What's new
What's new

Work holding a Featherweight 18" straight edge for machining

The support bars are about 4.5" long. They're actually about 1.128 thick (I didn't feel like milling it any more - meh). I'm trying envision how I would use them perpendicular, since they can't stick out past the front of the wedge. I will turn them around tomorrow and see if I can't make that work. I have some other hardened and ground parallels that were in a tool chest I bought that I can also use, instead of these, if narrowness is an advantage.

So if I understand you correctly, the idea of the epoxy shim is to make up for the unevenness of the casting - couldn't I just use a thin piece of soft wood to do the same thing? Or even some thick but soft card stock? I really only need that shim for the first operation, right? Once the flat is machined, I should be good to prop them up on the bars I have on the flat,

I'm trying to picture the other ideas you are offering, but having a hard time envisioning what you're meaning, plus, I am not so sure about making all those fixtures. May very well be outside my ability to make in the time I have available.
 
The support bars are about 4.5" long. They're actually about 1.128 thick (I didn't feel like milling it any more - meh). I'm trying envision how I would use them perpendicular, since they can't stick out past the front of the wedge. I will turn them around tomorrow and see if I can't make that work. I have some other hardened and ground parallels that were in a tool chest I bought that I can also use, instead of these, if narrowness is an advantage.

So if I understand you correctly, the idea of the epoxy shim is to make up for the unevenness of the casting - couldn't I just use a thin piece of soft wood to do the same thing? Or even some thick but soft card stock? I really only need that shim for the first operation, right? Once the flat is machined, I should be good to prop them up on the bars I have on the flat,

I'm trying to picture the other ideas you are offering, but having a hard time envisioning what you're meaning, plus, I am not so sure about making all those fixtures. May very well be outside my ability to make in the time I have available.
I am sort of spewing ideas, I will admit that.

But the problem with soft wood is that it will indeed cushion the deflection and reduce it. But it will compress more where it has no real end point so the casting can squirm around in response to clamping loads until it finds its own equilibrium. And it varies locally in hardness because of grain. Epoxy on the other hand sets up quite hard and uniformly stiff nicely filling gaps. Once it sets, it will only compress slightly due to heavy loading and it will set with the casting in a relaxed state---no squirming. Mixing some 5-min epoxy with saw dust, flour, or metal filings would add 30mins to the setup.

Making a simple column by turning in a lathe or simply grinding a 1.128 stub of 1" round stock would not take long. Same for taking a 3 inch long bar and using an angle grinder to grind away all but 2 bumps---one on each end would be pretty quick.
Here is a drawing that looks beautifully smooth and precisely machined. But, the real essence is three bumps of about the same distance from the mill table. It could be very crudely made and still work well.

3-Point (2).jpg

I do not want to go too far off into the weeds. But, my sense is the 3-point idea is worth exploring as I think it is the best of all. It could be as simple as just tacking two 1/4-20 nuts to a bar to make the bumps and turning or angle grinding the column. tolerance could be +/- .005 and it would still work fine. No twist or bend induced in the SE!

But, Mule, this is YOUR project and I understand you have time limitations and may not agree with my ideas. I just want to give you a set of options and figure you'll determine what would work best in your shop. And there is the broader audience as well that may or may not find the discussion useful and a starting point for their own solutions to related problems.

Denis
 
If you’re looking for advice - I’d have had slot stops in the rear tee slot so you can push the casting up to them. Obviously you’d need some small parallels to reach from the tee slot stops to your castings current position. I’d also block off the casting at either end. Having a DTI bearing on the casting as an indication of movement is a good idea but if it does move you’ll soon find out.
I personally wouldn’t walk away from the job to do something else. Be prepared to be bored for 1/2 hour.

Regards Tyrone
 
If you’re looking for advice - I’d have had slot stops in the rear tee slot so you can push the casting up to them. Obviously you’d need some small parallels to reach from the tee slot stops to your castings current position. I’d also block off the casting at either end. Having a DTI bearing on the casting as an indication of movement is a good idea but if it does move you’ll soon find out.
I personally wouldn’t walk away from the job to do something else. Be prepared to be bored for 1/2 hour.

Regards Tyrone
Sounds like good advice to me.

After an initial cut or two and everything is proven to be stable, I am guilty of not standing over the machine for an entire cut. I do let my attention go to other very nearby activities, like sweeping up swarf, organizing a drawer in my cart, and similar low-energy endeavors. I certainly do keep an attentive ear constantly on the progress of the cut listening for any change in sound and I do not leave the immediate vicinity of the work in progress.

I do routinely block in work as described above.

Denis
 
Here is a drawing that looks beautifully smooth and precisely machined. But, the real essence is three bumps of about the same distance from the mill table. It could be very crudely made and still work well.

View attachment 399186


OK. Now I see what you are trying to get at. Get the SE face in a plane. I think I have exactly what I need to do that without having to make any more tooling. I have bought several machinists tool chests that were packed with tooling and have these partial brass spheres. I can set them on these other blocks. That should give me the single plane, minimal twisting as long as the clamps are positioned as close to center of the spheres as possible.

I have a drawer full of B&S and shop made parallels, too. I guess my "investments" are starting to pay off? 😂

IMG_0358.jpeg
 

Attachments

  • IMG_0354.jpeg
    IMG_0354.jpeg
    739.3 KB · Views: 3
  • IMG_0355.jpeg
    IMG_0355.jpeg
    745.9 KB · Views: 3
  • IMG_0357.jpeg
    IMG_0357.jpeg
    578.6 KB · Views: 3
OK. Now I see what you are trying to get at. Get the SE face in a plane. I think I have exactly what I need to do that without having to make any more tooling. I have bought several machinists tool chests that were packed with tooling and have these partial brass spheres. I can set them on these other blocks. That should give me the single plane, minimal twisting as long as the clamps are positioned as close to center of the spheres as possible.

I have a drawer full of B&S and shop made parallels, too. I guess my "investments" are starting to pay off? 😂

View attachment 399201
Those domes look great! So nice to just pull them out of the toolbox ready to go. Being soft metal, the casting surface will press into them a bit and they will not tend to skate around---perfect.

On the two-dome end an ideal way to keep the strapping pressure centered over the domes would be to use a piece of 3/8 x 1" flatbar 3 inches long. Put a couple thin spacers on the inside surface of the SE about where you think the dome centers are located. Bridge the spacers with the flat bar and then put the strap tip in the middle of the flat bar. Pressure is now transmitted straight through to the domes without any tendency to bend the SE face.

I do anticipate some ringing of the SE when so supported. If it happens a couple wooden "doorstops" between the mill table and ends of the SE should damp it down.

Are we havin fun or what?!

Denis
 
Sounds like good advice to me.

After an initial cut or two and everything is proven to be stable, I am guilty of not standing over the machine for an entire cut. I do let my attention go to other very nearby activities, like sweeping up swarf, organizing a drawer in my cart, and similar low-energy endeavors. I certainly do keep an attentive ear constantly on the progress of the cut listening for any change in sound and I do not leave the immediate vicinity of the work in progress.

I do routinely block in work as described above.

Denis
Any set up that is even slightly hazardous needs your full concentration. I don’t stand over the job like a hawk but like you I’m never more than a step away from the emergency stop. I also never sit down when working on a machine. I like to be able to leap out of the way if the machine decides to throw something at me.
Setting up work on the table is a skill in itself. More or less anybody can put a job in the vice. Most components on the table will have three degrees of freedom. Take the straightedge in question. It can move upwards, side to side and front to back. A good set up will take care of all those possible movements.

Regards Tyrone
 
On the two-dome end an ideal way to keep the strapping pressure centered over the domes would be to use a piece of 3/8 x 1" flatbar 3 inches long. Put a couple thin spacers on the inside surface of the SE about where you think the dome centers are located. Bridge the spacers with the flat bar and then put the strap tip in the middle of the flat bar. Pressure is now transmitted straight through to the domes without any tendency to bend the SE face.

I'm going to give this a go after work today and probably start cutting.

Are we havin fun or what?!

Learning (from my mistakes) = Fun!
 
Here is the way to NOT do it. This is for one of Richard King's 18" straightedges. Fortunately no harm was done to me or to the machine, but I had to mill off some extra material from the face to get rid of the f**kup marks left by the shell mill.


As they say, hindsight is 20/20. I should have clamped a stop block to the table, it would have taken about 60 seconds and avoided the drama.
 
Here is the way to NOT do it. This is for one of Richard King's 18" straightedges. Fortunately no harm was done to me or to the machine, but I had to mill off some extra material from the face to get rid of the f**kup marks left by the shell mill.


As they say, hindsight is 20/20. I should have clamped a stop block to the table, it would have taken about 60 seconds and avoided the drama.
Yep, an end stop at both ends is the way to go. As you say it’s a 60 second job. Always remember the “ three degrees of freedom “ and do your best to cover all three bases.

Regards Tyrone.
 
Here is the way to NOT do it. This is for one of Richard King's 18" straightedges. Fortunately no harm was done to me or to the machine, but I had to mill off some extra material from the face to get rid of the f**kup marks left by the shell mill.


As they say, hindsight is 20/20. I should have clamped a stop block to the table, it would have taken about 60 seconds and avoided the drama.

You’re a better man than me. I would have sworn. In whatever language came out first :-)

What was the reason for climb milling?
 
Here is the way to NOT do it. This is for one of Richard King's 18" straightedges. Fortunately no harm was done to me or to the machine, but I had to mill off some extra material from the face to get rid of the f**kup marks left by the shell mill.


As they say, hindsight is 20/20. I should have clamped a stop block to the table, it would have taken about 60 seconds and avoided the drama.
Damn. That had to hurt on the inside. Glad it came out OK.
 
So I tried for about 2-1/2 hours to make the brass domes work. It wasn't happening. I couldn't get it to balance at all, the back strap is too heavy. And getting the clamp in the back of it was impossible. If I did get it to "balance" I couldn't get the toe of the clamp in the right spot over the dome, and it would cause the SE to fall off kilter.

I went back to sort of my original setup, although I used 2x4 blocks instead. This might be a bad idea, but, if @ballen can recover from his mishap, I think I'll be able to recover from this. Worse case, I have to machine it again, better case, I have a lot of scraping, best case, it's already flat! 😉

So far, I've taken about .130 off the bottom. I am getting a really nice cross hatch pattern, so I am happy with the tram of the head. I might take off another .060 to get a little more of the chopped ends gone before setting up to machine the prism.

The 1-2-3 blocks on the back are just a back stop for positioning.

IMG_0360.jpegIMG_0364.jpegIMG_0366.jpeg
 

Attachments

  • IMG_0361.jpeg
    IMG_0361.jpeg
    691 KB · Views: 4
Looking very good. Since this is the first time through with this setup, I'd be tempted at this point to pull it out of the mill and set it on a surface plate and use a feeler gage to get a sense of how flat you are. Then, I'd be tempted to mill the inclined face and see how that goes. You might well end up needing to recut both faces (or not) but that would be no big deal. But it might be nice to see how the setup seems to be working. I agree that your tram looks great. Just curious as to what parameters you are using--- RPM, IPM, DOC. I'm betting you are going to be happy with your flatness.

When this is all said and done, I think the thread will need to be renamed "LilMule's KickAss Featherweight Machining Method" :)

Denis
 
Thanks very much! 🙂 I am really nervous and really enjoying this challenge. 😜

Once I pull it out of this setup, I will be checking it on my surface plate. I think the probability that it will need machining a second time is reasonable. But I am going to take a cleanup pass with a ground insert before I do that. And that's after I take another .060" off the bottom.

I'd like to get the mill nodded to as close to 45 degrees as possible before cutting the inclined face. Not really sure how to do that with the tools I have. I suppose that digital angle finder will get me "close enough." The other thought is to mound a DTI in a collet and run the spindle down a machinist triangle. I have a 45 degree one, but it's extremely thin. I have a short sine bar, but it's really short. I doubt it will work for me. We'll see. I'll experiment some before I set it back up.

I might try the brass domes on the setup for the inclined face. I'll have a little extra surface area to work with. Maybe getting the clamps in there will be easier when it's the bottom on the mill table rather than the narrow prism face, especially with the back strap being at the top and not hanging over the back.

For RPM, according to the dial on the mill head, 350 RPM, so take that for what it's worth. The DRO is telling me I am feeding at 2.75 IPM (70mm/min), and I am taking approximately .020" cuts (by moving the knee up and the table out .015" each). I'm not sure that's completely accurate since the fly cutter is not at a true 45 degrees, and because spatial geometry is hard sometime 😵‍💫 I'm better off drawing it in Fusion and checking the math that way. So I think I am taking more off the converging edge than the back on each pass. Or maybe it's the other way around? My brain hurts. 😂

Side note: I have maybe an extra 1.5" of travel on the mill table for this setup. If it was any longer, I'd have to use a smaller diameter cutter and take multiple passes. 😳 I have the fly cutter set to it's minimum diameter.

Side Side note: Lil' Mule is my Jeep. I'm just the driver. 😉
 
Mule,

I think the sole starts out around .420 thick. So, if you take another .060 off, you will have about .240 remaining which is about as thin as I like to go based on nothing more than intuition. That said, to fix up any lack of flatness should only require removing a few more thou (assuming the second cut is set up ideally).

It sounds like you are taking .008" thick chips at your current RPM and IPM. That seems generous to me but likely harmless.

I knew "LilMule" did not refer to you, but I was stretching to try to get "Mule" and "Ass" into the title. :)

BTW, your prism should be not quite 2 pounds lighter than when it arrived via UPS. And, I love the sound of smoothly cuttng cast iron...

Denis
 
Once I pull it out of this setup, I will be checking it on my surface plate. I think the probability that it will need machining a second time is reasonable. But I am going to take a cleanup pass with a ground insert before I do that. And that's after I take another .060" off the bottom.

I'd like to get the mill nodded to as close to 45 degrees as possible before cutting the inclined face. Not really sure how to do that with the tools I have. I suppose that digital angle finder will get me "close enough." The other thought is to mound a DTI in a collet and run the spindle down a machinist triangle. I have a 45 degree one, but it's extremely thin. I have a short sine bar, but it's really short. I doubt it will work for me. We'll see. I'll experiment some before I set it back up.



For RPM, according to the dial on the mill head, 350 RPM, so take that for what it's worth. The DRO is telling me I am feeding at 2.75 IPM (70mm/min), and I am taking approximately .020" cuts (by moving the knee up and the table out .015" each).


Side Side note: Lil' Mule is my Jeep. I'm just the driver. 😉
Mule,

I think the sole starts out around .420 thick. So, if you take another .060 off, you will have about .240 remaining which is about as thin as I like to go based on nothing more than intuition. That said, to fix up any lack of flatness should only require removing a few more thou (assuming the second cut is set up ideally).

It sounds like you are taking .008" thick chips at your current RPM and IPM. That seems generous to me but likely harmless.

I knew "LilMule" did not refer to you, but I was stretching to try to get "Mule" and "Ass" into the title. :)

BTW, your prism should be not quite 2 pounds lighter than when it arrived via UPS. And, I love the sound of smoothly cutting cast iron...

As far as hitting 45 is concerned, if I am wanting to be good and close I use the protractor head on my Starrett 12" square or the vernier machinist protractor to get a bit closer. You could always take a cut, measure, and tweak your nod.

Denis
 
I think the sole starts out around .420 thick. So, if you take another .060 off, you will have about .240 remaining which is about as thin as I like to go based on nothing more than intuition. That said, to fix up any lack of flatness should only require removing a few more thou (assuming the second cut is set up ideally).

My calculations are completely wrong. I mic'd it in a few places as best I could and I was seeing .350". I didn't measure it before I started, but I know I have come up and out .096", and I was using that number to calculate the distance traveled, but what I was using the wrong formula. I've actually only taken half of what I thought. 🤷🏼‍♂️

It sounds like you are taking .008" thick chips at your current RPM and IPM. That seems generous to me but likely harmless.
I use FSWizard (an app on my phone) to set RPM and IPM. I will slow down the feed for the "final" pass.

I knew "LilMule" did not refer to you, but I was stretching to try to get "Mule" and "Ass" into the title. :)

I totally missed that. LOL! I suppose I can be an ass from time to time. 😉

BTW, your prism should be not quite 2 pounds lighter than when it arrived via UPS. And, I love the sound of smoothly cutting cast iron...

As far as hitting 45 is concerned, if I am wanting to be good and close I use the protractor head on my Starrett 12" square or the vernier machinist protractor to get a bit closer. You could always take a cut, measure, and tweak your nod.

I did weigh it on a bathroom scale before I started. I think it was 18 pounds. It'll be interesting to see the results post machining. I love the ease of machining. My wife doesn't love the rust spots I leave in the shower.

I have an old Starrett protractor, I'm sure I can figure out a way to use it. It's pitted from being rusty when I found it, but I am sure it still has a decent level of accuracy.
 
I like “ Bridgeports” and if I was looking to buy a milling machine I’d be happy to have one but the lack of table space, especially the width, used to drive me mad. On the other hand their sheer versatility takes some beating.

Regards Tyrone
 








 
Back
Top