Rail chamfering Jig

[Rolky]

Mr Ron,

How about using a router with a 90 degree cone grinding bit?
http://www.mcmaster.com/#grinding-bits/=gpdoil
(Select 90 degree cone on left-hand side)
Use a router table, or make a guide, so that the grinding bit takes off almost 1/2 of the edge, but not enough to cause a very sharp point. That way you will keep your raw edge reference on both sides of the grinding bit.

Eric

[Mr Ron]

Here is a jig that I want to build to machine a 45° bevel on the edge of some 1x3/16 steel strips. The amount of material to be removed will be 0.100" at a 45° angle. The jig will be held stationary in the milling vise and the strip pulled through the jig. Can this be done?

I've done it with free machining (leaded) brass with excellent results, cutting a larger chamfer. If memory serves, it was 3/16". I did not build a fixture, choosing, instead, to make a table setup with parallels that were properly oriented, allowing the material to pass through without moving away from the cutter (I used a 45° multiple flute countersink. I suggest you consider that as the cutting tool, too, so cutting pressure loads the material against the bottom).

If you make the fixture properly, the material will be held captive and can't move away from the cutter. The only real problem, then, is to overcome cutting pressure in feeding the material. If you find it difficult, you may wish to make the cut in two passes.

Do not attempt to climb mill. Guaranteed, that will end in disaster. The drawing you show indicates a climb mill cut. Also, do not stand in line with the material as it is being fed to the cutter. Under less than ideal conditions, it may be propelled towards you.

Harold

I agree with the 45° countersink and applying the pressure downward rather than upward. I guess I'm just going to have to try and see if it works. I was also thinking of rigging up a device to pull the strip thgrough the jig. A winch from a 4x4 is one thought, or a cable wound drum driven by a variable slow speed drill.

[atomarc]

Is there another way to skin this cat? Is there a better way to get what you want without the use of that flat bar with the chamfer on it...a different design perhaps. Don't get trapped 'in the box'!

As has been stated above, if you alter only that one edge, the strip will naturally relax and turn into a banana.

Stuart

[Mr Ron]

Is there another way to skin this cat? Is there a better way to get what you want without the use of that flat bar with the chamfer on it...a different design perhaps. Don't get trapped 'in the box'!

As has been stated above, if you alter only that one edge, the strip will naturally relax and turn into a banana.

Stuart

I'm beginning to believe that I will never be able to attain a perfectly straight rail without first starting out with a perfectly straight strip. I'm thinking precision ground stock, but it's too expensive and probable isn't available 7 ft long. I've seen rails with the profile I want, but it is VERY, VERY expensive. It is sold by linear motion makers; over $800 for a 6 ft long piece.

[Metalman]

You're chamfering one edge at 45deg, right? How does chamfering on one corner have any effect on the straightness of the workpiece? The original edges are still intact and straight, assuming they started out that way.

Ahhh! Not so, grasshopper.

When a chamfer is applied to bar stock, stress is relieved on two faces. The result *can* be a piece bowed in two directions. I would expect that to be the case on material of the length in question.

Harold

I had 5/16" X 2.5" X 8'-1" cold rolled steel "planed" with a 45 on one corner similar to the piece being discussed here only the cut needed to be almost a knife edge. This was to replace the bending edge on my old Geo. A. Ohl & Co. sheet metal brake. The planing machine was giant, moved the material against a single fixed cutter (like a lathe tool) in multiple passes. This came out with considerable bow along the 2.5" dimension. I had to force the piece onto the machine with clamps but it did end up straight because fortunately there was a machined step in the machine to back it up and the screws hold it. The consensus was the material should have been stress relieved in a oven with slow cooling prior to planing. That was over 20 years ago, still using it.

A previous bending edge was done by a local machine shop. It wasn't bowed when I received it from them but at that time I had no clue how they did it. I can only assume now that they machined but really don't know.

[Mr Ron]

Thanks for all the replies. I know it can be done, the problem is I don't have access to the machines to accomplish it. If it were a small 6" long piece, I wouldn't even have to ask. My shop is limited as to what can be done, so I will have to rethink my options and maybe come up with a new idea.

[Patio]

Use round rods with bearings mounted to angle iron to create a captured rail.
My twin brother is building a CNC router with this method. I will take some pics or make a drawing for you, if you do not understand the method.

[Mr Ron]

Use round rods with bearings mounted to angle iron to create a captured rail.
My twin brother is building a CNC router with this method. I will take some pics or make a drawing for you, if you do not understand the method.

I'm familiar with most of the linear motion rail systems. The problem is LM systems have to be dead straight, so tryingto fabricate one that is straight will require machines and tools not readily available to amateur machinists and are cos prohibitive. A picture or sketch would be welcome just in case I missed a way.

[Torch]

What about buying lengths of drill rod or shafting and coupling them together somehow? Maybe turn a partial cone on one end and a mating female on the other with a threaded connection between them.

[Patio]

You can make things as straight as can be, but I think because you are using MDO (my brother is using MDF), that the rigidity, will not be enough to make the tolerances you may be trying to get, significant. He is using black iron pipe for his rails. He made blocks on the ends of the rails to make them adjustable. There is also a cross cable system under the bed to keep both sides of the Y axis traveling together. He is using all thread, with a split coupler/anti-backlash setup for axis screws.
He also only has aspirations to cut wood, for the most part, and some aluminium. If you are after long, critically straight lines, then you may be on the right track. Most people I have seen use linear rails for large machines that will cut wood and aluminium, to a high degree of accuracy.

This is a carving of a picture he made.

Vcarving.jpg (17.58 KiB) Viewed 3674 times

This is a piece of aluminium he carved for my other brothers gate.

A light stand for growing starts, cut from MDF.

I don't know what you are trying to achieve, so it is hard to say what you needs are, but this is done with a simple system. Once this one is completed, it will be used to make a larger and a more rigid one.
I am no expert, and there is a lot of info on the net about making CNC routers. I do hope it works for you.

[stevec]

Thanks Pat, very interesting. One word of caution, being that you are relatively close to B.C. I would recommend sticking to the term "light stand" as opposed to "growing start", we don't know if the DEA monitors this site .

[Patio]

Hi Steve
It is a light stand, and it is for growing starts, for food! I have no interest in being politically correct. One can read into things what they want.
Thanks for thinking about my safety though. That sentiment I do appreciate.