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foose89
07-27-2004, 06:27 PM
Looking for input as to how to grind a complex profile cutter for the lathe.

John Stevenson
07-27-2004, 07:47 PM
You don't give any iea on size, shape and complexity.
One thing to take into account is that if the tool is too wide for the machine a lot of rigidity and torque is needed to cut without serious chatter.

It's suprising what can be achieved by hand on a couple of thin wheels and a template.

If it's something that ultra critical also think about having the shape wire eroded onto the end of a piece of HSS or carbide stock.
This way they can very accuratly cut the shape needed with front relief so all that's needed is to lick the top face to sharpen and still keep the correct profile.

I have just had three gear teeth cut onto the end of a HSS blank so I can cut an internal gear on the slotter and get the true involute gear shape.

John S.

Rustybolt
07-27-2004, 08:41 PM
There are tool makers that specialize in that kind of thing. They have all the T&C grinders and wheel profilers to do a really good job. If you're determined to do it yourself someplace like "Somma Tool" has high speed steel dovetail blanks that you can grind on your surface grinder. Dovetail holders are real easy to make.

Rustybolt
07-27-2004, 08:42 PM
<font face="Verdana, Arial" size="2">Originally posted by Rustybolt:
Sounds like you're talking about a form tool.There are tool makers that specialize in that kind of thing. They have all the T&C grinders and wheel profilers to do a really good job. If you're determined to do it yourself someplace like "Somma Tool" has high speed steel dovetail blanks that you can grind on your surface grinder. Dovetail holders are real easy to make.</font>

Forrest Addy
07-27-2004, 09:31 PM
I use the undersized wheels left over from my abrasive cut-off saw for detail grinding in the nooks and crannies form tools. I can dress them to a "V" and make sharp inside corners.

Gotta make a bushing so they center on the bench grinder spindle.

zl1byz
07-27-2004, 10:59 PM
Good idea mounting cut off wheels on bench grinder, but watch out for mis match spindle speeds. Can be dangerous.

John.

Rich Carlstedt
07-28-2004, 12:17 AM
I do all my form tool grinding "offhand", as I do not have a T&C grinder. I do this on both lathe tools and endmills.
Patience is the first critera.
I have two bench grinders, so that gives me 4 wheels to work with, and I also have 6 inch and 1 inch belt sanders. Also used is a Dremal with abrasive cutoff wheels and a 1/4 air grinder for bigger cutoffs.
Last tools are a 10 power glass, a 10 power comparitor(pocket) and the magnifiers that fit on your head like a ball cap, and give about 2 1/2 mag...this I use while grinding.
here are some things that help me.

1: Always learn to hold parts/tools while keeping your small finger on a tool rest so you get/keep good control of your bit..NO FREEHAND

2: sharp belts are imperative, and for small relief sections, I will put a new belt on the one inch i.e. and turn it on, and then use a utility knife on the back side !!! to cut the belt to a 1/8" width i.e....removing the 7/8" band, leaves a nice narrow abrasive strip for needed work.

3: learn to use drill shanks as measuring instruments. lets say I want a .1285 radius on a lathe tool to make a bead, so that means the lathe tool is concave. I use a drill shank to confirm its size..dressing the corner of the grind wheel to match.
A 10 power glass will show a mismatch, a "radius gauge" may not..

4: likewise, drill shanks are great for precise angle measurement.Say you want a ripple wave at the end of your 3/8 tool bit and one ripple is .040 deep and the other is .056 (or what ever) by slipping two appropriate diameter drills (not radius here !)into the groves and holding the tool square to a plate , you can confirm depths or other dimensions..you don't need a 10,000 dollar comparitor.

hope this helps..
Each time I do this, I promise to buy myself a T&C grinder..then I see I have no place to put it..and besides it is not that hard

Rich Carlstedt
07-28-2004, 12:21 AM
# 4 above....should have said
" for depth, or angular (trig it !)measurement

SGW
07-28-2004, 09:04 AM
If you're going to machine just a few pieces with the cutter, or if you're machining relatively easy materials, you might consider making the the cutter out of drill rod by suitable machining, then hardening afterwards. Grinding a precise radius is hard, but it's pretty easy to machine one (a concave one, anyway).

ulav8r
07-28-2004, 09:22 AM
Go to www.sommatool.com, (http://www.sommatool.com,) look for formtooldesign.pdf. About 30 pages of how to design form tools, including calculations on how to allow for top rake changing the dimensions.