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7/8 shank boring bars (nearly) non existent??

hvnlymachining

Hot Rolled
Joined
Jun 21, 2019
Location
St.Onge
My problem begins with owning a Wohlhaupter clone boring head that holds 7/8 shank tooling. I have so far only found and bought an Everede bar, with 7/8" but it seems to enjoy a good chat whenever it gets acquainted with any work piece.

I have run across a few listed used on eBay and purchased a couple but they were incorrectly listed bars. ( Measured across the flats apparently) with 1" shanks.
No luck......

Other than modified shank tools ( I have made a few) , I'm a bit short on bars. Any ideas? I'm looking for indexible bars if possible, but HSS and brazed carbide are acceptable for certain work.

Thanks
 
This is the current problem, err.. project. 6" deep 4.5" bore. Badly galled and chattering unbearably.
 

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I have a Wolly #4 with 7/8" holes. I turned down the shanks of 1" boring bars and have also found a few 7/8" shank bars on Ebay.

But I have never used a boring head on a radial drill. Could the machines rigidity (or lack of) be causing the issues?
I've got a couple bars turned down, unfortunately I recently had to shorten my 8" to 5", so no good for this job now.....

The machine rigidity is decent, but undoubtedly not as good as other machine types. Unfortunately I don't have one of those "others" large enough to swing this 58" part.

I have done many other boring jobs with this machine with decent success.
 
IME insert type boring bars aren't ''that'' hard and will turn quite easily.

OMHO reducing the shank of a larger dia' bar is more rigid, than making sleeve for a smaller
When Toolmex outlet sold 32mm bars for cheeeeep I did that. Center drilled the insert end (enough room) and they turned great. Only had to remove .010” and went well.
 
You've got a lot of spindle sticking out. If you are going to pretend it's a boring mill, then use it like a boring mill. Make a stub bar like guy says, short as possible. Then run the spindle inside the bore to get your reach. A 7/8 bar sticking out 6" is never going to be a productive tool.
 
I used a smaller boring head on a stub shank, but the tooling that I have for that was too light for the conditions. ( HSS ain't cutting it.) No pun intended! But resharpening every pass gets old considering how much material has to be removed. I've been chipping carbide too on account of inclusions and deep rust pockets.

I use this head frequently on the Cincinnati mills also, so any extra tooling is a good investment either way.

I agree with the stickout problem vs bar diameter. I'm guessing I'll have to build a stub on Monday if all else fails.

With hardened shaft steel galled into the soft bore adding to the trouble I'm looking into every option. ( And trying a few)

Thanks for the suggestions.
I'm listening!
 
Throw that boring head in the scrap bin if that's the kind of work you plan to do.

Boring heads like that are a joke. I can't believe what people give for them.

What you need is a cartridge boring setup. A boring bar or boring ring to fit the spindle then the cartridge adjusts right out at the cut. This make the bar wicked rigid and the adjustment very accurate.

I use Devlieg. The 1" and larger shank cartridges can really hog if you have the machine to run them.

Here is an example of a good setup- https://www.ebay.com/itm/1258348180...UoTqRz9UtWfD4XYcRN3E9uAA==|tkp:Bk9SR-yk9Y38Yg
 
Garwood,

Thanks for the info, it's always nice to hear from a voice of experience.

I've been looking into that type bar, but there's little info out there on these beyond sales flyers.

If they're actually that capable I'll definitely keep an eye out for good deals. I've been curious about those for a long time, but usually don't have time to order one and hold the job for it to arrive. I thought by the design they were more of a finishing tool. But that's why I came here!

Is there one brand to look for or avoid?

Yes, boring heads are much better suited to shallow work. But much more universal and can be invaluable at times.

That said, I'll be building one like that on Monday to give it a try. Unfortunately I can't order and wait on this job either. My spindle is an MT5 on that machine, so I should have a decently rigid connection for it.

Since I have 4 machines with more power than I'd ever put to a boring bar, those heads sound like the way to go.

Thanks again
Jacob
 
This is the current problem, err.. project. 6" deep 4.5" bore. Badly galled and chattering unbearably.
Sir,
I don't think that your problem with chatter is from a lack of rigidity in the machine or the tools that you are using. The part that you are trying to bore, and its setup is the issue at hand. If you were to use that clamping arrangement in a lathe or a VBM you would have a very rigid machine with a flimsy set up and having the same results. Steel is a very elastic material and is most always unstable.

My advice is to stabilize that upper portion and grab a high-speed steel tool bit, slow the spindle down so as not burn it up. I know it is counter intuitive to do this with high-speed but otherwise you will spend more time at the grinder or throw away your profit on inserts. Another advantage with the high-speed tool is the ability to experiment with the geometry to attain the desired results of fit and finish.

I think it is just a matter of "The hurrier I go the behinder I Get."

Good luck,
Bob....not the cat.
 
No, it's definitely not a great machine to be using either. I've run a lot of radial arm drills and they are not very rigid hanging way out there from the column. Just not a good place to be boring, especially at that diameter. A well placed outboard support under the rail and a clamp with a long stud down to the base might do wonders. Even then it's iffy though. Just sticking out way too far with the only support at the base of the arm. If you take peepee cuts with just the right tool geometry I'm sure it could be done, but it would be a lot of time invested compared to just using a more rigid machine and setup.

Adding some screw jacks on top of riser blocks around that periphery between the two flanges may help a little too.
 
Bob,
Thanks for the input.

Stabilizing that upper portion is going to be extremely difficult, the upper ring of plate steel can be flexed fairly easily and wouldn't provide any real rigidity. The lower portion is far more rigid due to a much larger plate sprocket underneath.( And out of sight in the picture) also that drum is heavy wall tube, this is a 100 ton winch spool, heavily modified with high "walls" on it. Giving a rigid center and bell like resonance. I have added some vibration dampeners to it now.

I don't mind the sharpening so much, but the rust and hard spots inside are wearing the cutting edges off of HSSco. before it makes it through one pass. Pictures do not do that bore justice! As far as feeds and speeds, 45-75 rpm, .005-.010 feed. No difference in wear, just a bit more chatter on the higher rpms. Painfully slow right now. Hence, my posting.
 
Hi All:
I've had good success (the very, very few times I've dealt with big stuff like this) tack welding outboard bushings onto the job (if it's a through hole) and then line boring it using the radial drill only to provide the driving power, but not the rigidity which comes only from the bushings.
True it's a bit of extra fucking around, but it makes the job itself much more straightforward to do.

There's an Aussie named Curtis (Cutting Edge Engineering) who posts quite a few line boring videos (in his case mostly earthmoving equipment reconditioning) and his videos are worth checking out if you have this kind of problem to solve.

He uses carbide and so far as I recall, they are set up in cartridges like Garwood describes in post #14.
The rigidity of the setup preserves the carbide...of course you have to select a tough grade too, but most modern line boring rigs use carbide so far as I know.

No need for fancy here...a bit of scrap, a handy MIG gun and a precision ground 4140 HTSR bar and you should be good.
If you want to really go to town you can line the bushings with aluminum bronze sleeves and if you REALLY want the Cadillac version, make them split tapered sleeves so you can adjust out the clearance.
Weld a universal joint to the top of the bar, and another to the end of a Morse taper shank to go in the radial drill, put a linkage between them and you're good for a lot of this kind of work.
Life will be good, and you'll be able to bore shit like this accurately and easily.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
EKretz,

You have it right, it's no HBM or lathe, not even close. And it's always my last resort for boring.
I had thought about a support, but I rested my hand on the arm and didn't really feel much going on there. I think the boring bar and possibly the head is my weak link right now. I'll give a different design a try Monday.

thanks for the suggestion.
 








 
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