Is this a safe setup for an interrupted cut on heavy part?

[winchman]

Saw this on a machining video. Heavy steel part with lots of stick-out in a big 4-jaw chuck. One jaw has corner contact only. Interrupted cut at large radius at 40rpm.


The cone-shaped piece in the tailstock was used to center the part before it was dialed in. A similar setup was used earlier for facing the other end and boring the part, but the fourth jaw contact was reversed.


Is this safe? What would you do differently?

[eKretz]

Not great, but ya' kinda gotta go with the judgment of the guy running the job. If he knows what he's doing he'll take pretty light cuts with a setup like that. A little safer change would be to add clamps over the face of the part using the t-slots in the face of the chuck. Better still with parallels bolted in under the back face using those t-slots also so the part can be clamped directly over the parallels.

[Ian B]

+1 on the "bolts in the chuck's tee slots". My 4 jaw doesn't have them, i suffer from tee slot envy.

Otherwise, take light cuts, stand out of the line of fire, it'll probably be ok - I've seen worse.

Ian

[mtraven]

CA glue? 😁

if I'm not mistaken, thats kurtis @ CEE? I've watched a lot of his videos, he works on big stuff & I've never seen a setup of his shift or anything.

hold downs in the chuck jaws would work, but I'm pretty sure he takes a face cut across the hole thing...so he would have needed to weld on some brackets on below the face he was cutting..certainly doable

which interrupted cut concerns you? the face? or the first cut of the bore? probably the face, but either way, tack a few tabs near midway(so they work for both faces) on the part to tie into those t slots, then she ain't coming loose unless you break a lot of stuff.

[The Metal Butcher]

Did the part come out?

Curtis is very sharp and has been doing this for a long time. If he felt it was likely to come out, then he wouldn't have done it. Pretty sure he still has all his teeth and digits, no?

I'd do that 8 days a week.

[winchman]

Yeah, Kurtis is really good and his equipment is top notch, but I cringe every time I see him do something like this. As an engineering rep, I spent a lot of time in industrial and government machine shops in the '60s and '70s, and I saw lots of big complex stuff being machined. I'm sure something like this would have never been allowed.

[Tungsten dipper]

I saw it too. My first thoughts were what is that doing to the precision bearings? How long would they last machining those day after day?

Could be done on the mill. Maybe twice the time?

[RMinMN]

If that bullnose center was used to center the piece, why not leave it in contact until the part was nearer to being completely faced? By the time the bullnose was in the way there would not be near the interrupted cut.

[Dan_the_Chemist]

I like RMinMN's idea and that got me to thinking... The machinist has already bored the part and there is a step for the seal. He could use a disk the same size as the seal ID to sit in the hole. That could be pressed into place with a live center on the tailstock. If that would get in the way, then use a long threaded rod through the spindle to pull the disk firmly into place.

[portlandRon]

Curtis stated it was not the best but he was going to take light cuts and run a slow speed.

[eKretz]

Ah, he's facing the part. I thought he was working on the bore. In that case, there are a few alternatives: he can either weld the clamping tabs on and knock them off after finished as mentioned by mtraven or just take it easy and use light cuts and a more relaxed feed rate. Another would be to grind the faces of the part on a large surface or Blanchard grinder. That is actually pretty fast on the big machines.

[Bented]

I see no problems with this work holding.

A Blanchard grinding operation for facing would be excellent if the job were dozens or hundreds of parts.

[A.K. Boomer]

What the hell is that irregular chunk of metal from anyways???

[Willy]

What the hell is that irregular chunk of metal from anyways???

https://www.youtube.com/watch?v=UnUgUb2VHJ8

[A.K. Boomer]

Thanks Willy - did not watch the whole thing but I now know why it's the shape it is...