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View Full Version : Thoughts on T+C grinder construction



strokersix
02-26-2011, 11:35 AM
The base of T+C looks a lot like the base of a mill/drill. Would a mill/drill or small horizontal mill with a grinding spindle instead of a milling spindle be a reasonable approach? Anyone done this? What are some options for the grinding spindle? Toolpost grinder?

Not after production, just would like to be able to sharpen milling cutters, endmills, maybe grind some shaft ODs. I understand that I will need to build or buy appropriate tooling. A mill/drill with an 8"x26" or so table would have lots of room for mounting whatever. Dovetail column style would probably be better than round column I think.

J Tiers
02-26-2011, 12:08 PM
Yes to the T/P grinder........ although I have mine on an ancient Greenfield T&C grinder base. originally has a belt driven plain bearing grinder head, I am told.

http://img.photobucket.com/albums/0803/jstanley/2lgrinder1.jpg

philbur
02-26-2011, 12:27 PM
I think speed of table motion is the issue.

Phil:)


The base of T+C looks a lot like the base of a mill/drill. Would a mill/drill or small horizontal mill with a grinding spindle instead of a milling spindle be a reasonable approach? Anyone done this? What are some options for the grinding spindle? Toolpost grinder?

loose nut
02-26-2011, 12:29 PM
The quality and accuracy of the ways would be an issue also.

strokersix
02-26-2011, 01:18 PM
Good and sensible points.

Thanks for the photo. That's what I need!

rohart
02-26-2011, 02:02 PM
J Tiers: Is the motor/spindle unit mounted on that massive cylinder in the background ? And you're set up for grinding the relief on the slitter - what do you do to grind the cutting face if you need to ? Do you mount the work holding axle vertically, or do you turn the wheel holding spindle vertical, or neither ?

philbur: What has to move quickly ? Do you mean you want to move the work quickly away from the cutter, index it, and move it quickly back to the cutter ?

Stroker: Most T&C machines have the wheel holding spindle horizontal, like the one in the photo. Were you going to do this, with your vertical dovetail mill set up?

I ask all this, because I'm prevaricating about whether to get going on my Quorn, or whether, like the OP, to make something of my own design (as if that wouldn't take a few months of cogitating !).

strokersix
02-26-2011, 02:38 PM
I was envisioning a horizontal grinding spindle, able to swivel about a vertical axis if possible.

philbur
02-26-2011, 03:41 PM
All grinders have rapid feeds relative to a mill. This is to avoid locally overheating the work-piece, which in the case of a T&CG is very easy to do because the thin cutting edge of the work-piece has limited ability to conduct the heat away. I assume this is one of the reasons why Jerry used a T&CG base.

Phil:)


J
philbur: What has to move quickly ? Do you mean you want to move the work quickly away from the cutter, index it, and move it quickly back to the cutter ?

Mcgyver
02-26-2011, 04:04 PM
My gut reaction is bad idea underscored by why bother given the cost of a good T&CG used....generally designs end up the way they are for a reason. Using a TP grinder works, but finding a good one used might be as hard and expensive as find the the whole T&GC.

otoh, getting things sharp is much less demanding that surface or cylindrical grinding - there you need a quality of motion and spindle to get the desired finish (not a trivial thing!) and to machine to a 10th......where as the the flutes of an endmill are less demanding.

you want some smooth, quick and low friction motion to the table. Inverted V ways and rollers are the two ways I've seen it done, can't see a dovetail being the best arrangement even if you replaced the feed with a rack and pinion or capstan. Stiction/friction is part of it, plus the nature of a dovetail is that some clearance is required along the dovetail - unless the fit is perfect this may be enough that it is frustrating when you want perfect repeatability for each tooth. Having scraped in a T&CG as well as a mini mill, I would suggest that the condition of the minimill ways might be termed abysmal out of the box.

If i was to make a Frankengrinder, a cheapo important surface plate with a ball bearing linear rails bolted to it and then half a mill x/y unit on top of that with a fine crossfeed screw would be one approach. Mount a tool post grinder or have a go at making a spindle; as i say it doesn't have to produce the finish of a surface grinder. Possible, but you never seem to see one as inevitably people realize it'll be cheaper and save years just to buy a used KO Lee or such for 500 or 1000. There's that German chap who built one but i think it was more love of the craft than most effective way to add T&CG capability

strokersix
02-26-2011, 05:27 PM
More good advice, thanks.

I'm showing my ignorance of cutter grinding processes. But I want to learn. I don't have any trouble freehand sharpening single point, twist drills, touching up tips of endmills, etc. But during my recent gear exploits I kissed a chuck jaw with the involute cutter and I don't have any practical way to fix it myself.

J Tiers
02-26-2011, 09:35 PM
J Tiers: Is the motor/spindle unit mounted on that massive cylinder in the background ? And you're set up for grinding the relief on the slitter - what do you do to grind the cutting face if you need to ? Do you mount the work holding axle vertically, or do you turn the wheel holding spindle vertical, or neither ?

philbur: What has to move quickly ? Do you mean you want to move the work quickly away from the cutter, index it, and move it quickly back to the cutter ?


Yes, the cylinder is the column. Originally a U-shaped casting sat on top, and could be rotated to any angle. Somewhere I have a picture that I was given of the original setup. That could use a cup wheel of standard size.

As for the face grinding....... that would give me more incentive to work on the new grinder head. The TP grinder is more -or-less an interim solution that does what I need done now.

However, the only thing that might cause a problem with doing the face is finding a flaring cup wheel that I could put on the TPG. Alternately, a thin wheel on the grinder, with it turned 90 deg so that spindle and table are perpendicular, would allow grinding the face if the table is adjusted vertically.

Right now, I don't need to do that, although I have at least one involute cutter that could use a touch-up. I might look into cut-off wheels to see if I can adapt one. Not the best grit type/size, but may be functional.

As for the speed, it is mostly to get done with the job this week sometime.... and probably some to avoid burning the surface. One generally sets the DEPTH of grind to avoid burning, and then it only takes a quick pass across and back to grind and spark out a thou or two.

the crank on the Greenfield base for table travel works a pinion that engages a rack on the table. Makes it much quicker than a screw.

However, a small production horizontal mill would likely be a good candidate for a conversion. They are often cheap, since they are not as useful without screw feed.

The table/way accuracy is likely good enough. Most cutters are narrow, and the table can't be that far off in a distance of 3mm or even 20mm. If you want to do large slab mills, maybe you should think about the table more deeply.

The item so far is a bit of a kludge, but it works. It will be improved if I don't find a better solution first.

http://img.photobucket.com/albums/0803/jstanley/2lgrinder3.jpg

RussZHC
02-26-2011, 09:47 PM
I've been thinking along the same lines lately as, locally anyway, it maybe that the machine(ery) and skill set to grind cutters has past since business is CNC and inserts. I am not saying it does not exist, I know of one place the refurbs end mills but...I also have this "thing" about being self contained.

It is an interesting exercise to look at the various machines at lathes.co.uk but to also look at EBay offerings. Lots of variations on the theme (as example how the motor height is changed) from Pratt and Whitney to Oliver Adrian and their "Ace" to copies of the Monoset.

There is a site out there (url escapes me at the moment) where the person more or less cut a lathe bed in half and used that and other bits to create their own tool and cutter grinder and, if it were me, what I would have considered with this
http://bbs.homeshopmachinist.net/showthread.php?t=46558