Tool Post Grinder

[sbwhart]

So far I've got these bits towards a Tool Post Grinder:- A sub spindle made her
http://madmodder.net/index.php?topic=1790.0  and a small electric motor




First job work out some pulley sizes to give me the speed ranges I want 4000 rpm for external and 14000 for internal.

Motor pulley turned up.



I'm going to use 3/16 redthane belting, to cut the belt groove I will use a method John suggested, that is to mill it with a 3/16 end mill.



With the pulley still in place the chuck was removed from the lathe and mounted on my RT, then the cutter was fed in from the side and the RT rotated to cut the groove.



Worked like a charm it gave me an accurately cut 3/16 radius groove.




And here's the pulley on the motor, just need to drill and tap it for a fixing grub screw and to chew out some of the meat from the middle to bring the weight down.



Have fun

Stew

[bogstandard]

Don't mince it out Stew.
 
Because you have a fairly small motor, the flywheel effect might help a bit if you hit a high spot.

Very nicely done BTW.


John

[Gerhard Olivier]

This one is looking more tempting all the time.

Like the way you did the small round groove.

Gerhard

[CrewCab]

Nicely done Stew 

This however brings me to raise a question gentlemen  .......... I have an old Boxford "Little Giant" toolpost grinder, it runs just fine, but it uses a flat belt, looks like the sort of stuff they band stuff on pallets with, and the pulleys are convex ................ I have no spare belt and the one on there doesn't fill me with confidence, so ........ has anyone any info on these belts or would I be better making new pulleys and using similar belting to Stew ............... 

Thoughts appreciated chaps  ................ I think 

CC

[sbwhart]

Hi CC

John as one of those boxford tool post grinder with flat belts I bet he knows where to get them from 

Stew

[bogstandard]

Stew,

I bet you a fiver John doesn't.

My Boxford 'Little Giant' came with two belts, and they will last me until I snuff it.


John

[sbwhart]

Stew,

I bet you a fiver John doesn't.

My Boxford 'Little Giant' came with two belts, and they will last me until I snuff it.


John

Whoops thats my beer money gone for this month 

Stew

[CrewCab]

So ............. it looks like plan "B" then 

CC

[NickG]

Nice 1 Stew, this is shaping, or should that be milling up nicely!

[raynerd]

Hey Stew - I like your method of grooving out the pulley. When I did mine and did the research I only saw it done on the lathe using a profile tool, never seen it done in the mill using a RT! I guess this would only work for round belts like you are using?

Chris

[bogstandard]

That way of grooving is an old technique that I showed people how to do when they wanted to make the bending rolls for small tubing benders. It is a perfect method for small half rounds, or even big ones.

Grinding up a round nose tool of exactly the right size and shape for use on the lathe is a real PITA. Doing it on the mill is like a walk in the park, just find the right sized cutter and away you go.


Bogs

[sbwhart]

Ok now for the spindle pulley.

So that everything will run concentric, I turned a mandrel that is a nice fit on the bore of the pulley.



Bolted the blank pulley to it.



Then moved the chuck with everything still in place over to the RT and milled the belt grooves as before.



Here's a little tip:- Keys set into shafts can be a bit of a bitch to get hold of to remove, put a little groove in one end of the key so you can prise it out with a small screw driver.



Next job cut some plate out for the base. I'm using some ally jig plate I picked up from the scrappy.

Find a bit of plate that doesn't have an existing hole in a strategic position.



Then with a jig saw with a metal cutting blade and with some help from WD 40 cut the bits out, if any one asks what the extra holes are for I'll tell them its to keep the weight down.  0



Ok first job with the bits of plate is to clean the burrs off as well as I can.

Then set a parallel up square on the mill table.



And with the best edge hard up against the parallel clean up one edge, then with this cleaned edge up against the parallel clean the next edge up etc etc until all all four edges have been cleaned up are are square with each other, its easyer to start with things square than to try and get them square later.



This is the plate cleaned and squared up, the smaller piece will make the grinding spindle mountings.



And as its always nice to see how things are looking this will give you an idea of how the finished job will look.



Ok thats it for know the Grand prix is on the box the family have bets on which lap I'll fall sleep on, my record is the warmup lap.

 

Stew

[bogstandard]

Looking great Stew.

Just think of all those nice precision finishes and truing up you will be able to achieve.

Next time you call round, ask me for a dressing diamond, if you already haven't got one.


John

[Darren]

That really is looking quite good now Stew, there is a sewing machine motor for sale near me.

Shame it's attached to the rest of the machine though ..... 

[sbwhart]

Ok now to mount the spindle:-

The chunk of plate was cut in half to make the two mounting, the cut ends cleaned up with the two clamped together so that they would be the same length. At each end of the mounting a 1/4 hole was drilled right through and followed by a 10mm drill 20 mm deep to take the head of the cap head, then the base plate was drilled 1/4 BSF:- why BSF well that was the size of the only cap screws I had that were long enough to go through the mountings into the plate.

I used the tapping feature on mY X3 to tap the holes:- getting more confident in doing this.



Now to open up the mounting to take the spindle, I could have done this in the four jaw just clamp the two plate together set them up in the four jaw and drill and bore them out to size as a pair, for a grinding spindle this would have got them close enough on the lathe centre height. But I though I'd do it another way that would get thing dead on centre, this is the best way for any of you making a cross hole drilling sub spindle.

Clamp the base onto the lathe tool post get it square.



Get it positioned clamp the cross slide up, then centre drill followed by bigger and bigger drill, this is the biggest drill in my armory 13/16 " .



Then swap over to the boring head. To start with I took 1 mm ish cuts then as I got closer to size 0.5 mm cuts then 0.25 mm cuts until I was within 0.3 of size then I just ran this cut through 2 or 3 times to take the spring out.



Used the flash on this shot to freeze the action love the curl of swarf.



Thats it a nice snug fit



I may split the mounting down the centre to make pinch clamps on the bearing, but I realy have got a nice fit so I'm thinking of just drilling and tapping for a grub screw to fix things.

Thats it for now

Stew

[NickG]

Stew,

This is coming along really nicely. Great pics and nice write up too.

Nick

[sbwhart]

Thanks Nick

I'm quite enjoying making it: I've had to use quite a few machining techniques you don't use too often.

Cheers

Stew

[CrewCab]

I'm quite enjoying making it 

I can tell  ................ nice going mate    cracking work

CC

[Darren]

Quite a reach on that boring tool Stew, did it chatter any 

[sbwhart]

Hi Darren

No it didn't chatter with the big cuts it gave a nice parallel finish, but I did get some chatter when I was doing the finish cuts taking the spring out of the bar, but having said that the finish was still quite good.

I've used the boring head with those boring bars a number of times and I've always been presently surprised at the result:- they are very easy to get an accurate result with.

I think I got them from RDG.

Cheers

Stew

[spuddevans]

Now to open up the mounting to take the spindle, I could have done this in the four jaw just clamp the two plate together set them up in the four jaw and drill and bore them out to size as a pair, for a grinding spindle this would have got them close enough on the lathe centre height. But I though I'd do it another way that would get thing dead on centre, this is the best way for any of you making a cross hole drilling sub spindle.

That is a really good way of boring the mounting exactly on lathe centre height  , I'll file that away for future reference as I'd like to make a toolpost grinder at some point in the future, thanks Stew 


Tim

[sbwhart]

I decided to clamp the spindle in the mountains with a couple of M6 grub screws I put a 4mm drill down the end of the grub screws and superglued a little slug of brass into for the screw to tighten down onto so it won't mark the spindle.

Then I made the mounting plate for the motor. I used a bit of 1/4" thick ally plate, it was a mater of drilling holes where required along with a bit of filing.

This is it fitted to the motor





It certainly looks the part as for working well yes and no for the lower speed pulley selection it seem to work OK, but when I swap it over to the higher speed pulley selection it slowly turn over and starts to let the smoke out I guess the motor is stalling. It just doesn't have the humf to drive the faster speed, I guess the spindle is to heavy for the motor, I was a bit uncertain about the suitability of this small motor, but small motors with the speed (6000 ish RPM) and the HP just don't seem to be out there.

This what was on the motor I tried



Perhaps some of you chaps who understand these thing can point me in the right direction as regard motor selection.

Cheers

Stew

[bogstandard]

I have only just noticed that all the posts on this topic are from the UK.

What's wrong lads, cat got your tongue or are you all scared to death of this sort of thing?

I think I have shown this link before for the benefit of our US cousins (or anyone else in the UK who doesn't mind getting a cheapo site transformer to give the 110 volts, about 40 squid). Just in case you don't fancy making one.

http://littlemachineshop.com/products/product_category.php?category=-1731696149

Stew, if you come round sometime, we can have a root thru the motors I have, we just might find one that will do the trick. But make it during daylight hours, they are in outside storage boxes.


Bogs

[Darren]

Oh dear Stew, and there's me having just come home with a sewing machine with motor .... 

[NickG]

Stew,

That motor has a max power output of 90w, which isn't very much anyway, and because that max power comes at 6000rpm this means the torque is very low since power is a function of torque and speed. Because you're gearing up even further, you'll need something with quite a high starting torque. But usually that means sacrificing some speed!

Nick