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Advice for machining 4140 needed

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Agreed -- and that would be my choice (an uncoated one with sharp edges) unless I needed to make a form tool.

Well ... there is always eBay. :-)

And one thing which might be a good starting point is to pick up an old machinist's toolbox, with measuring tools, already custom ground HSS toolbits, and (usually) a few puzzles to figure out. :-)

I wound up getting tools with lots of inserts from eBay, and then buying the *right* tools from MSC to fit the inserts and maximize my rigidity. (That is, 5/8" shanks to fill the slots on the quick-change tool holders, instead of the 1/2" (which are a bit too wimpy under certain conditions, or the 3/4" ones, which I had to modify with a surface grinder to make fit the tool holders. :-)

Those will help with damping of vibration, and some with rigidity.

*But* you want to be careful to not fill too full, or you will have problems clearing chips. What I would suggest is to make forms like rectangular funnels to cast the concrete (or lead) in place, so your chips slide on down instead of forming a un-movable tangle under the carriage.

Just as you want sufficient clearance under the bed for the chips to flow out of these chutes and into the chip pan.

Good Luck, DoN.

Reply to
DoN. Nichols
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Agreed. There are lots of tricks to make it somewhat better, such as putting miniature jacks between the throws to maintain a bit more rigidity in line with the pressure of the headstock center and the tailstock center (except, of course, in the place you are actually cutting at the moment.

Was that 1/2" diameter at the journals, or the overall diameter of the initial stock?

I have read of people silver-soldering in a block of steel to fill the gap while machining other parts of the crankshaft.

And adding a steady rest on the nearest bearing journal which is on center helps, too.

Picking the right order of bearings to cut helps, too. I

*think* that the order would be to cut each individual throw and then silver-solder in a block to reinforce it before going to the next. Once all throws are cut, and filled with silver-soldered blocks, then you cut the main bearing journals.

Perhaps you leave the entire diameter of the stock until you have all the bearings cut -- and ideally finish ground with a toolpost grinder, before you start milling away stock to leave just the throws and the counterweights.

But is a finicky job in any case.

That is even better. :-)

Enjoy, DoN.

Reply to
DoN. Nichols

Ah, good idea...

I'm thinking of uh... the kind that has the plate on top with a bunch of bolts sticking out. LOL. Some good clamp pressure and a pair of soft cast aluminum plates should get a nice clamp force on a toolbit... better than Gingery's old slotted shoulder bolt (lantern?) post anyway. Oh, and 1/2" bits. I can promise you I won't use that wirey 1/4" boring bar shown in the book. ;-o

How so? The bottom of the bed is completely open, and right now any chips that don't fall on the way will just sit on the table. If I don't put any screws on the way plate to attach the lead/cement to it, I'll still be able to remove and replace it from the bed casting. Underneath, I wouldn't fill the cells more than full, as that would stick out, and make it somewhat difficult to attach to my base castings (which bolt flat on the bed underside). There's 2 1/2" or so of space between the bed and table.

I think you forgot that I put a way plate on top of the thing. ;)

Would be nice if I did it that way though... hmmm..

/me comtemplates the days when he can handle 50-100lbs of liquid iron...

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

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Reply to
Tim Williams

Hmmm. I just ran some on a HF 9 X 20, ~.015 radius on HSS, about 50 smf, very light feed, no sweat. IF I want to hog like I was running a

7A J&L, I'd go where there is a 7A J&L. Spent too many years being in a hurry to hurry now, I do it because I like it, not because I have to.
Reply to
Lennie the Lurker

We used to have a J&L 7C (I think it was a C, the one with the sliding headstock and a saddle type turret) that was used for finishing large bronze castings. It was guaranteed to put a pound of bronze chips in each front pocket by lunchtime, and give you good workout cranking that pilot wheel back and forth to index the turret.

Ned Simmons

Reply to
Ned Simmons

Hmmm, Lemme see. Mostly used 433 size inserts, could take a half inch off a side at .015 feed, about 370 rpm and 4 inch diameter. Had rapid traverse on the saddle, if it's set right, it kicks off when the turret settles to the next station. Rapid on the cross slide too, older ones were mechanical, newer ones hydraulic motors. Had a couple of jobs, core drilling before they went to the chuckers, 1 17/32" .100" feed, 123 rpm. Drill would last all day with coolant flood, but just barely. (8620 normalized BHN 240 (I think)) When the name of the game is rough it out, that's what we did. On the flip side, could hold .001" with no problem. 125rms wasn't a problem either when we had to. Nice machine to run, but probably the reason my left hand doesn't work anymore.

Used to laugh, the in process size on most of the bores we did was tighter than the finish size. (Bores used for hobbing and external grinding before internal grinds.)

Reply to
Lennie the Lurker

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