plunge to depth.  This will drill a hole the size of your slot drill.  Then enlarge the hole you just made by traversing the boring head slide.



Isn't that what I said earlier ?


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## Ken from ontario (Sep 8, 2018)

BaronJ said:


> Hi Guys,
> 
> 
> 
> Isn't that what I said earlier ?


Yes , it happens often ,the solution gets repeated in different posts  but one gets acknowledged. I now know it's not personal.


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## BaronJ (Sep 8, 2018)

Hi Ken,

Thanks for your reply.
I know its not personal.  It was just reading four posts that essentially said the same thing.


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