Machining question

[BigSki]

I'm building a set of soft jaws with a V groove in each one to capture a railroad spike so that holes can be drilled and tapped into the shanks of the RR spikes.

I don't have a V groove cutter, I'm trying to work with what I have available. My plan is to clamp the stock into the vise using my sine bar set up for 45* and using a straight cutter to remove material. I plan to walk the cutter up the to material, touch it and advance on X then move Y back and forth, pretty basic stuff. What I'm trying to figure out is: If I have a center line mark scribed on the material that I'd like to be the center of the V, how do I compensate for the cutter so that when I advance on X, the center of the cutter is the center of the V groove? It doesn't really matter if the center of the V isn't exactly on the scribed center line, I thought it could be a good lesson to learn. The two V grooves will match in each jaw, so when close it forms a square shape. The RR spikes are, on average, .625 square. I'll make the square opening .580 to allow for variances in sizing.

I've always had the correct cutters before so it was as simple as running in on X and finding the center mark. This new method that I'm doing is a bit different. I'm drawing pics on paper and trying to rationalize it, but some advice from someone who knows how to do it the way I'm attempting it would be beneficial.

[QuesoDelDiablo]

It's just a bunch of trig you need to do. It gets to be a little unruly because you have to factor in your tool lengths and doc et, but it should be pretty straight forward if you draw it tilted on a 45* and set the coord system to be on a 45* so that a lot of the angles are eliminated..

Have you got CAD software? The easiest way to figure this out would be to model it.

Or just go buy a v groove tool and save yourself a bunch of thinking..

[JohnRobHolmes]

If doing it visually is ok, scribe both sides of the v channel to mark the width. Then it is a matter of using x and z to ease towards the marks. If your fixture is repeatable, you should be able to lock z after the first jaw and only use x to advance the depth of cut while Y controls feed rate.

Swap x and Y if it makes sense for the cut.

[JohnRobHolmes]

Easier to see in drawing. If your setup and scribes are accurate, it will be far better than the accuracy of the stake. For a .58" square in 4 jaw chuck, the width of v slots will be .41".

[BigSki]

Thanks for the replies guys. I woke up around 3am with the realization that I was looking at a trig problem. ( a few of them, actually) so I went as far as I could with pencil, paper and the Ti-34. After I hit a mental roadblock I fired up Inventor ( SW license is still on the way..) and made a simple model that replicated what I need to build and dimensioned everything. The software makes it nice, I was just a bit let down that I couldn't remember how to do all of it from memory.

[Etype R]

Would a simple 90deg chamfer tool not do the job?

[BigSki]

Originally Posted by Etype R

Would a simple 90deg chamfer tool not do the job?

Maybe, but I don't have any. I have to use what I have available to me.

[C*H*U*D]

How confident are you at cutting both grooves to the same height? If they're off, the spike will be clamped crooked.

If it was me, I'd probably just cut one jaw, but make it a bit deeper than planned. Then the second jaw would just provide the force to keep the spike seated in the groove.

Since you're only drilling and tapping, machining forces shouldn't be a concern.

Make sure you post pictures when you're done

[BigSki]

Originally Posted by C*H*U*D

How confident are you at cutting both grooves to the same height? If they're off, the spike will be clamped crooked.

If it was me, I'd probably just cut one jaw, but make it a bit deeper than planned. Then the second jaw would just provide the force to keep the spike seated in the groove.

Since you're only drilling and tapping, machining forces shouldn't be a concern.

Make sure you post pictures when you're done

Fairly confident that I could completely screw it up !

Sine bar inside of the vice and a straight edge straddling both jaws that the material will touch, keeping it in the same plane. I might even try cutting both soft jaws at the same time so that they will match, I can add the holes for the mounting screws afterwards using a steel jaw as a layout tool, the vise is a chinese clone of a Kurt, and not a very flattering copy at that.

[j.krug]

Any chance you can just clamp a v block in your vice and us that to hold the RR spikes?
Simple and very accurate/repeatable if you have one.

[C*H*U*D]

So are you drilling and tapping into the corners of the spike? Now I'm curious to see what you're making.

[QuesoDelDiablo]

Originally Posted by C*H*U*D

So are you drilling and tapping into the corners of the spike? Now I'm curious to see what you're making.

Good point, me too!

RR stuff is some seriously high grade steel..

[BigSki]

Originally Posted by j.krug

Any chance you can just clamp a v block in your vice and us that to hold the RR spikes?
Simple and very accurate/repeatable if you have one.

If I was just doing a few, that method would be ok. I'm looking at about 50 spikes, I need quick repeatability.

Originally Posted by C*H*U*D

So are you drilling and tapping into the corners of the spike? Now I'm curious to see what you're making.

Centers.


some type of iteration of this.

Originally Posted by QuesoDelDiablo

Good point, me too!

RR stuff is some seriously high grade steel..

The carbon content isn't all that high, generally around 0.25%. These spikes are just basically really big nails.

[C*H*U*D]

I see now. For some reason I was thinking that the slots you were making were horizontal and the spike was laying on it's side.

[BigSki]

My first thought was to make a split bushing to use the 3 jaw chuck on the lathe but after measuring a half dozen of these used spikes, the dimensions fluctuate enough that it wasn't a great idea to use the lathe for this, the shanks wouldn't stay centered in the bushing. My thinking is- by making the square opening in the soft jaws I can establish a stable location and keep everything pretty close to center, plus the part isn't turning like it would be in the lathe.

I'll take a pic once they're made, since it isn't a RC car part it wouldn't be appropriate to document it in here.

[C*H*U*D]

Originally Posted by BigSki

I'll take a pic once they're made, since it isn't a RC car part it wouldn't be appropriate to document it in here.

You're using tools and showing a procedure. It's not like you're posting pictures of a laughing jackass

Sorry...couldn't resist

[QuesoDelDiablo]

Originally Posted by BigSki

The carbon content isn't all that high, generally around 0.25%. These spikes are just basically really big nails.

Good point again, it's not like the spikes have received the years and years of cold work hardening that the rails do..

Still though, those spikes are going to be better quality steel than the recycled offshore junk of questionable alloy that we buy nowadays...

[C*H*U*D]

Originally Posted by BigSki

...The RR spikes are, on average, .625 square. I'll make the square opening .580 to allow for variances in sizing...

I was just thinking about this again. So if the spikes vary that much, why not clamp them square in the jaws with a vise stop on the fixed jaw and zero from there. Then as you measure each one, just divide by two to get your center in X and Y.

Clamped in the 45 degree slots, you'd only have to adjust in Y but you'd still have to make jaws. If you only had a few to drill, you'd probably be done by the time you finish slotting the jaws.

[BigSki]

Originally Posted by C*H*U*D

I was just thinking about this again. So if the spikes vary that much, why not clamp them square in the jaws with a vise stop on the fixed jaw and zero from there. Then as you measure each one, just divide by two to get your center in X and Y.

Clamped in the 45 degree slots, you'd only have to adjust in Y but you'd still have to make jaws. If you only had a few to drill, you'd probably be done by the time you finish slotting the jaws.

I had though of this at first but when I mocked up a spike in the jaws, the head of the spike was wider than the shank section so the jaws couldn't close. I thought about using my 1,2,3 blocks as spacers but then it just gets cumbersome. This mill is in a 'Maker Space' where they give a 3 hr. "introduction" class to basic mill operation, then turn the 'boots' loose on the equipment.

Every time that I'm in there using the equipment, I have someone watching. I don't want to show inexperienced people new ways to destroy the equipment or to hurt themselves.

[BigSki]

I had a bit of time, so I got started on the jaws. While the end result will work just fine, my number-crunching went wrong somewhere along the line, the center of the 'V' groove isn't in the center of the jaw like I wanted ( no big deal really, I just wanted to nail it).

The maker space didn't have any gauge blocks, even though they said that they did. What they had were parallels. so the sine bar wasn't going to work without making a spacer the correct length. I didn't have any extra material with me to do that, so I used the 45* edge of a carpenters square to set my angle in the vice. Better than nothing !

This is the only pic, I just wanted to get finished with the angle cuts. I'll go back the first weekend of Dec and make the holes to mount this in the vice, then start cutting up railroad spikes.