Will a horizontal mill work on this job?

moonlight machine · Feb 8, 2021

I have some BMW race car trailing arms that we are putting big bearings in. I need to mill a bearing seat 4.919" diameter, then the shoulder the bearing sits on is 4.4" diameter, then the other bearing pocket is also 4.919" diameter. I am using my Narex boring bar to do the bearing pockets. These 2 bearing pockets need to be concentric. The 4.4" diameter is non critical, the bearing pockets are +-.0003 the 4.4" diameter is 1.978" +- .002 long. I have been doing this job on a Bridgeport and it is hell to line up the second bearing pocket after turning the arm over looking down the 4.4" bore to indicate the finished bore. I was thinking
I could set up a horizontal mill to do the first bearing pocket then reach through the 4.4 diameter to do the other bearing pocket. does this make sense? Is there a better machine or process? To make this an even bigger PITA there is no flat or square surface to clamp down on. The arm is supported on 3 2" sq solid steel pillars that are raised or lowered with shim stock to get it trammed in.

Cole2534 · Feb 8, 2021

So basically line bore the pockets on an H mill? I don't see how that wouldn't work if your setup will allow it.

Mud · Feb 8, 2021

Sounds like an excellent way to do it. An alternate way would be to clamp it to a rotary table on the horizontal and rotate the assembly 180° to do it as if it was a horizontal boring mill.

BT Fabrication · Feb 8, 2021

Why not make a slug that goes in the first bore to line up the second then indicate off that?

moonlight machine · Feb 8, 2021

BT Fabrication said:
Why not make a slug that goes in the first bore to line up the second then indicate off that?

That is how I do the front, I make the entire front upright so it is a no brainer to center it on a slug while it is still flat on both sides. This trailing arm is 30" long, heavy as hell and the bores are on one end. If it sags at all the bores will be off.

mhajicek · Feb 8, 2021

If I'm visualizing your part right, you don't anything more than a 3 axis VMC. Mill the top pocket and thru hole, then mill the other side with a T-slot cutter.

moonlight machine · Feb 8, 2021

mhajicek said:
If I'm visualizing your part right, you don't anything more than a 3 axis VMC. Mill the top pocket and thru hole, then mill the other side with a T-slot cutter.

Do you think you can hold a .0003 tolerance without a boring bar?

EmGo · Feb 8, 2021

I know you don't have one, but perfect job for a 2B-36.

gbent · Feb 8, 2021

To further EG, a 2B-36 with an index table. Once you know your centerline of rotation its easy. A sloppy job on a DeVlieg will be better than a good job on a BP.

UncleFrank · Feb 9, 2021

We used horizontals for that. We normally used a "back boring" bar for the outside bore to keep the bottom flat.

Richard Winn · Feb 9, 2021

you need one with angular contact spindle bearings

one with tapered timken's will make your life miserable

boslab · Feb 9, 2021

With wibly wobbly shapes I tack weld some legs on myself, or pads, curvy frames are buggers to set up
Mark

GregSY · Feb 9, 2021

I'm having a tough time envisioning why any trailing arm part would have .0003" tolerances. Is that to retain the bearing or?

DDoug · Feb 9, 2021

moonlight machine said:
I have some BMW race car trailing arms that we are putting big bearings in.

Nope....must be done on a "SIP" or "DIXE" only .....

gbent · Feb 9, 2021

I have used old school horizontal mills as poor man's boring mills. That is not what they were made to do, and it is a pita. The horizontal I have now has rear controls as well as front controls and the rear controls makes the task much more doable.

It is still difficult to tram in a feature as you just can't get up next to the spindle to see what is going on as easily as a BP or boring mill. The machine controls were never designed for frequent fine manipulation. The machines have short handles on heavy feel screws moving heavy loads. Once set, they do the job with power and rigidity. Getting there is the challenge.

To answer your question "Is there a better machine?" Yes, as EG said the DeVlieg 2B36 with an index table would be a much better machine. The downside is good ones are hard to find and they weigh 14,000#.

Mud · Feb 9, 2021

A Deckel FP4NC with a rotary works like a small DeVlieg.

AlfaGTA · Feb 9, 2021

Mud has it....Deckel FP4NC.....
"Y" axis moves like a boring mill, sensitive quill on the horizontal ...One with a universal table can rotate and tilt in two planes...easy to tram the part....
Rotary axis displayed on the control (its manual) good to .001*
Run with a "Capto" setup for the boring....Accurate and repeatable.

I do this sort of work on mine all the time....pretty fun....
Cheers Ross

boslab · Feb 9, 2021

I did like the kerns littlest hbm, a fine machine, there an ozzy YouTube guy with one, the hardest one was a TOS, good machine but I kept forgetting which controlled what, nothing you couldn’t fix with 70xx! You could even knock it out with a line boring rig, mine was stolen which annoys me, esp when I have 2 worn out excavators, I think I’m going to have to DIY one
Mark

Mtndew · Feb 9, 2021

moonlight machine said:
Do you think you can hold a .0003 tolerance without a boring bar?

You can but you'd probably have to creep up on it and play around with the speeds and feeds a little.
Of course the cutter would have to be running almost perfectly with respect to runout which is something I almost never see in that style of a cutter.

Mike1974 · Feb 9, 2021

Mtndew said:
You can but you'd probably have to creep up on it and play around with the speeds and feeds a little.
Of course the cutter would have to be running almost perfectly with respect to runout which is something I almost never see in that style of a cutter.

Speaking of runout, worked at a place that had an old Hurco the spindle was so bad 4 flute endmills cut like single flutes.

The good news, you could rotate the endmill in the holder a bit and get a new cutting edge.

Will a horizontal mill work on this job?

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