Is there a trick to setting the cutting edge height on a lathe?

R

rhofer1

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Hi, all,
I run two Emco lathes--a Unimat 3 and a Compact 5. Each uses the same size QCTP and I only have a small number of tool holders, so I'm constantly resetting the height of tools from one to the other. Other than buying a whole bunch of tool holders and dedicating some to a particular machine, is there some easy trick to mark the just-below-center height on each lathe so I can easily realign the cutting height? (I hope I've stated this in a comprehensible fashion)
Ron Hofer
 
If you're using a 3 or 4 jaw chuck, rotate the chuck so that a jaw is perfectly level. A small toolmakers level is good for this. Once you have a jaw level, scribe a short line across the face on center. Any time you need a center mark, whip out the level and put the jaw level.

Or make a height gage that sits on the cross slide and shows center.
 
You can place a piece of flat stock between the cutter and the item to be turned, bring in the cross slide until contact and the flat stock is supported by lite pressure. If the flat stock is "plumb" with a small machinist level then the cutter is at center. If it tips away on top cutter is high, if it tips towards you the cutter is too low.

Mark
 
Put a pointed center in your tailstock, and line up your cutting tool with that. My SB 10K has a line scribed on the tailstock, as well.
 
For sure, I would not tolerate having two lathes with the same size holders without setting up the tool posts so the holders always landed on center on either lathe.

For a while, I had two lathes with AXA size tool posts. I found it easy enough to mill off the bottom of one post to make it precisely the same height from center as the other one.

I'm sure you can make a riser plate for a too-low holder.

As to setting tools on center, I'm absolutely amazed at the number of novel ways folks go about it. I think the easiest way is to make a dedicated center height gauge for each machine.

Mine is, a little tool I made immediately after reading the tip submitted by G.A.Ewan in the Home Shop Machinist Forum. He'd made his from an old layout height gauge, but lacking one, I used a cheap machinist square that wasn't accurate. I just cut off the end of the blade to make a pointer, screwed it back on, and set it to center height:

toolheightset.jpg

It's quick and dead certain to be exactly on center when I can't see daylight above the tool.

I just
 
Ron

First thing I would do in this situation is look at whether I could put a shim washer under one of the tool posts so that they were both exactly the same height above the compound. That way each tool holder would work on either lathe without being reset.

Valuable info to know is the distance from the centre line of the lathe to the top of the compound, the diffference will tell you how thich the shim needs to be.

As for setting the tool height I have a couple of methods I usually use.

1 Swing the tool holder around and bring the cutter up to the tailstock centre point.

2 Feed the tool bit in towards the stock with a spring shim between the tip of the bit and the work. A 6" pocket scale works as well, but I don't like messing up my scale, so I use a length of spring steel shim stock.

3 to fine tune after 1 or 2, take a facing cut. If the bit is centred, it will not leave a nib. If either too high or too low, there will be a nib left on the end of the workpiece.

The height guages shown by other posters works really well, but one more piece to have floating around by the machine.

Walter
 
Hey rhofer, put a lantern tool post on there you will be an expert in no time. lol Myself I use
as said either my scribed line on the tailstock, but usually the pinched spring steel method.
The biggest pain = to set up for threading with these things. QCTP someday. sam
 
I use the same method as Tony Wells...

--Highly visible (for me at least)
--The level works on every lathe in the shop
--Its quick and efficient


I also use the level method for indexing sometimes, like when I'm dragging 3 flats
on the shank of a S&D drill bit, or a countersink/chamfering tool. You can do the
indexing and dragging quicker than you can type this...

BTW, just feed the cross slide in about .005" per stroke when dragging. 15 to 20 mils off for each
flat is plenty for a drill chuck to grip onto. OH, and use a 3 jaw chuck. :D

Nivlek
 
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