I don't have a set of those angle blocks. Normally I'd just order a set -- they're pretty cheap on ebay. But the guys selling them on ebay I haven't had a lot of great experiences with, and anyway nowadays I have more time than money and I don't *need* a whole set anyway. I just need a 10° setup wedge, 6" wide (like my Kurt vise) and about 1/4" thick. I can think of a few ways to make this part but they're all a pain in the butt. I do have a
5" sine bar and a set of spacer blocks. Also, a milled finish is OK, I don't really need a ground finish. Anyone got any really clever ideas? This NG has so many great machinists on it, I had to ask.
You're gonna want to start with rough cast iron shapes. And, short of hand corrections (e.g., scraping), your results will be limited to the errors of alignment in your machining tool, which are likely far worse in magnitude than your sine bar gages.
I would like to hear suggestions too. For a low tech reasonable accuracy, I would rough the part out with the band saw. Mill the bottom flat. I would then put the piece back in the vise and set the angle with a sine bar. Mill the top flat.
For something that thin, I draw up what I want in CAD, draw a couple 1/8 holes parallel to and just below the angled surface. Dimension it out, rough out your blank, drill the holes. Place pins in holes, set in vise so pins rest on top of jaws, and clamp. Machine until it cleans up. You can also at this time either leave a step at one end for a stop, or drill/ream a few holes for removable stops. If it's for a repeat job, I layout and put the holes in one side of a pair of soft jaws. Q&D fixturing!
I've done similar things with steel or aluminum and a 2.5" sine bar in my shaper. That makes a nicer finish than a miller does. Even nicer is to rough it out on the shaper or mill, and use a surface grinder (again with the assistance of the sine bar) to grind a much better finish.
My sine bar is 1" thick. Also, if I set up the angle on the sine bar in the Kurt vise, it sticks right out the top. I could use some kind of spacer block to make the moving jaw bear on the part (spacer block above the lower part of the sine bar) but then the Kurt vise would only be clamping on one side. Same issue with my grinding vise.
One block between the work piece and the movable jaw.
If you're worried about your cutter hitting your sine bar, just place a spacer under the work piece, on top of the sine bar. Using the rolled surfaces of CRS stock should be sufficient (in tool making, manual mills are roughing tools).
Or, you could do what you would do on the grinder and that is to clamp the work piece to an angle plate. Use at least two clamps. Obviously, once the part is clamped to the angle plate, there is no need for the sine bar. Make sure the cutting forces go _into_ the angle plate, not away. Obviously, you'll need to clamp the angle plate to your mill. I suppose you could clamp it in the vice in a pinch, but you're kind of stacking errors at that point. Better to use strap clamps or similar to clamp directly to the table.
Grant Erwin wrote in news: firstname.lastname@example.org:
Another way might be, lay it down on the table. You could use a straight edge and the sine bar to position it (and you could create the straight edge in place in a first pass, so no gauging). Seems to me this would be pretty accurate, I'm curious what others think.
======================================================= There were many good suggestions given, however I think there is a simpler way.
In too many cases we get so used to using accessories and attachments such as vises, we forget that these are sometimes not the only or even the best work holding solution but rather were developed for speed/ease of production by semi-skilled operators.
I suggest that you begin by squaring up a suitable piece of material, and drilling two holes to bolt this to an angle plate. On a surface plate, mill table or other flat surface, use your sine bar and a parallel to set the material to a 10-degree [or what ever] angle with the edge poking up over the top of the angle block. Bolt the material to the angle plate [or use toe clamps]. Put the sine bar, parallel, etc. away. Bolt the angle plate with the attached material to the bed of your milling machine, and bolt down. Mill down the material to form the 10-degree wedge, taking care not to hit the top of your angle plate. Be sure your mill head is accurately trammed to avoid concave and or slanting surfaces.
Note that by first using a sine bar to accurately set the vertical angle, and then using the sine bar to set the horizontal angle from the face of the angle plate to a reference datum on the mill table, you can accurately drill holes or machine surfaces at compound angles (with a little computation) with almost no cost for tooling/fixturing.
While I am sure there are many suppliers of suitable angle plates, Enco has one that should be appropriate for this use at about 13$US. [See
details.] If you want better accuracy you can get these with a ground rather than machined finish, or go for the high priced spread and buy from Suburban.
Square up your material, scribe a line at 10 deg with a combination square, bandsaw off excess material, clamp in vise and mill to scribe line. Now that you are close, set your new angle block on your sine bar (set at 10 deg). use a dial indicator to check the height from one end to the other. Now, clamp the angle block in the vise(without the sine bar). Use the dial indicator mounted in the spindle to adjust the top of the block to the same reading as you got with the sine bar. Now take a cleanup cut.
If you've seen my article in MWN on making my lathe tool holders for carbide inserts,
you'll note that I casually mention my 5 degree wedges. I made these pretty early in the game before I had gage blocks and a sine bar. I squared up a piece of 1/2" square rod about 2" long and clamped it lightly in my milling vice. Using a dial gage in the mill head and one on the X-axis, I (patiently) tapped the piece into position such that over a 1" length, the rise was Tan(5), 0.0875". I then took light cuts (so as not to shift the piece) until I had taken a bit off the low end. I made the second by supporting it on the first since I now had a 5 degree angle block.
I know it sounds crude but several years later when I had a sine bar and gage blocks, I measured the angles. One came out as 5.01 degree and the other as 5.00 degree as close as I could measure them.
Since I'm done now, I thought I'd post a summary of sorts.
1) Square up the block (this step goes for all succeeding methods)
A) Ted's method below: use 90° opposed dial indicators (rise/run) to dial in the angle in a mill vise, mill gently unsupported. B) Dial in an angle plate square and set up the sine bar in front of it and use parallels to raise the block so one edge is above the angle plate. Clamp and mill. C) Clamp a thick parallel to the mill table and dial it in dead parallel. Put a sacrificial piece of MDF up against it. Lie the sine bar/spacers on its side up against the parallel and hold the part firmly against the sine bar and clamp it in position. Remove the sine bar and parallel and add clamps and then mill the angle. D) Put the block on parallels in the mill vise. Use the DRO to locate, drill and ream 2 holes at the correct angle. Press in 2 dowel pins and then hang the part from the dowel pins on the top of the vise jaws and clamp firmly and mill.
I wound up using (D) above and it was easy but somehow the angle came out quite a bit wrong. Maybe a chip got under one of the dowel pins or maybe the part moved, anyway it was off by about .008" over 4". I simply used shims under the dowel pins and remilled one pass. Then I transferred it to the grinder vise and, using the same shims, ground the angle face. Upon rechecking, I saw an error of about .001" in 4" so I added a layer of one Zig-Zag (cigarette paper) and reground it. It's now very close. Then I used that block to machine another one (the complementary part I'd previously bandsawed off, love that bandsaw) and it came out dead on.
Once I had 2 angle blocks machined to the same angle, I used them in the vise to clamp the (otherwise basically rectangular) toolpost I've been making in the vise, and quickly milled the angled slot in the side.
Thanks to all who contributed. Lots of great ideas. By the way, I've had terrible trouble doing cutoff on my 9" South Bend forever. I talked to two of the best machinists I know both of whom owned and ran SB9s for years, and they just shook their heads and said "Been there". The MLA rear toolpost I made is done enough to cut with now (still a few cosmetic touches to go) and the first test cuts are very very promising. Like buttah in sticky mild steel. Today or tomorrow I'm going to part off a 1.5" piece of 4140 and that will be the test. So far I'm real real happy.
Just to overgild the lily, I'm going to list all the things I'd tried before:
1) Armstrong cutoff toolholder with HSS blade held in SB rocker TP
2) Aloris #7 with HSS bit held in an Aloris AXA TP
3) Aloris #71 with .125" carbide inserts held in AXA TP
4) cutoff blade/block with .087" carbide inserts held in AXA TP
All of these had in common being held in toolposts mounted on the compound. I think the compound on a SB9 isn't really rigid enough to do parting. The rear toolpost is mounted very solidly indeed to the MLA cross-slide table which has T-slots. I'm using a 1/8" Cleveland Mo-Max bit held in an Armstrong toolholder upside down in the rear TP and my first cuts didn't need any cutting fluid and weren't very sensitive to feeds and speeds. I didn't even hone the toolbit. Major giant huge difference. It now does cutoff better than my 15" Cincinnati lathe which is about 10 times as massive.
I made my rear TP exactly to Andy's plans. There isn't much point in me posting a picture. See