OD turning with a boring bar in a HBM

Garwood · Jan 19, 2022

I need to weld up and turn the shaft ends on a large flail mower drum. The drum is too big to fit in my big lathe, but I can get it on my 4" HBM, sweep it in and find center. I do not have a facing slide nor large enough boring head that takes bars. I do have lots of cartridge/insert style boring bars and an assortment of Varilock parts.

The flail drum shaft is 2.5" diameter and I need to reach 8". I'd like to use a 2-3" diameter tool with a carbide insert to efficiently rough the welded up shafts.

Should I just weld something up for this one job or has anyone built a tool with adjustable range for this kind of thing?

Thanks!

Garwood · Jan 19, 2022

I have a heavy lathe compound, but it's knackered enough I wouldn't trust it's rigidity/accuracy if a heavy bar was mounted to it and spun at 300+ RPM.

I have a 24" fly cutter made from a solid round cut from 1.5" plate. I might put that up on blocks in a CNC and drill/tap a grid of holes in it, then machine up a mating block with 4 or 6 bolt holes to match the grid spacing. Bore the block to fit a Devlieg cartridge bar or turn the bar to fit a varilock extension.

I gotta finger out what range I've got on the cartidge bars I'd like to see to see if the hole spacing is feasible. But that would probably be a worker.

DDoug · Jan 19, 2022

Garwood said:
I need to weld up and turn the shaft ends on a large flail mower drum. The drum is too big to fit in my big lathe, but I can get it on my 4" HBM, sweep it in and find center. I do not have a facing slide nor large enough boring head that takes bars. I do have lots of cartridge/insert style boring bars and an assortment of Varilock parts.

The flail drum shaft is 2.5" diameter and I need to reach 8". I'd like to use a 2-3" diameter tool with a carbide insert to efficiently rough the welded up shafts.

Should I just weld something up for this one job or has anyone built a tool with adjustable range for this kind of thing?

Thanks!

I might have something, it's a heavy bar with (IIRC) dovetail fit on the working end that
holds the cartridge (carbide insert)
So you would make a faceplate with a hole close to what you need (radius from C/L)
and then the bar would be able to move maybe 1/2" in/out.

Alternatively, how about a balanced boring set-up ?
Flame cut 3" plate in a large "C", bolt to faceplate, machine pockets to hold your cartridges.

gbent · Jan 19, 2022

DeVlieg made a range of "L" shaped adapters to hold their cartridges for outside boring. Different holes in the base for rough adjustment. I don't think I've seen ones that would go 8" deep though.

Landis made hollow mill cutters to use in place of chasers for their die heads. Have a 4" lying around?

Maybe search hollow mill for ideas?

Garwood · Jan 19, 2022

thermite said:
Cartridges are typically seriously short range, but VERY precisely controllable as to using what they have, so THAT part passes the sniff test.

As to "coarse(r) adjustment"?

Think mounting of work to table on a mill.

Introduce a ramp at a shallow angle. Pusher screw. Clamping.

No dovetails nor traverse leadscrew as a general-purpose "permanent" rig would need.

Probably HAVE all the goods you need within arm's length?

Clumsy? Add counter-balance mass? Slow it down? Both? Run HSS instead of Carbide?

You did say "one-off"?

I try to avoid HSS. The cost of indexable tooling is factored into the rate. Me trying to remember how to sharpen the right HSS bit for the job and touching it up 12 times throughout the job plus carbide speeds and feeds are burned into my brain. I know HSS works, but it's not what I'm invested in.

Every tool I buy or build for this HBM I go at with the mindset of how can I make it as versatile as possible? The machine itself is a swiss army knife and I use it that way. The more I use it the faster I get at setups and it's quickly becoming the money printer of the manual machines in the shop. So if I put a few hours of shop time into making a tool to do this job I'd like it to be real versatile.

boslab · Jan 20, 2022

Outside turning with a boring bar on a HBM was fairly common in work, everything was big, we had coromat bars up to 3” dovetail ended, don’t forget to tighten down the clamp, good thing if it moves the turning gets bigger as the cartridge is thrown out as opposed to internal where welding during lunch to fix the balls up
Mark

Tyrone Shoelaces · Jan 20, 2022

That’s why a machine with a built in facing slide is invaluable. Easy Peasy with one of those.

Regards Tyrone.

AJ H · Jan 20, 2022

The Axle Surgeons used to have a purpose-built machine that did this for semis. They'd weld it up and "turn" it back down to the correct size for the bearing races. I can't seem to find any pictures or videos of it. Of course, they patented the process and then started cutting off and welding on new stub shafts instead at twice the money.

DDoug · Jan 20, 2022

AJ H said:
The Axle Surgeons used to have a purpose-built machine that did this for semis. They'd weld it up and "turn" it back down to the correct size for the bearing races. I can't seem to find any pictures or videos of it. Of course, they patented the process and then started cutting off and welding on new stub shafts instead at twice the money.

It's probably a "Journal Squirrel".
journal squirrel lathe at DuckDuckGo

eKretz · Jan 20, 2022

Garwood said:
I need to weld up and turn the shaft ends on a large flail mower drum. The drum is too big to fit in my big lathe, but I can get it on my 4" HBM, sweep it in and find center. I do not have a facing slide nor large enough boring head that takes bars. I do have lots of cartridge/insert style boring bars and an assortment of Varilock parts.

The flail drum shaft is 2.5" diameter and I need to reach 8". I'd like to use a 2-3" diameter tool with a carbide insert to efficiently rough the welded up shafts.

Should I just weld something up for this one job or has anyone built a tool with adjustable range for this kind of thing?

Thanks!

I'd make up something adjustable if you can. It sounds like it could come in handy with the direction you're headed. I have used some really big versions of these, but they were pretty primitive. Basically a fabrication that looks similar in shape to the modern versions with linear bolt hole patterns to roughly move a large extended tool holder, then bumping the tool out in the holder for successive cuts. There were different length holders to bolt on for different turning lengths. (Short extensions for a short turned length, longer extensions for longer turned lengths).

DDoug · Jan 20, 2022

I drove out to the shop today, and found it.

Garwood · Jan 20, 2022

digger doug said:
I drove out to the shop today, and found it.

That looks handy. Sending PM...

PDW · Jan 20, 2022

Tyrone Shoelaces said:
That’s why a machine with a built in facing slide is invaluable. Easy Peasy with one of those.

Regards Tyrone.

Yeah that's how I've done it on the couple occasions I've needed to. Wasn't any sort of drama, I used HSS on one occasion, a TCT boring bar on the other.

PDW

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