Grind stone for drill grinding jig

Tried out one of these today. Results were hit and miss but I got two good drills out of it from a short try.

The worst part was the grindstone as it spun would only contact on a tiny part of the wheel and vibrate everything as it did so.

With the stone being the one to come with the grinder would a better stone have less axial run out? Even better is there any sort of stone designed to be used on its face?

The grinding wheel has to be dressed so that it is perfectly round prior to sharpening tools. A separate grinder, just for sharpening drills and cutters is recommended. See link for dressing with a rotary type tool. Diamond tipped dressing tools are also available.

**LINK**

Edited By Paul Lousick on 15/06/2017 23:44:32

Issue is that instead of using the periphery of the wheel this jig uses the side. I don't think I could do a very good job of dressing it to be perfectly flat.

I have a cup like wheel on my bench grinder, so I can dress the wheel both on the periphery and the side.

Thor

As an apprentice, we were taught NEVER to use the side of a grinding wheel !
BobH

I was also taught not to use the side of the wheel but I suppose most of us do use it lightly on occasion. Like Thor I have a cup wheel mounted on one end of my bench grinder, great for grinding drills and "Splitting the drill point"

I was also given that advice but in the real world I used the side for all types of grinding where necessary. It's perfectly safe with care i.e. don't ram the cutter/drill into the side of the wheel, take it gently!!!!

Tony

There are several reasons why you don't use the side of a grindstone, I've listed some below....

1) They are designed and constructed for face on use only

2) it causes imbalance in the stone

3) it weakens the structural integrity of the stone

4) with side use it can result in stones exploding (I've seen it happen)

5) the rest doesn't wrap around the sides

6) the guard screen doesn't cover the sides

7) Repeatedly using these types of drill sharpener can result in a large groove in the stone effectively cutting off a ring of stone

We all do it, We don't think about it when we do, Done within reason it's probably perfectly safe.

Health and safety applies even in home workshops (even if not legally enforceable)

Wear goggles not glasses, use with care & common sense !!

Tony

Maybe it's me but, I don't see why that type of drill grinder cannot be used on the face of the wheel, after all, the face is flat at the point of contact.

Brian

Hi Rainbows,

I think that one of the key problems with using a jig and a bench grinder is that most grinders have rubber feet allowing them to vibrate independently of the jig. The first job IMHO is therefore to firmly fix the grinder body to the same base as the jig. Then as others have said dress the grindstone face that's being used.

The only decent way of doing this for accurate grinding is with a controlled single point diamond IMHO. You can use devilstones or diamond matrix dressers but IME it simply results in a wheel face that's still very uneven and pitted IMHO. Ok for freehand grinding but not much use for precise jig work.

I don't see any reason why you can't use the drill grinder jig on the front of the wheel but it would mean getting your other grinding rests, if you have them, out of the way somehow. Harold Halls mag-bases would provide the obvious answer to achieve this though... **LINK**

Grinding on the front edge also means your drill cutting edges would need to be horizontal when they are ground. The primary clearance facet would be flat enough in the end but the secondary clearance (assuming a 4-facet drill grind) will end up hollow-ground but under most circumstances that's just fine.

HTH

Jon

With a decent grinding rest (I use a Harold Hall design) it is quite practical to use, and dress the side of a grinding disc. With a wiping action, no grooves are worn and the HH rest actually has an optional attachment for using the side of a wheel.

My drill sharpener (similar to that shown) has a moving base parallel to the wheel face and works quite well after I added HH's 180° rotation stop.

As for safety, always wear goggles/ face mask when using machinery in the workshop.

Have fun, stay safe * Danny M *

but it does still mean ......

you are using a stone for a purpose it wasn't designed for.

you are still making the stone narrower

You are still undermining its structure

I advise goggles based upon the fact that sparks always find away around Glasses and masks into the eyes !!

But It's you're choice....

Tony

I've used the side of my grinder for years with my reliance drill grinding jig you can pick them up at autojumbles sometimes,they're really good, what I do is [depending how blunt they are] hand grind on the front as you "should" then they just need a tickle on the reliance, & as for dressing the wheel we allways used a single point diamond when I worked in the glass trade but a better way and cheap as well I just bought a diamond stihl saw or 4" angle grinder blade the cheapo ones not the genuine ones[unless a "bargain "] then I cut them into segments like cutting a cake so they're a couple of inches wide at the periphery & they'r fantastic for dressing & no grooves.I won't add the old H & S stuff we should all know it off by heart now!!

+1 for putting both grinder and jig on the same base without rubber feet.
The real reason for workshop warnings about using the side is because halfwits jamming a tool into a clogged wheel heat up a ring and it is thermal stress that breaks the wheel - not a problem with sensible people.
A single diamond dresser is quite fragile so not suitable for use on a bench grinder. They are for taking off a few thou on a rigid T&C machine.
The root of the problem is the wheel mounting unless you are using an ancient jumble sale worn machine. Check your flanges and mounting washers. Don't leave out the plastic or cardboard washer though thinking that direct metal contact will be more accurate - it is there to allow for thermal expansion.

There was a thread on here about 3 years ago describing improvements to these jigs and significantly how to set up and use them. Was that Harold Hall? I recall more than is on his website.

I have a CBN wheel with side and face abrasive surfaces. I have a base board with the drill jig on it, the grinder and an xy tee slotted table. You can safely use the side of the CBN wheel as it is a metal substrate not a bonded grit wheel. There was a recent thread on the subject of these CBN wheels.

On my grinder one wheel is the original used for roughing work the other is the replacement CBN wheel, they complement each other well.

Martin C

Those CBN wheels look lovely, that said I don't have the cash to splash on a grinding wheel like that. Will put it on the wish list.

After finding cup wheel dimensions I found a 150mm wheel has only 10mm of abrasive, as mentioned not too good.

Will try remounting everything more solid and then have a go trying to dress or otherwise shim the wheel and see how that goes.

Hi Rainbows. Keep trying with this basic jig. once you get the hang of them they do an acceptable job for most sizes down to about 6mm. the shortness of the drill becomes the problem then. The vee shaped sliding support at the back, in front of the thumbwheel; doesnt need to be as long as it is. I have cut away about half of mine and this enables you to get much shorter drills into the jig.

Two things that I have noticed in using it, that I didn't forsee are -- 1 the projection from of the tip at the front is different depending on the drill diameter and for me was smaller than I expected. and 2 --- . the need to turn by 180 degrees is important. Harold Hall explains both these very well on his website and in his excellent book on grinding and sharpening tools. He also explains very clearly why these types of jig will not work very effectively on the front of the wheel.

I have made a little angle gauge from a piece of scrap 1/8 plate so I can check the angle of the centre rib on the drill . this should be 130 degrees from the cutting edge and by getting the correct amount of tip projection it sets this angle this angle right . basically use one reference to check the other.

I agree with JS that the issue of side loading the small wheels on our usual home grinders is very low risk and the main issues with wheels bursting goes back to days when very different types of bonding agent were used to make the wheels, compared to the modern speciality adhesives we have today.

That said, using the side of the wheel is not covered by your normal installed protective guard and so a separate additional piece of impact resistant plastic sheet mounted on a simple stand between you and the wheel and drill jig is an easily made and very effective protection measure that costs pennies. This is in addition to your safety goggles or glasses, whichever you choose to use.

Keep practicing with it. once you suss the jig, it becomes a pleasure to have nice easy free cutting drills. It will never match a four facet grind, but the jig is cheap and imho you get good value for what you paid.

Just as a little sideline to this, a few years back I bought a set of cheap diamond files with 4" blades, they are the most useless and disappointing things I ever bought, but, for dressing a wheel they are excellent, I've even put grooves into a wheel for certain jobs (a spare wheel). Just remember to have your rest nice and close to the wheel or use the file freehand a good way up from the rest.

For drill sharpening I use a little adjustable rest that I made for sharpening lathe tools, this keeps the cutting edge at the right angle, then all it needs is a lick on the side of the wheel to give a tiny bit of clearance, (this is the only time I ever use the side of a wheel).

I always find the HSE guidance very good for this type of question, now everyones going to say - health and safety only designed for stopping people working I've been doing it for X years without anything happening etc., but when you actually read the guidance you do find very good advice, with surprising results of what is actually illegal (very little as it happens) and what is just good practise (or not), the key is always taking the correct precautions.

With regards to side grinding they do not recommend it but do recognise that sometimes it is necessary, have a look at section 38 of the guidance for grinding wheels:

**LINK**