Milling Angles, How Do You Do It

[epicfail48]

So, whats best practice for milling a relatively precise angle on a long piece of stock? To be clear, im thinking cutting a 60 degree edge onto a piece of bar stock to make a dovetail straight edge, or other situation where youd have to hold the workpiece at an angle and cut along the X direction. If the piece was short enough i know you can clamp in in the vise and mill along the Y direction instead, but thats not really an option for a longer piece.

So, whats the standard for a task like this? Mount a vise to a sine plate? Special vise jaws? One of those funky angle vises? Im thinking a sine vise would be the best way to go in terms of both cost-effectiveness and work-ability. I did also consider an angle cutter of the proper angle, but ruled that out because, well, that only does a single angle

[MrFluffy]

I just clamp big things flat to a larger sine table I have for this reason, a combo of strap clamps, stop blocks and kant twist clamps keep it snug and let the cutter pass unhindered. Mostly it sees more action on the grinder than the mill though.

[3 Phase Lightbulb]

If you have a big boy mill, just angle the head

[Doozer]

I think my Bridgeport is the smallest mill that I own,
but I keep it around because you can tilt the head.

--Doozer

[Danl]

I always kinda wondered why no one ever put an accurate vernier on milling machine nod and tilt axis from the factory. Perhaps because it is so quick and easy to tram them in?

It does seem to me that a vernier would help get closer to a desired tilt or nod angle quickly, prior to using a sine bar or whatever one uses.

Dan L

[SGW]

Stress-relieve the stock first. Otherwise it will twist when you unclamp it.

[754]

It's a bit like asking how long is string,
A pic of the work, or accurate description... would lead to better answers.
Too many scenarios out there

[Paul Alciatore]

You want to make a dovetail straightedge so the initial precision of the angle is probably not all that important. You could probably tolerate a range of 0.5 degree or so and count on scraping to bring it to the final value. (Sine(0.5*) x 0.5" = 0.004" to be scraped away).

But you do not say how long this straight edge is going to be: 2", 6", 12", several feet? Obviously an angle vise would be just fine for up to 4" or so. With some parallels you could extend that to 8", 10", or even 12" or somewhat more. You would put the parallels in the angle vise and mill one end of the straightedge. Then slide it down by 4" or so and do the next section; continue until it is done. Heck, you could do 10 feet that way with some outboard supports.

I have used three simple vises on a milling table to hold long, thin panels (3.5" x 19") for milling. There is no reason why you could not use three or more angle vises in a row to do a longer straightedge. Put them all on the table and set the angle on one as accurately as you wish. Place another one next to it and use the work piece (straightedge) clamped in that first one to set the angle on the second one. Repeat for the rest. Then spread them out on the table and again use the work piece (straightedge) to align them: check with a DTI.

Of course, you could buy an angle cutter. These are somewhat difficult to find, but they do exist. Then you just clamp the straightedge to the table top. But then, you already thought of that.

[BCRider]

It's all so dependent on what you have to work with.

But if it were me that wanted to make a 12 or 14 inch long bevel edged straight edge like object one option that springs to mind on my tilt but no nod mill would be to use the Y axis to make up an angled support block. That block would then be cut into pieces that I could use to support the work piece along its length at suitable spacing. Sort of like a set of small sine tables spaced at some distance that limits any flexing. These supports would be trammed and clamped and finally the cut would be made on the suitably supported work piece.

Another option would be to set up some similar supports that are clamped in place. Then mill a U channel across all the supports. Against one end I'd put a length of drill rod that would support the work up on the proper angle. The width of the saddle grooves and diameter of the drill rod having been checked in CAD to provide a good seating for the work piece such that the proper angle is produced.

There's likely a lot of other options. These are just two related ones that sprung to mind.

[J Tiers]

For a dovetail straightedge, you do NOT need an accurate angle. In fact it is much better if the angle is somewhat less than that of the dovetails you will be doing. That way it fits in, and is easier to get to lay flat against the work for spotting. So if you want to do 60 deg angles, you can make the angle of the straightedge less than that (more acute), so that it always fits in. Maybe 55 deg. If you think you might need to do 45 deg dovetails, you may want to go with less than 45 deg, so that you do not need to make another one..

That way, your angle is fairly arbitrary for the SE, and your need for accuracy is a lot less.

For accurate setting of angle, make up an angle block for each angle, as you need it. Need not be more than an inch or two wide.

Yes, you CAN make the thing at a precise angle if you like, but you may find it pretty limiting.

[Peter.]

I made a dovetail straight edge by scraping a piece of cast iron that had been milled at an angle. It came out nice and did the job I asked of it, but when I went to use it again 6-9 months later I checked it on a plate before use and found it had about 3-5 tenths bend in it. Had to re-scrape it flat again.

[gzig5]

I made a 13" prism for dovetails by setting up in the 6" Kurt which was mounted on an adjustable plate. Tag ends were supported with machinist jacks, but not perfectly rigid. Had to slow the feed down when way out on the ends but worked fine, it scraped in quickly. Probably got more variation from the wear in the table over that length than the setup.

[Mcgyver]

as has been said, you do not generally use the straight edge to gauge or set the angle, although you can. I would leave the straight edge acute as there is rarely a need to get the angle exact (do you want redo your straight edge because the next dovetail is 59.9 degrees?). Make it quite a bit less and it ill work on 55 degree dovetails as well. You only need one side of it flat and thats done by scraping, the other is just clearance - put it on by tilting the head.

[epicfail48]

The dovetail straight edge was more an example of the type of angle, not any sort of actual project. Not yet at least. Just a question I've had floating around for a while. I know that the big boy mills can nod the head to accomplish this, I was wondering how people accomplish it with mills that can't nod, like the smaller benchtop mills or a horizontal mill

[kitno455]

I made a single sided dovetail straightedge by placing one edge of the stock in the T-slot in the table, rotating it to the desired angle, and holding it down with various clamps.

allan