Anyone have a pic or plan of a radius grinding jig?

[DICKEYBIRD]

I was grinding a HSS tool (5/16" radius form tool) on my H/F carbide grinder and a thought occurred to me. I want to make a (hopefully) simple grinding jig that clamps to the grinder table that would allow a bit to be clamped in place and swung back & forth to grind an accurate radius. It took several attempts along with some wasted HSS toolbit length and lost A/O wheel grit before I got a usable tool. By the way, the slow speed 12v motor drive for the diamond wheel worked great for the final honing to a keen edge!

I'm thinking it could pivot on a 1/8" hard dowel pin slid into a piece of thin-wall hard brass tubing. It needs to be able to get close as possible to the wheel for a small a radius as possible. It could be a 2 piece sliding dovetail affair for the basic adjustments of the radius with a fine infeed adjustment handled by a simple 10-32 screw.

Surely a device like this exists in the real world?

[madman]

I think SARS from china sells a nice one for 190 bucks. i bought one along with a magnetic surface chuck for my Grinder and was amazed how cheap.

[Norman Atkinson]

DickeyBird, I thought that we had flogged the Tool and Cutter grinder subject to a point of boredom or rage( it depends)

Almost all the tool and cutter firms offer a radius attachment. i have one for my Clarkson and if you fancy a look, Google -- lathes.co.uk. If you want to have a CD, ask Uncle John. If you want- you could build a Quorn one( did I hear mutterings in the ranks?- Behave yourselves)
Again, if you Google Hemmingway Kits, the Worden grinder has, I believe a simple one.

Now, please can we have a moment away from t&c's except to mention that the kind Peter Neill has E-mailed me with the words and music to the Stent------- for which one can-- Roll of drums, sounds of trumpets- add a modified radius device from the ---------------------------------Quorn!

[Bill Pace]

These things are REALLY handy, and you sure cant beat the price --- theres several vendors on the bay handle them...

http://tinyurl.com/6mslpn

I know 800watt hasnt got a very good reputation, but Lane and I both have gotten several items from there and so far have had good service.

[DR]

These things are REALLY handy, and you sure cant beat the price --- theres several vendors on the bay handle them...

http://tinyurl.com/6mslpn

I know 800watt hasnt got a very good reputation, but Lane and I both have gotten several items from there and so far have had good service.


That isn't a radius grinding fixture though, is it?

[DICKEYBIRD]

T&C grinding isn't a bore for me yet avie and the only rage I get into is when I screw up the last feature on an involved part....or one of them SUV's with big wheels pulls up beside me at a stoplight with the stereo rapping my eyeballs into a blur. Now THAT"S rage.

I've seen those cool grinding jigs that 800 watt sells and I want one but I don't think they'll do what I want.

[Norman Atkinson]

I'm pretty deaf so 4X4's with loud music don't trouble me- Pardon eh?

All these radius things are basically ungeared rotary tables with nothing more complicated than a tool holder capable of holding an angle to be ground. You do have to adjust it to get a pivot point but really that is all that there is to it.

Now I like your pictures but they aare not availsble on this side of the pond.

Good Luck, anyway

Norm

[oldtiffie]

I was grinding a HSS tool (5/16" radius form tool) on my H/F carbide grinder and a thought occurred to me. I want to make a (hopefully) simple grinding jig that clamps to the grinder table that would allow a bit to be clamped in place and swung back & forth to grind an accurate radius. It took several attempts along with some wasted HSS toolbit length and lost A/O wheel grit before I got a usable tool. By the way, the slow speed 12v motor drive for the diamond wheel worked great for the final honing to a keen edge!

I'm thinking it could pivot on a 1/8" hard dowel pin slid into a piece of thin-wall hard brass tubing. It needs to be able to get close as possible to the wheel for a small a radius as possible. It could be a 2 piece sliding dovetail affair for the basic adjustments of the radius with a fine infeed adjustment handled by a simple 10-32 screw.

Surely a device like this exists in the real world?

Thanks DD.

There has been a very good solution around for many years.

It is essentially a round tool that is tilted inward (about 10 degree from vertical) with about 5 degree back rake in a tool-holder in the lathe tool-post. A 5/16" radius would require a 5/8" "tool bit". There is no need for it to be HSS as an old file with the teeth ground off will do the job for reasonably soft material at slow speed.

Lane made an excellent set and posted them here not do long ago. If he reads this post he may post the link to the thread for that tool. He used scrap round HSS tool bits, shanks of old or broken end mills and centre drills etc.

Lane's work was excellent - as always. It would be a good useful learning project as well and should cost very little.

You can actually "rough it out" with a normal tool and then finish off with a round file and emery paper. A 5/8" diameter washer should do as a radius guage as well.

But back to the question as to what one looks like.

Use this link:
http://www.cdcotools.com

Select: "Quick guide" and pan/scroll down to "Grinding machine tooling".

You will choke on the prices. Here are the pics:
http://www.cdcotools.com/picture/284
which is $295

and:
http://www.cdcotools.com/picture/32
which is $395

[dp]

You need some variation of the following:

http://littlemachineshop.com/products/product_focus.php?Focus=X-Y+Tables

Steve Bedair's ball cutter: http://www.bedair.org/Ball/ball4.html

A simple spin indexer: http://www.penntoolco.com/catalog/products/products.cfm?categoryID=1464

Assemble them into a cohesive unit and you will have something close to this: http://tinyurl.com/5prubr

[lane]

Dickeybird try this
http://bbs.homeshopmachinist.net/showthread.php?t=26214
Easy to make for any radius you want.
I thought hard about what you want and at one time tried to make something like you described but the pivot has to be to small and change to much .I could not come up with a good design to make it work right . But you are willing to try go for it.

[DICKEYBIRD]

Tiff, were you referring to Lane's tangential cutters here? http://bbs.homeshopmachinist.net/showthread.php?t=26214&highlight=radiust=26214&highlight=radius Thanks for reminding me; I'd forgotten how very nice those are. I may have to make a couple. Definitely a good solution for cutting radiused grooves. Maybe a couple different sizes with a slit bushing to use 2 tool diameters per holder.

Those tools you & Dennis linked to are really purposeful looking devices! I'd have to take lessons to learn how to use them though!;) I'm not sure they would do the little round-nosed tool I made?? Maybe I don't clearly understand how they work.

EDIT: Oops! Looks like Lane posted before I did. Thank you sir, those are great tools and great pics as well.:)

[dp]

This should look familiar to you. If you mount the spindexer on a swivel plate (Steve Bedair's ball cutter with minor mods) you can cut radii.

http://i57.photobucket.com/albums/g227/DBAviation/EndmillFixtureSpinDex.jpg

[oldtiffie]

Thanks DB.

Going for that radius in one go is a "big ask" - just as plunging in for a large-ish screw thread is as they are both "form-tooling".

One that I've used often is the end of a flat file. Just grind the teeth off so as it is flat. Then grind - in this case - a 1/4" radius with about 5 degrees front clearance. Use a machine/nut washer with a 1/2" hole in it as a radius guage to form the cutting edge. You will be surprised at just how accurately you can grind that radius - just use the washer/guage as you would an Engineers/machinist's try-square - just hold it up to the light. If I am grinding a radius like that I use the front of the wheel (not the side) on my pedestal grinder and get a good result using a good "hand-and-wrist" motion. I only use the side of the wheel for flat surfaces. I really prefer the use the "rolled edge" on my sander as it does a really good job. I hardly ever use the disk and bevel guides as I learned to grind all "off-hand". I just change the belts - coarse/fine/worn etc. required.

http://i200.photobucket.com/albums/aa294/oldtiffie/Belt_sander/Belt_sander1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Belt_sander/Belt_sander2.jpg

But back to the "file as a form tool".

Hone a very fine edge, fit a solid bit of steel bar in your tool-post as close to your work-piece as you can and set it so that the top of the file is at centre height. Use the file as a wood-working machinist uses his "gouges" - but dead slow with lots of "suds" or cutting oil. That 1/4" radius will turn out that 5/16" radius easily - just a bit at a time. Just use your hands, arms and wrists - and brace yourself.

I think you will be quite pleased with the result.

Its another one of those "eat an elephant jobs" - its "do-able" if you take it slowly and takes lots of bites.

[Edit]
Use a 5/8" diameter washer or rod etc. as a radius guage for the 5/16" radius cut.

Use a file and/or emery/"wet and dry" paper as required. Finish off with a Kitchen scouring pad (eg "Scotch-brite") for a good final finish as required.

[End edit]

[oldtiffie]

Dickeybird try this
http://bbs.homeshopmachinist.net/showthread.php?t=26214
Easy to make for any radius you want.
I thought hard about what you want and at one time tried to make something like you described but the pivot has to be to small and change to much .I could not come up with a good design to make it work right . But you are willing to try go for it.

Thanks Lane.

That's it.

I thought later that it was one of your threads and that I should have been able to find it easily enough.

Thanks for the bail-out.

[JRouche]

DickeyBird, I thought that we had flogged the Tool and Cutter grinder subject to a point of boredom or rage( it depends)

Now, please can we have a moment away from t&c's

What!!?? Are you crazy.. NO!! No we cant stop talking about these subjects.. Hell man!!! Thats what this site is all about, that is ONLY whats its about.

Talking about the stuff folks want to know about and folks like YOU, that know things, talking about it. Thats all there is. That IS this site.

Yes!!! Bring up the old subjects. If its lathes, mills, shapers, drill bits, drill presses, end mills, counter bores, counter sinks, spot drills or center drills, grinders of every sort, metals and what to use, safety, voltages and currents, finishes or rust removal, tool holders or work holders, lighting, shop arrangements, speeds and feeds, cast or steel... It goes on and on.. This is the HOBBY!!..

Never stop talking about the hobby.. Never know when a new member just pulled up and reads the "old" topic but hasn't been here before, so its new for him.. We can ALL learn from each other. Im a believer of that... JR

[BadDog]

Other than suggestions and comments already offered, I have little to say about making a round grooving tool of that size or less. I've done it well enough using radius gages when needed, but the largest radius was something like 0.125 and THAT was a bear in the cut...

However, I will share a tip from a friend of mine for doing the opposite. If you need to make a (reasonable size) corner rounding bit, you can start by free-handing to a radius gage (or convenient pin, drill rod, drill blank, or even drill shank...). When you get close, find a conveniently sized (or turn) a rod of some material softer than your bit (don't use a HSS lathe bit or drill lank! :D) and "load" it with some Clover compound or equivalent. Put it in the lathe (or drill chuck, whatever) and spin it at reasonable "lapping" speeds (not too fast). Use this to finish/polish the cutter, including the relief. The result is a near perfect corner rounding tool AND a tool to polish or touch-up the edge as needed.

[Norman Atkinson]

With failing eyesight, I seem to have misposted onto Lane's Necessity is the mother of invention. Call mine 'Felicity is the Mother of Kittens!'

[oldtiffie]

For Dickey Bird.

I have had a re-think on this.

If the objective is to machine a 5/16" radius on the circumference of a cylinder and is not necessarily to make a radius cutting tool or a radius tool grinder there may be another way.

Mount a chuck or collet adaptor onto the rotab and centre the work-piece to the rotab centre.

Mount your rotary table in the vertical position (axis horizontal and aligned to the "X" axis of your mill).

Fit the work into the chuck or collet.

Fit a 5/8" end milling cutter into the milling head spindle collet adaptor.

Lower the mill head (vertical - none-knee mill) or raise the table (knee mill) until the centre on the end-mill cutter flutes are about centre-height of the rotab/chuck/job.

Use the "X" feed to position the job where the groove is to go so that it is opposite the 5/8" cutter.

Lock/clamp the mill head/knee and "X" slide.

Start the milling cutter.

Feed the job into the cutter using the "Y" feed until the cutter starts to cut.

Wind the rotab worm drive and rotate the rotab table at least one full turn.

Repeat until the cutter has cut the groove to the correct depth.

You may be surprised at just how easy and fast this is. The finish will be pretty good too. But to get it better, put it in the lathe and use a round or half-round file and "wet and dry" paper to polish to a required finish.

I hope I did not ambush you as I focused on the required outcome and worked back-wards through the possibilities.

I found that I did not need to make either a radius tool/cutter or a radius grinding jig/fixture.

I remembered doing this years ago. Another variation was using a side-and-face cutter instead of an end-milling cutter to cut radius-ed grooves up to 3" radius. I have used a fly-cutter to cut grooves up to 6" radius. The principles are the same in each case.

I try to avoid the "set-piece" or "tradional" or "book" methods if I can as it gives me a lot more options and latitude.

I hope this helps.

[DICKEYBIRD]

Tiffie & all, I screwed up in my 1st post and typed 5/16" radius when I meant to say 5/32". A 5/16" dia. rod fit the radius I was trying to duplicate and I got fixated on that.

I'm still sketching a jig that might work to grind a radius that small but Lane's solution looks like the best way to go. McGyver's method of turning the cutter smaller on the cutting end and leaving the shank the same size takes care of having to make a dedicated holder for each size cutter.

[Jim Caudill]

Build one tool holder (like Lane's) to fit the punches from a Whitney Jr punch set. Then use (or slightly modify) the Whitney punches to use as the cutting tool. One less operation you would have to perform, and the punches are readily available and should be of good quality. $11 each for the set from Irvan-Smith, probably cheaper elsewhere.
http://i72.photobucket.com/albums/i183/Ferrofab/untitled.jpg

[Timleech]

Tiffie & all, I screwed up in my 1st post and typed 5/16" radius when I meant to say 5/32". A 5/16" dia. rod fit the radius I was trying to duplicate and I got fixated on that.

I'm still sketching a jig that might work to grind a radius that small but Lane's solution looks like the best way to go. McGyver's method of turning the cutter smaller on the cutting end and leaving the shank the same size takes care of having to make a dedicated holder for each size cutter.

If the radius is that small, what about forming the radius in your grinding wheel?
Radius dressers are quite simple, could be shop made, & not necessarily expensive to buy.

Tim

[lane]

Dickeybird I had ti do some digging to day to find it.But I did Sorry I dont have a picture . But their is a fixture made for doing just what you want to do . will fit on carbide grinder are any bench grinder are belt sander . Sold under the name Romer III Radius / Angle Fixture Found it in a J&l tool catalog Travers used to sell it also I think I am sure it may be in some others also . The picture is not good enough to build from though are i would have one and I have never seen one in person .That would be all it would take. You might try Google. Lane.