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Tiger
18th May 2006, 01:50 PM
Dear all,

I've been sharpening a lot lately and the technique has improved but I still can't work out the following:

I have some cheap spindle gouges that I got as part of a set. I use these to practise my sharpening. When they come off the grinder one seems to always have a ragged edge no matter how lightly I sharpen, needless to say it doesn't cut all that well. Another cheap gouge feels sharp then as soon as I try and turn with it, it goes blunt immediately even on pine:eek: . I am sure that I haven't raised the temper of the tools, any thoughts on why this is happening? Even if I had destroyed the temper some time ago, the ruined bit has been ground out. One of my gouges is stamped HSS and yet it still has a ragged edge. I have another gouge (expensive one) that stays sharp for long periods so it can't be my sharpening technique can it:confused: . I know you should always use the best tools but some of the other cheap tools eg the skew retain their edge far longer. Any thoughts on this?

CameronPotter
18th May 2006, 02:53 PM
Have you polished the flute? Your probably have a badly ridged flute on the cheaper tool, meaning that there isn't a good meet between the bevel and the flute - causing weak serrations that break/wear off quickly leaving a blunt tool.

Christopha
18th May 2006, 02:59 PM
Just because it's stamped HSS doesn't necessarily mean it IS..... Your expensive tool, made from good quality stell retains its' edge and the cheapies don't. I think you have answered your own question mate!

Tiger
18th May 2006, 03:32 PM
Thanks, guys. I would have expected a cheap tool to at least perform 1 cove on pine before it gave way.

weisyboy
18th May 2006, 04:07 PM
try dipping the tip of the tool in cold water straight after sharpening this will harden the tip some what and it will stay sharp longer.

soundman
18th May 2006, 05:50 PM
:( Dipping high speed steel in any coolant when hot from sharpening will not improve its temper. In fact it may cause microscopic surface cracking adjacent to the sharpend edge causing premiture failure of the shapened edge.

High speed steel responds completely differently to high carbon steel found in hand chisels and most plane irons.

Even then quenching high carbon steel without proper attention to temperature and so forth is unlikley to restore temper which is a bit more complex than that.

the likely causes of this problem may be
( as mentioned ) crappy steel
( as mentioned ) good steel treated badly at manufacture
( as mentioned ) top of flute not smooth.

It is certailnly noticable how much better "some tools" hold their edge better than others on good high speed steel you have to try hard to raise anysort of bur some of my cheap tools a bur seems to curl up over the top of the edge with little provocation.

I have a set of the cheap hare & forbes red handled jobs, even between the tools in that set there seems to be quite some diference.... all the flat steel seems to be better than the gouges.

cheer up tiger if you can shapen the dodgy ones you'll have no problem with good stuff.:D

I cant say I've got any that won't cut at least half a dosen beads though


cheers

Tiger
18th May 2006, 06:02 PM
I have a set of the cheap hare & forbes red handled jobs, even between the tools in that set there seems to be quite some diference.... all the flat steel seems to be better than the gouges.



Actually Soundman I have exactly the same thing with my Hare and Forbes red jobs, the gouges are useless at holding an edge while the straight stuff is fine.

Spindleshanks
18th May 2006, 06:49 PM
I was having similar problems with good quality HSS gouges. Turned out that my grinding wheel was dirty and blunt. Try dressing your wheel with a diamond dresser. Are you using a good quality wheel?

Tiger
18th May 2006, 07:20 PM
Spindleshanks, at first I thought that might have been the problem so I redressed the wheel, it didn't make any difference, as for the quality of the wheel, it seems ok, it does a reasonalbe job on the skews and parting tool.

Skew ChiDAMN!!
18th May 2006, 07:43 PM
Check the angle of the bevel. If it's angled too much the edge will wear at a ridiculous rate (not enough supporting steel at the tip). Similarly, if it's not enough it doesn't make a good cutting edge for normal use, although it'd probably work alright in shear mode.

Tiger
18th May 2006, 08:00 PM
Skew, the angles are pretty much constant around the 35 degree mark, but I might try a different angle and see what effect that has.

Skew ChiDAMN!!
18th May 2006, 08:21 PM
That's within working bounds, so I'll go with the others and say 'tis dodgy steel then.

Still, as Soundman said: if you can sharpen it you'll have no problems with decent tools. :)

Tiger
18th May 2006, 08:26 PM
Skew, you can probably guess my next question, is it worth firing up the oxy-acetylene plant and trying to salvage the tools? Anyne know whether dodgy steel can be brought to an acceptable level. The tools are cheap but I'm starting to build up a collection of next to useless gouges and I'm curious as to why they have all suffered this fate.

Christopha
18th May 2006, 11:18 PM
try dipping the tip of the tool in cold water straight after sharpening this will harden the tip some what and it will stay sharp longer.

No it won't!

RETIRED
19th May 2006, 12:11 AM
There was a thread on here (the board) about tempering steel. Might be worthwhile doing a search.

Sometimes the base metal is good but something went wrong in the hardening process.

BTW: I agree with Chris. Hardening is an exacting sort of thing.

hughie
19th May 2006, 01:29 AM
[
quote=Tiger]Skew, you can probably guess my next question, is it worth firing up the oxy-acetylene plant and trying to salvage the tools? ]

Tiger,

HSS steel is far more complicated to harden and temper than any carbon steel. The temps are critical and most require triple tempering.

All HSS steels are not equeal......bummer I know but there is little you can do unless your friends with a really good toolmaker who does his own heat treating.
hughie

Skew ChiDAMN!!
19th May 2006, 03:12 AM
The HSS steel one, no. But any other "unmarked" ones are worth trying to retemper. They're probably only CS so you should manage to revive some of 'em at least.

Come to that, if the HSS one is totally useless for turning, you may as well give it a try. At the worst you'll have had your revenge on it for pissing you around and at best it'd work, indicating the HSS marking was bogus. I doubt it, but... [shrug]

As said, there's a thread (or three) on retempering on this board, definitely worth reading before you make up your mind.

CameronPotter
19th May 2006, 10:08 AM
The only way that steel will harden (and it is the carbon in the steel that produces the effect - along with other fancy stuff in some of the HSS) is to get it the right temperature.

Solid steel has three phases. I can't remember all the names righ now but martensite is one (google it for more info). When the steel is hot enough to harden, that is called the transition point. The metal bonds break down and the steel actually stops being magnetic. At that stage if it is quenched (properly) then it will harden - but it will also be too brittle for turning.

Basically, there is no way that a grinder will heat the steel enough. What dipping it in water does is stops the steel from losing its temper.

Cam