Building Harold Hall's Simple Grinding Rest

[pontiac428]

With a white cup wheel, I can do 1/4" 2-flute end mills easily. I could probably do 1/8" 2-flutes but haven't tried

With a CBN cup wheel, the smallest I've done is sharpen face only on 1/4" 4-flute mills. If I wanted to do more than the face, I would need a nice flaring wheel in order to reach the relief cuts and back cuts. That is all moot if I can't grind fine gashes. I need another wheel for that. Flaring wheel helps with those clearance and back cuts and will gash 3/8" 4-flutes (white wheel).

I don't know what the smallest flutes I can sharpen are. Probably pretty small, like 3/16". It's easy but dependent on having a fluting fixture. It also changes the diameter of your mills and drills, so I only do it when the flutes are dull. Keep spare band-aids on hand for this.

 

[HBilly1022]

For sharpening the ends of end mills I made one of these HH jigs. http://homews.co.uk/page124.html. This was the first of his jigs that I made and still use it for all my end mill sharpening (ends only). I have since made the simple rest, the advanced rest, the end mill flute sharpening jig, the lining tool and many other jigs. But I still use the end mill sharpener in the above link. I have one wheel on one of my old grinders that is dedicated to this use. It is so simple to use and does a GREAT job. I have found that there are 2 important issues to pay attention to for a successful grind; 1) the width of the primary land should be very small and 2) the side relief angle is very important. If either of these is not adequate the end mill will rub instead of cutting and will cause all kinds of grief.

BTW, for the spring steel on the slitting saw fixture, I used some of the metal banding that is used for wrapping heavy packages. It works very well and it's my favorite price, free.

 

[stioc]

@pontiac428, that's pretty neat you can sharpen endmills that small with the tool grinder. I think 3/16" will be tough to do on this one.

@HBilly1022 glad to see there are a few others with Harold's rests out there. I wish I had made the advanced rest, it seems easier to use. Oh I've seen that endmill jig on Harold's site before but it's redundant for me with having made the simple rest first. The rest requires a bit more setup time but I'm getting more comfortable with it. Still making more accessories.

Last night I made another go at the 1/2" endmill holder., The hole is concentric up to 3/8" but going to 1/2" makes it out of center in two planes by about .030". Not sure what the deal is. I'll just skim the .030" off the square bar so it's concentric to the hole's center on all four sides.

I ran with it anyway using this 1/2" shank endmill as the test subject, it was pretty buggered up:

During (creating the gash and back clearance):

Done:

Cut two steps as a test:

Also did the chisel again.
Before:

After:

Edit: nevermind my previous comment about the rest's position. He was sharpening on the right side of the endmill, I sharpen on the left. duh stioc!

 

[stioc]

@pontiac428 I got the Norton cup wheel and as I'm thinking about the adapter for it I have a couple of questions about the width and also the plastic bushings.

1. So when I took off the existing cheap wheel, it has a plastic bushing in its arbor hole. Is that needed for the cup style wheel if I'm making the flange/adapter out of aluminum?

2. Below is what I'm thinking of making. What should the width of the flange/step be that the new wheel will sit on. See the red lines in the pic. Should I make it slightly thinner than the actual width of the wheel's hole? That way when I tighten the original clamp it clamps the the wheel and not the adapter. So may be .05" thinner?

 

[Technical Ted]

Look inside the HH book you have... he has drawings for what he recommends. I made these and they work well. In fact, I'm now using them on my KO Lee tool and cutter grinder.

No, you don't need the plastic insert. It's just a spacer for a 5/8" grinding wheel to adapt it to a 1/2" arbor. Just make your wheel adapters to fit your grinder's arbor.

Ted

 

[stioc]

@Technical Ted thanks for the info. I didn't know KO Lee tools and cutter grinder uses a 1/2" arbor.

I did see Harold's design, he uses a two piece system (a bit more work -I'm lazy) but I'm hoping a simpler one as pictured above will do an adequate job since they were/are sold for the same purposes.

 

[Technical Ted]

@Technical TedI didn't know KO Lee tools and cutter grinder uses a 1/2" arbor.

Depends on the model. Some use a tapered spindle like a lot of surface grinders do. Mine has 5/8" straight arbors.

The good thing about Harold's design is using two halves held together by bolts helps keep the wheel in the place on the arbors. Since you can't have a really tight fit, since the holes in grinding wheels are not held to tight tolerances, when you remove/re-mount a wheel it will not be in the same place on a simple sleeve as it was when first mounted and dressed. It will require more dressing to get it to run true every time it is mounted. His design will minimize required dressing in the same way the wheel adapters do in surface grinders. Make the ID of the sleeve fit the grinder's arbor with a nice,, tight slip fit. This would only be an issue if you change wheels for different grinding operations. If you leave one wheel on all the time it's a moot point.

Oh, forgot to mention, for the nicest grinds, you'll want to dress your wheels accurately so they run very true. You can use your grinding fixture, one of the holders you made for it and a diamond dresser to do this. This isn't absolutely necessary, but will really make some nice grinds. You can dress by hand with a dressing stick, like a Norbide stick, etc., but the diamond does a better job. I even make a little holder for a diamond for my pedestal grinder where I hand sharpen bits.

Ted

 

[pontiac428]

Make one arbor per wheel of the locking type. When you dress that wheel, it sets it's center based on the relationship between spindle, wheel, and arbor. Thus, the arbor and wheel are married. They change as a pair, one arbor per wheel.

 

[stioc]

Make the ID of the sleeve fit the grinder's arbor with a nice,, tight slip fit. This would only be an issue if you change wheels for different grinding operations. If you leave one wheel on all the time it's a moot point.

This! I won't be changing wheels, if/when I feel the need I'll put a different wheel on the other side of the grinder. So back to the simple adapter/sleeve - I measured the width of the grinding wheel's hole and it's .47" - probably .5" nominal size so I'm going to make the step of the adapter .40" that way the clamping washer puts the force on the wheel and not on the aluminum flange.

Thanks for the other tips and truing up the wheel etc guys, makes perfect sense.

 

[stioc]

I got the adapter done tonight and excited I mounted the new wheel...holy vibration batman! Not that the grinder didn't vibrate before but this is worse.

I put an indicator on the two surfaces that the grinding wheel sits on, the back and the center of the adapter- both are just about .0005". The fit is a nice slip fit on both the arbor and the wheel, I was actually proud of myself there.

So, I don't know what the deal is...I haven't trued it up, so may be that will help?