Thinking about a possible project.

Currently, when I need to make a specific angle cut in an mandrel bend or a sch10 elbow, I just sort of eyeball it. Seems to work fine most of the time, but I would really like to be able to get the cuts precise to a degree without having to carefully measure each and every time.

So I was thinking of a jig, that when mounted on a bandsaw or chop saw, could retain an elbow and position it for the correct cut.

Does such a device exist? If not, I would like to discuss ideas for creating one.

This is what I think the functional requirements would be:

1) Adjustable for any angle between 0 and 90°
2) Adjustable for any CLR from 1 to 12"
3) Capable of clamping any OD from 1 to 4"
4) Capable of clamping bends without "legs"
5) Adjustable longitudinally and transversly, to get the cut under the blade

Constraints:

1) Inexpensive
2) Cannot get in the way of the cut


Modified by beepy at 6:24 PM 2/3/2006

 

Just use A tape measure and lay it on the outside of the bend where it starts and where the bend stops..say your measurement is 4" from begining to end of bend on A 90* bend, so that would make the 2" mark 45*, 1" 30*,and 3" mark would be 60*, I hope that came out right but anyway's you get the idea..

 

I made something similar...holds a 90* elbow and I use the bandsaw adjustment to change the angle....measure it out with a tape measure where it has to be and line everything up. Works great....Id show ya pics but then again I didnt spend half a day making it to make everyone else's life easy

 

I made a giant protractor for 3" pipe w/ a 4.5" CLR. It works really well. I'll post a pic next time I take my camera out to the shop.

Evan

 

a jig for cutting those stupid elbows would be great. anyone have any pics for a visual learner?

 

I have a pretty good design that I think will work great on bandsaws. Still trying to figure out chop saw mounting since the cut area is much longer.

Will post pics when I get it mocked up in SOlidWorks.

 

Doubt you'll be able to get it on most bandsaws. Well actually verticle bandsaws could be possible.

 

interested

 

Here is my preliminary design:



Need to add mounting holes, clamping bolts for the moving parts, and some way to clamp the pipe to the holder.

This design is good for 1.25" - 2.5" pipe. I would need another mounting method for tubing.

 

I anybody is still interested in this idea, it would work with 1.25" to 2.5" schedule10 or schedule40, and the operation is simple.

With the pointer in place, the pointer is simply kept in the center of the cut groove while the radius bar is moved along the protractor to the desired angle. With the design the smallest angle possible is about 10°, and largest about 80° (which is just the other end of the 10° cut)

It is either mounted on a chop saw, with the blade of the saw over the cut groove, or on a vertical bandsaw on some sort of sliding apparatus.

Securing the moving parts is easy. I am still trying to figure out how to secure the elbows to the mounting plate securely enough to be safe.

 

i use a compound mitre saw that i got from lowes, and the saw itself is able to swivel up to 50 degrees i think, and it goes either way, compared to my chop saw from harbor freight its amazing

 

That design doesn't look like it would cut on radius to me?

Maybe make something more specialized? Make a jig to hold only one size pipe/radius. You could make it much simpler, yet likely get better results.

I've been contemplating making a base that would allow the work to rotate to the correct angle, then use spacers to compensate for the correct radius. I don't really have any way to post up my thoughts in a visual manner though.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 99_GS-T &raquo;</TD></TR><TR><TD CLASS="quote">That design doesn't look like it would cut on radius to me?
</TD></TR></TABLE>

It's mathematical. Since elbows are 90° and don't have legs, the center of revolution is where the planes of the faces intersect. Since the elbow is butted against the holder, the intersection of the two planes that make up those faces is also the center of revolution.

Since the actual point has to be removed to clearance for the chop saw blade, a temporary pointer is used to mark the spot. So change the angle on the protractor, then move the pointer into place, and voila, perfect radius cut.

 

Ah, I see what you are doing now. Makes sense.

The biggest concern in my eyes is holding the piece securely. What are you planning on doing for a clamping system?

It doesn't matter how accurate your jig is, if the part can move around in the jig.

 

Yo. That's the next challenge to tackle in the design.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beepy &raquo;</TD></TR><TR><TD CLASS="quote">It's mathematical. Since elbows are 90° and don't have legs, the center of revolution is where the planes of the faces intersect. Since the elbow is butted against the holder, the intersection of the two planes that make up those faces is also the center of revolution.

Since the actual point has to be removed to clearance for the chop saw blade, a temporary pointer is used to mark the spot. So change the angle on the protractor, then move the pointer into place, and voila, perfect radius cut.</TD></TR></TABLE>

it still woudlnt cut the radius unless the pivot was about that corner.
rotate it in your mind to the farthest point left (0* i would say) then youll see what i mean. it would be like 4" to the left of where the blade would be


you need to make the jig rotate at the corner.

 

That's what I was seeing too. But he could probably get up to a 45 degree angle with that setup. That's all you need.

 

without rotation about the corner, there wont be consistent cuts perpendicular to tangent lines.

 

Reevaluating for a third time, I think I'm going back to my original answer.

Shifting the center would reduce the off radius nature of the cut, but I'm thinking he's right and it wouldn't work out to directly on radius.

That would have to be something I held in my hands or sat down and drew out closer as it kind of creates and optical illusion that it would work, when the logic in my mind tells me it wouldn't work.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dfoxengr &raquo;</TD></TR><TR><TD CLASS="quote">

it still woudlnt cut the radius unless the pivot was about that corner.
rotate it in your mind to the farthest point left (0* i would say) then youll see what i mean. it would be like 4" to the left of where the blade would be


you need to make the jig rotate at the corner.</TD></TR></TABLE>

yup i agree, that jig wont do it. hold on, let me get out my CAD drawing jobby...

 

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bailhatch &raquo;</TD></TR><TR><TD CLASS="quote"> </TD></TR></TABLE>

Haha thats pretty decent.

 

dont mind the 120* weld el

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bailhatch &raquo;</TD></TR><TR><TD CLASS="quote">dont mind the 120* weld el </TD></TR></TABLE>

Haha, i was wondering where you'd find those!

 

so what are you saying toe-knee?! my order hasn't shipped yet?