Any advice on how to cut/file a 45 degree chamfer on a 1mm steel sheet to EXACTLY 45 degrees?

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John

I have resisted the temptation to participate in this discussion, until now ... and I am making just one comment, which I hope you will accept as supportive :

Your 'actual question' used the term "EXACTLY" ... but now you have downgraded to "We emphatically don't need perfection, we just need it to be as accurate as we can get it within reason."

Before asking people to 'focus on the specific issues and actual questions'; you might like to consider how many orders of magnitude that change of specification embraces.

MichaelG.

In answer to Q1 I was thinking of the small 20mm diameter grinding wheels that fit on a mandrel and are used in Dremmel tools. At the cheap end 8 wheels plus a suitable 3.17mm mandrel cost £3.45 from a well known auction site. Better ones are no doubt available elsewhere.

For Q2, for the volume you are planning to make I was thinking of making the table from a small piece of Plywood, MDF or other suitable smooth material that was big enough to cover the base of the proxxon. Glue or screw a strip of thin timber or plastic (say 10mm wide & 5mm thick) to that base. Then place it on the proxxon base and clamp it down (depends on what clamping arrangement the Proxxon has) at the correct distance from the grinding wheel.

Coming in late, as usual

Cutting by hand is MOST unlikely to result an edge at "exactly 45 degrees"My suggestion would be to cut /file the strip to width (making the minimum allowance for the 45 degree chamfer, ) with the ends square to the straight face.

The illustration of the machine ( 23/3/2021 12:36 ) shows a T slot along one side of the Table. That is the ideal means of clamping a fence in position.. The fence may need to be wide enough for the workpiece to overhang the edge so that the grinding wheel can pass below the level of the top of the Table.

The fence can also be used as the basis for the clamps used to hold the workpiece...

Running a small grinding wheel along the outer edge, with the "pistol drill" set over at 45 degrees would seem to be the method.

This would allow a long strip to be ground, so that it could then be sheared to provide several lengths, with the required chamfer.. The long strip can then be sheared to produce the lengths required.

Shearing across the sheet may well produce a burr which will need tom be removed by gentle use of a swiss file or a diamond file.

The grinding wheel will wear, so the vertical position of the "pistol drill" will need to be slightly (The wheel will only be operating over metal of just less than 1.5 mm width  adjusted regularly to present an unworn part of the wheel to the workpiece. Hopefully, one grinding wheel may last long enough to do all 32. If unsure, lay in a store of wheels.

Howard

So what's wrong with the running a cutter through idea. It's an old woodworkers trick. ?

regards Martin

Hi John Smith 47, unless you are extremely good at filing, I doubt you would file an exact 45 on a strip of steel. First of all it would need to be flat and the edge would have to be straight and unless it is clamped along its full length, it will just bend as you are trying to file it and then how and what with, are you going the measure the angle that you have filed. As has been said, it may be best to get a strip a gauge plate, similar to 1mm x 15mm Gauge Plate and then with what tools you have, is cut the width of you pieces and then do each one or a pair in the same jig using the same settings each time.

I recently made a couple of gibs for a friends lathe and I made a block with a step on one edge, clamped it down on my mini mill and trued up the step. I then clamped a stripe of gauge plate on it and milled one bevel with a dovetail cutter and then flipped it over and milled the other bevel. Took a little while to do each one as I couldn't do very heavy cuts, but the bevels came out without any detectable error, using my M&W precision Vernier bevel protractor.

Regards Nick.

Edited By Nicholas Farr on 23/03/2021 19:51:58

1 mm is very thin. Even if your 45 degree angle is absolutely perfect, you're going to have problems ensuring that the parts remain flat enough to obtain a <0.1mm gap all the way along the edge.

Given lack of space, equipment, etc., I'd make a simple jig out of MDF, flat-topped, with a piece of steel plate screwed to it, and an angled support at 315 degrees to it to clamp the part to. Use appropriate fences and dowels (through previously drilled holes in the part, as per your drawing) to register the part so that the edge to be chamfered is just above the steel plate.

Then file the chamfer level with the plate. You can let the file contact the plate to guide it. It will last long enough for the purpose.

Add fences, stiffening webs, etc. Draw filing is probably the way to go.

Few thoughts, first, the more information about the requirement the better. Engineers are tortured by customers wanting to implement their solution, however impractical, rather than allowing the expert to suggest better ways of doing it. Secret specifications are particularly evil, because it's so easy to make simple jobs difficult by accident. Putting it another way, be careful what you ask for!

In John's specification, it may be there's no need to put a difficult to make accurate 45° chamfer on the strip. If John's requirement is for two parts to butt together accurately, it's only necessary for them to be chamfered at the same angle which is much easier to do.

In the drawing below, both 45° and 40° chamfers butt equally well.

My approach, ideally with a milling machine, and I think a Proxxon or Sherline would do, would be to mount a long strip of metal flat and drill a sequence of hole pairs spaced 20mm along the strip, widely spaced to allow crude sawing. Then I'd mount the strip in a jig at about 45° and run an end mill along the top tilted edge, thus producing a strip long enough to make several pairs all with the same chamfer, and therefore able to mate accurately.

The parts can be separated with a hacksaw and then tidied to size by milling or filing. In both cases I'd make another jig to hold several pairs together in a stack by bolting them through the holes, thus letting me square the side edges to the required dimensions in groups, not one at a time.

The limitation of the approach is pairs have to come from the same strip unless an angle jig is made to guarantee a repeatable chamfer. If 45° really is essential, same basic approach except much more effort goes into making an accurate jig.

Although a milling machine considerably simplifies the job, it could all be done by hand, creating the chamfer by carefully filing down to the edge of the jig, and centre popping the holes. Hand would be cheaper, but don't underestimate the amount of practice needed to do the job accurately. I'm too clumsy and impatient to do good work with hand tools!

Dave

Edited By SillyOldDuffer on 23/03/2021 20:13:19

Dave, you need to read what little spec we do have, John wants the parts to meet at 90deg not butt together, you won't get that with two 40deg chamfers.

This is where Martin's suggestion of cutting in pairs has some merit as they will meet at 90 and will compensate for any inaccuracy in the tilt of the Multitool.

Doh! I think I'll have a glass of wine in front of the telly, something mindless is bound to be on. Armchair engineering is so much safer...

Dave

Maybe treat your little Proxxon as a mini overhead spindle moulder, and hold the workpiece in a second hand V block off ebay or similar.
Beware not all V blocks have an exact 90° groove, but a length of suitable shim, flat on the table along side the fence should suffice to get the angle correct.
1mm is really quite thin, so an inverted cone shaped stone (end on), or maybe a carbide burr (side on), would cut the bevels evenly.

Bill

However accurately, and however slap dash, a part can be made, I will find you a group for each case who can be fairly described as the 'we' for whom the result is the very best they can do. So, the spec we are given is no spec at all.

Sorry

Tim

That's useful to know. It'll save me wasting time on a none existent problem. It might be prudent to put your seatbelt on though.

Andrew

You need a small milling machine, buy a sieg x1

Thank you, everyone! [Crumbs, Too many posts to reply tonight, but I'll make a start...]

Michael Gilligan - Yes, you make a sound point. To get clear, I was hoping that when one puts ANY of the 32 pieces that I will have made together, such that the 45° chamfers are meeting each other, that one would get a pretty good 90° corner, that is within say 2 or 3 degrees of being exactly 90°. That's the target.

It may/may not be possible at a reasonable cost, but that was my target.

In order to get there, I would consider spending up to say GBP300 (or even GBP500?) on good quality hardware (e.g. a milling machine) that will be a useful addition to my home workshop.
Please let me know if any of you have any specific recommendations (if that is allowed on this forum??)

Peter Cook 6 - can you provide a link or photo of what you mean?
Did you mean something like this:

A)

Or B) more like this:

TBH, what held me back was that the grinding wheels that I saw were more like B) [above] and only seemed to be about 2 to 3mm thick, which doesn't leave much margin for error, particularly if one ends up getting uneven wear.

Either way what would be the best material for a durable grinding wheel?
Silicon Carbide or Aluminium Oxide?

* * *

Regrading "finishing" off with a diamond cutter, I don't quite understand how one hopes to get a really flat surface if the central screw is sticking out. e.g. like this one:


Go to go!

​​​​​​​J

It's 1mm thick x 16mm long and the angle needs to be within 2 0r 3 degrees of 45?

Tape a piece of coarse emery paper to a flat bench top. Lay a 12" piece of thin-walled 1" angle iron on top of it, open side down. Each side of the angle iron is now at 45 degrees to the bench.

Lay the job on one face of the angle iron with the bottom edge against the emery paper and rub it back and forth two maybe three times and you will have your chamfer.

The job could be double-sided taped to a wooden block to make it easier to hold.

First you cut with a disc either with the work angled and tool vertical or you keep work flat and angle the tool using just part of the disc much like a circular saw cuts wood

You then change to a diamond coated disc and feed the work across the blade so the diamons just takes the last 0.1mm off.

As for budget I think you need to think again, even the SX1P mentioned above will cost more than your £500 once delivered, you then need to add in some tooling such as Vice, Collet Chuck, DTI to set vice true, Digital Angle box or other means of setting angle, cutting tools, book on how to use a mill, etc

Considering that it's just sheetmetal, and the number of parts required, I'd be more tempted to file a clamp-on jig and buzz the whole lot across a cheap belt sander.

45 degrees on a 1mm part is more like sharpening a blade than chamfering.

45

Have a look at this Tom Lipton video.

https://www.youtube.com/watch?v=q4kaXRgUHGs

Iain

I'm with Andy Stopford's method.

I was thinking of the second kind. I used a green (silicon carbide?) one the other day to take the point off an M4 HSS tap, so 1mm mild steel is going to be no problem. You might want something to dress the wheel with to keep it square, but a bit of HSS steel would probably do although at the price I would be tempted to swap the wheel if it showed signs of wear.