Tool Problems

[Offcut]

I have been making some floating shelves for the wee ones bedroom last weekend. I was using my hollow chisel morticer to create the pocket for the wall fixings.
The shelves are made from Beech and oak.
The problem I have is that I have managed to break the tips on the hollow chisel. See pic below.

Has any come across this problem before and could enlighten me on how to stop it happening again.

I find that with hardwood the tool heats up fairly quickly and requires a fair amount of cool down time.
The tips were broken on a downward plunge and not by moving the wood before removing the tool. After the first broke I carried on just to get the shelf finished before the tool was given the heave ho and was surprised that a second one went.

Andy


Could just be a cheap tool as I think it cam with the morticer.

 

[WellsWood]

After the first broke I carried on just to get the shelf finished before the tool was given the heave ho and was surprised that a second one went.

Andy

Shouldn't have come as much of a surprise really, once one corner had gone the amount of force needed to drive the chisel would almost certainly do further damage. Without all 4 corners cutting equally the chisel would probably try to bend towards the remaining good points putting undue stress on them as well as causing the bit to come into contact with the inside of the chisel.

The initial problem may have been a poor quality/blunt tool as you say, or it could have been a clearance issue when setting up - pretty much guarateed to cause overheating. There should be about 1.5 - 2mm clearance between the chisel and bit, the easiest way to do this is the "coin trick" (another version here).

FWIW I burnt out more than one chisel before I learnt this method

Hope this helps

Mark

 

[Scrit]

I find that with hardwood the tool heats up fairly quickly and requires a fair amount of cool down time.
The tips were broken on a downward plunge and not by moving the wood before removing the tool. After the first broke I carried on just to get the shelf finished before the tool was given the heave ho and was surprised that a second one went.

Andy

There's a world of difference between the quality of steel/hardening in Chinese tools and their equivalents in British/Japanese makes. If the tool is properly sharpened and a "coin clearance" is set and also the mortise is taken in smaller bites you tend to get less overheating and breakages, i.e. work to say 3/4 in depth of cut on smaller machines, then another 3/4in and so on until the desired depth is reached. Am I right in assuming that the auger bit is blackened? If so that certainly confirms the overheating, I'm just surprised that the tips of the chisel bits aren't discoloured, or could it be that the wings on the auger actually struck the corners on the chisel and broke them off? I'd recommend that you replace the entire set with either a British set or with a Japanese set - personally I favour the Japanese-style as they have two exhaust slots and seem to clear the waste somewhat better than the traditional (Clico/Ridgway) style.

Scrit

 

[Anonymous]

Don't buy them off ebay these are usually chinese rubbish.

 

[9fingers]

Whilst we are talking of morticer chisels, does the team have favourite ways of setting the face of the hollow chisel parallel to the fence. Small chisels seem particularly tricky to get right

I've wondered about machining a flat on the shank where the grub screw seats. Any disadvantages to this?

TIA

Bob

 

[Nick W]

I've wondered about machining a flat on the shank where the grub screw seats. Any disadvantages to this?

I'd have thought the main disadvantage would be getting the flat in the right place to start with, or at least the consequences of not having managed to do so. :?

I use an engineers square held against/clamped to the fence. You can then square the chisel by holding it tight against the blade.

 

[9fingers]

Thanks Nick,

I would be confident in machining the flat within fractions of a degree but another snag I've just thought of might be that the hole for the grubscrew might not be perfect especially on a chainwanese machine.

Regards

Bob

 

[newt]

I had some of these useless chisels, however I spent a day sharpening and polishing the outer faces (notice yours look as though they have been machined with a rock grinder) just like a hand chisel. They worked just fine in Oak.

 

[Nick W]

... polishing the outer faces ...

Public Health Warning: Be careful when you do this - if you end up with tapered sides the chisel can get wedged very hard in the mortice. For this reason most people try not to do anything to the sides of their chisels, apart from the very minimum of burr removal after sharpening the inside faces.

 

[Anonymous]

Whilst we are talking of morticer chisels, does the team have favourite ways of setting the face of the hollow chisel parallel to the fence. Small chisels seem particularly tricky to get right

snip

I hold a bit of scrap straight lath e.g. 25x6 about 12" long against it with fingers and thumb, and then align by sighting through to the fence or other straight reference on the bed.
Mine are quite good quality it seems - I've used them a lot for many years now. I think they are Jap and Record.

cheers
Jacob