Using an arbor support on a large TOS horizontal boring mill for line boring

CC · Nov 13, 2019

My company builds very large mill equipment that utilizes large pin joints. The weldments weigh as much as 6500 lbs. For 40 years we clamped the weldment to the mill table (50" x 50") and then bored 4" to 6" holes thru multiple plates that may be 36" wide. There is an arbor support available but they never took the time to set it up. Did I mention that the material was A514? We use brazed carbide lathe tooling in a large bar. They extend the spindle as far out as needed then feed the part into the spindle. The spindle speed and feed must be extremely slow because the spindle is extended so far. I want to try using the arbor support but can't convince the shop to try it. Anyone have any thought on using an arbor support?

E189552 · Nov 13, 2019

Back when the earth was flat & the Buffalo were plenty....

A shop I worked in used the outboard support when we “core drilled” 3”-4” dia holes through castings about 3-4 feet in length.

So, yeah it will work.

Bill D · Nov 13, 2019

I can not imagine not using the arbor support for that deep a cut at that diameter. I am sure increased cutting speeds will more then pay back the time to set up the arbor support if you already own one. Why do they refuse to think the machine makers know at least as much as they do about their machines?
I bet they do not use seatbelts since they know they will not help in a crash.
Bil lD

Bobnotthecat · Nov 14, 2019

My only though sir is that it is a pain in the ass to mic these bores with a supported bar in place.

Bob.... not the cat.

DDoug · Nov 14, 2019

CC said:
My company builds very large mill equipment that utilizes large pin joints. The weldments weigh as much as 6500 lbs. For 40 years we clamped the weldment to the mill table (50" x 50") and then bored 4" to 6" holes thru multiple plates that may be 36" wide. There is an arbor support available but they never took the time to set it up. Did I mention that the material was A514? We use brazed carbide lathe tooling in a large bar. They extend the spindle as far out as needed then feed the part into the spindle. The spindle speed and feed must be extremely slow because the spindle is extended so far. I want to try using the arbor support but can't convince the shop to try it. Anyone have any thought on using an arbor support?

THIS is in "NW Pennsylvania" and I helped in the purchase and install.

Old by any means, but it has the outboard support (the owners requirement for purchasing)
Synchronized to the head, as well as several bars up to 4" dia.

Also, the bars have toolbit holes every 12" or so.

On this job with (2) bushings, the toolbits can be set in both places at the same cut dia.,
and thereby increasing production.

DDoug · Nov 14, 2019

Bobnotthecat said:
My only though sir is that it is a pain in the ass to mic these bores with a supported bar in place.

Bob.... not the cat.

No it isn't if you make an adapter for you measuring tools.....

redraptor · Nov 14, 2019

Bill D said:
I can not imagine not using the arbor support for that deep a cut at that diameter. I am sure increased cutting speeds will more then pay back the time to set up the arbor support if you already own one. Why do they refuse to think the machine makers know at least as much as they do about their machines?
I bet they do not use seatbelts since they know they will not help in a crash.
Bil lD

If the machine time, and possible rework doesn't cut into your profit margins too much over the last 40 years then it must be an acceptable practice for the bore tolerance. Sounds like change is hard in this company and CC has his work cut out for him.

Matt_Maguire · Nov 14, 2019

CC said:
My company builds very large mill equipment that utilizes large pin joints. The weldments weigh as much as 6500 lbs. For 40 years we clamped the weldment to the mill table (50" x 50") and then bored 4" to 6" holes thru multiple plates that may be 36" wide. There is an arbor support available but they never took the time to set it up. Did I mention that the material was A514? We use brazed carbide lathe tooling in a large bar. They extend the spindle as far out as needed then feed the part into the spindle. The spindle speed and feed must be extremely slow because the spindle is extended so far. I want to try using the arbor support but can't convince the shop to try it. Anyone have any thought on using an arbor support?

If this is an older TOS W100A type he may have the spindle supports that clamp to the facing head (like 18-24”dia). In that case → HELL YES!

They both clamp to the facing head, one clamps tight to the bar and could take the tool past the table center (this one limits spindle speed to 220ish RPM). They also had one with a bearing in the end that allowed spindle speeds to 800ish RPM with the facing head locked & not turning. They both look like traffic cones.

If they can be talked into the live spindle (high speed) support, if it heats up fast then you’ll have to do some scraping on the support bearing to settle it down. BTDT...

OTOH if it's the foot support & align bar setup then they work OK except it's a little weak cutting in the center of the table...

Good luck,
Matt

Tyrone Shoelaces · Nov 15, 2019

Are we talking about a spindle support housing that will allow you to extend the travelling spindle further out ? Or are we talking about using the outer steady bearing which allows you line bore ?

Regards Tyrone.

CC · Nov 19, 2019

Talking about the outer arbor support.
Update: It takes us quite a while to bore (1) 5" diameter hole for a distance of about 30".
There are (5) plates that vary in thickness from 3" to 6" that need to be line-bored.
The starter holes are about 1/2" diameter under the finish bore.
Any thoughts on the amount of time it takes us to bore a hole?

Bobnotthecat · Nov 19, 2019

Every TOS horizontal boring mill I've ever seen had a built in rotary table. If that's the case here, why couldn't you just turn the work around and line up on the previously bored holes, thus keeping your boring bars as short as possible.

Bob....not the cat

Aejgx6 · Nov 19, 2019

If they couldn't see the light in 40 yrs you will probably not succeed in showing them. You might be better off buying your own hor bore and offer to do it for them. Base your price off their time.

eKretz · Nov 19, 2019

I have run HBMs with the outboard support countless times. Never for bores that small. Usually 12" diameter plus and 48" length or more. Anything much smaller and you'll likely spend more time getting the bar in and out than the machining will take. What is the spindle diameter? How long are the bores taking you? Ideally with the setup you're describing I'd hit them from both sides on a turntable, holding bore centers inline with measuring spots cut in a setup at 90° to the bores. Shouldn't take long at all.

Bobnotthecat · Nov 20, 2019

CC,Sir

I have on occasion seen and used self aligning bearings mounted on plates with bushings sized to fit boring bars or the spindle itself to support the boring, either ahead of the bar or after. Moving from one bore to the next. Perhaps you could do this just on the heavy roughing cuts and finishing cuts sans bearings. These were held in place with clamps and/or tack welded in place.

Bob....not the cat.

CC · Nov 20, 2019

Thanks for the reply.... I wish I had more experience machining this big stuff. My goal is to TRY and make the process better and get the job done in as little time as possible with the equipment we have. As far as time goes, what do you think approximate average time would be to open a 4.75" diameter burned hole up to 5.25" with a bore length of about 29" using a machine that is not "PERFECT"...lol. The actual cutting thickness is 19" of metal in the 29" bore length. The material is A514 and the starter holes are burn table torch cut so there is a hard crust on the first cut. Does "Shouldn't take long at all" mean an hour or a day per bore after everything is setup and bolted down? Any way you look at it, the machinist has a tough job...
Would you please describe how you use "measuring spots"?
Thanks for your help!

DDoug · Nov 20, 2019

CC said:
Thanks for the reply.... I wish I had more experience machining this big stuff. My goal is to TRY and make the process better and get the job done in as little time as possible with the equipment we have. As far as time goes, what do you think approximate average time would be to open a 4.75" diameter burned hole up to 5.25" with a bore length of about 29" using a machine that is not "PERFECT"...lol. The actual cutting thickness is 19" of metal in the 29" bore length. The material is A514 and the starter holes are burn table torch cut so there is a hard crust on the first cut. Does "Shouldn't take long at all" mean an hour or a day per bore after everything is setup and bolted down? Any way you look at it, the machinist has a tough job...
Would you please describe how you use "measuring spots"?
Thanks for your help!

Simple process.

Send the next job out, "NW Pennsylvania" has several capable shops.

Shouldn't have to truck it more than 50 miles, and 6000 lbs is nothing.

Then you have some numbers (even with profit figured in)

Next job, tell inside shop to "equal the time, or this job is gone"

Bobnotthecat · Nov 20, 2019

CC,
Sir,

How do you burn a 4 3/4" hole through 29" thick plate. You say that is the bore length. I'm confused.

Bob.... not the cat.

CC · Nov 20, 2019

The weldment is made up of 2 to 3" thick plates welded down to a main base plate.
Imagine a house with 6 parallel walls and the bore goes thru all of the walls and is parallel with the floor.

CC · Nov 20, 2019

The goal is to do the job in house. I'm just trying to become knowledgeable about the process so we can get er done efficiently as possible.

Bobnotthecat · Nov 20, 2019

Cc
Sir,

So the spread is around 29". Makes a lot of difference! If I bid this for my shop I'd say 6 bores X 3 hrs/bore = 18 hrs plus time for de-burring, handling and setup/teardown time.

I am not looking for work though.

Bob....not the cat.

Using an arbor support on a large TOS horizontal boring mill for line boring

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