Help! > Mistakes, muckups, and dangerous behaviour

Slitting saw and destroying my mill

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redhouseluv:
Oh dear, oh dear ......... yeah, I've done a proper job this time; the saw was 3" (75mm) in diameter BTW as per Jason's calculation. What sort of depth of cut should I go for at the speed specified?

I've just spent the last 1/2 hour dismantling the mill top end and it looks like (and smells like) its just the motor that's cooked (see pics); the gearing all seems to be fine. Looks like the motor is single unit so will have to do straight replacement - fingers crossed they have one otherwise I'll be out of action for a while.


--- Quote from: Jasonb on September 18, 2023, 08:23:54 PM ---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

--- End quote ---

hmmm, so I can use a hacksaw, that's interesting, the original article is what led me down this path. It suggested a 1/16" slitting saw as far down the length of the shaft as possible. Which bit of the arbour is incorrect, it may look odd as I turned the piece around halfway through the cutting fiasco, so I haven't cut the arbour in half, but cut a little out of each side hence its appearance

A lesson learned, a costly one; I won't be doing that again ........

john mills:
as said the dia of this slitting saw should be run  slow   often the trouble is the machine has not got a slow enough speed so that has to be
it can be run slower that Jasons 95 rpm wont damage the cutter and make it last longer.Usually the slitting saw should do the full
depth of cut in one go.   a proper cutting oil can be ok but a modern soluble cutting would be better.
John 

Jasonb:
It was the part cut down the opposite sid ethat made me say it was incorrect. You could have cut right through that in one steady pass though a saw with less teeth of similar diameter would be better a sthe bigger gullet between the teeth won't clog with swarf, keep the finer toothed saws for things like slotted screw heads.

As John says some smaller hobby machines can suffer with stalling due to  acombination of slow spindle speed and the large dia of the cutter. If you mill has high/low speed range use the slow range and you may have to overspeed a little to stop stalling and/or cut say half depth at a time.

Looking at that motor I wonder if it is just the brushes that have overheated as that is really the only place it looks cooked

Here is a video that first shows a smaller mill stalling (no hi/lo option) when trying to cut at calculated speed, Speed then increased to when it will cut. The feed is not very even as I was doing it one handed due to holding the camera you should have both hands on the handwheel rim to keep a constant feed  and would also have added a bit of cutting fluid with a brush is doing it for real.

http://www.youtube.com/watch?v=_nOcZWfiI2A

redhouseluv:
Thanks a lot for the advice and I will definitely proceed with a more cautious approach once the mill is back in action. So slower speed and one pass is the correct way, I was trying to do the opposite i.e. a little at a time along the length, then come back to the beginning and start over

I have now seen a few mentions of issues with the motor units on these type of mills (notwithstanding operator misuse :) ). I too wondered if it could be just the brushes and will see if that maybe a cheaper option. I have found the same motors on eBay so it'll be interesting to see the price Warco quote me!

Charles Lamont:

--- Quote from: redhouseluv on September 18, 2023, 08:38:11 PM ---What sort of depth of cut should I go for at the speed specified?

--- End quote ---
Don't think about the depth of cut. Feed a slitting saw very gingerly by hand. Mike said how a slitting saw should sound when cutting. It will not be running dead true and if you are using it within its comfort zone it will only cut on part of the turn. Use the table slide lock to give a little bit of resistance so that it cannot grab. Do not climb cut, but if you have to, you need the slide pretty stiff.

It can be a good idea to run clockwise when looking at the outboard end of the arbor so that if the saw wants to jam it just unscrews the clamping screw.

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