Hi all,

I've been thinking about buying a magnetic drilling machine for a while,
and recently I've seen a few at affordable prices on eBay. I need one
for drilling steel plates which are too big to fit in my drill press,
and also for drilling frameworks which must be drilled after they've
been welded together for reasons of alignment. I've seen Rotabroach
cutters in sizes from 6 mm upwards, but suppose I want to drill a 3 mm
hole? Can I fit a Jacobs chuck and a twist drill to a magnetic drilling
machine?

Many thanks,

Chris Tidy

On Sat, 20 Aug 2005 23:48:56 +0000 (UTC), Christopher Tidy
wrote:

Hi all,

I've been thinking about buying a magnetic drilling machine for a while,
and recently I've seen a few at affordable prices on eBay. I need one
for drilling steel plates which are too big to fit in my drill press,
and also for drilling frameworks which must be drilled after they've
been welded together for reasons of alignment. I've seen Rotabroach
cutters in sizes from 6 mm upwards, but suppose I want to drill a 3 mm
hole? Can I fit a Jacobs chuck and a twist drill to a magnetic drilling
machine?

That depends. I suppose a adapter could be made for the ones built
for rotabroaches. But normally you use a different type of mag drill
that already has a chuck. Look at the Milwaukee line of mag drills and
you'll see what I mean.

Wayne Cook
Shamrock, TX
http://members.dslextreme.com/users/waynecook/index.htm

Wayne Cook wrote:
On Sat, 20 Aug 2005 23:48:56 +0000 (UTC), Christopher Tidy
wrote:


Hi all,

I've been thinking about buying a magnetic drilling machine for a while,
and recently I've seen a few at affordable prices on eBay. I need one
for drilling steel plates which are too big to fit in my drill press,
and also for drilling frameworks which must be drilled after they've
been welded together for reasons of alignment. I've seen Rotabroach
cutters in sizes from 6 mm upwards, but suppose I want to drill a 3 mm
hole? Can I fit a Jacobs chuck and a twist drill to a magnetic drilling
machine?


That depends. I suppose a adapter could be made for the ones built
for rotabroaches. But normally you use a different type of mag drill
that already has a chuck. Look at the Milwaukee line of mag drills and
you'll see what I mean.

Thanks Wayne. I had a look at the Milwaukee range and I see what you
mean. I've only ever seen the Rotabroach kind for sale in England, and
I'd quite like to be able to use the Rotabroach cutters, so I was
wondering if an adaptor was available? As you say, it might be possible
to make one.

Presumably the kind of magnetic drilling machine which is built with a
Jacobs chuck spins faster, so drilling with twist drills on the
Rotabroach kind of machine might take a while? I don't mind that too
much, though - most of the time my drill press is set on the lowest
speed because the belts are so fiddly to change.

Chris

There are a variety of machines and ways to attack this problem. Smaller
cutters are very fragile and so I have made up 7/16 drills to fit the
rotabroach.
If I remember correctly the shank of the cutters is 3/4 diameter. I would
center drill a piece of cold finish about an inch long to match the 7/16 bit
then braze a HSS drill bit in the sleeve. I would cut the bit in an
abrasive chop saw since I only needed the end of the drill bit. If you are
only drilling one or two standard sizes this is one approach.
The lightest rotabroach mag drills will not accept the adaptation of a
Jacobs chuck. The larger, heavier, and expensive magnetic base drills such
as Milwaukee will operate either way and have a Morse taper in the spindle.
They come with variable speed.
A 3mm hole is only 1/8th. I cannot see why you would bother since I can
push a 3/16th hole through one inch plate in less than a minute with a hand
drill.

Randy


"Christopher Tidy" wrote in message
...
Hi all,

I've been thinking about buying a magnetic drilling machine for a while,
and recently I've seen a few at affordable prices on eBay. I need one
for drilling steel plates which are too big to fit in my drill press,
and also for drilling frameworks which must be drilled after they've
been welded together for reasons of alignment. I've seen Rotabroach
cutters in sizes from 6 mm upwards, but suppose I want to drill a 3 mm
hole? Can I fit a Jacobs chuck and a twist drill to a magnetic drilling
machine?

Many thanks,

Chris Tidy

R. Zimmerman wrote:
There are a variety of machines and ways to attack this problem. Smaller
cutters are very fragile and so I have made up 7/16 drills to fit the
rotabroach.
If I remember correctly the shank of the cutters is 3/4 diameter. I would
center drill a piece of cold finish about an inch long to match the 7/16 bit
then braze a HSS drill bit in the sleeve. I would cut the bit in an
abrasive chop saw since I only needed the end of the drill bit. If you are
only drilling one or two standard sizes this is one approach.
The lightest rotabroach mag drills will not accept the adaptation of a
Jacobs chuck. The larger, heavier, and expensive magnetic base drills such
as Milwaukee will operate either way and have a Morse taper in the spindle.
They come with variable speed.

Thanks for the advice. It looks like there is a way to do it. Most
likely I will only need two or three of the smaller sizes. The drilling
machines I was looking at are made by Unibor. Any thoughts about this brand?

A 3mm hole is only 1/8th. I cannot see why you would bother since I can
push a 3/16th hole through one inch plate in less than a minute with a hand
drill.

Wow, some hand drill! I've never been able to do that with steel plate.
Actually, my main concern is not speed, but making square holes as I
want to tap them afterwards. Most of the holes would be for M6 screws.
The very smallest holes (3 mm) would be for pop rivets.

Chris

Drill yourself a block to line up the drill square for starters if drilling
square is a concern. Center punch your locations. Spot the drill to make a
large dent. Set your block and bit over the dent and drill.
If you look up the speed for a 1/8th bit using HSS it is 4 times the cutting
speed divided by the diameter. 4 X 100 fpm / .125 = 3200 rpm. That is the
speed of a loaded air drill. Use good quality bits such a Dormer or if you
really want to splurg SKF. Order stub drills with split points. If you
were to cut one thousandth of an inch every revolution you would cut over
three inches in a minute at 3200 rpm.
I don't think you need a mag drill. If I was brave enough I would tap with
a variable speed electric drill with a tap chucked. Damn I hate breaking
taps off in holes though.
randy




"Christopher Tidy" wrote in message
...
R. Zimmerman wrote:
There are a variety of machines and ways to attack this problem. Smaller
cutters are very fragile and so I have made up 7/16 drills to fit the
rotabroach.
If I remember correctly the shank of the cutters is 3/4 diameter. I would
center drill a piece of cold finish about an inch long to match the 7/16
bit
then braze a HSS drill bit in the sleeve. I would cut the bit in an
abrasive chop saw since I only needed the end of the drill bit. If you
are
only drilling one or two standard sizes this is one approach.
The lightest rotabroach mag drills will not accept the adaptation of a
Jacobs chuck. The larger, heavier, and expensive magnetic base drills
such
as Milwaukee will operate either way and have a Morse taper in the
spindle.
They come with variable speed.

Thanks for the advice. It looks like there is a way to do it. Most
likely I will only need two or three of the smaller sizes. The drilling
machines I was looking at are made by Unibor. Any thoughts about this brand?

A 3mm hole is only 1/8th. I cannot see why you would bother since I
can
push a 3/16th hole through one inch plate in less than a minute with a
hand
drill.

Wow, some hand drill! I've never been able to do that with steel plate.
Actually, my main concern is not speed, but making square holes as I
want to tap them afterwards. Most of the holes would be for M6 screws.
The very smallest holes (3 mm) would be for pop rivets.

Chris

R. Zimmerman wrote:
Drill yourself a block to line up the drill square for starters if drilling
square is a concern. Center punch your locations. Spot the drill to make a
large dent. Set your block and bit over the dent and drill.
If you look up the speed for a 1/8th bit using HSS it is 4 times the cutting
speed divided by the diameter. 4 X 100 fpm / .125 = 3200 rpm. That is the
speed of a loaded air drill. Use good quality bits such a Dormer or if you
really want to splurg SKF. Order stub drills with split points. If you
were to cut one thousandth of an inch every revolution you would cut over
three inches in a minute at 3200 rpm.
I don't think you need a mag drill. If I was brave enough I would tap with
a variable speed electric drill with a tap chucked. Damn I hate breaking
taps off in holes though.
randy

Thanks. I don't have an air drill (because I haven't got round to buying
a compressor yet, but it's on my "want" list). I just have an electric
pistol-grip drill, and I'm rather scared of burning it out. A guide
block is a good idea, so I might try making one for small diameter
drills, but I still need to drill some 12 mm and 14 mm holes in 6 mm and
10 mm plate. This would be really hard with an electric pistol-grip
drill, and I have a 230 V - 110 V transformer which could run a
magnetic drill, so you can see where my thinking was going.

Will think about it some more...

Chris

For the 12 mm definitely go for a mag base. You don't need an air powered
drill for those small bits... just a good quality electric at full rpm.
I found labourers are brutal on small annular cutters. If you get a mag
drill that cannot take a chuck then make up brazed bits like I suggested in
the sizes you need. It is a lot cheaper than the cutters.
A tip on electric hand drills: They expire because people abuse them. When
you are done drilling a hole pull the trigger and run the drill flat out for
five to ten seconds. The fan will cool the armature. If you don't then
when you lay the drill down all that heat sinks into the armature windings
and breaks down the insulation. This practice will significantly increase
the life of your electric drill or any electric tool that has been working
hard.
Randy



"Christopher Tidy" wrote in message
...

Thanks. I don't have an air drill (because I haven't got round to buying
a compressor yet, but it's on my "want" list). I just have an electric
pistol-grip drill, and I'm rather scared of burning it out. A guide
block is a good idea, so I might try making one for small diameter
drills, but I still need to drill some 12 mm and 14 mm holes in 6 mm and
10 mm plate. This would be really hard with an electric pistol-grip
drill, and I have a 230 V - 110 V transformer which could run a
magnetic drill, so you can see where my thinking was going.

Will think about it some more...

Chris

"R. Zimmerman" wrote in message
news:32UNe.75041$vj.40912@pd7tw1no...
snip----

A tip on electric hand drills: They expire because people abuse them.
When
you are done drilling a hole pull the trigger and run the drill flat out
for
five to ten seconds. The fan will cool the armature. If you don't then
when you lay the drill down all that heat sinks into the armature windings
and breaks down the insulation. This practice will significantly increase
the life of your electric drill or any electric tool that has been working
hard.
Randy

Yep! I do that, too. You can feel the heat coming off----there's no
question it's a good idea.

Harold

Go to www.hougen.com and look at their mag drills. I have a HMD904 that
is quite robust and will accept a Jacobs chuck with an adapter. I also
have a smaller Hougen frame mag drill that takes Roto-Lock cutters and
it will not accept a chuck.

Thanks, Steve

Harold and Susan Vordos wrote:
"R. Zimmerman" wrote in message
news:32UNe.75041$vj.40912@pd7tw1no...
snip----


A tip on electric hand drills: They expire because people abuse them.

When

you are done drilling a hole pull the trigger and run the drill flat out

for

five to ten seconds. The fan will cool the armature. If you don't then
when you lay the drill down all that heat sinks into the armature windings
and breaks down the insulation. This practice will significantly increase
the life of your electric drill or any electric tool that has been working
hard.
Randy


Yep! I do that, too. You can feel the heat coming off----there's no
question it's a good idea.

Harold



How did I get to my age without learning that one?

Good idea, I'll try to start doing just that.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

On Sun, 21 Aug 2005 02:06:39 +0000 (UTC), Christopher Tidy
wrote:

Wayne Cook wrote:


That depends. I suppose a adapter could be made for the ones built
for rotabroaches. But normally you use a different type of mag drill
that already has a chuck. Look at the Milwaukee line of mag drills and
you'll see what I mean.

Thanks Wayne. I had a look at the Milwaukee range and I see what you
mean. I've only ever seen the Rotabroach kind for sale in England, and
I'd quite like to be able to use the Rotabroach cutters, so I was
wondering if an adaptor was available? As you say, it might be possible
to make one.

Presumably the kind of magnetic drilling machine which is built with a
Jacobs chuck spins faster, so drilling with twist drills on the
Rotabroach kind of machine might take a while? I don't mind that too
much, though - most of the time my drill press is set on the lowest
speed because the belts are so fiddly to change.


Again it depends on the machine. Mine has a 3/4" chuck single speed
version that goes 350 rpm max. But they also make two speed versions.

Wayne Cook
Shamrock, TX
http://members.dslextreme.com/users/waynecook/index.htm

"Jeff Wisnia" wrote in message
news
Harold and Susan Vordos wrote:
"R. Zimmerman" wrote in message
news:32UNe.75041$vj.40912@pd7tw1no...
snip----


A tip on electric hand drills: They expire because people abuse them.

When

you are done drilling a hole pull the trigger and run the drill flat out

for

five to ten seconds. The fan will cool the armature. If you don't then
when you lay the drill down all that heat sinks into the armature
windings
and breaks down the insulation. This practice will significantly
increase
the life of your electric drill or any electric tool that has been
working
hard.
Randy


Yep! I do that, too. You can feel the heat coming off----there's no
question it's a good idea.

Harold



How did I get to my age without learning that one?

Dunno! But, for me, the idea came to me when I realized that I tend to
cover the vents when holding the drill motor for some things. I don't let
that worry me unless I have a lot of holes to do, but I always free wheel it
between holes to insure it's not over heating.

Harold