Post by rrmrd66 on May 27, 2017 9:51:53 GMT
Good morning everyone.
Here is something I came across whilst getting use to my new milling machine (of which more anon when all issues with it have been satisfactorily sorted).
The milling machine is a Super Major Vario. It was supplied with an R8 collet system.
The problem arose when attempting to tighten the nut on the ER32 collet. The only way that I could find to apply an equal and opposite turning effort was the captive nut on the top of the draw bar. There is no spindle lock on this machine.
(As a matter of interest do vertical milling machines have spindle locks any more? I am fairly certain that when I did my tool making apprenticeship, eons ago, it was possible to lock spindles on vertical millers. Maybe not?)
The picture below shows the problem.
The collet nut thread measures approx 40mm dia and the draw bar nut about 12mm dia.
This gives a torque multiplying factor of approx 3.33.
The eagle eyed will not that the nut is held captive by a spring pin, about 1/8" dia and is made from chocolate.
Following a scary episode where I managed to get a 1/2" end mill to start undoing itself when milling the sides of the horns on my Hunslet (see 5" gauge Hunslet thread build in General Chat) I tried to do extra tightening and sheared the pin.
The milling machine supplier was very good and sent me a replacement by return. (The UNF thread at the other end was not right so a die and stock had to be obtained to run down the thread form to correct it, but that is another story.)
So, what to do.
After scratching my head and reading several threads I came up with the idea of a strap wrench applied to the only bit of surface on the tool holder that was available. Someone recommended milling two spanner flats on this portion as he had had a similar problem. I though that was a high risk strategy and looked for something less risky.
The solution? A Boa (constrictor) strap wrench supplied by UK Tool Centre. It is very effective. The 1" wide rubber strap grips like whatsit and appears to allow safe milling once more.
The picture shows me tightening a edge finder "wobbler", which obviously does not need to be super tight. However, for the purposes of illustration you get the idea.
The chocolate pin has been replaced with a new one turned from silver steel and the nut has been permanently attached to the draw bar with a couple of tacks of weld. It should not come loose in the future should I revert to putting a spanner on it.
Thanks for reading
cheers
Malcolm
Here is something I came across whilst getting use to my new milling machine (of which more anon when all issues with it have been satisfactorily sorted).
The milling machine is a Super Major Vario. It was supplied with an R8 collet system.
The problem arose when attempting to tighten the nut on the ER32 collet. The only way that I could find to apply an equal and opposite turning effort was the captive nut on the top of the draw bar. There is no spindle lock on this machine.
(As a matter of interest do vertical milling machines have spindle locks any more? I am fairly certain that when I did my tool making apprenticeship, eons ago, it was possible to lock spindles on vertical millers. Maybe not?)
The picture below shows the problem.
The collet nut thread measures approx 40mm dia and the draw bar nut about 12mm dia.
This gives a torque multiplying factor of approx 3.33.
The eagle eyed will not that the nut is held captive by a spring pin, about 1/8" dia and is made from chocolate.
Following a scary episode where I managed to get a 1/2" end mill to start undoing itself when milling the sides of the horns on my Hunslet (see 5" gauge Hunslet thread build in General Chat) I tried to do extra tightening and sheared the pin.
The milling machine supplier was very good and sent me a replacement by return. (The UNF thread at the other end was not right so a die and stock had to be obtained to run down the thread form to correct it, but that is another story.)
So, what to do.
After scratching my head and reading several threads I came up with the idea of a strap wrench applied to the only bit of surface on the tool holder that was available. Someone recommended milling two spanner flats on this portion as he had had a similar problem. I though that was a high risk strategy and looked for something less risky.
The solution? A Boa (constrictor) strap wrench supplied by UK Tool Centre. It is very effective. The 1" wide rubber strap grips like whatsit and appears to allow safe milling once more.
The picture shows me tightening a edge finder "wobbler", which obviously does not need to be super tight. However, for the purposes of illustration you get the idea.
The chocolate pin has been replaced with a new one turned from silver steel and the nut has been permanently attached to the draw bar with a couple of tacks of weld. It should not come loose in the future should I revert to putting a spanner on it.
Thanks for reading
cheers
Malcolm
