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Mcgyver
07-21-2009, 11:50 AM
Ringer's TG got me thinking......so what makes a T&C grinding head 'sensitive' or not? does it ride on bearings or something?

thinking of building one but have no idea whats in side

on another T&C note, I'm thinking of a horizontal mill cutter sharpener...but more than just centres, something that holds the cutter using bearings, maybe lightly sprung angular contacts....something more 'sensitive' than centres...but maybe I'm gilding the lily...what do you experienced tool grinders think?

oldtiffie
07-21-2009, 07:01 PM
The word "sensitive" as we usually know it doesn't apply here. I have no idea why it is used.

"Sensitive work-heads" are used for indexing on a grinder.

For a list of illustrations see:
http://www.chitseng.com/product5.htm

Sharpening most slab mills and the like is best done on a mandrel, but side and face cutters (sides anyway) are done on an arbor mounted in a (so-called) "sensitive work-head" and the like.

There are numerous combinations and variations.

Lane made a fabulous example of a sensitive work-head. Check it out.

Mcgyver
07-21-2009, 07:33 PM
OT, I've seen that sheet, in fact have one of the chevalier T&CG that its based on.....but it doesn't help me with what the guts are.

I've seen Lane's work, fantastic, but to my knowledge he hasn't shown a sketch, disassembled parts or plants etc....Lane if you're listening, inquiring minds want to know :)

The use of the word sensitive made me think perhaps the work moved during grinding....or its it fixed and only the table moves. if that's the case looks to
like a fairly straight forward thing (still lots of machining but no mysteries) - block accepts 5c collets and can be rotated, indexed and locked with the head....that plus angular adjustment...does that about cover it or am i missing something

BobWarfield
07-21-2009, 07:48 PM
The "sensitive" refers to the need when sharpening the length of a flute for the cutter to move smoothly along that length and maintain proper alignment of the flute with the grinding wheel. So it has to make a helical motion. Air bearings and the like are often preferred. A "finger" aligns the flute and you move the sensitive head while keep the flute in contact with the bearing.

See for example: http://www.axiosequipamentos.com.br/FC-32A.pdf

Cheers,

BW

lane
07-21-2009, 08:18 PM
The use of the word sensitive made me think perhaps the work moved during grinding....or its it fixed and only the table moves. if that's the case looks to
like a fairly straight forward thing (still lots of machining but no mysteries) - block accepts 5c collets and can be rotated, indexed and locked with the head....that plus angular adjustment...does that about cover it or am i missing something
Reply With Quote
You got it down. Just a housing that will move in at least 2 planes.
Then a spindle that a 5C collet will fit in and spin on precision bearings . And some way to index .I used 24 position index on mine
http://i178.photobucket.com/albums/w277/lane5263/Picture006.jpg
http://i178.photobucket.com/albums/w277/lane5263/workhead008.jpg
http://i178.photobucket.com/albums/w277/lane5263/Picture010.jpg
http://i178.photobucket.com/albums/w277/lane5263/workhead1288.jpg

May be this will help. Lane

Mcgyver
07-21-2009, 09:08 PM
so there is some mystery - seems there is more going on than i thought. it does have roller element bearings....hmmm...whats their function?...just to rotate to index to a new position or is it for the option of rotating the work against a tooth rest??

thanks for the pics lane, i wont get tired of looking at that great piece of work

lazlo
07-21-2009, 09:26 PM
This is an application guide from the K.O. Lee Grinder Accessories Catalog:

http://i164.photobucket.com/albums/u15/rtgeorge_album/KOLee.jpg

oldtiffie
07-21-2009, 10:04 PM
I think that Bob Warfielld may have the idea for the "sensitive" bit as it will apply it a "finger" is used for fine angular adjustment as opposed to using the normally fixed holes on an indexing plate.

With the "ratchet and pawl" arrangement, you can adjust using a "finger". This applies to situations where the cutter etc. is not required to rotate during the grinding process - as with the peripheral teeth on a "straight-toothed" side and face cutter.

It is quite possible - with a low friction head with bearings like Lanes to have the "finger" with its base "off-table" and its finger on the spiral flutes - to grind the helical teeth on a spiral cutter - end mill or "staggered tooth" side and face cutters.

A good look at the pic that Lazlo posted will show that there are a lot of pretty well limited or "single-purpose" "heads". There are some quite clever hybrid ones as well.

I will post some pics of some of mine later.

It really depends on what you want to grind or sharpen and how accurate you want to be.

Mcgyver
07-21-2009, 10:18 PM
OT, the Q on sensitivity really just came from curiosity.

I'm fairly well tooled to grind end mills, drills and special lathe tools like V threading, acme etc....the only capacity i don't have and want is for horizontal cutters and I'd like to something a little more creative than a set of centres...i have ideas for a 'sensitive' set of centres :)

specialty heads? the value would be just for the sake of the project; ie I've got a dozen or more ball end mills that rarely get used - I'd be better off buying a new one once every 4 years than spending a month or two building a radius attachment; that sort of logic..

....but now with the horizontal mill, I've got get going on some grinding tooling, a set of 'sensitive centres and something like lanes for narrower straight cutters. i was ploughing a bunch 3/4" side slots 1/2" deep in steel with a dull cutter and it made Elliot labour a bit :D

oldtiffie
07-22-2009, 12:11 AM
Thanks Mcgyver.

As it seems that you are (only?) wanting to grind straight and not spiral cutters (at least for now), and if the number of teeth is a sub-multiple of 36 (ie 2, 3, 4, 6, 9, 12) you can do quite well with an arbor to suit your largest C5 collet in your "Spindexer" and a 1" spigot to suit the bore of the milling cutter on the other.

This presumes direct indexing using the "0" in the Spindexer. You can use the vernier to get down to 1 degree if you wish.

The better way is to leave the indexing pin out and fit an adjustable flexible "sensitive finger" to the grinder table and index off the the teeth of the cutter themselves.

There are some simple math required for setting the clearance angles (primary and secondary) and they are quite accurate. All that is required is the clearance angle required and the diameter of the cutter.
The same process can be used to grind the clearance angles on the side faces of the side and face cutter.

The whole set-up should not take longer than an hour the first time and only minutes after that.

I'd suggest "side-wheeling" on a T&C or surface grinder as opposed to using the periphery of the grinding wheel.

You may or may not require a cup and/or a saucer wheel.

A cheap (preferably "Norton" for quality and balance) aluminium oxide wheel (hand-dressed) will be more than adequate in the short term.

There may not be a need to make anything to get you going, but at least you will have some breathing space to make your better tool/project when it suits you.

The Spindexer makes a pretty handy tool too for grinding spiral cutters too as a "quick" solution. Its one of the most under-rated and "rubbished" tools in the shop.

JCHannum
07-22-2009, 07:56 AM
This is my semi-sensitive grinding fixture I made using a Spindex spindle and a couple of left over KO Lee pieces. I made it to do the ends of end mills rather than using the air bearing fixture.

It has a latching index plate to do 2, 3, 4 & 6 flute end mills, but other index plates could be fabricated.

http://i320.photobucket.com/albums/nn351/jchannum/P1040775.jpg

I agree that the Spindex is a handy tool, and often overlooked. It can be used for many jobs on the T&C or surface grinder.

oldtiffie
07-22-2009, 09:04 AM
Jim.

I prefer to index off the cutter teeth rather than a set of holes or slots or even ratchet and pawls as there is less chance of error.

A simple spring "finger" does it well and is easily adjustable.

While I would agree that an air spindle is the ideal answer, it is by no means the only one for spiral flutes either.

The Spindexer spindle is a pretty good finish and fit in the body (well, my "John Stevenson" model from ArcEuro is) and with care it will work very well as a spindle for straight and spiral grinding. It may not be as good as my lapped air and non-air spindles but it will still do a very good job and will recover otherwise wasted end milling and horizontal side and face and "form" (ie gear) cutters. I would even chance doing a 2" and at a real stretch, a 4" long slab cutter. Add the tail-stock to the Spindexer and you have a very good tool even better.

I have some pics somewhere of a set-up I did some while ago on that bloody imfamous "air spindle" thread. I will see if I can find them and will post them.

JCHannum
07-22-2009, 10:08 AM
At the time I built the fixture, I had a Cuttermaster air spindle. It was very long, and cumbersome to set up for grinding the ends of end mills. I basically duplicated the fixture and indexing features in a shorter version. I have since replaced the C/M with a different fixture that has the same indexing feature.

If a finger is the preferred method of location, it is easily enough incorporated into the design.