My Tool Grinder.

[Draw-Tech]

Hi DJP,



I agree with you about the motor cooling ! It would be nice to have a fan on the motor shaft blowing air over it. I'll have to keep an eye on the temperature when I start to use it in anger. I don't see any problem with using a cup wheel like you are doing. My concern is that side pressure on my wheel which is only 1/4" inch thick, could cause the wheel to burst. The other concern is failure of the Triac that is used to control the speed. These like to fail short circuit ! If that happens the motor will take off at maximum rpm, about 26,000 rpm which is way over the safe 5200 rpm speed for my wheel.



Whilst I can sharpen drills by hand, after a fashion, I really need to make a jig to help get them just right. My eyesight isn't what it was either...



I wouldn't say that mine is particularly brilliant ! Really just a means to an end. Having a motor handy and some bits of 1/4" plate helped though.

Any more pictures of your tool holder ?

Hi Baronj
I like your idea, have been thinking of a grinder for years, (boxes full of dull end mills) anyway why dont you use a couple of gear belt pulleys and gear belt to slow your motor 4:1 will give you slower spindle speed and increase the torque, when I build my grinder I will mace the holder to fit my set of 3C lathe collets. just a thought. I will be watching your posts.
Jack
Draw-Tech

 

[BaronJ]

Hello Jack,
Most of the motors I have or can easily get my hands on are universal ones. Even the washing machines today don't seem to use induction motors any more.
I believe that most if not all tumble dryers use an induction motor simply because they run at low speeds. One motor that I have from one only runs at 850 rpm though it does have a 1/2" shaft.

But I'm afraid that until I can get the mill sorted those projects will have to take a back seat.

You mentioned collets. I saw some in the local scrapyard the other day. About 1" diameter, maybe 2.5" long. Next time I go I will have a look at them ! See what they are and if they are any good.

 

[BaronJ]

I like your soft jaw setup, if I want to use soft jaws I will have to buy a new chuck, but I will keep your design in mind.

Paul.

Hi Paul,
Its an old trick that I was shown many many years ago and one that I have used from time to time. There is nothing special about them at all. In fact the aluminium came from a belt drive gear that I had kicking around. That is why it looks as if its got teeth. The holding screws are 2 BA. They are just bits sawn off a 50 mm long bolt with a hacksaw cut across the end.

 

[BaronJ]

Apologies but this was written in some stately Scottish ruin on an unfamiliar iPad.

,an ah that
Norman

Hi Norman,
Your wisdom is always welcome. Ipad or not. :hDe:

And yes I agree about the dust from the grinding wheel ! Not only does it get everywhere but sticks to anything the slightest bit damp or greasy. A dust extractor is called for.

Oh no... Another round tuit.

 

[BaronJ]

Hi Guys,

Well I got some more done on the mill gears. I also got the other gear that I was waiting for. So I now have the pair for the primary drive from the motor.

I finished the brass bushing and got the gear pressed into place. Put it into a pan of boiling water to heat it up first. It pushed on quite nicely. Put it back into the lathe and skimmed of the bit that protruded on the other side of the gear. Turned it round. Clocked it up and found that it was spot on. So I turned down the other end ready for the large gear.

Photos below.

 

[goldstar31]

Baron,
Thank you kindly. I wonder if I still have an unloved and maybe complete Quorn rusting away under a damp bench. I was jolted by the sad passing of Ron Chernich who made one.
Better looking than mine but mine certainly did what it was told.
Will write again when I get back to some form of civilisation. Piss-instantly raining here in the Trossachs

Regards meantime
Norman

 

[BaronJ]

Baron,
Thank you kindly. I wonder if I still have an unloved and maybe complete Quorn rusting away under a damp bench. I was jolted by the sad passing of Ron Chernich who made one.
Better looking than mine but mine certainly did what it was told.
Will write again when I get back to some form of civilisation. Piss-instantly raining here in the Trossachs

Regards meantime
Norman

Hello Norman,

Yes I was saddened to hear about Ron's passing. He was a nice guy who always tried to help, with good advice and a kind word or encouragement if you were stuck.

A Quorn... Rusting, unloved, under a damp bench... Sacrilege ! Sacrilege I tell you. You must love, care for and cherish it... Or pass it on to someone who will. :hDe::hDe::hDe:

Sorry to hear that you have got our rain ! But I don't mind. You can keep and make good use of it. :hDe::hDe::hDe:

Seriously though, I hope all is well with you both. Take care.

 

[BaronJ]

Hi Guys,

Got a little more done. Bored out the second of the two gears for the twin ones.
I've included pictures of the boring tool that I used and the stack of shims that go underneath it to get it to the correct hight.

I'll be glad when I get the QCTP that I started a while back, finished. Its frustrating not having the mill working.

Also the intermediate shaft and gear that drives it. This is one of the two stainless steel gears. And now that the soft jaws are finished with a picture of those.

 

[BaronJ]

Hi All,

Well I've got a little further on and machined the small gear that fits onto the end of the motor shaft. I've also discovered that this 10 mm diameter shaft has a 4 mm wide keyway slot. All the others have 5 mm ones.

Pictures below. One shows the arrangement of the two driving gears when assembled. There are also pictures of the original bronze gear and the motor shaft.

 

[DJP]

Consider using a brass key or some other type of shear pin. Those steel gears look like serious business and any part failure will take place elsewhere in the machine. It could be more expensive to fix next time.

My mini mill has a circuit board that shuts down the motor when there is a current spike. If you have the same feature then the brass key idea is secondary protection and maybe not required.

My thoughts for your consideration.

 

[BaronJ]

Consider using a brass key or some other type of shear pin. Those steel gears look like serious business and any part failure will take place elsewhere in the machine. It could be more expensive to fix next time.

My mini mill has a circuit board that shuts down the motor when there is a current spike. If you have the same feature then the brass key idea is secondary protection and maybe not required.

My thoughts for your consideration.

Hi DJP,

Mmm ! I'd thought about that. Those new gears will transmit an awful lot of power. The question would be where to put a shear pin. The ideal place I suppose would be in the second gear, the one driving the speed change spindle. Because that one is the easiest place to get at.

I might be tempted to use a plastic key in that one. I wonder how effective that might be. I'm sure that some one here might know or at least where to look to get that sort of information. I'll have to research that...

As far as I am aware there isn't any motor protection other than a fuse to protect it and the electronics. I do have some 240 volt thermal overload trips that are adjustable between 2 and 10 amps but they take a two seconds or so to trip. I could hit the stop button first !

When I first got the mill I took some current load readings and the mill only took a few hundred milliamp's off load and about 1.2 - 1.3 ampere taking a cut with a 12 mm cutter. It seems to be the start up current that gets up to anywhere near the 8 amp fuse rating.

 

[BaronJ]

Hi All,

Well I got the large gear machined. I put it in the four jaw using plastic shims to protect the teeth and then trued it up. I bored it out to 0.940, cleaned it up. It was a nice press fit onto the brass bushing.

All I have to do now is put in the 5 mm keyway slots. The motor keyway is 4 mm wide. The brass should be fairly easy but the stainless steel will be much more difficult.

 

[DJP]

I think that gas powered lawn mowers have a key that sheers under the flywheel should the blade hit an construction. It saves the crankshaft. Outboard motors in the olden days had a small brass dowel instead of a key at the propeller shaft. It would shear to save the propeller from severe damage.

I only had one accident with my mini mill and it involved a fly cutter. When it hit hard the power was immediately cut to the motor and there was no damage to the plastic gears. That circuit saved a big repair so I was thankful that it worked. My bigger and older Burke mill and Southbend lathe run on belts that will slip. So if faced with the repair you are doing, I'll change to belt driven instead.

Making a key out of Delrin or HMW Plastic should work well.

 

[BaronJ]

Hi DJP,
The way this mill is constructed makes it very hard to do a belt conversion. There is nothing above the spindle top bearing that you could use to attach a pulley. I feel that replacing the gears is the only sensible way to go.

I will try a plastic shear pin by replacing the 4 mm key with a plastic one and see how that goes. Since its just under the motor mounting plate, removing six M6 cap screws and the gear is immediately accessible.

 

[BaronJ]

Hi All,
I didn't get too much done today. Hospital appointments got in the way.

The previous threads discussing shear pins and the like got me thinking about the security of the dual gear inside the main casting and how difficult it is to get access to it once the mill is re-assembled.

I'm conscious of the possibility of the gears slipping on the brass bush and then failing to provide drive. In order to prevent any possibility of a gear coming loose on the brass bush I have decided to pin the gears to the bush.

I used a 4 mm slot drill and drilled holes opposite each other on the joint line between the brass and steel. I was very careful not to drill right through the gear. I then tapped the holes 2 BA and inserted 1/8" inch by 2 BA hex socket grub screws. Now there is no way that the gears can slip on the brass bush. I've only had time to do one side today.

Note. Looking at the photographs you can see how the brass has distorted slightly when threaded whilst the steel hasn't.

 

[goldstar31]

Baron,
Hope your hospital visit went well. Workshops are getting to be memories now.
Got the wiring done- after the 'Gas man cometh' with apologies to Flanders and Swann.

Regards

Norman

 

[BaronJ]

Baron,
Hope your hospital visit went well. Workshops are getting to be memories now.
Got the wiring done- after the 'Gas man cometh' with apologies to Flanders and Swann.

Regards

Norman

Hi Norman,
Its getting very frustrating No one wants to commit themselves to a firm diagnosis. They want to run some more tests and have me take a CT scan. I've to go for the vampire on Monday morning for more blood tests. I've been told not to book any holidays. About the only thing that seems to be sure is the amount of time and passing around that is taking place.

Gears: !
Anyway I got the other side of the dual gear drilled, tapped and pinned this afternoon. I just have to figure out how I'm going to put keyways into the brass bush and the motor spindle gear.

I'm toying with the idea of putting some kind of lubrication system into the mill head so that I can ensure that the gears get properly lubricated. The original grease that was stuffed in, apparently, was intended to lubricate the plastic to metal tooth contact. I've cleaned all that gunk out along with bits of sand and metal shavings. Probably from when the casting was machined. I've also discovered that at one point the casting has been ground away and welded to fill in or otherwise repair a bad casting.

The more I dig into this machine the less enamoured I become.

 

[goldstar31]

Baron,
Be positive. Whatever your present thoughts, they can do great things that only a year or two ago, t were impossible.

As for lubrication of mills, the only way forward is for you to strip out and clean and then re-grease.

I hope all is well. To hell with a bit of sand, eh?

Norman

 

[Griffin]

Baron

I agree with Goldstar, be positive, I too have been in that situation, still go every 6 weeks, vampires next week, GP can't keep up lol, and I have four consultants for the past 5 years, but today I cut my first backgear for the lathe, was so chuffed it actually worked, and that was out of polypropylene, next one is going to be a 77 tooth gear when I get the material for it, its taken me 4 weeks to get to this stage. I hope all is well soon, I always keep an eye out for your and other posts like it, it never fails to intrest me.

Mark

 

[BaronJ]

Thanks, Norman, Mark,

Sorry about having a chelp about my frustration. It is just getting passed around and nobody seems able to make a decision. Anyway thankyou both for your kind words.

Mark,
Congratulations ! Cutting gears is anything but easy or straightforward as I'm sure Norman will agree. I wonder if your next one is also going to be polypropylene or are you going to try steel or cast iron ? Either way cutting your first gear is an achievement that you should be proud of.

Norman,
Once this mill is re-assembled there is no way I'm going to take it apart again just to lubricate the gears.

I'm considering drilling a hole in the side of the casting and fitting an oil nipple with some internal pipe to distribute lubrication to the gears...

See next post.