"Dave Baker" wrote in message
...



Perhaps he should just clock the hole?

Most hobby machinists have a plunger type DTI knocking about but not so
many
have a lever type which is what you'd need to get inside a hole as small
as
1/2" to clock it up. I was being charitable enough to assume

Assumptions at work can cost thousands of dollars in a heartbeat. Or perhaps
a life. Perhaps I'm being dramatic (although absolutely not overstating),
but I can't imagine anyone who works in a shop gets far on assumptions...

that the OP
didn't either or he'd be using it already instead of the edge finder and
we
wouldn't be answering the question in the first place so I was giving him
some methods that didn't rely on him having one.

Why would you assume he didn't have one (or wasn't willing to purchase one)?
Because he was using an edge finder the way he was, I wouldn't assume
anything regarding the contents of his toolbox.


If on the other hand he does have a lever type DTI, the primary use for
which is to clock up holes,

I rarely have the need to clock a hole. I use my DTI primarily for traming
the mill head, squaring the vice, and roughing on a surface grinder.

and he knows how to use it and still hadn't
thought to apply it to this task I guess it would be rather like standing
next to your car in the driveway scratching your head and still being
unable
to work out how you were going to get to the store 10 miles away without
walking.

Again with the assumptions. You assume everyone here has either gone through
a formal apprenticeship (or two) or has precisely no knowledge in
metalworking (and no tools to boot)?


The best method to use depends on how much accuracy you need, how much
space
you have between the quill and the job to fit DTIs into, what operation is
going to be performed after the centralising and a bunch of other stuff
all
of which require a brain to foresee any pitfalls with. A lever type DTI
might be best if you need to be centred to within a thou but other methods
are far quicker if you don't.

True, but we don't know what the application is. He might be drilling
clearance holes in angle iron for some structural job, or he might be trying
to bore out an engine block.


You can still cock the job up badly with a DTI if the mill head isn't
aligned to the direction of hole in the workpiece properly and you move
the
knee down to make room to mount the DTI and then move it back again to
mount
the tool.

Of course, but the resulting hole will be flawed as well - but that wasn't
the original question and your previous suggestions didn't address any of
these issues.


I cut valve seats in cylinder heads on my Bridgeport. Every seat I cut
means
getting the mill head aligned exactly with the direction of the hole in
the
valve guide and then centred on the hole in the valve guide. I don't use a
DTI for any of this because it isn't the fastest or best way to do it.
None
of the purpose built valve seat cutting systems use a DTI either for
exactly
the same reasons.

Your right in that there is a possibility that none of the suggestions in
this thread have correctly addressed the original poster's question.
Naturally, it is the fault of the original poster for not providing enough
information about his application. It is certainly not the fault of the DTI.

Regards,

Robin