Hello all,

I have a very simple problem that probably calls for a simple solution.
That said, I am open to "doing it right" if that is an option with
what I have available.

The problem? Given two rings, OD=2.468", two different IDs, and both
0.440" thick (all pretty much within a thou or two), I need to drill and
tap for radial 8-32 set screws. The plan is to have holes at 120 degree
intervals.

Setting aside my pride and desire to learn new techniques, all I really
need is to get the holes to be radial; I can do that with a vise and a
well-placed stop. It would be nice if they were reasonably accurately
placed around the circumference.

The closest thing I have to a dividing head is my H/V RT. I have a
tailstock for it, but I doubt that will be of any help because the
"tubes" are so short. A lathe chuck comes to mind, but I do not have
one for it, and am not in a hurry to spend money on one given how close
I am to buying a lathe. My understanding is that the chucks are
different (plain back vs. backed for the spindle), so I will probably
end up with both, just not all at the $ame time.

Given the circumstances, how would you locate the holes?

Bill

On Tue, 20 Nov 2007 16:11:54 -0500, Bill Schwab
wrote:

Hello all,

I have a very simple problem that probably calls for a simple solution.
That said, I am open to "doing it right" if that is an option with
what I have available.

The problem? Given two rings, OD=2.468", two different IDs, and both
0.440" thick (all pretty much within a thou or two), I need to drill and
tap for radial 8-32 set screws. The plan is to have holes at 120 degree
intervals.

Setting aside my pride and desire to learn new techniques, all I really
need is to get the holes to be radial; I can do that with a vise and a
well-placed stop. It would be nice if they were reasonably accurately
placed around the circumference.

For reasonably accurate with not much to work with, I'd scribe a
concentric circle on the face of the parts with dividers. Without
changing the dividers, step around the circle and lay out six evenly
spaced points. Clamp the part in the vise with two of the points that
define a diameter flush with the top of the jaws. Center and drill,
unclamp, and use the next appropriate pair of points to reclamp,
repeat.

A more accurate technique is to use a hex collet block with an arbor
turned to hold the rings. If you have 5C collets, the collet block
sets are a great bang for the buck - I probably use them 20 times for
every time I use a rotary table or indexer.

You could also scab together an arbor to attach the rings to a large
hex nut and clamp the nut in the mill vise.

--
Ned Simmons

Bill Schwab wrote in
:

Hello all,


Given the circumstances, how would you locate the holes?



I'd do it one of two ways.
1. face clamp it to the RT, zero it in, move off the R of your BC,
drill, tap, move 120 deg on the RT and rinse & repeat. 2. Clamp it in a
set of V-blocks in a vice (supported), center up, then trig out the 3
bolt hole centers.

--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

Anthony,

I'd do it one of two ways.
1. face clamp it to the RT, zero it in, move off the R of your BC,
drill, tap, move 120 deg on the RT and rinse & repeat. 2. Clamp it in a
set of V-blocks in a vice (supported), center up, then trig out the 3
bolt hole centers.

That sounds like what I would do for holes parallel to the axis???
These are radial. Sorry if I'm missing something - thanks either way.

Bill

On Nov 20, 4:33 pm, Ned Simmons wrote:
....
A more accurate technique is to use a hex collet block with an arbor
turned to hold the rings. If you have 5C collets, the collet block
sets are a great bang for the buck - I probably use them 20 times for
every time I use a rotary table or indexer.

You could also scab together an arbor to attach the rings to a large
hex nut and clamp the nut in the mill vise.

Ned Simmons

Good suggestions.

This device is my favorite for milling or drilling something made on
the lathe:

http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=33228729

It's much more rigid than a spin index as long as the collet closing
ring and the spindle clamp are snugged up *tight*.

You can get 3 and 4-jaw chucks on a 5C shank that let you move larger
work like these rings between the lathe and the mill. The repeat
accuracy is pretty much the play between the collet slot and the
locating pin.

Center it, or the collet block, under the spindle by putting a milling
center finder in a collet and another one in the chuck and aligning
the points. You could also use edge finders. Slide the collet one in
far enough to grab the sliding portion. Once you've aligned it you
can drill a small hole in the top to make it easier next time.

A simple free way, if done carefully, is to draw on paper three radial
lines at 120 degrees and a circle the OD of the part, align the part
with the circle, and use a small square block as a guide to scribe the
lines onto the ring. I've done similar layouts on a freshly plotted
CAD drawing that were accurate to better than 0.010". That's how I
lay out the mounting holes for a power supply or amplifier when
transfer punches won't pass through.

Jim Wilkins

Jim,

This device is my favorite for milling or drilling something made on
the lathe:

http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=33228729

My wallet was cringing, but that's cheap. Definitely on the to-buy list.


You can get 3 and 4-jaw chucks on a 5C shank that let you move larger
work like these rings between the lathe and the mill. The repeat
accuracy is pretty much the play between the collet slot and the
locating pin.

Interesting. Of course, that is starting pile up some metal. However,
you have just added on to my bag of tricks, **if** I am smart enough to
remember it

Enco has an $80 4-jaw lathe chuck that I will probably end up getting
for my RT. I would have to make a backing plate for it, but should be
easy enough (now I've done itg).



Center it, or the collet block, under the spindle by putting a milling
center finder in a collet and another one in the chuck and aligning
the points. You could also use edge finders. Slide the collet one in
far enough to grab the sliding portion. Once you've aligned it you
can drill a small hole in the top to make it easier next time.

Got it - I think.


A simple free way, if done carefully, is to draw on paper three radial
lines at 120 degrees and a circle the OD of the part, align the part
with the circle, and use a small square block as a guide to scribe the
lines onto the ring. I've done similar layouts on a freshly plotted
CAD drawing that were accurate to better than 0.010". That's how I
lay out the mounting holes for a power supply or amplifier when
transfer punches won't pass through.

That is a great idea. I use the 1:1 printed drawing trick fairly often.
Recently, I ended up cutting a drawing as I worked down into a stepped
part, leaving the part that told me where to cut next. More accurately,
it told me which dial revolution was correct - a poor man's DRO.

Thanks!

Bill

Bill,
Here's another way.

Put a peice or two of mdf on the rotary table, screw it down, and
place face up on the mill.
Face off the surface, to provide a flat and true surface.
Machine a round pocket so your rings will index on the inside of the
pocket. the pocket is about .005 less depth than the thickness of your
ring.
Machine outside the register pocket, so your drill will not be
starting on an angle.
Mill a 1/2" hole in the exact center of the mdf.
Stand the rotary up, put a 1/2" dowel pin in the center hole and dial
in center, and the surface, remembering to allow for whatever crush
was allowed.
Place the ring in the register, and clamp thru the 1/2" hole.
Drill radial holes, and tap.

Another way, I'll assume you are using a lathe to make these, and a
three jaw chuck:
After machining the OD.
Put a 1/8 spotting or center drill in a 1/8" pencil die grinder,
mounted in your boring bar holder.
Using a dial indicator, locate one jaw, the indicator travel must
allow jaws to pass, so you can get to the next 120 deg position.
Drill using low pressure to keep from burning the drill.
You will still need to finish the hole at the drill press, but that
angle is easy to fake in.
..
DJ

Bill Schwab wrote in
:

Anthony,

I'd do it one of two ways.
1. face clamp it to the RT, zero it in, move off the R of your BC,
drill, tap, move 120 deg on the RT and rinse & repeat. 2. Clamp it in
a set of V-blocks in a vice (supported), center up, then trig out the
3 bolt hole centers.

That sounds like what I would do for holes parallel to the axis???
These are radial. Sorry if I'm missing something - thanks either way.


No, I missed it Bill. I thought the holes were with the axis.
If you have a lathe available, turn out a stepped mandrel that you can
face clamp to the RT that gets the part far enough away from the RT
faceplate that you can get the mill quill close enough to the part to do
the holes. To clamp the ring to the mandrel, I'd split the mandrel 4x-6x
depth of the part you want to machine with a saw and put in a couple of
set screws on one side of the split, pushing against the other. Center
up mandrel on RT, slide ring on mandrel, tighten set screws, and have a
go at it.

If you don't have a lathe....

Pair of V blocks to hold the part, angle plate (or parallel) narrow
enough to fit between the v blocks to square the part up to. You would
have to trust your layout skills to mark the 120 angles.

Also, just as a note, when you are trying to find the center of a round
part on the mill with the part horizontal (looking for the highest
point), just running an indicator across the top will not find it
accurately. There is a significant distance across the diameter
(depending on diameter), where you will see no perceptable movement of
the indicator as you travel. For really accurate pickup, you want to
move the indicator to some distance away from center where you are
actually getting indicator movement as you move the mill axis. Then set
the indicator to 0, take note of your axis position, then move to the
other side of the round, and move til the indicator reads 0 agian. Take
the total distance moved of the mill axis and divide by 2 to get the
true center of the round part from your present position.


--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

On Nov 21, 5:17 am, Anthony wrote:
...
... For really accurate pickup, you want to
move the indicator to some distance away from center where you are
actually getting indicator movement as you move the mill axis. ...
--
Anthony

Good point. I generally use an edge finder and then move the radius
plus 0.100 but runout or out-of-roundness will throw that off. Lacking
a DRO I can't locate both sides and average the readings.

For usually adequate pickup, balance a 6" aluminum scale across the
round piece, like a seesaw, and carefully lower the center drill onto
the center line. Move the table until the seesaw is level. You could
stack a few pieces of wood etc on the table for a reference to sight
on.

Anthony,

I'd do it one of two ways.
1. face clamp it to the RT, zero it in, move off the R of your BC,
drill, tap, move 120 deg on the RT and rinse & repeat. 2. Clamp it in
a set of V-blocks in a vice (supported), center up, then trig out the
3 bolt hole centers.
That sounds like what I would do for holes parallel to the axis???
These are radial. Sorry if I'm missing something - thanks either way.


No, I missed it Bill. I thought the holes were with the axis.

No problem.


If you have a lathe available, turn out a stepped mandrel that you can
face clamp to the RT that gets the part far enough away from the RT
faceplate that you can get the mill quill close enough to the part to do
the holes. To clamp the ring to the mandrel, I'd split the mandrel 4x-6x
depth of the part you want to machine with a saw and put in a couple of
set screws on one side of the split, pushing against the other. Center
up mandrel on RT, slide ring on mandrel, tighten set screws, and have a
go at it.

Good - I wasn't crazy I did not come up with quite that solution,
but getting the part parallel to the RT in its vertical position did
occur to me.


If you don't have a lathe....

I am working on it, but have not taken the plunge yet.



Pair of V blocks to hold the part, angle plate (or parallel) narrow
enough to fit between the v blocks to square the part up to. You would
have to trust your layout skills to mark the 120 angles.

Are you thinking of using the v-blocks to hold it like a long cylinder?
The parts are probably too short for that (0.440"), or would it still
work? Perhaps that is why you stressed something narrow? My guess is
that I am envisioning something different than you are describing.


Also, just as a note, when you are trying to find the center of a round
part on the mill with the part horizontal (looking for the highest
point), just running an indicator across the top will not find it
accurately. There is a significant distance across the diameter
(depending on diameter), where you will see no perceptable movement of
the indicator as you travel.

Understood.


For really accurate pickup, you want to
move the indicator to some distance away from center where you are
actually getting indicator movement as you move the mill axis. Then set
the indicator to 0, take note of your axis position, then move to the
other side of the round, and move til the indicator reads 0 agian. Take
the total distance moved of the mill axis and divide by 2 to get the
true center of the round part from your present position.

Interesting.

My thought was to measure the OD, and arrange a stop to make contact at
the 9 O'clock position. However, the flaw might be that there is no way
to be certain about the contact between the stop and the curved surface.
I would find the edge using my super-nice Indian made v-block against
the stop. That makes sense for a squared work piece, but probably not
for a round one.

After that digression, I suspect you are going to recommend the
indicator approach. Sounds fine to me.

Thanks,

Bill

[*] It's so flat and square I keep looking over my shoulder for NIST
agents

Bill Schwab wrote in
:

Are you thinking of using the v-blocks to hold it like a long cylinder?
The parts are probably too short for that (0.440"), or would it still
work? Perhaps that is why you stressed something narrow? My guess is
that I am envisioning something different than you are describing.


Yup, like a cylinder laid down in the vice. And that is the reason for
specifying the word narrow. I don't recall exactly how big of a diameter
you said, but the purpose of the parallel end or angle plate is to get
the part square and vertical to the vice.
You could actually machine notches for the V's out of a piece of square
stock slightly smaller than the clamping diameter of your part, this way
you catch most of the face of the part you want to machine, plus you
could clamp it in place on the vice and use it for a location stop along
the x axis.

This way you can be assured of the part being square to the vice.

Yes, I advocate the indicator approach. I have to use this method often
when setting up gauges to measure round parts. I have a +/- 5 micron
tolerance on the parts, so centering has to be _exact_.

--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

Keywords:
In article , Bill Schwab wrote:
Jim,

This device is my favorite for milling or drilling something made on
the lathe:

http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=33228729

My wallet was cringing, but that's cheap. Definitely on the to-buy list.

Don't get too excited. The $45 price is for a blank indexing ring. The
actual indexer that is shown in the photo goes for $260.

Doug White

....
Don't get too excited. The $45 price is for a blank indexing ring. The
actual indexer that is shown in the photo goes for $260.

Doug White

MSC had a good image. The less expensive import version I have is
sometimes on sale for around $50-$70. Unfortunately they don't have a
unique common name like "spin index" and are harder to search for.

Anthony,

Bill Schwab wrote in
:

Are you thinking of using the v-blocks to hold it like a long cylinder?
The parts are probably too short for that (0.440"), or would it still
work? Perhaps that is why you stressed something narrow? My guess is
that I am envisioning something different than you are describing.


Yup, like a cylinder laid down in the vice. And that is the reason for
specifying the word narrow. I don't recall exactly how big of a diameter
you said, but the purpose of the parallel end or angle plate is to get
the part square and vertical to the vice.

Given that they are more rings than tubes, it strikes me as easier to
let the vise grab the flat surfaces, and use the indicator to locate the
center along the x-axis. I sometimes use squares to get parts
perpendicular to the table, but just don't trust it (or myself??) as
much as a firm grip with a vise and/or snug parallels.


You could actually machine notches for the V's out of a piece of square
stock slightly smaller than the clamping diameter of your part, this way
you catch most of the face of the part you want to machine, plus you
could clamp it in place on the vice and use it for a location stop along
the x axis.

I think I follow. But again, if considered to be tubes, the parts are
so "short" that it makes sense to grab them on the ends using a vise.
They will have little choice but to be square, and an indicator will let
me find the center along the x-axis.

In terms of machining, the remaining step is to drill radial holes. Not
(yet?) having a spin indexer, I will probably resort to the CAD drawing
idea.


This way you can be assured of the part being square to the vice.

Yes, I advocate the indicator approach. I have to use this method often
when setting up gauges to measure round parts. I have a +/- 5 micron
tolerance on the parts, so centering has to be _exact_.

=:0

Thanks!

Bill