开云体育

----- Original Message -----
From: Harvey White
To: UNIMAT@...
Sent: Tuesday, January 16, 2007 2:00 PM
Subject: Re: [UNIMAT] Some newbie questions


On Tue, 16 Jan 2007 18:42:17 -0000, you wrote:

>I am learning and having fun, so please bear with me on some newbie
>questions. I have a DB200.
>
>1) Cutting Off: If you are supporting a workpiece between centers or
>even just on a chuck, what are you supposed to do when you get the
>part just about cut off? If if falls off, it will hit the ways. It
>is still rotating so you can't grab it.

Generally, you let it fall. You could put something over the ways to
keep the ricochets down, but that can get in the way and become a
safety problem.

>
>2) How does one match up at the point where I need to rotate the
>workpiece after turning between centers? I can only cut to the point
>just before my cross slide hits the chuck or the lathe dog. Then I
>turn it over to turn down the part that was previously in the chuck or
>lathe dog. I can never seem to get it totally matched with the
>previously turned section. I usually end up with some sort of a mark,
>either high or low.

This is a problem with any 3 jaw chuck and reversing the work on any
lathe. You need to either

1) consider the amount of material in the chuck as scrap, and cut it
properly.

2) use a 4 jaw chuck, and center for exact roundness

3) do all of your turning operations without removing the work,
leaving only an end facing operation till last.

A collet would give you better centering, as well.

You will probably get closest in your work if you rotate the work 180
degrees when placing it in the chuck. Not the best, but perhaps
closest.

You can also try shims, or try to rotate the work in the jaws to give
the minimum runout.

main problem is that no 3 jaw chuck is completely accurate for
centering.

>
>3) Do people tend to leave their belts on the pulleys when they are
>done for the night or do they tend to take them off? Do the belts
>last longer if they are not under tension or doesn't it really matter?

Mine have deteriorated for old age before they expand too much for
tension unless they're rubber.
>
>4) How does one face a workpiece when using the live center? There
>doesn't seem to be much room to get a cutting tool in there to face
>the workpiece.
>

Best you can do is to use an angled tool and face as much as possible.
You could use a steady rest if you had one (supports the end of the
material being turned).

>5) I don't have an indexing attachment. Are there any commercial
>rotary tables that work well with the Unimat? If not, has anyone made
>the rotary table as described in Rex Tingey's book available in the
>Files section?

I do, but it uses the 3 jaw chuck and is thus best for milling.
Therefore, no idea except that the smallest rotary table I know of is
a 4 inch, which is way overdone for the unimat. Taig or Sherline
might have something in the right size, or at least, point you to the
right size.

>
>Thank you for your answers.

You're welcome,

Harvey