Slitting saw and destroying my mill

[uuu]

Your arbor is also not shaped like the drawing showed. You simply need a cut that goes right through and splits the arbor in half.

A simple hacksaw cut is all that is needed and is a lot less costly

Or... how about a thin blade in an angle grinder.  I find these surprisingly controllable - OK not the precision available in the mill, but a good alternative to a hacksaw.

Wilf

[redhouseluv]

The steel in question was sold as BRIGHT MILD STEEL SQUARE BAR GRADE - EN3B

Does this mean anything in terms of my approach future concerns? Maybe I should buy a particular type of steel?

[jadge]

...do you apply that 4thou to all the teeth or just the ones making contact each time round...

It would depend upon the eccentricity. I've never measured it but work on the assumption that a good quality arbor and slitting saw should be a couple of thou at most. I apply the 4 thou per tooth as an average. If the total run out is 2 thou then the cut per tooth will vary from 3 to 5 thou. So not that much variation; it would be less for higher chip loads. The important thing is that all teeth are cutting albeit at slightly different depths.

If we assume an eccentricity of 2 thou and a chip load of 4 tenths of a thou then quite a few teeth will just be along for the ride. That might explain the need for a very slow feed as only a few teeth are cutting.

Andrew

[jadge]

The steel in question was sold as BRIGHT MILD STEEL SQUARE BAR GRADE - EN3B

Of the mild steels EN3B is not the easiest on which to obtain a good finish, it's a bit gummy and prone to tearing. But in the original pictures what I assume is a turned finish is awful. Either the material isn't what it purports to be or there is something badly amiss with the technique.

Andrew

[Jasonb]

I think we have put that one down to a knackered insert

https://www.modelenginemaker.com/index.php/topic,11579.msg271583.html#msg271583

[redhouseluv]

The final few thou, I cut with a new smaller tool, which was gave a better final finish not the one shown, which admittedly looks bad.

I think my over zealousness with the speed had a great deal to with my problems. Also the arbor I used wasn't the best type (see 1st pic); given the info above I will invest in one of the better, more solid types (see 2nd pic) before attempting another cut

[redhouseluv]

Hi all

I have a new motor installed, new arbor and slitting saw; I have reduced the speed to a sensible rpm (without the saw catching), applied some cutting oil and the results so far are excellent. No smoke, no excess heat, no broken machinery and no tearing my hair out

I'm not sure if the workpiece will be useable, but I can always make another - thanks all for your words of wisdom and I have attached a video

Best regards
Sanjay

[BaronJ]

The motors on these mills are total rubbish ! The brush holder spade connections make poor contact and get hot reducing the electrical contact further. The clue is in the last picture showing the melted insulation on the wires.
The major problem with these type of motors is the heat generated by the armature windings has nowhere to go other than out through the bearings at the ends. So if you want to monitor how hot the motor is getting its the armature shaft that you need to check, not the outside case temperature. I check mine by feeling how hot the armature is in the center of the bearing at the top of the motor.
Having said that I recently replaced the motor on my mill with a larger 2.25HP treadmill motor, its more than twice the power of the original 1HP motor but happily uses the existing speed controller and is a much better quality motor.

[Jasonb]

I think a lot is down to the user, anyone continuing to try and push a slitting saw that has lost all it's teeth through a workpiece is asking for trouble.

Treat them with respect and they last well, 16years and still going on my DC brushed mill and 14 on the lathe

[john mills]

I think it is very likely a lot of the the damage to the the original motor was probably already done with previous use with other more robust cutters  also run to fast and blunt cutters the complete failure failure just occurred when the slitting saw was used.Narrow slitting slitting saws   when used at better speeds should not take much to drive .
John

[Jasonb]

But trying to friction weld that saw to the work would have drawn one hell of a current. Heat look more likely to have come from arcing brushes than the spade connectors

And if those 4 grooves were done in 10thou deep passes it was run blunt for a fair amount of time.