Author Topic: Parting tool, what angle is yours?  (Read 350 times)

Offline Twisted Trees

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Parting tool, what angle is yours?
« on: March 21, 2020, 01:59:39 AM »
Many years ago I started sharpening my 6mm parting tool at a weird angle... well 35° each side this was under instruction for a particular cut it was being used on, I just carried on using it, my 3mm one was 25° which is I believe the stock size of a new one, though I have not bought one in a long time. I do have one of the Sorby fluted parting tools I seldom use for anything other than scraping micro bead patterns not sure what the angle on that is as I only ever hone the top (non fluted) to what it already is, my thin parting tool again I have no real idea it is a Crown one that came my way from somewhere I can't remember, but I have long ago ground that to 20° on the bottom angle and 30° on the top bottom angle is a short section that I can quickly touch up on a diamond file.

Perhaps it is cabin fever from trying to avoid that zombie flu outside my safe workshop, but today it sort of struck me that they are all different, as I seldom use more than one of them at a time they just evolved that way and I seldom take any notice. They all work, do the job they are intended for but I was just wondering what angle/s are yours and why?



TT, AKA Pete, but that name is taken :-)

Online Les Symonds

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Re: Parting tool, what angle is yours?
« Reply #1 on: March 21, 2020, 05:13:53 AM »
I always go for between 20 and 25 degrees on the double bevelled tools, and about 45degrees on my single bevelled, thin blade tool.

Some of my students bring their tools with them and invariably they are really badly sharpened. The worst I've come across has been just under 60 degrees on a double bevelled tool, so that gave the the tip a combined angle of about 120.....needless to say, when we re-ground it, they couldn't get over the difference.

Les
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Offline bodrighywood

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Re: Parting tool, what angle is yours?
« Reply #2 on: March 21, 2020, 07:56:46 AM »
To be honest I havn't gpt a clue what angles any of my tools are. I have a couple lof parting tools for example that are different angles and as long as they are sharp and do the job I am happy.. What works for me may not work for someone else but when I started turning ** years ago no-one mentioned that I should sharpen the files to a specific angle. Stopped using files long ago but the angles are still all sorts.

pete
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Offline Bill21

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Re: Parting tool, what angle is yours?
« Reply #3 on: March 22, 2020, 10:00:09 AM »
Same here, I’ve no idea of the angles. These are the instructions though for my thin Firmager parting tool.

http://www.crownhandtools.ltd.uk/Melvyn%20Firmagerc.pdf

Offline Twisted Trees

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Re: Parting tool, what angle is yours?
« Reply #4 on: March 22, 2020, 12:13:48 PM »
Interesting that even the instructions don't give an actual target angle. also slightly amusing that so far nobody has any fixed ideas on how they should look.
TT, AKA Pete, but that name is taken :-)

Offline Paul Hannaby

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Re: Parting tool, what angle is yours?
« Reply #5 on: March 22, 2020, 01:16:07 PM »
Nothing to do with angles specifically so just adding to the confusion! ;-)

I used to have a HSS diamond parting tool which I ground to the design suggested by David Ellsworth in his book with a convex lower bevel and a concave upper bevel. This asymmetric grind is said to prolong the cutting edge by making it a little more durable. In practice that seemed to hold true so I continued with the practice for a number of years.

A local shop was closing down and I bought a similar M42 diamond parting tool for less than half price and ground it the same way as the HSS tool. the M42 tool didn't cut anywhere near as well as the HSS tool, even though they were ground to the same angles. I reground the M42 tool with shallower angles top and bottom and that resulted in a much better cut so I have stuck with the shallower angles. I don't measure them so couldn't tell you what they are but in this instance, shallower angles (i.e. longer bevels) work better.

Offline Twisted Trees

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Re: Parting tool, what angle is yours?
« Reply #6 on: March 22, 2020, 01:38:32 PM »
Thanks Paul, more confusion is good to have   ;D Only reason I know my angles is I switched to the ProEdge, and now set the table to a stated angle, they evolved to somewhere close to where they are now on a wheel, and as they work I just keep them the same.

I have been playing with the Stuart Batty 40/40 grind after watching an old video of his. it is a very quick way of making a bowl! but it couples with a 60° bottom gouge. This got me in the mood to ponder why my tools are how they are, I suspect by week 12 I will be measuring shaving thickness!
TT, AKA Pete, but that name is taken :-)

Offline Bill21

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Re: Parting tool, what angle is yours?
« Reply #7 on: March 22, 2020, 02:38:40 PM »
I have a 5 or 6mm wide parting tool and I too grind the bottom angle flat but with a convex grind to the top and it seems to work well.