The Artful Bodger's toolpost grinder.

[John Hill]

Work is progressing and there are even a couple of pictures to show!

The camera was not handy when I started the spindle but thats not special, just a steel tube with a bearing in each end and a shaft right through the middle.  The shaft is 3/8"  (about 9mm) and the ball bearings are salvaged from a photo copier.

The first picture show the base plate being trimmed using a fly cutter.



Of course no project would be complete without Sally Shaper doing her bit and here she is trueing up the side plates of what will become the tool post grinder.



The two side plates are moved to the lathe after chain drilling the rough shape of the motor cradle, here is the cradle being finished again with the trusty fly cutter.



Starting to look good,  the frame is basically complete and is mounted on the compound in what will be it operating position and getting ready to drill and bore the holes for the spindle.



Holes bored, the spindle sitting in place and motor resting in its cradle..




Progress so far...



I still have to do a few things,  the motor needs to be fixed to the cradle, I need to make some sort of chuck and of course I need to make pulleys and fit a belt.

The pulleys are the question, the motor claims 1/2hp at 27,000 RPM which I think is too fast for anything except very small diameter stones?  So what ratios should I  make the pulleys?   How about 1:1 for internal grinding with the small stones?  What is the slowest speed I should aim for?

As it stands the design would have the stone rotating same as the normal lathe spindle direction but if I added a lay shaft I could flip the motor and reverse the direction and get the speed down to say 3000 rpm, do I need a speed that slow bearing in mind the shaft is only 3/8"?

So many questions...

[dsquire]

John

Looking good. I like to see sally shaper earning her keep. I think your probably ok on the high speed for the internal but I think you may want a bit more than 3000 for external but a lot will depend on the diameter and specs of the wheel that you use.

Cheers 

Don

[John Hill]

Thanks Don, I am thinking I need to find the stone(s) I will be using for external work! I wonder what the maximum diameter stones I can find on a 1/4" mount?  

[sbwhart]

Hi John

Nice job 

For external you want about 5000 rpm but it depends on the wheels you are going to use the bigger the wheel the slower the speed so check on your wheel size and see if you can get hold of some they should state on them max RPM for internal you want about 15000 rpm.

What spindle are you using ?.

Cheers

Stew

[John Hill]

Stew, at this time the spindle is nothing more than a 3/8" shaft.  I am intending to fashion a chuck for 1/4" mounted stones for the internal but I do not know if I can mount a suitable stone for external work on the same mount.

To be frank I do not even know why I would need a bigger stone for the external work?

[bogstandard]

John,

You don't really need overly large wheels. Mine are about 1/4" in width so that you can get into tight spaces, and around 2" in diameter. I do have a 3" green wheel for tungsten grinding.

As shown in Stew's post, Little Machine Shop carry spare wheels for their grinders.

I usually pick them up at trade shows, or you can sometimes get them off ebay.

Don't worry about central bore size too much, if it is too large you can soon turn up a reducer and if slightly small then a bit of hand work with an old drill or diamond files can usually get it to the right size. A 6mm bore will soon open out to 1/4". Do a good 'ring' test after you have finished, just to make sure you haven't damaged the integrity of the wheel. If it don't ring, dump it.

What you do need to get organised is a single point diamond dresser. Without one one, you will end up with a worse finish than when you started.

John

[sbwhart]

Hi John

When I get my motor mounting sorted:- Just spent 2 hrs this morning and got it completely wrong, a mental block, so got to start again with a new base.

I'll be turning my spindle up for wheel mounting and for taking a quill that you use for internal points, so you can get some ideas from this.

Cheers

Stew

[HENNEGANOL]

John Hill,

That is a lovely little shaper, am I right in thinking that it is a motorised version of the Adept?  I understand that they were marketed in Australia as A TNC.

I have an Adept No. 2 hand shaper, which to date I have never used.  However I am in the process of adapting it so as to be able to use it as a slotter or keyway cutter.  I 've decided how to mount the tool holder and I'm waiting on delivery of an angle plate which I intend to mount on the machine to hold the work piece.  If all goes to plan I will have a slotter whilst still retaining the original shaper function.

Gerald

[John Hill]

Thanks John Bogs,  I am going to search around our town today to see if I can find anyone with a selection of grinding stones to choose from. 

There are a number of 1/4" mounted stones of various hues in my drawer that came with a couple of Dremmel type devices and a I have a couple of ideas for mounting those as well as plain wheels.

I do not understand the advantage of the single point dresser over the block-on-the-handle type I already have?

Stew, that is a bummer,  I hate having to start over and that explains the pile of started but abandoned projects under my bench.

Gerald, yes the little shaper is an Adept 2 on a very nice stand that someone has made for her.  Sally Shaper is the only machine in my shop that gets a name!  Although it is only a small machine I can do things I would never attempt by other means.

[John Hill]

Still no sign of a small grinding wheel so meanwhile I put it all together sans the layshaft and here it is in the high speed mode with a small mounted stone and fitted to the compound slide:






Ready to do some business on a part of old rock drill I found near an abandoned quarry:

[bogstandard]

I do not understand the advantage of the single point dresser over the block-on-the-handle type I already have?

John,

What you have to realise that what you are making isn't something you are going to be grinding paving slabs with, it is going to become the equivalent of a precision tool, in fact more so, because sometime you will be using it to put cuts on of less than 1/10th of your normal measuring range.

The single point wheel dresser is the only way you will be able to dress the wheel fine and true enough.

Say you had a bit of Kiwi meat stuck in your teeth, would you use a pickaxe or a toothpick to remove it?



John

[John Hill]

John, if I had that problem I would just leave my gob open until a passing kea solved the problem.. http://www.youtube.com/watch?v=OMLpPoOeays..

Now about this stone dresser, I assume the tool has to be fixed to some sort of stand on the lathe and the stone moved across it?  Surely hand holding would not get the accuracy.

[Actually, I make no claims that this is a precision machine as the nose bearing is a simple ball race taken from a photo copier of long ago.  I do not get a mirror finish on the work but I do not get any obvious patterns either.]

[dsquire]

John

Since you tube has seen fit to disable the video that you posted I will post the link below for the video in the above post. Copy and paste it into a new browser and remove the 3 spaces before and after "youtube" then press enter.


http://www.   youtube   .com/watch?v=OMLpPoOeays


Them is smart birds John, I watched a couple of the vids. Thanks for posting it.

Cheers 

Don

[bogstandard]

John,

I mounted mine on an old mag base that can be stuck onto a rigid part of the lathe, then the wheel is fed against the diamond tip using the axis control you will be using for the grinding, or 90 degrees to it if you are going straight in. That dresses the stone so that it is prefectly in line with what you are going to be grinding.

If I get a chance later, I will take a piccy of my grotty old setup that works perfectly.


John

[John Hill]

Thanks Don,  I guess I should have tested after I posted!  Those darn birds would steal the gold out of you teeth if you dont keep your mouth shut.

Thanks John, I have a couple of clamps and I might be able to adapt one for the purpose, no spare mag bases though!

[Darren]

Those darn birds would steal the gold out of you teeth if you dont keep your mouth shut.

Are they edible, they look like they may be easy to catch ..... 

[John Hill]

Those darn birds would steal the gold out of you teeth if you dont keep your mouth shut.

Are they edible, they look like they may be easy to catch ..... 

They are easy to shoot, just leave a loaded gun around and one will be looking down the muzzle when another pulls the trigger.

[Bernd]

Are they edible, they look like they may be easy to catch .....  


They are easy to shoot, just leave a loaded gun around and one will be looking down the muzzle when another pulls the trigger.

Sounds like some of the inner city people in the US of A.  

Bernd

[bogstandard]

As promised John, here is a shot of my bodged up wheel dresser that works a treat.

John

[John Hill]

Thanks John, I should be able to manage something like that!

[John Hill]

One problem with using a router motor is the speed of the belt.  I tried a round section 6mm urethane belt which I got welded together no problems but on the machine it just balloons out and quickly flies across the room!   Next thing I tried was a metal belt made from curtain wire (the coiled spring type) but I was doubtful the join would hold, well it did hold but the wire itself broke in about 2 minutes.

About the only 'belt' that seemed promising was about 6 turns of cotton fishing twine which not being heavy did not have the problem of the urethane belt but didnt last much longer than the curtain wire.  I ran one for about a minute then stopped to see if there was any sign of stress, what I found was that the strands had moved and some strands were loose and others near breaking.  Drawing on my world-famous 'Bodger-sense' I struck upon the notion of soaking the cotton belt in glue so that the strands could not move around, it seems to work quite well!  Am I brilliant or what????*****





*****Well that remains to be seen as 5 minutes is hardly an exhaustive trial!

[bogstandard]

John,

Mine are actually like a loose woven flat belt running on convex surface pulleys.

I personally, in your situation, would try flat vacuum cleaner belts or toothed belts running inside out, running in flange sided flat faced pulleys (easy to make).

The belts shouldn't run tight, maybe that is where you are going wrong.


John

[John Hill]

Good information John, I might have to try a few things yet but I did try the glued-string belt for a good 1/4 hour with no problems and it does not seem to be coming apart either.

[John Hill]

I am satisfied I have solved the belt and pulley question and my 'long nose' spindle for the small mounted stones is judged as useable although it might improve a little with a  new bearing.

The intention is to make another spindle, which will be interchangeable, to handle the 75mm gray grindstone I have found (aluminium oxide?).  It will have a bigger pulley (for about 7000rpm), be shorter for rigidity and will have a 1/2" shaft. 

I have a choice of shaft material, a length of unidentified steel or silver steel.  The silver steel is new, unblemished and I presume straight.  Is silver steel suitable for this application?

[bogstandard]

Silver steel is perfectly fine John, but doesn't normally turn or thread to a superfine finish.

What you need to do is use your toolpost grinder to get a good finish on it.


Chicken and egg spring to mind.


John