Author Topic: How to sharpen carbide scraper?  (Read 2324 times)

Offline PekkaNF

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How to sharpen carbide scraper?
« on: January 14, 2017, 11:07:12 AM »
I have Sandvik (and similar) carbide insert scraper.

I have been trying to find out how to sharpen them properly. I can find pretty good information about business end radius etc, but sharpening details evade my googlings.

I knw that the diamond disc is used to shape it and in the end it needs to be honed, but any furher details are mixed.

1: Would normal diamond cup wheel of maybe 120 grit work on shaping?
http://www.arceurotrade.co.uk/Catalogue/Diamond-Tools/Diamond-Grinding-Wheels/Diamond-Grinding-Wheels---45-Dish

2: Honing is bit more tricky. I don't have copper plate or such to make discs, but I have some cast iron I could charge it with diamond.

What grit?

What rpm for about 100 mm dia?

Pekka

Offline chipenter

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Re: How to sharpen carbide scraper?
« Reply #1 on: January 14, 2017, 01:30:38 PM »
I use one of those diamon disks on a bench grinder , and for honing I use a 600 grit diamond sharpening stone http://www.toolstation.com/shop/p56163?table=no , leaves a good finish .
Jeff

Offline PekkaNF

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Re: How to sharpen carbide scraper?
« Reply #2 on: January 14, 2017, 04:46:08 PM »
Thank you.

I will buy one of those diamond cup wheels.

I have some diamond hones, manual ones, have to try some.

Honing is still mystery, I though I'll need something like this:
https://youtu.be/pGZjUYXlL9I

Pekka

Offline Pete.

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Re: How to sharpen carbide scraper?
« Reply #3 on: January 15, 2017, 03:32:51 AM »
http://www.ebay.co.uk/itm/152210190653

These will make your life easy. Use the rough one for setting the radius and the fine one for honing an edge.

Offline chipenter

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Re: How to sharpen carbide scraper?
« Reply #4 on: January 15, 2017, 03:39:57 AM »
It's the same principal as a wood chisel , ground and then a higher angle for honing then polish the flat to loose ant burr ,
Jeff

Offline RobWilson

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Re: How to sharpen carbide scraper?
« Reply #5 on: January 15, 2017, 04:38:20 AM »
Hi,

      Pete, If I remember correctly,  did you make your own cast iron rotary lap to sharpen your shop made scrapers?


Rob



Offline Pete.

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Re: How to sharpen carbide scraper?
« Reply #6 on: January 15, 2017, 06:21:20 AM »
Yes Rob you remember correctly - I did but I have stopped using it since these discs have become so cheap and available. Instead of charging the lap and using it to hone the scraper I simply turn on the grinder and give it a very quick 2second swipe across the disc, and the results perfectly good for scraping.

Offline RobWilson

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Re: How to sharpen carbide scraper?
« Reply #7 on: January 15, 2017, 06:31:51 AM »
Arrh! I see Pete,    thumbup:


I will see about getting hold of a set of those plates. I still have to do the scraping of the 626 mill ways, looking forward to using the TCT scrapers you made for me to do the job with.     :dremel:



Rob

Offline PekkaNF

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Re: How to sharpen carbide scraper?
« Reply #8 on: January 15, 2017, 06:40:36 AM »
http://www.ebay.co.uk/itm/152210190653

These will make your life easy. Use the rough one for setting the radius and the fine one for honing an edge.

Thank you. I have to get set of those. What RPM you use?

Zero left on that seller.

Which ones are fine? I have heard that very often they are not that straight and then some folks resor of pressing the tool against it very hard to keep it straight.

Pekka

Offline Pete.

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Re: How to sharpen carbide scraper?
« Reply #9 on: January 15, 2017, 07:09:12 AM »
They are too thin to use without a backing plate. I made one from aluminium but I then had to make a steel hub for it, mainly because of the tiny shoulder on my cheapo bench grinder's spindle which dug into the ally plate and stopped it running true. Pressing hard isn't a good idea - make them run true and use a light touch. I use mine on my 6" bench grinder which is 300rpm but they would be better used at much lower speed, less likely to scorch the disk. A dab of coolant like paraffin does a lot to help.

Any disc from 1500-up will give a good enough finish for scraping.

Offline awemawson

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Re: How to sharpen carbide scraper?
« Reply #10 on: January 15, 2017, 07:30:27 AM »
That's perhaps 3000 rpm Pete not 300 to avoid confusion of any future readers  :scratch:
Andrew Mawson
East Sussex

Offline gerritv

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Re: How to sharpen carbide scraper?
« Reply #11 on: January 15, 2017, 07:54:16 AM »
Zero left on that seller.

Which ones are fine? I have heard that very often they are not that straight and then some folks resor of pressing the tool against it very hard to keep it straight.

Pekka
Just search eBay for  6'' Inch Diamond Coated Flat Lap Wheel Grinding Disc , there are lots of them available as singles.

Gerrit

Offline PekkaNF

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Re: How to sharpen carbide scraper?
« Reply #12 on: January 15, 2017, 08:45:20 AM »
Thank you. Just ordered some discs from different sellers. Some look the same...some different maybe some of them will be fine.

Planning to make a backing and a wide clamping nut.

Pekka

Offline Pete.

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Re: How to sharpen carbide scraper?
« Reply #13 on: January 15, 2017, 09:24:41 AM »
That's perhaps 3000 rpm Pete not 300 to avoid confusion of any future readers  :scratch:

Yeah 3000 rpm - sytandard bench grinder speed. I have a 4-pole motor lined up which is half the RPM but it's a way down my list of things to do just yet.

Offline PekkaNF

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Re: How to sharpen carbide scraper?
« Reply #14 on: January 20, 2017, 07:50:50 AM »
So I ordered some of those discs and this week-end I should buy ONE diamond cup wheel for shaping these carbide scraper blades. I have seme good carbide scraping inserts and one chipped sandwik 30 mm square, which is othervice almost unused. Why it is chipped is way beyond me.

Question 1: which diamond cup wheel for shaping carbide inserts? Resin bonded? 100 grit? Cup wheel? As wide rim as i can find?

Question 2: I would like to order some loose diamond powder. To make lap if those I bought does not work. AND/OR to try lapping some granite surface plate. Will any particular type work on both of these? Or are all of those cheap synthetic unspesified diamond powders alike and as soon as I choose grit 1500 I can lap (a little).

Pekka

Offline chipenter

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Re: How to sharpen carbide scraper?
« Reply #15 on: January 20, 2017, 02:53:35 PM »
I have a 18 degree resin diamond wheel that just seems to last forever , and gives a realy good finish , http://www.arceurotrade.co.uk/projects/d_wheels/dwdoc.html .
Jeff

Offline PekkaNF

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Re: How to sharpen carbide scraper?
« Reply #16 on: February 01, 2017, 05:37:59 AM »
OK. Some "lapping plates" started dripping from china and just got the diamond cup wheel from ARC.

ARC cup wheel looks rough outside, but most likely fit is good and does not cause too much problems.

I have 90W 2800 rpm extra motor I'm planning to gear down with flat belt or round rubberthane or whatever those heat splice round belts are. Since this is fabrication, I have been thinking to use one of following methods to clamp the thin lapping disc to backplate:

1: Clamping ring/boss + nut (maybe a knurled one) to clamp the centre

2: Couple of supermagnets on the back + retaining pin on the middle. Ejection? "captive" nut or something like #1 to clamp/eject?

3: Small vacuum. I have a small quiet pump, not much is needed, but needs a rotary union or other induction. A bit over engineerin.

I would love to settle on #1, will it work. If it does - KISS, but I don't want to simplify it too far.

Pekka

Offline PekkaNF

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Re: How to sharpen carbide scraper?
« Reply #17 on: February 11, 2017, 06:56:24 PM »
Bit progress.

Any suggestion on round belt small pulley dimension. I think I read somewhere that drive wheel is V type, just like standard V-belt sheave?

Pekka