Hi,

Advice needed. I'm converting a drill press to CNC. Need to bore the
pinion shaft associated with the rack and pinion head feed setup.
Picture of the shaft with gear is attached;

http://i.pbase.com/u26/eldata/large/...G_2138copy.jpg

Gear is threaded on the shaft so it can easily be removed. Normally,
one would just face off the slotted portion to flat then center bore
using center drill, drill then ream. In this case I want the slot (or
what would be left of it) to remain. Shaft is about 1/2" and bore will
be 1/4" so 1/8" of slot will be left on either side.

What would be the best starting procedure in this case seeing that the
tip of the center drill won't be reaching the flat? I'll be pressing a
1/4" shaft in the bored hole that will be coupled to a motor so the
bore has to be fairly accurate.

In article .com,
says...

What would be the best starting procedure in this case seeing that the
tip of the center drill won't be reaching the flat? I'll be pressing a
1/4" shaft in the bored hole that will be coupled to a motor so the
bore has to be fairly accurate.

You won't be able to get this bore accurate unless you set it up in
a lathe. Best way is to chuck up the part and simply go at it
with a boring tool. It's going to be an interrupted cut so go easy
until you are at the bottom of the slot, at which point you can
then drill to open up the hole to the desired depth, and continue
on after that with a boring bar.

Jim


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snip
Gear is threaded on the shaft so it can easily be removed. Normally,
one would just face off the slotted portion to flat then center bore
using center drill, drill then ream. In this case I want the slot (or
what would be left of it) to remain. Shaft is about 1/2" and bore will
be 1/4" so 1/8" of slot will be left on either side.
What would be the best starting procedure in this case seeing that the
tip of the center drill won't be reaching the flat? I'll be pressing a
1/4" shaft in the bored hole that will be coupled to a motor so the
bore has to be fairly accurate.
========================
This is one of the very few cases where you can successfully use
an end mill in a jacobs style chuck. I suggest you get a 4 flute
[two flute end mill or drill will tend to grab in the slot] 1/4
inch end mill, and slowly and carefully feed the endmill in the
required depth.

GmcD

Just remember doing it his way you WILL get a hole larger than the endmill
so be prepared to custom make the pin you press in.

If the hole has to be *exactly* on size (or a touch under for a press fit)
I'd under drill it with a smaller end mill and then go at it with a boring
bar.

--.- Dave



This is one of the very few cases where you can successfully use
an end mill in a jacobs style chuck. I suggest you get a 4 flute
[two flute end mill or drill will tend to grab in the slot] 1/4
inch end mill, and slowly and carefully feed the endmill in the
required depth.

GmcD

In article , F. George McDuffee
says...

This is one of the very few cases where you can successfully use
an end mill in a jacobs style chuck. I suggest you get a 4 flute
[two flute end mill or drill will tend to grab in the slot] 1/4
inch end mill, and slowly and carefully feed the endmill in the
required depth.

I would respectfully suggest this is a 'bad idea.'

If he is really interested in a bore in this shaft that is
concentric, and to size, and end mill in a jacobs chuck is
very nearly the worst way to do this.

Even glossing over the interrupted nature of the cut which
will tend to pull the jacobs chuck off its taper, if it is
Morse taper mounted.

Jim


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Best way is to chuck up the part and simply go at it
with a boring tool.

Thanks, but let me make sure we're on "similar pages"...If there was no
slot, I would have used a #3 center drill followed by a letter size "C"
drill then finally a .2495 chucking reamer. With the slot, I'm thinking
of starting with a "D" drill (just slightly larger than the shaft of
the center drill) to a depth just short of the flat then continuing
with center drill on the flat, then "C" drill then chucking reamer. Is
this similar to what you had in mind? Already have the parts mentioned
(I do a lot of 1/4" boring) and yes, I'm using a lathe.

In article .com,
says...

Thanks, but let me make sure we're on "similar pages"...If there was no
slot, I would have used a #3 center drill followed by a letter size "C"
drill then finally a .2495 chucking reamer.

This approach does not give good concentricity. Unless you
bore the part before reaming, you stand a sizeable chance of
getting a hole that is several thou off center.

Jim


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wrote:
Hi,

Advice needed. I'm converting a drill press to CNC. Need to bore the
pinion shaft associated with the rack and pinion head feed setup.
Picture of the shaft with gear is attached;

http://i.pbase.com/u26/eldata/large/...G_2138copy.jpg

Gear is threaded on the shaft so it can easily be removed. Normally,
one would just face off the slotted portion to flat then center bore
using center drill, drill then ream. In this case I want the slot (or
what would be left of it) to remain. Shaft is about 1/2" and bore will
be 1/4" so 1/8" of slot will be left on either side.

What would be the best starting procedure in this case seeing that the
tip of the center drill won't be reaching the flat? I'll be pressing a
1/4" shaft in the bored hole that will be coupled to a motor so the
bore has to be fairly accurate.

I'd plug the slot with a bit of steel and soft solder it in place, then
proceed as for a non slotted bar. When finished, soften the solder and
remove the two halves of the plug.
If you don't like the idea of soft solder, use Loctite.

--

Regards, Gary Wooding
(To reply by email, change feet to foot in my address)

This approach does not give good concentricity. Unless you
bore the part before reaming, you stand a sizeable chance of
getting a hole that is several thou off center.

Cannot recall getting more than .002 runout on the pressed shaft (done
without the slot that is). My headstock and tailstock were aligned
especially for drilling with a lathe like this. Also, I use stub drill
bits instead of jobbers. Probably shouldn't have used the word boring
since a boring bar isn't being used. At first I had my doubts too and
would press a 5/16" shaft then turn it down to 1/4" but the difference
in runout wasn't worth the effort. Other than possible
headstock/tailstock misalignment, what else do you see wrong with
drilling/reaming with a lathe?

Simple,

1) Drills don't make straight or accurate holes, and

2) Reamers follow the existing hole.

Long story short....Not an issue provided the center drill has an
unobstructed path to the flat. My only concern was how best to present the
flat to the center drill. Don't see any reason for using an end mill to
clear a path if a normal drill will do, and so far no one has suggested that
it won't.

"Gene Kearns" wrote in message
...
On 18 May 2005 13:51:26 -0700, wrote:


Other than possible
headstock/tailstock misalignment, what else do you see wrong with
drilling/reaming with ....

... any machine tool...

Simple,

1) Drills don't make straight or accurate holes, and

2) Reamers follow the existing hole.
--

Homepage
http://myworkshop.idleplay.net/machine_shop/index.htm

On Thu, 19 May 2005 02:54:13 GMT, "oparr" wrote:

Simple,

1) Drills don't make straight or accurate holes, and

2) Reamers follow the existing hole.

Long story short....Not an issue provided the center drill has an
unobstructed path to the flat. My only concern was how best to present the
flat to the center drill. Don't see any reason for using an end mill to
clear a path if a normal drill will do, and so far no one has suggested that
it won't.


Just face off a spot with a regular HSS tool bit for your center
drill.

In article , Gene Kearns says...

Other than possible
headstock/tailstock misalignment, what else do you see wrong with
drilling/reaming with ....

1) Drills don't make straight or accurate holes, and

2) Reamers follow the existing hole.

That's it in a nutshell. If he doesn't
care that the hole is truly concentric, a reamer will
make a hole, someplace in the shaft, when it follows
a drilled hole. Kinda hard to tell where.

Jim


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In article pdTie.9662$E05.5496@trndny09, oparr says...

Long story short....Not an issue provided the center drill has an
unobstructed path to the flat.

Actually no.

Doesn't matter even if it *does* have a faced surface to
start the C-drill on. The twist drill that picks up that
centerdrill will make some kind of hole that cannot be
guaranteed to be better than a few thou within center.

If it's off by five thou, your reamed hole will be
off by five thou.

Have you considered the tolerance you need for the
application?

Jim


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Just face off a spot with a regular HSS tool bit for your center
drill.

Will do. Thanks.

That's it in a nutshell. If he doesn't
care that the hole is truly concentric, a reamer will
make a hole, someplace in the shaft, when it follows
a drilled hole. Kinda hard to tell where.

Actually, I'm more concerned with the runout of the pressed shaft. The
hole doesn't have to be concentric provided an oversized shaft is used
then turned down to the desired diameter **and** the difference in
diameters is much greater than the eccentricity of the hole. In fact
that procedure should provide the most accurate shaft since it caters
to a less than precise shaft as well. But I digress since that isn't
even necessary in this case.

In article . com,
says...

That's it in a nutshell. If he doesn't
care that the hole is truly concentric, a reamer will
make a hole, someplace in the shaft, when it follows
a drilled hole. Kinda hard to tell where.

Actually, I'm more concerned with the runout of the pressed shaft. The
hole doesn't have to be concentric provided an oversized shaft is used
then turned down to the desired diameter **and** the difference in
diameters is much greater than the eccentricity of the hole. In fact
that procedure should provide the most accurate shaft since it caters
to a less than precise shaft as well. But I digress since that isn't
even necessary in this case.

Where's Harold when you need him. sigh

You are correct that your plan will work. But it's just as easy,
in fact, *easier* to do it the right way, which is to form the
bore for the add-in shaft with the correct geometery to start
with. As a long-time bodger myself, I recognize that when projects
start to include features that 'can be corrected later in another
stage' that's a sign that maybe things need re-thinking.

Jim


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But it's just as easy,
in fact, *easier* to do it the right way,

Easier.....Right......All relatives as far as I'm concerned. You seem to
have a major misconception when it comes to precision drilling on a lathe.
Just to prove a point I chucked a 1/2" diameter 3" long aluminum shaft,
checked the runout then proceeded to drill/ream a 1/4" diameter hole 1/2"
deep in it. I then pressed a 3" piece of 1/4" precision steel shaft in the
hole and checked runout.

It took exactly 10 minutes between the starting of the center drill into the
aluminum shaft and completion with the pressing of the steel shaft. The
runout of the pressed shaft was less than .001 up to 1.25" from the point of
entry. It was .0015 at the end of the pressed shaft at 2.5" from the point
of entry.

You're blowing hot air buddy. Here's a shot of the final setup;

http://i.pbase.com/u26/eldata/large/...G_2151copy.jpg

"jim rozen" wrote in message
...
In article . com,
says...

That's it in a nutshell. If he doesn't
care that the hole is truly concentric, a reamer will
make a hole, someplace in the shaft, when it follows
a drilled hole. Kinda hard to tell where.

Actually, I'm more concerned with the runout of the pressed shaft. The
hole doesn't have to be concentric provided an oversized shaft is used
then turned down to the desired diameter **and** the difference in
diameters is much greater than the eccentricity of the hole. In fact
that procedure should provide the most accurate shaft since it caters
to a less than precise shaft as well. But I digress since that isn't
even necessary in this case.

Where's Harold when you need him. sigh

You are correct that your plan will work. But it's just as easy,
in fact, *easier* to do it the right way, which is to form the
bore for the add-in shaft with the correct geometery to start
with. As a long-time bodger myself, I recognize that when projects
start to include features that 'can be corrected later in another
stage' that's a sign that maybe things need re-thinking.

Jim


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In article MDbje.11840$KQ6.10960@trndny02, oparr says...

It took exactly 10 minutes between the starting of the center drill into the
aluminum shaft and completion with the pressing of the steel shaft. The
runout of the pressed shaft was less than .001 up to 1.25" from the point of
entry. It was .0015 at the end of the pressed shaft at 2.5" from the point
of entry.

Great. You got lucky. Go at it for the real deal then.

Sounds like you have it well under control.

Jim


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In article , Gene Kearns says...

If this is the case, I guarantee unacceptable run-out in the finished
hole.

I think he's got his setup well under control and is sure he will
produce a fine part with his approach. Honestly I don't think
he even needed any help from the folks here to produce an
acceptable outcome.

Jim


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he will produce a fine part with his approach.

And that I did (runout of 2.5" pressed shaft is less than .0015 as
expected);

http://i.pbase.com/u26/eldata/large/...G_2248copy.jpg


Honestly I don't think
he even needed any help from the folks here

Not to decide whether to bore or drill. I already indicated where my
uncertainty was. You're still missing something though since you seem to
believe that drilling on a lathe is as error prone as drilling on a mill or
drill press. The rotating instead of stationary workpiece on the lathe makes
all the difference in the world.

"jim rozen" wrote in message
...
In article , Gene Kearns
says...

If this is the case, I guarantee unacceptable run-out in the finished
hole.

I think he's got his setup well under control and is sure he will
produce a fine part with his approach. Honestly I don't think
he even needed any help from the folks here to produce an
acceptable outcome.

Jim


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In article U25le.12$Ib.7@trndny03, oparr says...

And that I did (

We're glad there was a successful conclusion.


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