Parting Blade Holder

[francist]

About a month ago I was doing something stupid and snapped my parting tool. I say parting “tool” and not parting “blade” because it was a tool I had ground from a piece of square high speed steel. It worked great and I got a number of years out of it, but then I broke it so end of story. And I didn’t feel like grinding another one from scratch again sooo....new project: parting blade holder.

I saw a number of good ideas here in recent weeks and was going to go with the one-piece block with the flexure slots, but at the last minute I decided to make a two-piece style with separate cap.

I started with a blank of 2” round, faced both sides on the lathe, and then squared up one edge for the nose.



Then I trimmed off the two adjacent sides, drilled and tapped some holes, and sawed the blank in half. One half for the bottom, the other for the cap. I trued them up on the shaper.







This is where my design got a little over complicated. I was trying to allow for using different types of blades in the same holder, so I designed in four adjustment screws that could be either wound in or backed out to depending on the blade. It looked good on paper, but in real time the available meat for the threaded holes was a little thin. I can still use the bottom two for ensuring the blade seats vertically, but I don’t know that the added effort and jigging around was worth it.



After a little cleanup and and a new T-nut I called it done. All in all it seems to perform as planned so I guess that’s a win. I’ve never used these P-type blades before so I’ll see how that goes. Thanks for looking!



-frank

 

[randyjaco]

Nice work and clever design.
Randy

 

[Ulma Doctor]

waaaay cool Frank!!!!!
very nice work

 

[francist]

Thanks guys, I appreciate that.

-f

 

[FOMOGO]

That came out really nice Frank. Those little band saws sure are handy. Mike

 

[mikey]

Came out really nice, Frank.

I wondered if you considered making a relief cut at the upper edge of the bottom piece to clear the wide part of the blade. That would allow that wide part to protrude into that relief and that would allow the flat part of the blade to rest up against the body of the tool to hold it vertical. Then all the top bolts need to do is apply downward pressure to hold the tool rigidly in place. If the relief is deep enough, just about any width P-type blade should fit your holder.

 

[francist]

Thanks Mikey, I did consider that and from what I saw that’s typically the way people do them. What I wasn’t sure of though was if all blades would have the same section, or what might happen if I decided to use other than a P type blade. Like a standard tapered blade, for instance.

So, my scheme was to have some degree of adjustment factored in. The screws were also supposed to allow for different thicknesses of P-style blade so that I could set it closer or further from the edge of the block. I incorporated a shallow “hook” into the edge of the cap so that it helps to grab the top edge of the blade if it’s really close to the edge.

Like I said though, I can’t be certain it was worth the extra effort and whether the simple two-stage relief for the blade would have gotten me to the same place in the end.

-frank

 

[mikey]

I understand, Frank, and you did a great job. I just thought I would raise the idea because it would allow for the greatest amount of rigidity given the solid support of the blade body. You're right in that a tapered blade would not fit this scheme so if you use those kinds of blade then my suggestion won't work. I never use them myself; I find P-type blades are more precisely ground and are more consistent so they cut better for me. Please understand that I wasn't being critical in any way.

 

[francist]

No worries mikey, all good.

-f