BP Drawbar Shear Pin Question
 

I couldn't find this info on Google. What is the proper material to use to
replace the pin on a Bridgeport drawbar? I tried a roll pin which was way
too soft and sheared too easily.

BP Drawbar Shear Pin Question
 

On Sat, 31 Dec 2005 20:12:48 -0500, "ATP*"
wrote:

I couldn't find this info on Google. What is the proper material to use to
replace the pin on a Bridgeport drawbar? I tried a roll pin which was way
too soft and sheared too easily.



In eighteen years of teaching high school freshmen and sophomores I
have never had a student break a BP drawbar in that fashion. Perhaps
you are putting WAY too much oomph into your spindle tightening.

Errol Groff

Instructor, Manufacturing Technology
H.H. Ellis Technical High School
613 Upper Maple Street
Danielson, CT 06239

New England Model Engineering Society
www.neme-s.org

BP Drawbar Shear Pin Question
 

"Errol Groff" wrote in message
...
On Sat, 31 Dec 2005 20:12:48 -0500, "ATP*"
wrote:

I couldn't find this info on Google. What is the proper material to use to
replace the pin on a Bridgeport drawbar? I tried a roll pin which was way
too soft and sheared too easily.



In eighteen years of teaching high school freshmen and sophomores I
have never had a student break a BP drawbar in that fashion. Perhaps
you are putting WAY too much oomph into your spindle tightening.

Errol Groff


I don't know, I'm not really putting that much torque on it, especially not
the last time. The hollow roll pin I put in there definitely doesn't take
much to shear.

BP Drawbar Shear Pin Question
 

ATP* wrote:
"Errol Groff" wrote in message
...

On Sat, 31 Dec 2005 20:12:48 -0500, "ATP*"
wrote:


I couldn't find this info on Google. What is the proper material to use to
replace the pin on a Bridgeport drawbar? I tried a roll pin which was way
too soft and sheared too easily.



In eighteen years of teaching high school freshmen and sophomores I
have never had a student break a BP drawbar in that fashion. Perhaps
you are putting WAY too much oomph into your spindle tightening.

Errol Groff



I don't know, I'm not really putting that much torque on it, especially not
the last time. The hollow roll pin I put in there definitely doesn't take
much to shear.


My guess is that it is NOT a shear pin, ie. designed to break first,
before something else does. It most likely is just the easiest way to
make it. I don't think my drawbar (aftermarket) has a shear pin.
I'd use a taper pin.

Jon

BP Drawbar Shear Pin Question
 

On Sun, 01 Jan 2006 00:18:02 -0600, Jon Elson
wrote:

ATP* wrote:
"Errol Groff" wrote in message
...

On Sat, 31 Dec 2005 20:12:48 -0500, "ATP*"
wrote:


I couldn't find this info on Google. What is the proper material to use to
replace the pin on a Bridgeport drawbar? I tried a roll pin which was way
too soft and sheared too easily.



In eighteen years of teaching high school freshmen and sophomores I
have never had a student break a BP drawbar in that fashion. Perhaps
you are putting WAY too much oomph into your spindle tightening.

Errol Groff



I don't know, I'm not really putting that much torque on it, especially not
the last time. The hollow roll pin I put in there definitely doesn't take
much to shear.


My guess is that it is NOT a shear pin, ie. designed to break first,
before something else does. It most likely is just the easiest way to
make it. I don't think my drawbar (aftermarket) has a shear pin.
I'd use a taper pin.

Jon

When I made up the 3 drawbars for the Gorton (uses any 30 taper), I
welded the hex on, after shearing the first pin.

Gunner

"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner

BP Drawbar Shear Pin Question
 

That is not a shear pin. It is an assembly pin. I have made many drawbars
and I have tried turning them from solid bar. This usually fails unless the
steel bar has been totally normalized (annealed). Even with a follower rest,
the bar bends as its diameter is reduced. So, it is much cheaper to pin a
Hex on a piece of hotroll bar and thread the other end. Normally a solid
straight pin around .150 is used.
Steve

"ATP*" wrote in message
...
I couldn't find this info on Google. What is the proper material to use to
replace the pin on a Bridgeport drawbar? I tried a roll pin which was way
too soft and sheared too easily.

BP Drawbar Shear Pin Question
 

"Steve Lusardi" wrote in message
...
That is not a shear pin. It is an assembly pin. I have made many drawbars
and I have tried turning them from solid bar. This usually fails unless
the steel bar has been totally normalized (annealed). Even with a follower
rest, the bar bends as its diameter is reduced. So, it is much cheaper to
pin a Hex on a piece of hotroll bar and thread the other end. Normally a
solid straight pin around .150 is used.
Steve

Thanks.

BP Drawbar Shear Pin Question
 

"Gunner Asch" wrote in message
...
On Sun, 01 Jan 2006 00:18:02 -0600, Jon Elson
wrote:

ATP* wrote:
"Errol Groff" wrote in message
...

On Sat, 31 Dec 2005 20:12:48 -0500, "ATP*"
wrote:


I couldn't find this info on Google. What is the proper material to use
to
replace the pin on a Bridgeport drawbar? I tried a roll pin which was
way
too soft and sheared too easily.



In eighteen years of teaching high school freshmen and sophomores I
have never had a student break a BP drawbar in that fashion. Perhaps
you are putting WAY too much oomph into your spindle tightening.

Errol Groff



I don't know, I'm not really putting that much torque on it, especially
not
the last time. The hollow roll pin I put in there definitely doesn't
take
much to shear.


My guess is that it is NOT a shear pin, ie. designed to break first,
before something else does. It most likely is just the easiest way to
make it. I don't think my drawbar (aftermarket) has a shear pin.
I'd use a taper pin.

Jon

When I made up the 3 drawbars for the Gorton (uses any 30 taper), I
welded the hex on, after shearing the first pin.

Gunner

Thanks, taper pin and mabe some loctite 609 it is.

BP Drawbar Shear Pin Question
 

FWIW I replaced the pin on my old Mill Drill with a .187 (3/16) piece of
stainless, never had any problems after that.

--.- Dave


"ATP*" wrote in message
...
I couldn't find this info on Google. What is the proper material to use to
replace the pin on a Bridgeport drawbar? I tried a roll pin which was way
too soft and sheared too easily.

BP Drawbar Shear Pin Question
 

According to Steve Lusardi :
That is not a shear pin. It is an assembly pin. I have made many drawbars
and I have tried turning them from solid bar. This usually fails unless the
steel bar has been totally normalized (annealed). Even with a follower rest,
the bar bends as its diameter is reduced. So, it is much cheaper to pin a
Hex on a piece of hotroll bar and thread the other end. Normally a solid
straight pin around .150 is used.

Hmm ... you might be interested in the drawbar for my Nichols
horizontal mill's vertical attachment. It consists of two parts:

1) The bar, with two different threads on the two ends -- one to
mach either of the common 40-taper holders threads.

2) A cylindrical piece, about an inch long, with different threads
in each end, and with a pair of opposed flats milled in the
middle.

So -- you swap ends on both pieces, and it serves as a drawbar
for the other style of thread.

You could mill three pairs of flats to give a final hex if you
so desired.

Obviously, if you are talking R8 collets, this is not a problem,
but someone somewhere up-thread mentioned 30-taper collets -- similar
enough to 40-taper so the problem might exist there as well.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---