lathe question-parting chisel

rdewinter · Post by **rdewinter** » Sun Feb 15, 2009 2:11 am

i used a parting tool to sever a piece of about 2" round. The parting tool got extremely hot, actually turned blue, I dipped in water to cool it. The tool had not been used at all that day and was sharp. You have to give constant pressure for the tool to work and I thought I wasn't to aggressive. Any thoughts? Could I have ruined the tool?

Bob
San Diego

ggurgiolo · Post by **ggurgiolo** » Sun Feb 15, 2009 10:53 am

You didn't ruin the tool. Just resharpen it on your sharpner and you will be fine. Anytime you get a tool so hot it turns blue just grind away the blue and you will be back to SS steel and ready to go as long as your tool is sharp. The parting tool gets the hottest of any lathe chisel. Happens to me all the time.

beeg · Post by **beeg** » Sun Feb 15, 2009 1:10 pm

Make your groove a little wider than the parting tool. I find that that help cut down on the heat build up.

charlese · Post by **charlese** » Sun Feb 15, 2009 1:35 pm

Hi Bob! As far as I know there are a few reasons to cause your parting tool to heat up that much. I am assuming you were using the standard diamond shaped SS tool.

-Dull Tool is eliminated, as your tool was not dull.
-Speed too fast. Fast speed could have contributed.
-The parting cut was as narrow as the tool itself. A "straight in" parting cut will allow the edges of the tool to rub on the shoulders of the cut, causing heat. Fix: make secondary cuts widening the shoulders a bit so the tool clears the shoulders.
-Approach of the tool to the work - - A scraping cut (below the axis of rotation will cause you to use more pressure and result in heat. - - Try holding the handle of the tool a little below the tool rest and allow the tool to penetrate the piece.

You shouldn't have to use hardly any inward pressure if the parting cut is going right. The tool should slide right into the wood without any push. Start the cut slightly above the rotation axis and hold firm on the tool. As you near the center of the piece, allow the handle to come up and the point of the blade to drop a little.

beeg · Post by **beeg** » Sun Feb 15, 2009 2:03 pm

charlese wrote:You shouldn't have to use hardly any inward pressure if the parting cut is going right. The tool should slide right into the wood without any push. Start the cut slightly above the rotation axis and hold firm on the tool. As you near the center of the piece, allow the handle to come up and the point of the blade to drop a little.

I start out that way, but once I have a small groove. I move the cutting edge to the top of the part, and ride the bevel. Then pull the tool back, till it starts cutting and then raise the end of the handle slowly to finish the cut.

chettrick · Post by **chettrick** » Thu Feb 19, 2009 5:52 pm

The design on the parting I believe is usually smaller at the cutting point which would make the part you are cutting smaller than the shank of the tool, which might bind.

I like to start my cut with the tool, then create a wider path for the blade, less chance of binding. Also it gives room for the tool to stay cooler with the air around it.

I think you went in to fast and it dulled the blade and it got hot.

JPG · Post by **JPG** » Thu Feb 19, 2009 6:08 pm

chettrick wrote:. . .

I think you went in to fast and it dulled the blade and it got hot.

And scraping?

If a diamond shaped tool, the point needs to be at the widest point of the 'diamond' or the cutting edge WILL be narrower than the 'widest' part.

charlese · Post by **charlese** » Thu Feb 19, 2009 11:05 pm

beeg wrote:I start out that way, but once I have a small groove. I move the cutting edge to the top of the part, and ride the bevel. Then pull the tool back, till it starts cutting and then raise the end of the handle slowly to finish the cut.

Excellent! Improvement on what I described!:D