# Repair old boring head?



## ScrapMetal (Aug 15, 2012)

Guys, I picked this old German made boring head on the cheap.  It looks like it's had a very hard life and the holes where the boring bars get mounted are egg-shaped.  I'm guessing they continually used too small of bar in there and it slowly beat them to this shape.







I've been giving some thought to maybe repairing them.  Should I even bother?  I was thinking that I could bore it out even more and put in sleeves but I'm open to any suggestions.

Thanks,

-Ron


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## 7HC (Aug 15, 2012)

ScrapMetal said:


> Guys, I picked this old German made boring head on the cheap.  It looks like it's had a very hard life and the holes where the boring bars get mounted are egg-shaped.  I'm guessing they continually used too small of bar in there and it slowly beat them to this shape.
> 
> 
> 
> ...



I can't offer you the benefit of much experience, but it looks in the first pic as though there's a definite joint line between the holder and the cross-slide.  If so, maybe you could separate the two and make a new holder, which might actually be less work than sleeving the old one?

M


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## Hawkeye (Aug 16, 2012)

I'm not so sure it needs fixing. If the hole had been pressed out of shape, some material would have 'flowed' out of the end of the hole. The ends are still perfectly flat and don't appear to have been dressed with a file. Looking at the intersecting curves, it looks like intentional diameters. It may have been designed to hold two specific shaft diameters. The end hole is identical to the side hole. Most machinists would use one hole more than the other, so they wouldn't be the same, unless they are still the original size.


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## pjf134 (Aug 16, 2012)

I do think the small dia. bar will fit in the extra rounded hole nice and the bigger dia. bar will fit nice in the bigger dia., try it out the way it is and the set screw will hold it I do think.
 Paul


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## 12bolts (Aug 16, 2012)

Ron,
I think if you sleeved it the sleeve material would be of insufficient wall thickness to resist being chopped out even faster.
But like Hawkeye says, the appearance of the holes seems to "similar"

Cheers Phil


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## 7HC (Aug 16, 2012)

What they said, and ignore mine.  Theirs makes sense.  

M


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## ScrapMetal (Aug 16, 2012)

You ALL made sense!  I'll take a closer look at it.  I just wasn't thinking about it being shaped that way on purpose.  I guess it would work though...  It would be nice to have some documentation on it so maybe I'll have to dig in to this strange "internet" thing and see if there is any out there.  Talk about a long shot! :headscratch:

As always, thanks much guys.  You've given me another way to approach this.

-Ron


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## Tony Wells (Aug 16, 2012)

It's made that way, Ron.


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## bjmh46 (Aug 16, 2012)

Tony Wells said:


> It's made that way, Ron.



+1

My old Flynn has the same shape holes--think about it--any round shank within reason will have 3 areas of contact: set screw, and two areas of line contact which will widen out to pick up sufficient area to carry the set screw load as the screw is tightened.  This is like a v-block and superior to to 2 areas of contact resulting from an "undersize" bar being gripped by a set set screw in a round hole.

Regards

Bob


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## ScrapMetal (Aug 16, 2012)

Thanks for confirming that guys.  Now I can look for a set or two of boring bars to go with it.  Anyone have recommendations on boring bars? - This will be for the horizontal mill on my Wells-Index. (I guess I need some for the Wohlhaupter boring head as well.  See - Tool Gloat!)

-Ron


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## gmcken (Aug 10, 2016)

I have an Armstrong boring head #84-211 that has the threads messed up on the inside of the boring head where the shaft that the dial shaft turns on.  It appears that the inside of the head has a soft material (lead ?) inside that is threaded for the 3/8 x 40 shaft.   Has any of the members encountered this with this boring head to advise how to remove this  material to install or make a liner to install in the head.  I have a tap to make the threads of I can get the metal out of the head.  I don't want to start drilling until I get some information. If anyone can help, I would appreciate any advice.


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## 4GSR (Aug 11, 2016)

That's an old Flynn boring head, want to say a No. 35 or 45. I don't recall them being made in Germany, but very well could have been.  The holes are purposely made that way for holding different styles of boring bars.  But mainly for getting out a boring bar that the shank has buger marks from set screw damage.  They have replaceable shanks on them in case you need another taper shank.  The shanks appear on eBay every once in a while.  Flynn made a nice heavy duty boring head in its day.  Criterion style boring head pretty much took over the market today with most being made in Asia.


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## Tony Wells (Aug 12, 2016)

gmcken, that material won't be lead. You're going to need to tear it down and remove that piece and make a new one, probably out of brass. Good thing you have the tap, that is a special.

This would be a good project for another "how to" thread. I'm sure someone else will run into this sooner or later and it would be nice to have a documented repair on record.


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## gmcken (Aug 12, 2016)

Thanks for the advice.  It appears that a sleeve is in the head and the threads are stripped.  The material is soft.  Pondering using a small burr or cutter on a dremel to remove as much as possible.


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## Tony Wells (Aug 12, 2016)

Before you get too far along, can we see some pictures? Might be a simple fix that someone has done before.


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## G MORSCH (Aug 12, 2016)

To All:

The design is made for a purpose.  There must be clearance between the hole and a shank to allow a cylindrical shank to enter.  When you have a simple round hole, the set screws apply force from one side directly producing line contact on the opposite side.  The result is two single lines of contact and no support in between.  When/if a small amount of material is removed, opposite the screw, the result is three lines of contact that add significant stability to the boring tool.  However, the tool should have
a shank diameter close to that of the bore diameter. 

The pictures below are of an old Erickson Tenth-set Boring Head.   The first photo has a .5000 gage pin in the bore, still snug after 25 years.

Best Regards,  Gary


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## gmcken (Aug 12, 2016)

I repaired the boring head today by making a sleeve out of brass rod.  The head was bored 7/16" .400 deep to hold the new sleeve.  The sleeve was made out of a 1/2" brass rod which was turned 7/16" .400 long.  The sleeve was bored with a Q  letter bit and tapped 3/8 x 40.  After parting to length, thread was cleaned and a test fit made on the parts.  Sleeve was locked in place with lock tight.  I hope this helps anyone needing to repair threads in another head.


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## Tony Wells (Aug 12, 2016)

Thanks Ken. It was a little OT, but it's nice to see how a repair can be done in a situation like yours.


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