Thread chasing recess tool

[Michael Beswick]

I am having trouble with my recess tool-or more likely the tool is having trouble with me. As the tool engages and starts to form the recess it is effectively cutting on three “edges”. In addition (see photo) it increases in width slightly as the recess deepens. So in many cases it “digs in”. What am I doing wrong?! I did think about moving the tool “in and out” a bit to enlarge the recess and only cut with two “edges”.

Should I sharpen this with a diamond home just on the top face or the bevels on my low-speed wet grinder?

 

[Bill Boehme]

Disclaimer: I am still a novice at chasing threads.

Your thought about enlarging the recess is a good idea. If you don't enlarge the recess slightly then you could have a situation similar to a parting tool getting trapped in the kerf. Also, I think that the tool could stand some serious squaring up. I don't like the rounded corner wedge shape.

Another potential cause of the problem might be that the recess tool is making contact slightly below center. If that is the case, the tool will self-feed into the wood. The solution would be to make sure that the tool is making contact above center,

Make sure that the tool rest is placed to minimize the tool overhang.

 

[Don Wattenhofer]

As the tool engages and starts to form the recess it is effectively cutting on three “edges”. In addition (see photo) it increases in width slightly as the recess deepens.

The tool should be configured like a parting tool except with the handle at 90 degrees. The parting tools have one cutting face with sharp corners and parallel sides so that it will only be cutting on one face. The way that tool is ground is way off and it is very understandable that it would dig in. Grind the end parallel or less the other way to the other side then grind the cutting face square and it should work much better plus it does not hurt to widen the cut some.

 

[robo hippy]

I only machine thread my boxes. I am not sure what that tool is supposed to do. For me, to get the relief at the bottom of the threads. I use a skew chisel with about a 30 degree angle from high to low side, or point to heel. Not sure if that tool you show is for that or not. For shaping the tenon or recess, I use various NRSs.

robo hippy

 

[Michael Beswick]

Thanks to all. I’ve experimented with tool rest height and whilst it makes a difference it did not overcome the problem. What you’ve said confirms my suspicion-a wedge shaped tool is not going to work. Back to work will the file and then the grinding wheel. I’ve emailed the (UK) supplier -it will interesting to hear their response. This was modified to give a 3-3.5mm recess and on closer inspection the “angled “ face is at right angles to the sloping cut out face, not the spine of the tool.

No doubt a skew will produce a recess - or a small carbide. I bought the recess along with the hand thread chasers. I spent a couple of weeks developing the technique and realised two things. Unless I thread regularly I would lose the knack and the slightest mistake and in most cases I’m sunk as you are cutting several threads at the same time. So I bought the Hope threading jig. The difference between me scraping at 250 rpm and the cutter at 2500 rpm and only cutting at a single point clearly makes a difference. I have two threaded boxes to prove it! Another 283 and the sunk cost will be absorbed….

I’m also learning more about suitable species for threading. CA glue is not the panacea that some of the claims would have you believe. There is a link between species and TPI that can be used. I currently only have 16 TPI so need what I’d describe as hard slightly oily wood. African Blackwood looks great but seems only available in small sizes. Ditto Boxwood but I managed to persuade a club member to let me have some off cuts to practice with.

Part of me thinks I should have carried on with hand chasing but I suspect that I would have quietly put the tools in the drawer.

 

[john lucas]

You need to be at or slightly above center on the cut. My homemade recess tool has a rounded tip. I push it in as deep as I want and then may push or pull it toward me to make a wider kerf if I think it needs it.

 

[hockenbery]

So in many cases it “digs in”.

Lots of good tips.
I did not see one on tool rest height and keeping the tool level( hard not to)
Correction @john lucas Just mentioned tool rest height.
When a scrapers bevel contacts the wood it will dig in or catch.

The rest needs to be set so the tool scrapes a little bit above center. Need clearance between the wood and the bevel.
If the rest is low the tool will dig in.

Flat on the rest and level with the floor also keep the bevel from contacting the wood.

 

[john lucas]

Here is my relief tool. Ground from a cheap screwdriver.