Page 3 of 4 FirstFirst 1234 LastLast
Results 31 to 45 of 59
  1. #31
    Join Date
    May 2010
    Location
    Not far enough away from Melbourne
    Posts
    4,200

    Default

    Lets take discussion about my heat treating workshop over here to keep this thread uncluttered. Making blades for woodworking tools - workshop
    I got sick of sitting around doing nothing - so I took up meditation.

  2. # ADS
    Google Adsense Advertisement
    Join Date
    Always
    Location
    Advertising world
    Posts
    Many





     
  3. #32
    Join Date
    Mar 2010
    Location
    US
    Posts
    3,076

    Default

    Quote Originally Posted by doug3030 View Post
    My offer is still open for a day in my shed after the restrictions are lifted, MA.

    With the current interest in plane making gaining momentum lately I might even consider a small group of like-minded people to come and have a play for the day. I have a forge and anvil, grinders and tempering oven (actually a toaster oven in the shed but it keeps me out of the kitchen and ensures domestic bliss).

    I won't set a date until we know we will be allowed to gather but PM me if interested - Hoppers Crossing Melbourne.
    a professional toolmaker here in the states suggests a toaster oven for all, dedicated to the shop. He has a "real" electric heat treating oven, but has pointed out often that many larger ovens have less good temperature control than a toaster oven, and that if you use a larger oven, you need to put one of those analog oven thermometers where the tool will go and see what it reads vs. what the large oven says (he's right about that - different areas in my oven yield about a 50 degree F difference. I have a spot in my oven that i use (no toaster oven here) and never deviate from it. It's in the air path of the convection fan and irons are consistently 25 degrees higher than the indicated temperature (but two next to each other are always within about 10ºF when checked with a non-contact thermometer).

    I've been told that non-contact thermometers can be inaccurate at high temperatures with honed or polished steels (possibly drastically), but mine seems to read right in line with tempering colors - like dead on.

  4. #33
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    I've also successfully used our kitchen oven for tempering. It takes longer to get up to temperature but I get more stable temperatures by placing the blades on a 200 x 200 x 20mm thick slab of steel to act as a thermal inertial load.

    Recently a knife making member of the local mens shed asked me about a problem he was having with his new tempering (toaster) oven which was taking a long time to get up to the 250ºC temperature he wanted and then the temperature was wandering all over the place.

    I asked him to bring the oven over and one look at the uninsulated large volume, the long glass covered elements, and all the plastic on it told me immediately this was not going going to be a successful long term approach.

    For $20 we have purchased a compact 2400W conventional oven element and for $40 a cheap PID kit.
    He's making an insulated steel box for it. I'll post something once we have it up and running.

  5. #34
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    Usual disclaimers when working with AC.
    The electrical currents involved are serious representing both serious and electrical and fire risks.
    The said item will be checked by the Men's shed sparky before being allowed to be used at the shed.

    This is what the Mens shed knife makers sent.
    There was a bit of misunderstanding about what I recommended but their hearts were in the right place.

    This is the insulating oven shell.
    The box is made from 5mm Al sheet and that is ordinary Rockwool as the max Temp used will be ~250ºC
    OvenShell.jpg

    Inside the shell was the steel box below.
    Ignore the small metal box with the black power cable in it - I've added that since.
    The slightly rusty 6mm thick steel plate box with the door houses the coiled 2400W oven element.
    "S" was supposed to be the stage where the objects being tempered.
    Plate "P" is just a cover to hold up the insulation
    Stageandelement.jpg

    I'm going to suggest they remove "P" and wrap the insulation directly around the steel box as there is plenty of room for at least knives inside the steel box itself.
    Also I'm going to recommend the door should be on the other side of the to steel box to minimise any interference with the element electrical connection box

    I then modified the internals of the element box as follows.
    As you can see there is heaps of room in there for knives.
    Mods.jpg
    IS is a stainless steel sage covering the element - on top of that they should dd a 6 - 10 mm thick steel plate to even out the heat.
    TC is a short stub of AL rod in which the thermocouple tip is screwed.
    The TC can be moved around to suit knife location - could even be put on top of knives if required.
    The element connection box is a diecast Al box from Altronics. SH is a radiant heat shield for the power cable.

    As shown below inside the die cast box, the oven side wiring is done with fibreglass insulated wiring from an electric heater.
    The white material between the IEC socket is a piece of PTFE teflon (good for 200ºC)
    The SS (SH) radiant heat shield for the plug was added later.
    When the oven it at 250º the die cast box reaches ~35ºC and the black power cord plug/socket gets to about 28º.
    HTwiring.jpg

    The PID control box looks like this.
    There's just a 16A no-volt switch and the PID controller visible on the outside.
    There's also an externally accessible 10A fuse - the most current I've seen drawn is <9A.
    The red value on the PID is the current temp, and the green one is the set point (desired) temperature.
    For $40, the "Inkbird" branded PID has heaps of features, alarms etc. We're only using temp control basics for this application.
    Controlbox.jpg

    Inside the control box looks like this.
    The black box at the top is the back of the PID
    The Grey box is a 40A SSR sitting on the top of a heat sink - the heat sink is not really needed in this app.
    PID1.jpg

    Even with the door partly open, lots of gaps at the edges and without any insulation, the PID holds the SS stage inside the steel box to +/-1.5ºC at 250º.
    Under these conditions the SSR is switching quite often - with those issues removed it should hold to better than half a degree.
    element.jpg

    Cost wise
    The Inkbird PID/SSR/heatsink and TC came as an ebay kit - $50 - there are even cheaper PIDs - as low as $28 that would do the job.
    Cable glands, fuse holder etc ~$10
    Element was from ebay $28.50
    Die cast box from Altronics $6
    The NV switch came from my stash of old switches.
    Cables/sockets/wiring came from sides from kerb side rubbish.
    The Grey PVC control box came from my stash - originally given to me by a MWF member - Thanks Phil!.
    All other materials were offcuts/scrap except for the SS plate which I paid $1 for at the steel merchant.

    It's now back to the Mens shed dudes to tidy up.

  6. #35
    Join Date
    Mar 2004
    Location
    Brisbane (western suburbs)
    Age
    77
    Posts
    12,094

    Default

    Better add the usual warning here! Get a friendly licensed sparky to do the wiring for you please, unless u r 1.....
    IW

  7. #36
    Join Date
    Aug 2006
    Location
    Canberra - West Belco
    Age
    63
    Posts
    646

    Default

    Quote Originally Posted by BobL View Post
    I've also successfully used our kitchen oven for tempering. It takes longer to get up to temperature but I get more stable temperatures by placing the blades on a 200 x 200 x 20mm thick slab of steel to act as a thermal inertial load.
    A couple of ideas out of the sour dough baking community for people who don't have big thick lumps of steel available

    Cast Iron baking dish.
    One or more pizza stones

    both add thermal mass and combined that with at least 60 minutes of preheat and heat soak time and you will have a remarkably stable temperature even in a larger oven. You can do the same thing with a toaster oven, add thermal mass devices and allow heat soak time before adding the item.
    One thing to be aware of though is does the oven with mass lose heat fast enough or even slow enough to meet the required temperature cool down curve.

    I've used toaster ovens for Electronic surface mount soldering were the curve up and down are really quite critical and measure in seconds and minutes so time frames and curves are so different but the principles apply.

  8. #37
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    Quote Originally Posted by Aussiephil View Post
    A couple of ideas out of the sour dough baking community for people who don't have big thick lumps of steel available .
    Thanks Phil.

    First - Love sourdough! . . . . . .too much.

    Good point about evening out temperatures using a thermal mass. The shape of our cast iron baking dishes would be unsuitable for longer blades which is why I went for thick lumps of steel in our kitchen oven. Thick lumps of steel can be bought for ~$1/kg from scrap merchants and provide better thermal transfer than tiles or stones.

    I forgot to add that the PID controlled tempering oven gets to temperature in under 10 minutes without over shooting by more than a few degrees and then reaches stable temp about 5 minutes after that.

  9. #38
    Join Date
    Aug 2006
    Location
    Canberra - West Belco
    Age
    63
    Posts
    646

    Default

    Quote Originally Posted by BobL View Post
    Thanks Phil.

    First - Love sourdough! . . . . . .too much.

    Good point about evening out temperatures using a thermal mass. The shape of our cast iron baking dishes would be unsuitable for longer blades which is why I went for thick lumps of steel in our kitchen oven. Thick lumps of steel can be bought for ~$1/kg from scrap merchants and provide better thermal transfer than tiles or stones.

    I forgot to add that the PID controlled tempering oven gets to temperature in under 10 minutes without over shooting by more than a few degrees and then reaches stable temp about 5 minutes after that.
    Haven't baked for a while, need to do a new batch of sourdough crumpets....

    Good point about buying scrap cheaper but i'll say that the partner acceptance factor of something in the oven is a lot higher if it's a pizza stone . I need to have a word to my son who does scrap metal recycling (mainly cars) on the side/weekends and see what he has lying around.

    Interesting you don't get much overshoot with the type of element your using, the PID controller must be reasonable at least .... I have some experience with PID controlled heating of build platforms on 3D printers, my big printer uses a 1500w 240v silicon mat under a 500x600 x 8mm ATP5/Mic6 Alu plate, watching that heat with a thermal imaging camera was instructive.

    I've not seen it mentioned but a thermal imaging camera would seem to be ideal in taking some of the guesswork out temperature of the part being heated....

  10. #39
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    Quote Originally Posted by Aussiephil View Post
    Haven't baked for a while, need to do a new batch of sourdough crumpets....

    Good point about buying scrap cheaper but i'll say that the partner acceptance factor of something in the oven is a lot higher if it's a pizza stone . I need to have a word to my son who does scrap metal recycling (mainly cars) on the side/weekends and see what he has lying around.

    Interesting you don't get much overshoot with the type of element your using, the PID controller must be reasonable at least .... I have some experience with PID controlled heating of build platforms on 3D printers, my big printer uses a 1500w 240v silicon mat under a 500x600 x 8mm ATP5/Mic6 Alu plate, watching that heat with a thermal imaging camera was instructive.

    I've not seen it mentioned but a thermal imaging camera would seem to be ideal in taking some of the guesswork out temperature of the part being heated....
    Yeah it would certainly show uniformity of heating. Although I don't know how much resolution would be available within a specific higher temp range.

    Its not for everyone by I have an optical pyrometer that can measure high temps (eg 1200ºC) to +/- 5º that I use on my gas forge.

    I posted about it on the MWF High temperature measurements using Optical Pyrometer

  11. #40
    Join Date
    Aug 2006
    Location
    Canberra - West Belco
    Age
    63
    Posts
    646

    Default

    Quote Originally Posted by BobL View Post
    Yeah it would certainly show uniformity of heating. Although I don't know how much resolution would be available within a specific higher temp range.
    Just to at least wrap up the thermal imaging camera that mere mortals could buy but it's still not cheap FLIR have FLIR TG297 | FLIR Systems for high-temperature industrial uses such as measuring the heat of glass furnaces, kilns, and forges that goes up to 1030C +-3c so the resolution is pretty good and you can spot measure different points with ease. The > $1.7k price tag though is eye watering for hobby use

  12. #41
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    Quote Originally Posted by Aussiephil View Post
    Just to at least wrap up the thermal imaging camera that mere mortals could buy but it's still not cheap FLIR have FLIR TG297 | FLIR Systems for high-temperature industrial uses such as measuring the heat of glass furnaces, kilns, and forges that goes up to 1030C +-3c so the resolution is pretty good and you can spot measure different points with ease. The > $1.7k price tag though is eye watering for hobby use
    We had a couple of FLIRs at work we used for uni student experiments. This is going back more than 10 years so I imagine the newer ones are quite a bit better. They used them to map heat distributions on the outsides of buildings.

  13. #42
    Join Date
    Oct 2009
    Location
    South Africa
    Posts
    950

    Default

    I’m just waiting for the iPhone app that does FLIR, and I’ll download that.

  14. #43
    Join Date
    Mar 2004
    Location
    Brisbane (western suburbs)
    Age
    77
    Posts
    12,094

    Default Update - Canola worked!

    Well, blow me down, once again the instructions were worth reading. I finally got around to buying a couple of litres of cheap canola oil today, cooked up another blade, swirled it in the oil and bingo! A good 35mm of the business end is now hard enough to cause a sharp file to skate.

    I'd still like to know what the difference is - I've used old sump oil for quenching O1 gauge plate steel quite a few times in the past and it came out hard. I wonder if it has to do with the slightly lower C content of 1080? Mr. Gargle tells me that O1 gauge plate is typically 0.95% carbon, so maybe I've been getting the O1 only partly hardened, but because it's got more C, it still appears to be plenty hard by my crude file test.

    And a cautionary note: The brine solution I used sure as heck got the blade I quenched in it nice & hard, but I mustn't have cleaned it off very well, 'cos when I looked at it a couple of weeks later, it was covered in a luxuriant bloom of rust! Fortunately, the rust was still pretty superficial and cleaned off with little evident pitting. I haven't flattened it properly yet, and there's more lapping to go on it before it goes into service, so it'll be shiny bright again before I finish - no real damage has been done.

    I must have gotten the old pair of pliers I was using as tongs liberally sprayed too, when I was dunking the blade They were also covered with rust, and the hinge partly seized the next time I picked them up. I think I'll quietly ditch brine quenching as a bad idea - most of my gear is a bit too close to the action in my small shed!

    Now, all I need is a quiet morning at home alone to sneak the hard blades into the oven for a couple of hours.....

    Cheers,
    IW

  15. #44
    Join Date
    Nov 2004
    Location
    Millmerran,QLD
    Age
    73
    Posts
    11,098

    Default

    Ian

    I will interested to hear how your tempering process goes. As this chart shows, that for light straw you need a temp of 229°C. I just checked our oven and it goes to 225°C listed on the dial so maybe a bit more.

    Heat treatment colours.jpg

    The other issue is exactly how accurate the indications on the oven actually are. An additional oven thermometer may be necessary to verify the temp. I intend to also investigate this path which is why I am particularly interested in you experience here.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  16. #45
    Join Date
    May 2010
    Location
    Not far enough away from Melbourne
    Posts
    4,200

    Default

    Quote Originally Posted by IanW View Post
    Well, blow me down, once again the instructions were worth reading. I finally got around to buying a couple of litres of cheap canola oil today, cooked up another blade, swirled it in the oil and bingo! A good 35mm of the business end is now hard enough to cause a sharp file to skate.

    I'd still like to know what the difference is - I've used old sump oil for quenching O1 gauge plate steel quite a few times in the past and it came out hard. I wonder if it has to do with the slightly lower C content of 1080? Mr. Gargle tells me that O1 gauge plate is typically 0.95% carbon, so maybe I've been getting the O1 only partly hardened, but because it's got more C, it still appears to be plenty hard by my crude file test.
    Ian,

    From discussions I have had recently with other knifemakers, there are a couple of reasons.

    Motor oil is formulated for lubrication of an engine first and foremost. There are specialized quenching oils you can get that are specially designed for heat treating which would not perform as well as motor oil in an engine. Better to use the product designed for the purpose or something as close to it as you can afford

    Canola is the closest cooking oil to the specialised quenching oils for high-carbon steels we are likely to use for blade making. It is consistent in its properties regardless of source. Sump oil on the other hand could be extremely variable in nature. It could be mineral or synthetic and of a vast range of viscosity. The sump oil you used last year that worked well and you worked out all your procedures on may well be very different from the sump oil you go to use tomorrow. Using a known oil and a known steel helps get consistent results.

    There are also claims that motor oil is carcinogenic, is harder to put out if you have a fire and smells worse.

Page 3 of 4 FirstFirst 1234 LastLast

Similar Threads

  1. ID for plane blade?
    By WA ANDY in forum ANTIQUE AND COLLECTABLE TOOLS
    Replies: 3
    Last Post: 18th February 2019, 02:37 PM
  2. The best Table Saw Blade for Box Making?
    By Joinathan in forum BOX MAKING
    Replies: 11
    Last Post: 19th July 2010, 02:50 PM
  3. Using an old plane blade
    By Arron in forum WOODTURNING - GENERAL
    Replies: 10
    Last Post: 12th January 2008, 12:42 PM
  4. Which plane was this blade from
    By BobL in forum HAND TOOLS - UNPOWERED
    Replies: 3
    Last Post: 15th November 2006, 10:13 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •