View Full Version : And I already altered my new lathe.

Deus Machina
03-18-2011, 07:09 AM
Three days, and I'm tired of using my two 5/16" tools in the lathe that utterly dominates my workbench.

How to fix that? Drop the compound slide!

Yank it out, measure it, lop off most of the measurement in my mill, chuck it up in the four-jaw, measure the alignment pin to zero cut down on the rotational runout (+/-.0005), turn the dial indicator to measure the facial runout (within .002 across 4" or so), and...

Right. How to face off the part that's supposed to be holding your tool on the other axis?

To the scrap bin!


It's hardly ideal, but that cutter was surprisingly solid. And now I should be sized to use 1/2" tooling, perhaps even needing a little shimming on that. No problem there--I'll have an AXA toolpost soon as my next paycheck comes.

Now, I hope everything's still in spec. It's a pain getting any kind of decent surface finish on cast iron at a 150 RPM interrupted cut.

03-18-2011, 11:38 AM
Umm, err, I'm not real sure what you are trying to accomplish. It looks like you just made a major mistake and trashed your compound. Maybe I'm missing something. Please enlighten.

03-18-2011, 12:12 PM

If he's going to fit a QCTP to the lathe, he probably needs to lower the compound height a bit for best adjustment. The simple 4-ways these lathes often come with are shorter and more squat. So the compound is a bit too high when you mount a QCTP.


03-18-2011, 12:15 PM
Okay. That makes more sense.

03-18-2011, 05:37 PM
Not a few ditch the compound and use a solid block toolpost mounted on the cross slide, especially for heavy jobs.

Don't jettison the temporary platform - you may need it again.

03-18-2011, 06:03 PM
You got balls. Id be shaving down the bottom of tool holders long before I even considered attacking my compound.

Then again, I guess one of the nice things about new chinese lathes is there is actualy a bats chance in hell you can buy replacement parts. Can't really say that about old iron unless its one of the super popular models, or your rebuilding a varispeed bridgeport head.

Deus Machina
03-18-2011, 09:43 PM
Well, I wouldn't have done it if it wasn't just $40 for a replacement part. I think I kept it as parallel as it started, but it's hard to measure when the thing's in a four-jaw. Does it actually need to be absolutely perfect? I mean, I would feel much better if it is, but I was making 400+ PSI pneumatic parts on what is essentially a stretched 7x10...

I'm keeping that temp post, but reworking the back section. The front is perfect (I milled the two sections to within .0005 or each other! :D ) but I will cut it so it doesn't need disassembly to remove. I would actually leave it like this, but there is absolutely no way I could make a .002" facing pass with only the carriage adjustment.

I may flycut a little off the top, too. I mismeasured and the top of that rig is to the height of the point the tools rest in the stock post.

Yes, it's to fit a QCTP. Now I'll have .1875" to adjust 3/8" tooling and can get 1/2" level, instead of having to drop a holder all the way down to fit 3/8" at all.

03-18-2011, 10:29 PM

I figured you were doing it for a QCTP. I don't think it will bother too much if it isn't perfectly parallel. Quick way to find out I suppose, is to try parting off a piece. If the tool binds you have a real problem. If the cut face isn't perfectly square, you may have to decide if it's good enough for you or not.

As was recommended, a plinth is about as sturdy as you can get. But isn't as convenient to use as a QCTP.


Deus Machina
03-19-2011, 12:02 AM
(Gah, why even have the 'quick reply' input box down there if it forces me to hit the 'reply' button anyway. Ahem.)

Just measured the bottom where I cut at the four sides, from the TOP of piece, it measured .7785, .7785, .779, and .782 front, back, and sides respectively. The .782 got a file until it fluttered between .7785 and .779.

Considering there's not even a spec for 'parallelism of compound slide' on the inspection sheet, I'm figuring I did pretty well. :)

Oh, that deep circular rough 'mistake' on the face in the picture around the circular part is a relief cut for the bolts, by the way. And they really did need it.

PS: I really should have put a piece of tape over that hole. Gotta clean that out now.

03-19-2011, 12:06 AM
And now I should be sized to use 1/2" tooling, perhaps even needing a little shimming on that. .

you'll tire of that, 1/2 bits take a lot longer to grind than say 1/4 and it would have to be a monster lathe for 1/4" not to be sturdy enough if well supported

Deus Machina
03-19-2011, 12:32 AM
True, but I'll also be able to use the 1/2"-shank knurling tool I had to make the QCTP for on my last mill, and use the various and sundry 1/2" indexable tools that my local place just doesn't carry in 3/8".

Also, with the QCTP, I'll be able to center things up easier without trimming the toolholders, and still be able to use my smaller tools.

03-19-2011, 12:34 AM
I'm still using 1/4 inch hss toolbits, though I did make a holder or two to get them to the correct height. The holder can stick out almost as far as the cutting edge to better support the bit. Never had a problem with that.

I for one have removed the compound and replaced it with a solid holder to which the toolpost can mount. It's much more rigid and I have more range to adjust the radial position of the cutter. I'm not scrapping the compound, just keeping it aside for when I actually need it.

I don't know if you can find a 'support group' for your particular lathe, besides this lot here, but I know for the 9x20 owners there's tons of mods people have done to improve those. Some of that work has to do with the compound. I haven't read through a lot of that, but you might get some ideas from it that you can use.