Split Point Drill sharpening

[Frank S]

When ever I replace the wheels on any of my bench and arbor grinders which is rare, the first thing I do is true all 3 sides of the wheel.
This aids in getting them balanced also reduces the likely hood that the wheel will have problems later in use life.Helps the grinder to run smoother and quieter.
in my 55 years of being around bench arbor and hand held grinders I can count on 1 hand the incidents I have seen a wheel fail none have ever been from grinding on the sides. I don't make a habit of using the sides of a wheel as the primary cutting surface but when or if the circumstances dictate I will use them.
Where I have seen people have problems in in not keeping their wheels cleanly dressed and grind until they have deep grooves in their wheels usually I see the groves directly associated with the angled "V" grove in the tool rest that so many use as a guide to sharpen their drill bits. I don't like having those made in groves and do not use them most of my bench grinders do not have one. I prefer to free hand and move the drill bit or tooling cutter across the entire face of the grinding wheel. My thickest grinding wheel is 1 " and even at that it does not have a wide enough surface area to sharpen some of my drill bits So I will get the profile as near as possible then finish up on the side or finish up on a belt sander.

[tonyfoale]

When ever I replace the wheels on any of my bench and arbor grinders which is rare, the first thing I do is true all 3 sides of the wheel. .....

In my experience even cheap grinding wheels are made very flat and of even thickness. If that is generally the case then any lateral runout must be due to the grinder itself. Bench grinders generally have wheel washers which are quite thin and which bear up against inadequately sized shoulders on the shaft. This locates the washers very poorly as regards to wobble.
This is easily attended to and only needs doing once for any particular grinder.

I junk the inner washers and make a combined washer and stub shaft to hold a wheel with a larger diameter hole. I make this washer/shaft piece to be a light push fit on the grinder shaft. Unless the grinder shaft is bent this ensures that the washer will hold the wheel with the minimum of lateral wobble. Only rarely have I needed to true the sides of a new wheel.

Click for full size images.
Wheel with oversized hole.


This shows the comparison to the usual stock wheel inner washer of the custom washer/shaft that I use.

I use the narrow style washer on the outside of the wheel because that is free to align with the wheel, all the location is done by the inner custom piece.

[olderdan]

Tony, I am in full agreement with your observations, on my bench grinder the locating shoulder for the inner washer is only 2mm larger than the thread, couple that with a cheap stamped washer its not surprising that run-out is common. The only only wheel that has run true from the off is my CBN cup wheel and that is the one I had to make a custom mounting for. The next time I need a wheel change I will copy your idea.

[DrengusCraic]

Thanks for finally explaining it well. Dad was a mechanical engineer (10+ us patents) and he could never explain it to me in simple lay terms as you have. My evidence is a box full of inconsistent bits. Now if I can find the time for resesutating 100 bits.

[bobneumann]

Thanks for your feedback. That's my whole purpose in making videos is sharing back some of the things I've learned along the way. Your post has made my day!

[NeiljohnUK]

Yup, life is 100% fatal.

[Toolmaker51]

Alright, I've a hack this thread reminds me of. Are there extra points if a thread hack and a work trick coincide?
Tony's 'bushed washer' for bench or pedestal grinders seems related, to an odd surface grinder application.
Lots of surface grinders carry 1.25 [31.75mm] ID wheels. Generally the wheel shroud/ guarding indicate largest wheel diameter, zillions are 6", 7" and 8". Average surface grinders, 5" x 10", 6" x 12", 6" x 18" use them, and lots of cutter grinders can. If you examine wheel catalogs, their prevalence is clear. . .

Between ticket work, I'm trying to get their shop more operative. Let's just call it a Herculean task. Like horizontal mill I've run, until riggers dropped it about 20 inches. . .but wait; there's more!
You know when someone thinks out loud? I'm writing the same way, working out day-end events. Follow along while I ramble.
For a reason I have no explanation, what look like comparable sized machines still have 1.25 arbors; inside a 12" shroud! Puzzled, I've looked for 1.25 x 12 wheels, knowing they'd be rarer than hen teeth. Yeppers, none found.
Examined the machine further, this case happens to be an auto-feed Thompson, cast iron everything. Even the base, with cast-in baffled coolant reservoir. Tag indicates a single voltage motor, but capable two different RPM 1500 and 3000, by switching leads [not direction, or change 220/440, RPM only]. Smaller wheels, higher RPM's. Bigger wheels, lower RPM, increased diameter creates the effective FPM [Feet Per Minute].
Our wheel storage is all 6 inchers, and one 8, still 1.25 bore. In a box of grinder stuff [I found], a weird looking bushing [I think] like Tony's but slightly different [I guess] for the 'front' of the wheel. 12" wheels are 3" bore. This spacer [steel] is 3 plus, maybe someone didn't finish it. I have to look, yes spindle is 1.25, but outer washer is larger than a 6", 7" or 8" would use, probably spindle flange is too? Checking that tomorrow.
Getting this machine on line's a benefit, especially with the 18 or 20 inch magnet.

[tonyfoale]

Tag indicates a single voltage motor, but capable two different RPM 1500 and 3000, by switching leads [not direction, or change 220/440, RPM only].

3000 rpm motors have two poles, 1500 rpm have four poles. Sometimes you find a four pole motor where all the winding connections are brought out such that with a bit of switching it acts like a two pole motor.
These two speed motors can be very useful on a machine tool, lathe or mill, because you can run at half speed with near double the torque compared to running a two pole motor at half speed with a VFD. This can often eliminate the need for back gears to go slow with high torque.
I had a lathe with a motor like yours 2/4 pole, I kept the motor when I scrapped the lathe (the bed was worn right down in one area due to its previous life) and I now use the motor on my shock absorber dyno. It is driven by a VFD but being able to switch pole numbers is handy.

Your motor must be 50 Hz not the US 60 Hz. The synchronous speeds for a 60 Hz (US made or sourced motor) would be 1800/3600 rpm. So under rated load yours should spin at around 3450/1725 rpm with reduced torque on American electricity or 2850/1425 rpm at specified torque on everyone else's electricity.

All the above assumes an induction motor.

[Okapi]

Click for full size images.
Wheel with oversized hole.


This shows the comparison to the usual stock wheel inner washer of the custom washer/shaft that I use.

I use the narrow style washer on the outside of the wheel because that is free to align with the wheel, all the location is done by the inner custom piece.

Speaking about washers which is another word for flanges as I understood, I give you an idea which comes from one of my fists parallels small jobs during apprenticeship, it was in a shop where they use one meter stone wheels for grinding paper cutters which surely doesn't exist now, they learn me to make flanges as possible with only a third of the diameter touching the stone, and now, making those flanges for 50 to 125mm. wheels in aluminum I make them with like a large band touching on the outside and a centered center as you explain, the recess is less than 5/10 of a mm., 300grams paper as inter-layer, that give good results when forming the outside profile with the Fluidmotion/Vertex tool which needs a very stable centering.

[Toolmaker51]

3000 rpm motors have two poles, 1500 rpm have four poles. Sometimes you find a four pole motor where all the winding connections are brought out such that with a bit of switching it acts like a two pole motor.
These two speed motors can be very useful on a machine tool, lathe or mill, because you can run at half speed with near double the torque compared to running a two pole motor at half speed with a VFD. This can often eliminate the need for back gears to go slow with high torque.
I had a lathe with a motor like yours 2/4 pole, I kept the motor when I scrapped the lathe (the bed was worn right down in one area due to its previous life) and I now use the motor on my shock absorber dyno. It is driven by a VFD but being able to switch pole numbers is handy.

Your motor must be 50 Hz not the US 60 Hz. The synchronous speeds for a 60 Hz (US made or sourced motor) would be 1800/3600 rpm. So under rated load yours should spin at around 3450/1725 rpm with reduced torque on American electricity or 2850/1425 rpm at specified torque on everyone else's electricity.

All the above assumes an induction motor.

'We' are correct; me barely, Tony accurate.
In my defense, the tag was very hard to read until cleaning it better.

RPM 1800/3600 60Hz 3PH 220V 4.7A



Side note, who is emulating who...?