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Grinding/making narrow grooving tools in HSS

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Rob Athome23/12/2021 00:55:43
6 forum posts


I need to make some narrow grooving tools capable of producing shallow grooves. I will be machining in brass and the grooves only need to be upto a maximum of 1.5mm deep. The groove widths I require will be in the range 0.6 to 1.4 mm wide.

Three options spring to mind - (1) use materials such as hacksaw blades or worn out drills for the tools. In this case how do I mount them on the crosslide ? (2) use existing parting blades and grind down the width to suit the required sizes and (3) use standard 6mm or 8mm square HSS tool blanks and grind away the end to leave just a stub corresponding to the width of the groove required.

Any thoughts or even other options ?

Happy Christmas to allsmiley


pgk pgk23/12/2021 02:02:39
2552 forum posts
293 photos

For one project I made a dremel type toolholder as below. For my project I was able to use a cutting disc in the tool but most such discs haven't got enough diameter for perpendicular access except near the free end of the work. Likely one could use dental burs instead with a straight shot to the side but you would need the appropriate collet to hold them - HP dental burs have a 2.35mm shaft diameter and can be got down to 0.8mm diameter bur. But you wouldn't have a flat bottom to your groove.

You can get micro rotary air-tools if you have a compressor... much thinner body diameter and can take dremel type accessories - for way better access. Under £20 on eBay and metal cutting discs and circular saw blades down to the widths of cut you're after. It’s not an endorsement cos i haven't tried them but in conjunction with slow lathe speed ought to work if you need accuracy on your groove widths.


JasonB23/12/2021 07:15:27
22588 forum posts
2641 photos
1 articles

6 or 8mm toolblanks will be rather wasteful, why not use 3 or 4mm ones or better still if you have any blunt or broken 6mm shank milling cutters or ctr drills use those. A simple square section holder with a reamed hole and grub screws at right angles to retain the cutter bit will make it easy to hold for grinding as well as actual use.

I just reach for the Minithin inserts.

not done it yet23/12/2021 08:05:42
6736 forum posts
20 photos

Short and stiff is a primary requirement, along with wear resistance. A hardened hacksaw blade may be sufficient if clamped between stiffeners and minimum stick-out. As it is only needing a couple of mm, or so, of stick-out the waste from a larger HSS blank is not that excessive, but smaller section is better (yes, less wastage - and much less work to get there).

As always, it may depend on where these grooves have to be cut - if in an awkward place, needing excessive stick-out, some extra thought may be needed.

Ramon Wilson23/12/2021 08:13:03
1283 forum posts
367 photos

Rob, I use cut off throw away cutter shanks for a lot of tooling. They would be my first to go for such tooling rather than HSS blanks. High quality tool steel, easily held in a holder and easily ground on the offhand grinder.


You may find grinding one as thin as .6 mm a bit of a task though so in that case I would source a small .6 thick slitting saw and mount it side on in the lathe with one tooth fixed at centre height ie it does not rotate - it works remarkably well as a grooving tool.

The shanks of HSS drills are not hard enough to use as a cutting tool generally - not saying it wouldn't work on soft material and never tried it but the FC3 cutters above make lovely tools


Regards - Tug

Edited By Ramon Wilson on 23/12/2021 08:14:01

Clive Foster23/12/2021 09:50:02
3104 forum posts
107 photos

Further to Ramons suggestion of throw away cutter shanks an equally good "thrown away" source of high quality HSS material are centre drills whose point has been broken off.

Not all of us use FC3 throw-aways but we all use (and break!) centre drills.


SillyOldDuffer23/12/2021 10:14:52
8495 forum posts
1900 photos

I'd go with what I have to hand that also fits into my tool-post. It happens to be a broken 8mm HSS parting tool, which would reduce the amount of grinding needed. Otherwise, I'd grind a new 8mm HSS blank, Rob's option 3. The hard part is 0.6mm! As I'm clumsy, 8mm gives me something to hold, and the finished cutter would go straight into the tool-post.

I'd be wary of repurposing a hacksaw blade because many of them aren't solid HSS. (Hard brittle HSS teeth supported by a soft tough backing often make a better saw that costs less.) Same problem with drill bits - the shanks are probably a tough steel rather than HSS because HSS is expensive and easily snapped.

To get a rough groove I've applied an ordinary hacksaw to the spinning rod. Can't recommend it for several reasons, but might do for a one-off.


Ramon Wilson23/12/2021 10:58:15
1283 forum posts
367 photos

Clive's suggestion of using centre drills is just as valid yes especially as he says you may not have a source of cutter shanks.

Another use for spent HSS cutters of any smaller diameter is to convert them into short length, single point boring tools.

I have (and still have) a narrow parting tool made from an Eclipse HSS hacksaw blade set into a small home made holder. I used this for the very deep slots on one of the Eta cylinder heads without any issues as I recall but Dave is right you need make sure it's solid HSS and not carbon backed.




Just found this - the grooves are (relatively) very deep. The differing groove width is due to push over as the next groove is done. Interestingly there should be more 5 more grooves in this particular head than shown but I felt that the width and thickness of them if done so would lead to disaster


Edited By Ramon Wilson on 23/12/2021 11:10:18

John Hinkley23/12/2021 11:24:12
1309 forum posts
424 photos

When I needed to make some narrow circlip grooves, I ground down a parting blade to a width of 0.8mm. I thought it would break, but it didn't. I ground the other end to 0.5mm and that didn't break, either, much to my surprise.

circlip groover.jpg

In the photo above it isn't in a holder. Stick-out should be the least you can get away with. The material it was used on was BMS.


Vic23/12/2021 11:45:39
3060 forum posts
8 photos

I don’t have any fancy grinding fixtures so the last time I wanted to shape a small HSS tool bit I did it on my mill with a carbide cutter.

duncan webster23/12/2021 12:08:15
3928 forum posts
61 photos

One of the Geo Thomas books has a luxury design of holder for round tool bits (Model Engineers Workshop Manual? perhaps someone can confirm)

Emgee23/12/2021 13:14:55
2406 forum posts
285 photos

Similar experience to Ramon's with a multi fin cylinder from EN16T for a Whittle V8 engine.
Tool is HSS ground to .6mm thick for 2,5mm length to suit 2mm DOC.
The tool did 10 cylinders before the tool tip went into the chip tray.
Link to the tool working video on Youtube below.



ega23/12/2021 16:47:55
2499 forum posts
200 photos
Posted by duncan webster on 23/12/2021 12:08:15:

One of the Geo Thomas books has a luxury design of holder for round tool bits (Model Engineers Workshop Manual? perhaps someone can confirm)

The relevant words and music are on page 62 of the Manual.

I could scan and post if there is any interest in this but the OP might like to take the opportunity to acquire a copy of this (to my mind) essential tool.

Rob Athome24/12/2021 21:01:19
6 forum posts

Wow, super response to my posting, thank you all very much. Plenty of ideas there. I have just found a stash of 1/16" parting blades ( ARC Euro ) that I got a while back. I may start by seeing how those will reduce down on the grinder or even in the mill with a carbide cutter.

Seasons Greetings to all.


Jeff Dayman24/12/2021 23:33:55
2223 forum posts
47 photos

groove-and-shoulder-tool-1.jpgHi Rob, I made the grooving tool shown in the pic from the shank of a broken tap. No idea who broke the tap, of course,... anyway the holder is just a scrap of mild steel bar cross-drilled to fit the shank of the tap, and the end drilled and tapped for a setscrew to secure it. Cheap as chips and been using it for years. By the way, make the holder before you grind the shank, that way you can use the holder as a handle for the grinding. groove-and-shoulder-tool-2.jpg

Rob Athome24/12/2021 23:48:28
6 forum posts

Hi Jeff, Thanks for your post and the pics. That looks like a fine idea.


John Reese26/12/2021 23:27:37
1035 forum posts

For those who do not want to grind their own tools there is a product called ThinBit.

Pete Rimmer27/12/2021 00:36:12
1219 forum posts
63 photos
Posted by John Reese on 26/12/2021 23:27:37:

For those who do not want to grind their own tools there is a product called ThinBit.

Ha! I aquired one of those in a box of bits and couldn't identify it.

Thanks John yes

JasonB27/12/2021 07:42:45
22588 forum posts
2641 photos
1 articles

Or the Minithin as I mentioned earlier as well as several other names, they all share the same effect of making your wallet thinner too.

Grizzly bear27/12/2021 20:19:18
300 forum posts
8 photos

If you can stoop real low, Allen (Hex) keys.


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