Broaching problems
 

Hello all

We have a Hansford/Davis Keyseater at work and we are getting a lot
of chatter in the bottom of the keyway. Sort of a wavy surface probably
3/4" between peaks and a couple of thou high. The keyway is 7/16 wide
in a 1-3/4" bore. The material is 1045 steel. We tried the original
broach, reground it, and bought a new one, getting the same chatter with
all three. I checked the the machine and there doesn't seem to be any
loose parts (the linkages inside seem tight with little slop) there is a
little backlash in the drive gears but nothing I can do about it.

Any suggestions?? Our inspector is getting on my case about the
chatter :-)

really 0.75 inch? That seems long for chatter. Can you cycle the machine
with no broach at all to see if anything that is supposed to be still is
actually leaping around?
--
Fred R
________________
Drop TROU to email.

Tom wrote:
machineman wrote:

Hello all

We have a Hansford/Davis Keyseater at work and we are getting a lot
of chatter in the bottom of the keyway. Sort of a wavy surface probably
3/4" between peaks and a couple of thou high. The keyway is 7/16 wide
in a 1-3/4" bore. The material is 1045 steel. We tried the original
broach, reground it, and bought a new one, getting the same chatter with
all three. I checked the the machine and there doesn't seem to be any
loose parts (the linkages inside seem tight with little slop) there is a
little backlash in the drive gears but nothing I can do about it.

Any suggestions?? Our inspector is getting on my case about the
chatter :-)

Have you tried Hansford themselves for advice?
http://www.hpproc.com/index.html

Tom
That is my next step, I thought I would check here first. I check out
the site but there is not a lot of info there. HH Roberts is a dealer
and has a copy of the manual on their site but there is no
troubleshooting section.

Fred R wrote:

really 0.75 inch? That seems long for chatter. Can you cycle the machine
with no broach at all to see if anything that is supposed to be still is
actually leaping around?
I think its aprox the same as the pitch of the broach, its fairly smooth
but sort of a ripple surface. Almost like its pushing off to form
these peaks and valleys. Short of dismantaling the whole machine and
rebuilding it from scratch, I havn't been able to think of anything.

the same as the pitch of the broach

That seems like a clue that would be useful to the Experienced Ones.

My mere speculation - could this be from the successive first
engagements of the broach teeth with the workpiece, to be helped by
making a tapering approach 'ramp' where the keyway will be?
--
Fred R
________________
Drop TROU to email.

What happens when you do a second pass on the broach?
I assume that you are lubricating the broach as you use it. Have you
changed the lubrication recently?

--
Why isn't there an Ozone Hole at the NORTH Pole?

machineman wrote:

Hello all

We have a Hansford/Davis Keyseater at work and we are getting a lot
of chatter in the bottom of the keyway. Sort of a wavy surface probably
3/4" between peaks and a couple of thou high. The keyway is 7/16 wide
in a 1-3/4" bore. The material is 1045 steel. We tried the original
broach, reground it, and bought a new one, getting the same chatter with
all three. I checked the the machine and there doesn't seem to be any
loose parts (the linkages inside seem tight with little slop) there is a
little backlash in the drive gears but nothing I can do about it.

Any suggestions?? Our inspector is getting on my case about the
chatter :-)
Have you tried Hansford themselves for advice?
http://www.hpproc.com/index.html

Tom

machineman wrote in
news:9ObOd.29487$tU6.22867@edtnps91:

Hello all

We have a Hansford/Davis Keyseater at work and we are getting a lot
of chatter in the bottom of the keyway. Sort of a wavy surface
probably 3/4" between peaks and a couple of thou high. The keyway is
7/16 wide in a 1-3/4" bore. The material is 1045 steel. We tried the
original broach, reground it, and bought a new one, getting the same
chatter with all three. I checked the the machine and there doesn't
seem to be any loose parts (the linkages inside seem tight with little
slop) there is a
little backlash in the drive gears but nothing I can do about it.

Any suggestions?? Our inspector is getting on my case about the
chatter :-)

Did you also replace the backing collar when you replaced the broach?
Since replacing the broach made no difference, the type of problem you
describe would almost have to be in the backside support for the broach.
That, or a feed speed problem (cyclic speed increase/decrease).



--
Anthony

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

Remove sp to reply via email

Anthony wrote:
machineman wrote in
news:9ObOd.29487$tU6.22867@edtnps91:


Hello all

We have a Hansford/Davis Keyseater at work and we are getting a lot
of chatter in the bottom of the keyway. Sort of a wavy surface
probably 3/4" between peaks and a couple of thou high. The keyway is
7/16 wide in a 1-3/4" bore. The material is 1045 steel. We tried the
original broach, reground it, and bought a new one, getting the same
chatter with all three. I checked the the machine and there doesn't
seem to be any loose parts (the linkages inside seem tight with little
slop) there is a
little backlash in the drive gears but nothing I can do about it.

Any suggestions?? Our inspector is getting on my case about the
chatter :-)


Did you also replace the backing collar when you replaced the broach?
Since replacing the broach made no difference, the type of problem you
describe would almost have to be in the backside support for the broach.
That, or a feed speed problem (cyclic speed increase/decrease).



I talked to Hansford's tech line today. they suggested that the
operator vary the release point at the bottom of the stroke. By backing
off the pressure at the same point every time it may contribute to the
problem. I guess the end of cut builds up and turns into the peaks and
valleys.