Ammco Shaper tool question...

Richard White (richardsrelics)

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So I have gotten far enough ahead on my other projects to allow me to finally play with this machine.
My intent is to cut internal key ways on a taper, yup gotta love a challenge.
So I have all aspects planned out, I will mount an $100 3 jaw chuck to a mounting plate so once I have it set I wont need to move anything. I will I will cut the key way at the bottom of the part so I do not have to make any movement other than up and down on the feed dial to cover the different size tapered holes and all the tapers are the same 5*.

So I made a 3/8 X 1 inch bar and silver soldered a 3/8 diameter rod to that on the business end I cut a notch on an angle and silver soldered a Cobalt bit on that end.
All went well as I was making cuts EXCEPT...ya one of those..

As the tool traveled forward the bit did not engage, even after turning the down feed dial to a point where it should have cut. And then all of a sudden it bit and bit hard and took the whole amount I have moved the dial at one time... My theory is this... the spring used to allow the tool to pick up when the machine is on the return stroke is weak and not holding the tool in the proper position during the power stroke.

My machine came with 2 springs in the position the are conical in shape. I think that putting a stronger spring there will result in proper function. I need to be that small on the tool as one of the parts I am making only has a .468 thru hole and I have to cut a 4mm key in that.

To test this I basically set up some flat stock and set the machine to take a cut with power side feed, it did the same thing, UNTIL I held the tool down during the power stroke. Once that was being done it cut just fine. So my long winded question is: What spec do I use for the spring, or do I just get stronger springs until it cuts properly?

I have attached a photo of the tool..
Shaper tool.jpg


Thanks

Richard
 
The spring should not come into play at all during the cutting stroke. Perhaps you have something set up backwards in the mounting of the clapper box or in that area. The tool should be solidly supported during the cutting stroke and the spring should allow it to clear the work during the return stroke. There is also way too much spring in the tool. Anything cutting metal wants a rigid setup. If there was a triangular piece welded in, backing up the round tool bar to the flat bar for reinforcement, you would have a much more solid setup. Also, does the tool really need to extend that far to reach the work? Some pics of your setup would be a big help to figure out what you are doing and why...
 
When cutting keyways you need to lock the clapper down. The cutting edge is so far forward it wants to lift. You gave it enough force with the spring to get it started then the front rake on the tool made it dig in.

Greg
 
Bob,
I understand the spring part, that it only comes into play on the return and that the power stroke the tool should be rigid. That is what has me puzzled, gravity is just not enough to hold this tool down I think, and as for a brace, not possible as the bore of the smallest hub is .468 give or take a .001 or .002. Now for my key way,( 4mm ), to be proper it needs to be .078,( 2 mm ), deep, so take .375, ( diameter of the bar) + .078, (depth of key), that puts me at .453, leaving a gaping gash of .013 total clearance.

The clapper box, is untouched by my hand other than to check that it actually moves.

As for length of the bar, that current length leaves me .500 of tool to work with one each end of the stroke, so I start the tool. 250 before and stop it .250 after...

This is clearly the worst case scenario, as the other 4 hubs I make the bore is greater, it goes to .562 thru, so that would allow me .09 extra for bracing the bar.
 
My Logan had that spring too. Smaller shapers can be ran fast enough that the clapper won't fall on the return stroke, the spring keeps it down.

Greg
 
One of the problem with shapers is the backlash in the tool head leadscrew. You need to tighten the gibs on the toolhead to the point that it is a bit difficult to run it down with the leadscrew. What happens is that the toolhead falls down via gravity against the leadscrew, then the work pushes it back up against the leadscrew taking out the backlash. This can lead to hard hitting and rounded corners on the front side of a piece of work being surfaced. I suspect that you were running the tool down and it dropped through the backlash, which is why it dug in. Tightening the gibs prevents it from droping through the backlash and staying against the driving surface of the leadscrew when you dial it down.
 
I understand the spring part, that it only comes into play on the return and that the power stroke the tool should be rigid. That is what has me puzzled, gravity is just not enough to hold this tool down I think,

Another thing you can do to overcome the problem is to rotate your part 180 degrees so that you are cutting the keyway at the top of the part. Of course your tool bit has to be reversed also so that the cutting edge is up instead of down. This eliminates the problem of the tool lifting on the cutting stroke.

Ted
 
Hi Richard,

Interesting job you've set yourself - and it's always a little difficult to visualise things from just a 'description' so I'll state my understanding first. I'm assuming that you are holding the work at the taper angle (of 5 degrees ?) such that the slot is uniform in depth. That the slot is 4mm wide and 2mm deep. You don't seem to say what width your cutting tool is but I'm assuming the same width as the slot. You are allowing 0.25 either side of the cut - front and rear - and cutting downwards, the clapper not being locked.

On that basis, the first thing I would suggest, is that you increase the length of stroke to allow at least 0.5" before the cut, as when slotting, there can be a tendency for the work/slot to hold onto the cutter a little longer on the return than with (for instance) plain surfacing. Although this mainly applies to deeper slots, it's not bad practice and although you maybe constrained at the back of the cut, I can't see why you would be so at the front, unless the taper length is very near the maximum stroke.

I fully agree with the point being made about the vertical head dropping because of backlash and tightening the gibs is one solution but will make 'ordinary' down-feeding more of a chore. If I think I'm having problems in this area, I sometimes use one of the gib adjusters to actually lock the slide between each feed (must get around to fitting a proper locking lever), which is slow but helpful. Slotting upside should also solve this problem and will (I guess) also effectively lock the clapper (I've not tried this myself but Stephan Gottswinter [search YouTube] has).

Final thought, I'm sure you been careful but when slotting 'to width' - side clearances are important - so it might be useful to check that your cutting tool is not very slightly angled. If it is, it will not only rub but may be contributing to the work 'clinging' to the tool as mentioned above...

Hope this helps but I'm sure you will find the solution anyway. Be interested to know what solves it for you.

Regards,

IanT
 
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