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Work holding a Featherweight 18" straight edge for machining

MyLilMule

Hot Rolled
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Jan 5, 2021
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Ohio, USA
I was lucky enough to acquire an 18" Featherweight straight edge from @dgfoster. I've read the thread on his work holding fixture, but wonder if it's overkill for a one off. I will only be machining the one, and need to figure out the right order of operations and work holding.

Wondering if anyone here can share some experience with machining one of these. I don't want to screw it up. But I also would like to avoid making a complex work holding jig that would be great for machining multiples, when something simpler would suffice for machining just the one.
 
If I were going to do it once, I think a fixed angle plate on one side and a height adjustable tailstock on the other, with a crap-ton of machinist jacks providing support in between them.

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You are basically just trying to fixture it between two points, with one of those points allowing you to adjust in X,Y and Z. All the rotational adjustment is handled by the jacks and a strap or two.
 
Say what kind of machine and machining process you plan to use.
Shaper is a good machine for such, but probably few use it.
If you use a mill, what tooling will you use?
Does the head nod or will you have to figure out other fixturing for any angles?
etc.

smt
I have a Bridgeport (Series 1, 2HP) and a K&T 2HL. Much less tooling for the K&T than the BP.

I haven't made specific plans yet, which is why I am asking the question about someone who may have machined one.

I have some tooling, but not everything. I was thinking I may use this tilting table I have. Determining order of operations, ie. which face to machine first and use as a reference, etc.

If I were going to do it once, I think a fixed angle plate on one side and a height adjustable tailstock on the other, with a crap-ton of machinist jacks providing support in between them.

View attachment 398920

You are basically just trying to fixture it between two points, with one of those points allowing you to adjust in X,Y and Z. All the rotational adjustment is handled by the jacks and a strap or two.

I have been trying to consider what face I would machine first (top or bottom) to use as a reference. I do have a foot stock, but I don't think my angle plate would be large enough for the other end. Of course, this would also mean drilling some accurate holes in each end.

My initial though is to machine the top surface first, and then using it as a reference for the bottom, clamping the top to the table and then using jacks and other "cribbing" to hold it in place.
 
I have been trying to consider what face I would machine first (top or bottom) to use as a reference. I do have a foot stock, but I don't think my angle plate would be large enough for the other end. Of course, this would also mean drilling some accurate holes in each end.
Well there is some risk that the material that you remove on the second side will cause movement on the first (reference), but that sort of weighs towards using the smaller side first as it is less surface to have to scrape twice. The holes on each side, if tapped, make an excellent place to thread in some handles (like on my little plate below) that make handling much nicer. If you are able to locate them close to the center of rotational mass, even handier!

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You can never have enough angle blocks, not having one that will work is an excellent excuse to shop for a bigger one! Get more jacks too, I love the Eron ones but they might be expensive or hard to find over there. Use a stud and a spherical nut/washer on the angle plate side, that way when you have the tailstock dialed in, you can gronk down on it without moving it off line.

Foster's stuff looks really good, I wish I had a need for one. I was going to get a little Rucker for the novelty of it, and I always get a chuckle from Windy Hill Foundry, but for serious work I suspect the Foster may have a leg up on them.
 
I have one of Keith Rucker’s little straight edges. Nice iron to machine and scrape and handy for small scraping jobs. Roughly same price as buying durabar. Really, we a spoiled for choice with straight edge castings now- get em while you can!
 
Well there is some risk that the material that you remove on the second side will cause movement on the first (reference), but that sort of weighs towards using the smaller side first as it is less surface to have to scrape twice.
Mule,

Movement of the casting between machining operations has never been an issue on these castings. (I think that is due to simply following recognized good practices of allowing the casting to initially cool in the sand and then doing a proper thermal stress relieve operation.) I have machined many many and I first do the sole, then the inclined face, and finally the top rail. The first surface has always remained flat and by that I mean within .001" of flat and actually I think almost always better than that. And the inclined face comes out equally well as does the top rail. So, I do not think you should worry about the casting squirming around with sequential milling operations.

I think I would make use of the versatility of the BP to make life easier. Though people tend to resist nodding the head since getting it back into neutral tram is a bit of a nuisance, that feature can make workholding a lot easier for you.

I would suggest beginning using two aluminum or steel blocks maybe an inch square and 4 inches long or so. They need not be milled or ground to particular accuracy. Bar stock would be fine. Place the prism on the blocks located about 25% in from the ends. Orient the prism so the open side is toward the mill column. The top rail will be off the table and it will rest just on the face and blocks. Use common straps, tee nuts, and bolts and by eye align it with the table slots. Have the straps bearing centered over the support blocks to reduce deflection. The intersection of the prism faces will not be exactly straight as the casting does not solidify perfectly straight. But you can make your best guess on this.

Nod the head to about 45 degrees. (On the raw casting the faces converge at about 43 degrees. So, you'll start cutting near the convergence.) Use a face mill with sharp inserts or a fly cutter if that is what you have. Make a light cut or two and see that the face is not milling only on one end but is generally cutting symmetrically. Now go ahead and just take an 1/8" or a little more off the face making cuts that are comfortable for your machine. I cut about 30 or 40 thou per passon my 1 HP machine. If your cutters are sharp, the casting will just warm a bit but it will not feel hot. For the final cut(s) I'd relax the clamps a bit to reduce racking and take cuts 3 or 4 thou deep traveling 4 inches per min and slower than that if using a fly cutter.

Lightly stone your table to remove boogers. Now place the machined sole on two flat 1x1 x4 metal blocks. I think machining the flats on those blocks would be a plus so that they are pretty parallel and flat. Strap itdown as before. Machine that face as before. Be careful not to nick metal off the front of the top rail---aesthetic concern only. Make fial cuts again slightly relaxed on the hold-downs.

Tram the head to neutral.

Now again lightly stone your table and place two strips of aluminum foil on the table similar to how you previously used the blocks. (The foil holds the sole off the table avoiding any warp of the table or bumps.) Let the sole straddle a tee slot so later you can mic the top rail to sole distance without unclamping. Cut the top rail down as much as you like. I try for less than .001 of parallel error in the rail to sole measurement. I often have to place an extra layer of foil on one end to get there.

Now use a simple end mill to face the top rail and back if you like. Clean up the ends if you like though they won't otherwise need machining. (I do cut them as I figure customers want that.)

I take (unnecessary?) pains to get the faces flat and find that tweaking the tram of the head is often needed to get a nice cross-hatched pattern and that pattern probably will happen in only one cutting direction. Sure, it should happen both ways, in theory. But real-world bearings being what they are, there must be some slight spindle deflection that allows a slightly different float angle when cutting left vs right.

The above should be taken with a grain of salt. IT IS NOT A METHOD I HAVE USED. But, based on my experience with my mill, I am confident that decent results can be obtained. If you are unsure about relaxing the clamping for final cuts, then just don't bother or maybe do a little blocking-in of the casting. I think aluminum support blocks offer the advantage of better friction between the table and casting than do hard steel blocks. (And nothing wrong with cyano gluing block to table and casting to block for security as well.)

I hope you will post whatever method you end up using and what recomendations you come up with based on that expereince.

I'll be following along to see what other folks here suggest as well.

Denis
 
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I am digesting this method. I think I am seeing the process you had in mind. I think I'll spend some time tomorrow doing a sort of dry run and see what I need to modify. Seems like it should work with minimal special tooling. I have some steel square bar that I could use for the risers. I'll have to look to see if I have any aluminum scraps that will work. If not, there are a couple metal suppliers near me that I can visit as well.
 
I'll have to look to see if I have any aluminum scraps that will work. If not, there are a couple metal suppliers near me that I can visit as well.
Mule,

If you do not have aluminum at hand, simple printer paper between table and block and block and part doubles the friction coefficient. Might be better than aluminum in that respect and no special trip required.

Printer paper is very uniform in thickness as is aluminum foil as is aluminum can wall material. Those are things I like to use as thin shim.

If you doubt the friction increase with respect to paper, just put a heavy part on your mill bare table and push it. Then put it on a piece of plain paper and push it.

Denis
 
On SE's i tend to do the big flat side first because everything else references to it anyway. and if it moves or if it seems useful to take a final skim cut on that side, the other features will now be in condition to use as reference surfaces to both indicate and grip for setting back up.

Depending what it is, i have often used softwood with no knots as the gripping medium on raw castings for first cuts.
Really soft like NE white pine, or WR cedar, e.g. OTOH it can be seen that on the planer set ups i used plywood.
The casting is still indicated/located carefully. First cuts are "gentle" to see if the casting wants to shift. Usually it is ok.
I am still making effort to balance forces between the wood jaws, and i am being careful not to grip in ways that would bend the casting.

For instance in the mill set-up, the castings are being gripped very near the end where there is an intersection of members and a biggish knot of metal that is unlikely to be easily bent or shifted so long as clamped in a way that does not flex the rest of the casting between the vises. Wooden snubbers are strapped to the table to butt the SE bow and keep it from ringing or shifting.

The magnet is effective and easy, but i have to control myself for depth of cut. Depending on tool geometry the casting can rock. But i have used it on the mill for angles, too. Where the head can nod, or the toolslide be set, it is often the better choice, especially for more than one.DSCN3849.JPGDSCN3847.JPGsmt_Whitcombblaisdell28.JPGsmt_Whitcombblaisdell27.JPGsmt_Whitcombblaisdell26.JPGsmt_Whticombblaisdell29.JPGsmt_Whitcombblaisdell30.JPGsmt_Whitcombblaisdell35.JPG
 
On SE's i tend to do the big flat side first because everything else references to it anyway. and if it moves or if it seems useful to take a final skim cut on that side, the other features will now be in condition to use as reference surfaces to both indicate and grip for setting back up.

Depending what it is, i have often used softwood with no knots as the gripping medium on raw castings for first cuts.
Really soft like NE white pine, or WR cedar, e.g. OTOH it can be seen that on the planer set ups i used plywood.
The casting is still indicated/located carefully. First cuts are "gentle" to see if the casting wants to shift. Usually it is ok.
I am still making effort to balance forces between the wood jaws, and i am being careful not to grip in ways that would bend the casting.

For instance in the mill set-up, the castings are being gripped very near the end where there is an intersection of members and a biggish knot of metal that is unlikely to be easily bent or shifted so long as clamped in a way that does not flex the rest of the casting between the vises. Wooden snubbers are strapped to the table to butt the SE bow and keep it from ringing or shifting.

The magnet is effective and easy, but i have to control myself for depth of cut. Depending on tool geometry the casting can rock. But i have used it on the mill for angles, too. Where the head can nod, or the toolslide be set, it is often the better choice, especially for more than one.View attachment 399007View attachment 399008View attachment 399013View attachment 399014View attachment 399015View attachment 399016View attachment 399017View attachment 399018
Stephen,

If you ever decide you don't need the planer, please let me know. I would LOVE to have a good one that could do up to 48's .

Denis.
 
Stephen,

If you ever decide you don't need the planer, please let me know. I would LOVE to have a good one that could do up to 48's .

Denis.
Nice set ups. Planed cast iron scrapes a lot easier than milled cast iron Initially Once you’ve got under the “ crust “ they are the same. Plus a good ” flat tooled “ finish looks like a million dollars.

Regards Tyrone.
 
On longer SE's, If your planer or mill is worn lay the SE on its side as the cutter will move up and down on the wear on the side. If the planner it worn in the middle and not on the ends as the table ride up onto the unworn area it will cut deeper. Keith Rucker milled one of my 24" camelbacks on his horizonal mills using a slab mill with it on its side. He did a YouTube show on it. Steven also planed a long one that way too.
 
In the last scraping class one of the students brought a 36" Foster camelback that he milled on his Bridgeport. he had to mill it 2 set-ups and it got a .004'' twist in it. high on diagonal ends. he learned how to remove it with a Biax.
 
In the last scraping class one of the students brought a 36" Foster camelback that he milled on his Bridgeport. he had to mill it 2 set-ups and it got a .004'' twist in it. high on diagonal ends. he learned how to remove it with a Biax.
Just to be clear “he” refers to the student—-the student did the milling. I use (borrow time on) a large Lucas Horizontal for my 26 and 36” straight edges so they can be done in a single pass finishing pass to be able to count on less than .0015 flatness error. I have done, years ago, 36’s on my BP in two setups. With a fair bit of care and fussing a straight and within .001 flat cut can be achieved. But, as Stephen pointed out, it might be more practical for a one-off to just get ‘er close and get after it with the Biax.

Denis
 
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I just remembered, Adam Booth another famous YouTuber used his 36'' Cinc. shaper to shape on of my SE's i cant recall if it was a 18 or 24'' camel back. he did a you tube show on it... Adam and Keith Rucker were or are members here several years ago, when the rules were lax.
 
@dgfoster - here is my first feeble attempt at a setup. I'd appreciate your input.

Using a digital angle finder, the angle I am getting is right at 41 degrees. With the head nodded at 45 degrees, the fly cutter (unfortunately I do not have a face mill large enough for this, so I have to use this), the cutting edge was a good 1/2" away from the back of the flat as compared to the front wedge. I suppose that's OK, based on what you wrote before. I will reset this to 45 degrees or there about before starting the cut.

I do have a small 2-1/2" face mill I could start with, making multiple passes, although that sounds like it might get complicated on the overlap - raising or lowering the knee and moving the table in and out.

I'm also thinking I should cut this left to right so the forces are pushing down? Or could that pull it out of the clamps and I should cut it right to left?

Open to inout from anyone. But I am going to start making cuts on this tomorrow, I have less than a week to get this machined and ready and plan on taking my time.

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I can not see for sure, but I think you have the inclined face supported on 2 blocks---one beneath each clamp strap. That should be a good way to start and should induce minimal torque/twist in the casting. It will cause some deformation naturally, as the surface of the inclined cast surface is not a perfect plane. When you get down to final cuts, relaxing the clamping pressure in the straps will let the casting resume its relaxed shape. Another thought that occurs to me that could be used to reduce the deformation related to irregularity of the as-cast surface of the inclined face might be to make up some clay-like thickened epoxy by mixing any fine powder with epoxy, placing a pad of it on each of the support blocks and then placing the SE on the uncured pads and just lightly (finger tight) cinching down the straps. Let epoxy set up that way. That will fill all the various gaps between SE and block. Then cinch down the straps to good workholding tension. I think less deformation would be induced that way. (Stephen may be rolling his eyes right now. I won't fault him for that)

And I think your head nod looks generally correct. If your setup shows just under 41 degrees inclination of the sole, maybe nod your head 43 so it intersects the face at about 2 degrees assuming your final intersection angle of the face and sole is intended to be about 45. So you will split the difference between sole cut and inclined face cut. There is a lot of meat there as I have milled these SE's to 50 degrees without any trouble.

I think it is probably best to cut so that the cutter is pushing the SE down onto the table. But I also think either way would actually work fine.

Your flycutter should do a very good job of cutting the surface. Its only downside is that it will be a lot slower than a face mill. Perhaps an upside, at least theoretically, is that it will put less pressure on the casting and will heat the casting less. My guess is that you will feel only slight warming of the casting even when you are making cuts intended to remove material and virtually no warming on final skin cuts. A single cut could take a half hour or more. So, good to have some other chore to do while the mill is making a cut.

And it might be worthwhile to put "tattletales" on the two ends of the SE in the form of DTI's resting on the table and with points bearing on the casting so that you can watch for any slipping of casting on table. That is not likely to be a problem, but, especially on final cuts when clamping is reduced, it can be reassuring to see that nothing has moved. And, it might be good to allow a bit of watery cyano glue to wick under your support blocks and to wick between SE and blocks if you do not use the epoxy. That stuff can really prevent creep and is so easy to use.

I always check to see that on my initial cuts that more or less the same material is removed from the left and right sides of the SE. It will not be perfectly the same. But it should look balanced. On the first cut I probably only am intersecting about a 3/4" wide portion of the face and that "slab" is on the intersection or point side of the face not the rail side.

But, overall, I think you are set up generally correctly.

I do not think your efforts are feeble at all. I can see you are being thoughtful and I think your methods look sound.

I look forward to getting to see that beautiful shiny metal that lurks just under the cast surface. ;-)

Denis

I hope other folks will also jump in with ideas and suggestions/criticisms
 
Thanks for the feedback. I have some stuff I can clean up while waiting for cuts to complete. Considering it's just a fly cutter, this is going to take a while. Many, many shallow cuts. I'm in no rush at all (well, 6 days to complete it isn't much like rushing).

The SE is resting on two bars that I machined to uniform dimension (+/1 .002"), running parallel to the SE. The strap clamps are in the center of those bars.

I did line up the top strap with one of the slots in the table. When I was setting this up, I was worried this wasn't going to fit! The ram is all the way forward! But clearance is clearance. 😉

I like the idea of the tattletales. I would have never thought to do that.

I think I am going to take an initial pass on the bottom, then the prism side as you suggested, to give me approximately 45 degrees. How important is it that the angle be accurate? Seems like it wouldn't need to be?

Then I was thinking I would take a final shallow pass on each side with a ground insert, using paper shims or CA glue, and the clamps relaxed a bit more. Not sure about this last bit, as I don't know that I would trust myself to get the setup accurate enough. Maybe. We'll see.

Appreciate all the input. I am hoping it comes out as good as I am wanting. It's all a learning process, which is stressful, but still fun.
 
Thanks for the feedback. I have some stuff I can clean up while waiting for cuts to complete. Considering it's just a fly cutter, this is going to take a while. Many, many shallow cuts. I'm in no rush at all (well, 6 days to complete it isn't much like rushing).

The SE is resting on two bars that I machined to uniform dimension (+/1 .002"), running parallel to the SE. The strap clamps are in the center of those bars.

I did line up the top strap with one of the slots in the table. When I was setting this up, I was worried this wasn't going to fit! The ram is all the way forward! But clearance is clearance.
😉


I like the idea of the tattletales. I would have never thought to do that.

I think I am going to take an initial pass on the bottom, then the prism side as you suggested, to give me approximately 45 degrees. How important is it that the angle be accurate? Seems like it wouldn't need to be?

Then I was thinking I would take a final shallow pass on each side with a ground insert, using paper shims or CA glue, and the clamps relaxed a bit more. Not sure about this last bit, as I don't know that I would trust myself to get the setup accurate enough. Maybe. We'll see.

Appreciate all the input. I am hoping it comes out as good as I am wanting. It's all a learning process, which is stressful, but still fun.
There is nothing sacred about 45 degrees. You just need the angle to be less than the vee-way angle you intend to scrape.

How long are those support bars? I was sort of envisioning maybe 3" length. And I would have tended to orient them perpendicular to the long axis of the SE. Having them long and parallel maximizes the opportunity for causing longitudinal bending due to the unevenness of the raw casting surface. The more I think about using epoxy shimming the more I am attracted to that idea. Having them be of precisely equal thickness is good but not very important. Having them bear rather uniformly would be a big plus. What I am thinking would be less than optimal would be for the SE to rest unclamped on 3 points on the bars but maybe there is a 6 thou gap between the fourth point and the SE. Cinch up the straps and you force the SE down onto the fourth point and that requires the SE deflect to accommodate that bearing. Using some sort of shim (Epoxy paste, shim stock, Wood's metal (I have used it and it is not difficult but is likely not immediately available to you) ) to take up the fourth-point gap could pay off.

Another possible consideration would be to use one bar and one column so that 3-pointing would be more likely to occur naturally. The column could be a 1.002 inch high (equal to your bar thickness) truncated cone 1.5 inches at its base and 1/2" diameter and slightly domed . It would replace the one bar. Your flycutter will induce weak bending forces and I think this would actually work. You might see some chatter/ringing of the casting. I often use simple wood wedges lightly tapped under corners of the casting to stop or minimize it. A nice heavy dead blow hammer or bag of shot can also calm the savage beast.

Denis

If you went with the bar/column method, why not relieve the bar in such a way as to leave a roundish bump at each end? Now you have 3 points for support. Make sure the strap applies pressure over the two bumps (not between them) and you have effectively 3-pointed the SE.
 
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