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Boring Big Hole on HMC / HBM

Ox

Ox

Diamond
Joined
Aug 27, 2002
Location
Northwest Ohio
Looking at boring some 20" D Holes in HRS.

Too big to swing in my lathes. Part isn't symetrical anyways - so not a real good "swinging" candidate to begin with.

Tols are +/- .001 with a 32RA

I have a tight 65K# HMC w/Cat50

What are the odds of being able to get close to that finish on a boring head? Part is 4000# - so harmonics in the part should not be an issue.

My only real "boring head" experience is limited to 2" & 3" Criterian heads in Bridgeports for the most part. Not sure I have even used one in a VMC?

I have seen mention many times of a Wolhopter (sp?) head with high regards. Would this be the ticket - and just what is so special about it? Are these balance-able maybe?

Also - as another option - I am not quite sure how HBM's doo this, but I know that they put boring heads on a through arbor for bores such as this. If need be I could rig up an "arbor support" on the far end. I would hafta dissmantle a cover and anchor to the ways somehow - but it should be doo-able. Would this make the application more possible?


I found some Wohlhaupter UPA5 units that look to be about the right size.
What are the rods with blocks on the ends used for?
Extensions?
And they don't have chatter issues?
Also see some in Morse Tapers. Any issues with them vibrating out of their sockets?



--------------

Think Snow Eh!
Ox
 
We used to bore 18" diameter by 12" deep through bore in cast iron with a 6" boring head that used 1" diameter shank tools. The tools we made from 1" CRS and had a brazed carbide 883 tool bit welded to the end. We usually ran around 40 to 50 rpm. If I had to hold +/-0.001 and 32 RA I would leave 0.002 to finish hone to size. The honing will not take very long and will make the job much easier to control. You do not say how deep the bore is nor if it is a through bore so maybe another approach is necessary.
 
There are various designs, but basically a foot deep and some are through while others are stepped.

Honeing? :eek:


----------

Think Snow Eh!
Ox
 
I am a big fan of Kaiser or Sandvik modualr boring heads. The dampened holders for the Sandvik heads would be a good choice IMO for as deep as you are going. They are balancable to a point, but at a 20" diameter you may not be spinning it fast enough to worry about that but could be an issue for the length of tool required.

That depth, finish and tolerance is achievable in a VTL with the proper boring bar, now a horizontal I have never did a bore that big. We do bores up to 10" on a HMC without any trouble but only a few inches deep.

I don't suppose that your HMC is capable of tornado boring? Not sure if that would be accuarate enough to hold +/-.001 but would allow you to use some more rigid tooling.

FWIW
 
In a bore of this size - I don't think I need to have a long bar. The boring head as well as the spindle nose will easilly fit in the hole.

No on the "Tornado" effect. AFAIK that is still only an Okuma (?) feature?

And I too would really wonder about the tol and finish ability of that.


-------

Think Snow Eh!
Ox
 
If ya want to go the cheap route- fab up a large disk with a hub to clamp on your bar, mount a tool holder on the side/OD of the disk and set the tool tip with an indicator. Very rigid boring tool for little $$.
Dan
 
Ox said:
No on the "Tornado" effect. AFAIK that is still only an Okuma (?) feature?

And I too would really wonder about the tol and finish ability of that.
Click to expand...

I have seen that option listed on some Mazak machines but have never seen one do it.

As far as I am concerned the boring system that JMC gave a link to is the standard all others base off of, they work extremely well when it comes to large hole and/or high precision boring.
 
No experience with HRS that dia. so comment is probably irrelivant. Back in my DeVlieg days I occasionally bored the bed units for the smaller Minster presses, I think 45 ton. Holes were through cast iron probably 18-20" dia 4" sid ewall thickness but had to be concentric from one side of the bed to the other. We had a big boring head, probably an 8-10" 50 taper. Used 1" dia boring bars with carbide lathe tool bits. Slow spindle speed and no coolant (cast iron). Can't imagine 12" deep in HRS!
 
Ox said:
In a bore of this size - I don't think I need to have a long bar. The boring head as well as the spindle nose will easilly fit in the hole.
Click to expand...

Will your spindle nose come close enough to pallet center that it will be to depth or do you not have enough travel?
 
Part could be mounted as required. No worries there.



20" with 0.001" tolerance?


WHY?????
Click to expand...


B/C that's what the guy with $ wants. :dopeslap:



So far the work that I am finding for my big toys is MUCH tighter than the stuff I run on smaller machines. LOTS of +/-.0005 or .001 stuff. Not exactly what I expected... Very time consuming.

"Thank you Sir, can I have them tighter next time Sir?" :bowdown:

Makes me hafta work for my supper!


-------

Think Snow Eh!
Ox
 
Ox said:
Makes me hafta work for my supper!


-------

Think Snow Eh!
Ox
Click to expand...


Any chance of pics of the boring op when you get a tool?

Biggest stuff I used to do was 11&3/4" left hand 55degree thread* and bored hole under it

Boris

*took 2 of us to pickup the tap wrench ;)
 
IF I git it - I will take a pic jist for you! ;)

Still trying to determine a cost.

One thing that I am starting to be concerned about would be tool wear during one pass! To git that finish I figger I would be in the .005 feed. This would make one pass >150,000 linear inches. I can see some taper in there with carbide. ???

May need to consider something better for finishing... But preferably something that doesn't need crazy speeds to work.


---------

Think Snow Eh!
Ox
 
As crazy as it may sound - I am still liking Dans idea. That would be WAY more rigid than anything else! Could make it with some heavy plate and so to have good mass in the tool as well to keep chatter out. Use a 1.250 or bigger shank LH boring bar mounted out the end. A setup to micro adjust it from behind. (Fine threaded screw) and then add a means to place some amount of counterweight as desired - and a guy could have something!

That would be the ticket for a through hole - however - that leaves the bottom of the bore and corner rad to need attention in a nother means... :scratchchin:


I'm bet'n that video had a LOT more open tols for size and finish than what I'm lookin at! Good grief - I think they searched to find the flimsiest lookin' machine to show how good it runs! That set-up looked shakey to me!



------------

Think Snow Eh!
Ox
 
Ox said:
Also see some in Morse Tapers. Any issues with them vibrating out of their sockets?
Click to expand...

Probably for older HBM's with MT spindles. Most all of those have a slot thru the spindle for a draw key to retain the taper shank in the spindle.

I think you can probably get the best results for surface finish and insert wear resistance by using a cermet for the finish pass. I've bored a 6 1/2" hole 30" deep in L6 tool steel using a tiny high positive cermet from Sumitomo with 4 passes giving no measurable insert wear.

Honing to final size would take all the butt clenching out of the job. I've got a vertical hone that's got a head on it that'll go to about a foot diameter. Uses Sunnen standard stones. I'll look at the shop tomorrow and see if the head has been modified for the large diameter or if it appears to be factory made extensions coming out off the adjustable part of the head. Never have actually used the hone, so I haven't looked closely at the head in the past. Nice thing about honing is that it would take out any taper and allow you to put the diameter wherever you want it within a couple tenths, and a 32 finish is a piece of cake.
 
If you buy the UPA5 you are most likely going to need the S6 model for a 20" bore.I've got 2 UPA5's & 2 UPA5 S6's,,been a while since I've used the UPA5 but I don't think I could bore a 20" hole with it.Chatter is an issue with the 7/8's bars so having the extra slide length on the S6 helps out enormously.And yes I have seen the taper shank come loose from the holder when taking lighter cuts.Under load never a problem.
 
I was figgering a cermet or whatnot for finish...


These bores have a bottom in them. The hone guys don't seem to care much for that.

You know something I don't? (about this enyway)



And yes I have seen the taper shank come loose from the holder when taking lighter cuts.Under load never a problem.
Click to expand...

That's what I figgered.




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Think Snow Eh!
Ox
 
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