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DIY parting tool

John Torchick

John Torchick

Joined
Jan 24, 2010
Messages
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Location
Cleveland, Tennessee
I'm kind of DIYer and was looking at making a parting tool. I obtained a piece of CRS that is 0.073 thick and about 2 inches in width, 10 inches in length.. Would this be too thin? I'm sure that this metal would have to be sharpened frequently but would like the "challenge" of making my own parting tool. Your help is appreciated.
 
U probably need at least 2, maybe 3 parting tools of different widths , it's what you get use to and some jobs and small blanks it would be advantageous, u might have one about .15 and compare the cutting experience.
 
That may be getting a little thin but if you grind it so the cutting tip well below center it should work. I have a paring knife that I use as a parting tools as well as a Hacksaw blade. Both are pretty thin
 
One technique I'm going to try for a "thin" parting tool -- a high quality bi-metal reciprocating saw blade. Grind off the teeth, taper it a bit at the top edge for clearance. One of our club guys has been making these for awhile now, and I've seen them used, pretty slick. (no handle, if memory serves)
 
For a really thin parting tool, I've used a piece of street sweeper bristle, 0.034" x 0.125". Grind the end like a big one, and hold in a vise-grip pliers with the long end below the handle for leverage. And use very close to the work.
 
I don't know what CRS is, but assuming that it is some type of Tool steel then it could be used, but 2" is too tall to be practical and 10" is too long. It will need to be a short stubby tool to minimize twisting. Except for plunging straight in (perpendicular to the spin axis) a tall parting tool is a problem when you need to make an undercut. Using my thin kerf parting tool as a guide, I would have the parting tool no more than 1 1/4 inches tall. I think that a blade length of five inches maximum would be about right. My thin kerf HSS parting tool is 2 mm thick. Your piece of steel is about 1.8 mm thick which is fairly close to mine.

A thin parting tool can bend and get stuck in the kerf. If that happens the tool will be will be violently jerked from your hand. That can be rather dangerous if you let it happen. I know because it happened to me. I wanted to cut a six inch diameter face grain piece into two bowl blanks. Even though I had been making clearance cuts, the tool grabbed, bent the blade and somehow pulled past the toolrest and made a full circle stuck in the wood. I the process I received a bad gash in the palm of my right hand. I straightened the blade and I am still using it.

UPDATE: Google just found the answer for me after a lot of searching and discarding options such as Catholic Relief Society and Congressional Research service (gee, I just noticed that I mentioned politics and religion in the same sentence ... I suppose that I need to ban myself). It looks like the answer is cold rolled steel. I suppose that you now need to know if it is full hard, half hard or skin hard, but I don't know how you determine that. Full hard is about 20% harder than hot rolled steel. Hot rolled steel is fairly malleable so a thin piece might bend. Cold rolled steel is a less likely to bend, but it appears that the difference is not substantial.
 
Cold Roll steel is usually, at least in my experiments, low in carbon and doesn't harden well. I use it mostly for support or shafts for metals that do hold an edge. Like you said I have no idea how to check it other than sticking in a grinder and looking at the sparks. I buy Drill rod when I need to be able to harden something because you can get the exact specs and it will tell you exactly what temps are needed to harden, anneal, etc.
 
Several of our more experienced club members use old knives and regrind them to parting tools. (Not dining knives, but kitchen knives or pocket knives). Good for relatively small diameter spindles.

Cold rolled actually typically has higher carbon content than hot roll (although unless they tell you the steel type, such as 1012 or 1018, we are speculating). The last two digits (12, 18) indicate the carbon content, in the US designations; 1012 is 0.12% carbon, 1018 is 0.18% carbon. Both of these are low carbon.

If you go to a flea market or a garage sale, get an old kitchen knife (such as a paring knife), then, re-grind to suit. Look for a really ratty, grungy, rusted knife blade! This indicates it's carbon steel rather than stainless, and it'll be easy to grind to shape and easy to sharpen (and resharpen as you use it).
 
Right I find the old butcher knives are excellent because they are wider on top. My favorite parting tools is one I ground from a Drywall saw. I bought it at the flea mkt for $1 brand new. Ground the teeth off and shaped the cutting tip. It's very thin and perfect for my lidded boxes.
 
Jamie Straw said:
One technique I'm going to try for a "thin" parting tool -- a high quality bi-metal reciprocating saw blade. Grind off the teeth, taper it a bit at the top edge for clearance. One of our club guys has been making these for awhile now, and I've seen them used, pretty slick. (no handle, if memory serves)
Click to expand...

Try the Milwaukee TORCH brand. They are really tough.
Or for a tiny one the Bosch Jig saw blades are really good steel.
 
Thanks to all. The cold roll steel is pretty much a standard in the appliance industry. I was going to make a handle for it so that would shorten the blade somewhat. Looked at parting tools online and in catalogues- a bit pricey for a piece of metal, IMHO. I have heard of them being made from hacksaw blades, knife blades, hand saw blades, etc. Thought I would give it a try.
John, I like the idea of a butcher knife. Need to look at some flea markets. May even buy some fleas for the dogs. lol
 
Jamie Straw said:
One technique I'm going to try for a "thin" parting tool -- a high quality bi-metal reciprocating saw blade. Grind off the teeth, taper it a bit at the top edge for clearance. One of our club guys has been making these for awhile now, and I've seen them used, pretty slick. (no handle, if memory serves)
Click to expand...

You definitely want to wrap the blade or glue a handle on a thin blade like that. One good catch parting a piece
and your hand will not be happy. Duct Tape or Masking Tape would work fine as a quick fix.
 
Mike, I intend on using my outstanding woodworking skills to make a handle plus I stayed at a Holiday Inn Express once. Worked with sheet metal many times and I know how sharp it can be.
 
Cold Rolled Steel is just that and the same as Hot Rolled Steel, it only is harder from the working of the steel, in being rolled while cold, heat it and it is the same as HRS, or take HRS and hammer it while cold and you’d have CRS material.
That is basically the same material as sheet metal, and a thin piece like that has no rigidity, I would not use that as a parting tool, could be quite dangerous as it could easily twist and grab, besides being so soft that it dulls in seconds.
The sawsall blades that have the hardened teeth and softer back would be better, also the butcher knifes are harder steel and tapered, using the thicker part of the blade up you’d have less problems with grabbing.
Even bandsaw blade steel would do better than CRS.
 
I'll check with my son, the engineer, as to exactly it is. I don't recall HRS being used much at all in appliances. Thanks, Leo. When are you gong to finish the glass of wine. You have been holding it for ages.
 
cold rolled steel is just hot roll that has been allowed to cool and then run through more rollers knocking the mill scale off and bringing it to a more precise dimensional tolerance.
It's more expensive and unless the appearance or exactitude of the dimensions are of concern it's just not worth the money. There are times I wish I'd bought cold rolled even with the added cost because to paint it or to TIG weld I gotta clean it really well with the grinder.

Cold Rolled is sort of a mis-statement because it ain't cold, it's plenty hot it's just lower in tempo than the Hot Roll which is done above the recrystalization temperature of the steel.

That mill scale ends up on boats to China where they smelt it into steel.

A tool for cutting wood will need to be made from one of the many tool steels.
 
I bought some inexpensive HSS bar stock on Amazon for a few dollars, including free shipping, and made a thin parting tool. It works fine. I wanted a thin parting tool so I bought a piece that was 2mm x 30mm x 200mm. I ground it to form a tang and turned a handle. I tried drilling for rivets so I could use flat piece of wood for the handle but I was unable to find a drill bit hard enough to make the hole for the rivet.

They have a bunch of different dimensions for sale, depending on what you want but 200mm (~8 in.) is as long as you can get there. I've bought a variety of sizes for different turning tools, and they all work for what I wanted. Sometimes it's marked SKH9, which is equivalent to M2 HSS, and from what I can tell it holds up at least as well as the budget HSS turning tools out there.

The only downside is that sometimes you have to wait a while for shipping.
 
I made a narrow parting tool four or five years ago from an old steel circular saw blade. I figured it cut wood fine when it was a saw blade so it should work fine as a parting tool.
The blade was probably fifty years old or more so likely high quality American made steel.
I cut it easily with an angle grinder and a metal blade and tuned it up with files and the bench grinder.
The blade is .068" thick or just over 1/16". It projects from the 12 1/2" maple handle about 3 1/4", so it wont cut very deep but it works well for my use. Blade is held in the handle with some barrel bolts I had on hand.
It's easy to sharpen and use and cost nothing but my time.

Parting tool 2017 01 08-01.jpg Parting tool 2017 01 08-03.jpg Parting tool 2017 01 08-04.jpg
 
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Bill Boehme said:
I don't know what CRS is, but assuming that it is some type of Tool steel then it could be used, but 2" is too tall to be practical and 10" is too long. It will need to be a short stubby tool to minimize twisting. Except for plunging straight in (perpendicular to the spin axis) a tall parting tool is a problem when you need to make an undercut. Using my thin kerf parting tool as a guide, I would have the parting tool no more than 1 1/4 inches tall. I think that a blade length of five inches maximum would be about right. My thin kerf HSS parting tool is 2 mm thick. Your piece of steel is about 1.8 mm thick which is fairly close to mine.

A thin parting tool can bend and get stuck in the kerf. If that happens the tool will be will be violently jerked from your hand. That can be rather dangerous if you let it happen. I know because it happened to me. I wanted to cut a six inch diameter face grain piece into two bowl blanks. Even though I had been making clearance cuts, the tool grabbed, bent the blade and somehow pulled past the toolrest and made a full circle stuck in the wood. I the process I received a bad gash in the palm of my right hand. I straightened the blade and I am still using it.

UPDATE: Google just found the answer for me after a lot of searching and discarding options such as Catholic Relief Society and Congressional Research service (gee, I just noticed that I mentioned politics and religion in the same sentence ... I suppose that I need to ban myself). It looks like the answer is cold rolled steel. I suppose that you now need to know if it is full hard, half hard or skin hard, but I don't know how you determine that. Full hard is about 20% harder than hot rolled steel. Hot rolled steel is fairly malleable so a thin piece might bend. Cold rolled steel is a less likely to bend, but it appears that the difference is not substantial.
Click to expand...
I had an incident similar to Bill. I bought a homemade, thin parting tool from a back-of-the- van vendor at a WT show once. It was about 1/16 inch thick, 1 inch wide and abt 6 inches long. The handle consisted of a piece plastic shrink tubeing. It too got seized while parting off a piece, folded into the slot, spun around, and hit my left hand, causing minor injury. I could just as easily hit me in the face.
My rule now is to make sure that handle of the too is wide enough and long enough that in the event of blade seisure the tool cannot get by the tool rest.
 
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We had an incident with a 16 year old student who purposefully did not make a relief cut to see what would happen.

What happened was he got into a tug of war with a little carba-tec lathe. The quarter hp won, pulled the tool out of the handle, and threw the tool across the room like a knife.

Luckily no one was in the path. A lot of noise but no damage to anything of value.
 
David, that is what I had in mind. I have found a bit of extra $$$ so I might just spring for a PT.
 
I guess for you box makers, the thinner, the better......but thinner also means more flexible, and that could be a problem. So how thin can you go, and still be safe?
 
I have used a thin hacksaw blade in its frame and a back and forth motion to get a thin kerf. As the blade is tensioned and supported at both ends it is safer then a thin parting tool.

I also made thin parting tool from an edger blade. Used in landscaping. It was hard and took a bit of time to drill holes for the handle.
It works well and is about 3/32" thick. No photo as it is in my shop in NY and I am not.

Stu
 
As mentioned, mine is 2mm wide, but it's 30mm 'tall'. That's about as thin as I dare, but I don't feel unsafe with one this thin. I hope that's not naive.:eek:
 
odie said:
I guess for you box makers, the thinner, the better......but thinner also means more flexible, and that could be a problem. So how thin can you go, and still be safe?
Click to expand...

Odie I just brought in some more firewood, and as I was out anyway, stepped into the shop to measure my thinnest parting tools that I made some years ago, and yes for making small boxes (round ones ;)).

It is .61 mm or .024”, flexible yes, but only 1.5” blade length, I feel safe using it and have and still do, picture here, the handle fits right to my hand and is very comfortable.
thin parting tool.jpg
The problem with boxes is that when making a tenon/recess for the lid you loose more wood showing than that very thin cut of the parting tool, not that bad with nice straight grain wood, but if not, that does show.

So my thought was to not use a tenon or recess but add a sleeve to fit the lid on, works nice, I’ve used contrasting and same wood for that, so now you have hardly anything off on the grain lineup.
box 1.jpg Box 1 open.jpg box.jpg box open.jpg Spalted Birch.jpg
 
Leo Van Der Loo said:
Odie I just brought in some more firewood, and as I was out anyway, stepped into the shop to measure my thinnest parting tools that I made some years ago, and yes for making small boxes (round ones ;)).

It is .61 mm or .024”, flexible yes, but only 1.5” blade length, I feel safe using it and have and still do, picture here, the handle fits right to my hand and is very comfortable.
View attachment 21688
The problem with boxes is that when making a tenon/recess for the lid you loose more wood showing than that very thin cut of the parting tool, not that bad with nice straight grain wood, but if not, that does show.

So my thought was to not use a tenon or recess but add a sleeve to fit the lid on, works nice, I’ve used contrasting and same wood for that, so now you have hardly anything off on the grain lineup.
View attachment 21691 View attachment 21692 View attachment 21693 View attachment 21690 View attachment 21694
Click to expand...

Leo,

Those boxes are beautiful.

Rich
 
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