This is how it was done before CNC!!!

[widgitmaster]

First I started with a chunk of round cast iron, because it is soft, east to machine and strong!

I faced both sides in my lathe and turned 1/2 the diameter until it was complete.

Then i bored and counterbored a hole in the center to accept a 1/2" diameter shoulder bolt with .75" long shank, making sure the head was slightly below the surface. The bore was a close slip fit for the shoulder bolt.

Then I grabbed another chunk of cast iron, and machined it to 3"x1.25x.750
Then I drilled a shallow hole in the center of the .750 wide side, 3/8 in from the end. Then I bottom tapped the hole for 3/8-16 UNC, to accept the thread on the end of the shoulder screw!

Then I drilled and tapped a 1/4-20 UNC hole in the other end of the cast iron block to be used by the handle.

Next, I took the cast iron disk and machined two flats 1/2" deep on the counterbore side, leaving a 3" wide parallel surface to be used when clamping it in the vise.

Next, I calculated the distance for the stop pins, as .375" + .125" =.500
Thats half the .740 block and half the pin. then I moved X-axis .75 on either side of center, and Y-axis .500 to drill anad ream two slight press fit holes for standard dowel pins.

Once the block was fastened to the disk with the shoulder blot, I dialed the disk in one more time and drilled & reamed a press fit hole in the rotating block for a 1/18" dowel pin. Drilling it after assembly ensures the 1/8 dowel will be exactly in the center of rotation!

Then I grabbed a 1/2 dia x 3" piece of 303-SS and drilled & tapped the ends for 1/4-20 UNC, then I ran a piece of 1/4-20 threaded rod in until it jammed tight in the bottom of the holes, and bandsawed off the excess, leaving a 1/2" of useable thread!

One end screwed into a little 1" dia plastic ball-knob, the other screwed into the rotating cast iron block.

then i made a little block from scrap cast iron, to be a clamp which holds my little parts on the pin in the slot on top of the rotating block!

I put the fixture in my mill vise, dialed in center, and again calculated the offset for the cutter. The cutter is a 5/32 dia 4-flute carbide endmill, so the offset is radius + (1/2 cutter diameter)

[widgitmaster]

Then I ran of each of the little 303-ss blocks, which all have been previously machined to .3125 +- .001, and have .126" dia reamed holes.

The spindle was running at maximum RPM (1875 on my mill), and there was little effort required to swing the part next to the endmill. I found that roughing it down to the last .002, and then blowing the chips away from the stop pins and then climb milling the last .002 gave the part a nice finish!

Then It became obvious that I needed to undercut the fixture about .025 smaller radius, so that I could get my little jewlers screw drive blade under the finished part to pop it off the pin!

Then I noticed the pin was tighter on some parts than on others, so I dismanteled the fixture, removed the 1/8 locating pin, and ground a small flat on either side of the pin. this helped compensate for any location error in the holes, and the remaining diameter of the pin would ensure the radius was centered on the hole!

[widgitmaster]

Now that all the parts have a .15625 R on the ends, I needed another fixture to machine a little 60° dovetail on the other end of my small parts!

So I grabbed a block of low carbon steel, and milled it flat and square. Then I milled 6 slots equally spaced and drilled & reamed 6 holes for more little pins!

This allowed me to mill a dovetail on six parts at a time!

The end result is a little dovetail clamp to be used on B&S BestTest dial indicators!

[mxpro32]

Hey widgitmaster, you always have such good results machining cast iron. I need to ask you what your technique is. I have the harbor freight rf clone and whenever i attempt to machine cast iron the endmill gets hot really fast and if i use hss the cutter gets ruined really quick. With carbide i have some success but it is still an excrutiatingly slow process. I've had the best luck with low rpm and slow feeds but i still have to stop to cool the endmill down between tiny passes. any advice?

[widgitmaster]

I use a carbide shell mill at 1875 RPM, it gives an excellent finish!
But at $10/insert, it better cut good!

HSS will work if you run it slow!

There are many grades of cast iron, some are really bad!

High grade C.I. doesn't have all the sand and scrap metal in it!

I buy mine from SpeedyMetals, it is really fine grain "GREY CLASS 40 CAST IRON" , and rarely has hard spots!

The only time i use coolant is to keep the dust down; however, I have used the spray mist without liquid to blow the chips out of a slot, so the endmill doesn't keep re-cutting them!


Eric

[miljnor]

Nice work man.

I found that when I was Manuall only I had to think alot harder to get things done right. Otherwise you end up doing things over again.

Thats one of the problems with all these guys coming from CNC schools, They try to overcompensate with programming and poor fixturing insted of using the old Brain pan!

[lakeside]

I went from manual machining to cnc not because I'm smart,But because I'm lazy.just ask my wife

[Chuck Pressure]

Eric,
Nice job on the radius fixture! I'm not cnc at home either, I'm looking for some widow to sell me a volstro rotary head for fifty bucks or so!!!

[Mcgyver]

Nice work Eric! both on the indicator bits and radius fixture

mxpro, what speed are you cutting at? - max speed of 80 fpm hss and maybe 200 fpm carbide. CI, unless its crap with chilled spots, machines beautifully once you are under the 'skin'

[widgitmaster]

Thanks Guys!
I have been busy making little stuff in my spare time!

Eric

[widgitmaster]

Today I made the second radius attachment for the fixture, it used two dowel pins to locate the small parts for milling the .15625 R The block was another piece of cast iron, and the procedure was the same except for the method of locating and holding the part! I had to drill and ream a 2nd set of 1/4" dowel pin holes in the fixture base, as these parts have a different starting and ending points for the radius!

The use of CAD enabled me to get the tangent points so good, that
I could not see or feel the start and end of the radius as it blended in to the rest of the part!

After the radius was milled on all 15 parts, I dismanteled the fixture and used the cast iron block in the mill's vise to drill and ream the small center hole!

Now that all the parts are machined and deburred, I pressed little pins in the new parts, and assembled all the indicator adjusters !

Now that was a fun project!
And the fixtures will make it much easier to make up another batch!

Total expense for dowel pins, springs, and 303-SS bar stock brought the cost of manufacturing these little adjusters to $11.47 each!

Want one? Send me a PM!

Eric!

[widgitmaster]

Well, I have been making another batch of my little indicator adjusters, but this time I made a movie of it!


VIDEO


That little radius milling fixture I made is a real brease to use!
Eric