Author Topic: Chris's Marion 91 Steam Shovel  (Read 575791 times)

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #1680 on: July 16, 2018, 01:17:32 AM »
Great progress Chris.  You must be working those elves overtime.  Sure hope they don't unionize, might set you back a bit  :ROFL:
That would be too much paperwork. They would probably just bungie cord me to the bed.   Again.


 :Lol:


Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #1681 on: July 16, 2018, 04:41:09 PM »
This morning I finished rounding over the top edges of the segments, and did some tests with a 1/8" radius ball end mill to undercut where the hinge fingers will go. It worked, but took several cuts to avoid overworking the ball end cutter. I am thinking I will do an experiment before continuing, making a 45 degree cut with the side of an end mill to remove the bulk of the material, then come back and do the finish pass with the ball end to just shape the curve. It will mean an extra set of passes on all the parts, but I think the end result will be better, and easier on the cutter - the ball end loses cutting efficiency the farther in towards to center you get at the end.
First, break for lunch!
Here is the first pair of test parts, all done on the ball end cutter. The one in the jig shows how it is held, the one behind it shows the finished shape.




Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #1682 on: July 16, 2018, 07:12:59 PM »
Just did some experimenting with the procedures. Started with milling a 45 degree angle to remove the bulk of the material before using the ball mill:


That would go in one pass, but getting the part in and out was awkward, and would take longer. So, tried one down flat, taking a notch into the recess area, stopping just short of where the curve would be (put in a trial part with the curve in place to judge from), with the cutter just below a 45 from the curve, so it removed a little more from the bottom than the vertical.


Then set up for the ball end mill again, and ran both test parts through, taking out the rest of the material in one pass. Results were interesting, both sets of parts worked, but the ones with the 45 cut took more effort to move the ball end mill, and heated up the part and the cutter more. Combine that with the awkward setup, and the 45 degree cut is out, going to do the rest with the flat notch approach.

I could do everything with the ball end mill, but that is at least 3 passes, changing the  position of the table each time, which increases the chances for error and reduces the accuracy compared to setting up each cut and locking down the table.
So, couple more passes through all the parts coming in the next day or so!

Offline 10KPete

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Re: Chris's Marion 91 Steam Shovel
« Reply #1683 on: July 16, 2018, 09:05:13 PM »
This sort of job is where a stout horizontal mill really shines...

lookin' good!

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #1684 on: July 17, 2018, 12:07:43 AM »
This sort of job is where a stout horizontal mill really shines...

lookin' good!

Pete


I bet it would!  Thats actually how I modelled it in 3d, drew up the profiles from ends and the sides, and extruded shapes to use to cut away the core block. Those shapes, if ground into horiz mill cutters, would be ideal for making these track segments.




If only I had that kind of big machine tools!


 :cheers:

Offline zeeprogrammer

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Re: Chris's Marion 91 Steam Shovel
« Reply #1685 on: July 17, 2018, 12:35:48 AM »
Results were interesting, both sets of parts worked, but the ones with the 45 cut took more effort to move the ball end mill, and heated up the part and the cutter more. Combine that with the awkward setup, and the 45 degree cut is out, going to do the rest with the flat notch approach.

From my amateurish point of view...I'm kind of not surprised. With the 45 cut, I would have thought the ball end mill would have more material to cut. Particularly (depending on geometry) at the very tip of the ball end mill that I find surprising can even cut.

In the other method, the very end of the ball end mill is hardly in play (right?) and the sides can do a decent job.

I'm not speaking from any experience.

Attached picture is my attempt to explain. On the left is the 45 degree and the circle represents the ball end.
On the right is the straight end mill with the circle (ball end) following.

Does that make sense?
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #1686 on: July 17, 2018, 01:08:39 AM »
Thats a pretty good representation Zee. I had not drawn it out, probably should have, just held the cutters up to the stock, and initially thought the 45 would need less from the ball cutter. The very tip of the ball can actually cut, its a center cutting mill bit, just like a center cutting flat end bit, with two of the four flutes extending right to the middle. The closer you get to the tip, though, the smaller the diameter and the smaller the flutes so less room for chips. Bottom line is that doing the square cut appears to work better.

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #1687 on: July 17, 2018, 01:41:56 AM »
Zee - here is a drawing closer to what I did, the relative dimensions match the part and the cuts:

The two initial cuts had to be within the quarter circle that the ball end mill would be making, or it would show in the final part. Looking at the two cutters, held up to the part at the time (did not draw it till now), I had figured that there was less material to remove with the ball mill with the angled cut, but I think the difference is that with the square cut, it is removing less material down near the tip and more up the side where it is a larger radius cutter, and the flutes are larger for better chip removal. Does that make sense? It definitely took less force to cut the second way, and generated a lot less heat in the part and cutter. Not what I expected at first, but it looks like this way will work out well. If it did not involve going through all those parts yet again, I'd be tempted to make another square cut higher and farther to the left, but since the cutter is just a 1/8" radius this is do-able in one pass.

Great idea to draw this out!
 :cheers:

Offline zeeprogrammer

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Re: Chris's Marion 91 Steam Shovel
« Reply #1688 on: July 17, 2018, 02:12:00 AM »
I'm glad I had the correct head on.  ;D

Your drawings are more accurate and more clear.

Although the area (amount of material to remove) seems larger in the 2nd pic. I was wondering if it could be less.
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Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #1689 on: July 17, 2018, 02:16:46 AM »
I'm glad I had the correct head on.  ;D

Your drawings are more accurate and more clear.

Although the area (amount of material to remove) seems larger in the 2nd pic. I was wondering if it could be less.
The area at the tip in the second is less, think thats the key since the shank cuts more easily than the tip.

Offline zeeprogrammer

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Re: Chris's Marion 91 Steam Shovel
« Reply #1690 on: July 17, 2018, 02:19:44 AM »
I'm glad I had the correct head on.  ;D

Your drawings are more accurate and more clear.

Although the area (amount of material to remove) seems larger in the 2nd pic. I was wondering if it could be less.
The area at the tip in the second is less, think thats the key since the shank cuts more easily than the tip.

Thanks! That's what I was going for. I think.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #1691 on: July 17, 2018, 07:27:54 PM »
Couple of sessions with the ball end mill, here is the first batch of complete track top halves. Bunch more to go, then I can start on the bottom halves.

One annoying thing happened on these - figured that I would switch to a fresh ball end cutter, might as well start with a fresh sharp one, I figured (the other one was also used to do the profiling on all the track plates for the Lombard, still was cutting well though). Put the fresh one in, couple adjustments to get the height correct, and made the first pass.


Very obvious right away that something was wrong, it was cutting hard, throwing off very hot chips, and sounded wrong.   :shrug:
Stopped the cut, backed it out and removed the cutter. Could tell from the shiny spots on the back side of the flutes, out near the tip, that they had ground it wrong, and did not have enough (or any) relief angle where it came around the end to the tip!

 :Mad:
So, put the first cutter back in, back to cutting well. With a few choice words....
Later took a close look under magnification and a straightedge, could see where the bad shape was, and did a little fine grinding there. Not sure if I got it all, or if the rubbing generated enough heat to screw up the hardness, have to try it on some scrap later on after finishing the rest of the parts. I've had a few drill bits like that, where they goofed the grinding at the front outside corners (were part of a large set of cobalt drills, most were fine, just a few that they swarfed up on).
Grrrrrrr!!!!

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #1692 on: July 18, 2018, 02:42:49 AM »
Some more sessions of cutting the overhangs, have 2/3rds of them done so far, should get the rest tomorrow.


I have been looking forward to the bottom halves, and am debating whether to make them steel or brass. Brass would be much easier to shape these complex forms, but steel would definitely be more strong...


 :thinking:

Offline zeeprogrammer

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Re: Chris's Marion 91 Steam Shovel
« Reply #1693 on: July 18, 2018, 03:20:42 AM »
I have been looking forward to the bottom halves, and am debating whether to make them steel or brass. Brass would be much easier to shape these complex forms, but steel would definitely be more strong...

Treads = steel. I don't see how one gets around that.  ;D
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Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #1694 on: July 18, 2018, 03:41:35 AM »
I have been looking forward to the bottom halves, and am debating whether to make them steel or brass. Brass would be much easier to shape these complex forms, but steel would definitely be more strong...

Treads = steel. I don't see how one gets around that.  ;D
True. Just that I keep looking at the shaping, and it makes me think brass would be so much easier to carve. It would be half steel, half brass, but you have a point, it would be kinda half-brassed to do it that way!


 :LittleDevil:


Given all the other hard work in this, I need to do it right.


 :cheers:

 

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