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veegates
12-28-2008, 11:38 AM
Hi,
I am hoping someone might give me some advice. I want to cut a spiral groove(similar to a thread) on a small approx 1/8th" hardened rod. The groove needs to have a specific shape. sort of an ogive. I need to do it on a small lathe. I found Norton makes a vitrified grinding wheel that would work. But the smallest size it comes in is 7 1/4 diam. Too big for my jewelers lathe. I was wondering if there were any mounted abrasives that once dressed to the profile I need would maintain their shape while grinding on hardened steel. I guess they don't have to be mounted, I could make an arbor. I have used Dremel cut-off wheels but in this instance they are too thin. Does anyone know of a small (approx 3"odx1/8") grinding wheel that would work?
Thanks to all!
Kevin

Carld
12-28-2008, 11:48 AM
Are you going to do this on a jewelers lathe?

veegates
12-28-2008, 12:54 PM
Hi,
Thank you for replying. I was going to use the Boley, but I need the threadcutting attachment on my Sherline. The groove that is ground in the rod needs a certain pitch and on top of that it is a double lead.
Thank you!!
Kevin

Oldbrock
12-28-2008, 02:51 PM
I would look at the mounted wheels in the dremel kit and dress the shape you need on one of those. Peter http://i273.photobucket.com/albums/jj232/brockley1_bucket/January07snowsofar29th002-1.jpg With a setup similar to this.

ckelloug
12-28-2008, 03:11 PM
I've had bad luck with dremel for simple mounted points I'd fear trying to do anything important. I got some old ones from the local hardware store and they pretty much exploded on contact with metal. I do know resin bonded wheels go bad after they sit on a shelf and Dremel merchandise often does.

I did a quick skim of the Norton catalog and it looks like they have some 3 inch wheels that sound more like what you want. The following catalog shows them. It may be tricky getting a distributor that has them but they're made by Norton:

http://www.ind.nortonabrasives.com/Media/Documents/S0000000000000001035/Norton%20Full%20Line%202007%20Vitrified%20Toolroom %20Wheels%20Type%2001%20&%2002.pdf

If you're lucky, maybe you can get a sample.

--Cameron

Carld
12-28-2008, 03:58 PM
For starters, the dremel may work but you will have to contour some wheels for the groove you want. You will also have to mount the dremel at the same angle on the tool post as the angle of the spiral.

Also, the work and the grinder wheel have to turn opposite each other. I think the dremel turns clockwise from the back of the tool so the lathe will have to run in reverse for grinding. Yes, you will have to use a lathe with threading capability.

You will need lead in time for the carriage to take up all the slop and because the shaft is about 1/8" the cuts will be shallow. The work will turn slow, say about 75 rpm and the grinder much faster. You will have to experiment on some material first and find the right combination. You may have to support the free end of the shaft.

Oldbrock
12-29-2008, 01:17 AM
Like Carld says, you will have to tilt the grinder to the helix angle but the dremel wheel should do what you want. Don't expect much depth of cut per pass though and you will have to spark out frequently before adding to the next cut. If you are too aggressive the wheel will quickly loose its form. You will probably hafe to use coolant to keep such a small section cool. Peter

davidh
12-29-2008, 09:49 AM
could a guy super glue a couple of those dremel wheels together and still dress them to contour ? i have never tried two together.

i super glue my single ones before i use them just to keep them from blowing apart so easily

Oldbrock
12-29-2008, 03:06 PM
seems feasible Davidh although I've never tried it. Don't know how wide a profile he needs but it should work, I'd try that as the cut off wheels cut quite well. Peter ( Carld. I don't think the rotation of wheel and chuck matter in his case, it's just like climb milling after all and shouldn't matter)

veegates
12-30-2008, 09:57 AM
Thanks to all for the great advice.
Wish me luck!!
Kevin

Circlip
12-30-2008, 10:34 AM
You don't state the shape of the groove. If it's a sharp vee groove, you could try the diamond wheels on a Dremel, but you can widen the shape by setting a shallower helix angle in the tool post.

Regards Ian.

Teenage_Machinist
12-30-2008, 03:18 PM
If you can find CBN mounted points they would hold shape.