Internal Groove Tool

[Barnaby WildeParticipant @barnabywilde70941]

I'd like to / desperately need to, cut an internal groove in a 10-16mm bore to place a circlip in, without the tool costing close to a weeks wages !

Grinding my own isn't going to happen.

I've spent all night on Google & can only get it down to £40'ish, surely some of you have been there before & sourced this cheaper. I need to cut 50+ of these.

I have a CNC mill fitted with a collett chuck.

[Barnaby WildeParticipant @barnabywilde70941]

[EmgeeParticipant @emgee]

What width and DOC do you need ? What material are you cutting ?

Emgee

[JasonBModerator @jasonb]

Can't you just buy a mini internal grooving tool and knock up a simple holder, this sort of tool. A member on here fave me a couple and that is what I did.

[Barnaby WildeParticipant @barnabywilde70941]

I'll be cutting into aluminium, most likely 6082.

I can't see how DOC matters but the dimensions of the groove will need to suit circlips that will fit in internal grooves ranging from 10mm to 16mm in dia'.

Hope this helps.

[Barnaby WildeParticipant @barnabywilde70941]

Posted by JasonB on 09/08/2017 20:02:47:

Can't you just buy a mini internal grooving tool and knock up a simple holder, this sort of tool. A member on here fave me a couple and that is what I did.

Cheers.

I think Google's algorythms got a bit confused about how much I wanted to spend.

[Anonymous]

Posted by Mick Charity on 09/08/2017 20:08:07:

I can't see how DOC matters…………………

Errr, because if the tool don't stick out far enough you won't be able to cut the groove deep enough.

Andrew

[JasonBModerator @jasonb]

Posted by Andrew Johnston on 09/08/2017 20:15:34:

Posted by Mick Charity on 09/08/2017 20:08:07:

I can't see how DOC matters…………………

Errr, because if the tool don't stick out far enough you won't be able to cut the groove deep enough.

Andrew

That will be depth of groove rather than DOC

[HOWARDTParticipant @howardt]

Diameter is more important than width. Although depends on what you are retaining, the position of the groove face that the circlip away from the thing you are retaining is important. So the width of the groove can be within reason anything so long as the circlip is near to its opposite side face. I would grind a piece of HSS, I know you don't fancy it but grooving tools are special hence the price.

[Barnaby WildeParticipant @barnabywilde70941]

Posted by HOWARDT on 09/08/2017 20:19:05:

Diameter is more important than width. Although depends on what you are retaining, the position of the groove face that the circlip away from the thing you are retaining is important. So the width of the groove can be within reason anything so long as the circlip is near to its opposite side face. I would grind a piece of HSS, I know you don't fancy it but grooving tools are special hence the price.

I hear what you say.

When I'm after a specific tool to do a specific job, it's like discovering I'm in the wrong job. When you realise that you can make more £money making & selling the tools to do the job than actually doing the job itself . . . then it's time to give up.

[Ian PParticipant @ianp]

Are you saying that the only machine involved is the CNC mill?

Whether a mill or a lathe the method is essentially similar but I suspect a bit trickier on a mill. An internal circlip is probably going to be in the region of 0.60 to 1mm wide but the tool required is somewhat dependent on how far down the bore the groove needs to be (and whether it a blind bore.

Not sure why you dismiss grinding your own cutter but what I am suggesting requires only minimal grinding and could be done using only a hand held oilstone.

What would work is to make a simple boring bar just for the grooving process. Cross drill a 0.8mm hole in an 8mm diameter steel bar a few mm from one end. At that end drill and tap an axial hole (M3[M4) to take a clamping screw that intersects the cross drilled cutter hole. The diameter of the cutter bit determines the groove width and so the only grinding involved is to remove half the diameter of the drill (so it looks like a very short 'D' bit). Only a very short length of the 0.8mm drill needs to project from the holder as the groove probably only needs to be about 0.5mm deep. Obviously care will be needed because the cutter tip is very delicate so only small cuts can be taken.

Ian P

Edited By Ian Phillips on 09/08/2017 20:43:50

[Jeff DaymanParticipant @jeffdayman43397]

You could make a tool like that shown below in less than an hour and from scrap cheap as chips. Shank is mild steel, cutter is a bit of a broken tap ground to shape. Setscrew can be any sort of screw, really, as long as it holds the cutter firmly. Pencil is extra cost though….

You use it like a boring bar, except once it's resting on the known-size bore at desired depth from end, you lock carriage travel and use cross slide dial to get depth of cut for the groove. If the cutter is ground to desired groove width less a thou or so it can't help but cut the groove to correct width. JD

[Neil WyattModerator @neilwyatt]

Get a bit of silver steel, about 1/4" in diameter.

Turn a length of it down to about 4mm.

Part or cut off leaving a disc on the end full diameter and as thick as you want the groove.

File away a 90-degree notch in the disc, looking at the big end, make the bottom horizontal part of the notch at 3 o'clock on the right. This will be your cutting edge.

Harden and temper.

Hold in the toolpost according to what you have and your ingenuity, like a boring bar.

Cut your groove.

I know this works because I have done it.

Neil

[Neil WyattModerator @neilwyatt]

Here you go, compared to the inserted bit boring bars, it's embarrassingly simple, but it's all you need and works in smaller holes.

[Neil WyattModerator @neilwyatt]

Obviously on the CNC mill, you will need file the disc down all round the circumference to create relief and move the tool in a gradually increasing spiral to cut the groove.

Much harder to do than on a lathe, but should work equally well.

[Tony Pratt 1Participant @tonypratt1]

Neil's got my vote or can you use a woodruff key cutter, difficult to say without exact dimensions

Tony

[EmgeeParticipant @emgee]

Posted by JasonB on 09/08/2017 20:18:48:

Posted by Andrew Johnston on 09/08/2017 20:15:34:

Posted by Mick Charity on 09/08/2017 20:08:07:

I can't see how DOC matters…………………

Errr, because if the tool don't stick out far enough you won't be able to cut the groove deep enough.

Andrew

That will be depth of groove rather than DOC

Same thing Jason !!!!!!

Emgee

[EmgeeParticipant @emgee]

Posted by Neil Wyatt on 09/08/2017 21:23:35:

Obviously on the CNC mill, you will need file the disc down all round the circumference to create relief and move the tool in a gradually increasing spiral to cut the groove.

Much harder to do than on a lathe, but should work equally well.

To make the tool to fit in the collet chuck in the vertical mode cnc milling machine If you mount the material in the 4 jaw lathe chuck and offset to a small eccentricity the tool will be backed off from the high point of the eccentric disc, cut the 90deg cutting face there to suit direction of cutting required.

If no 4 jaw pack under 1 of the jaws on a 3 jaw chuck to achieve an eccentric disc, make the disc same thickness as required width for circlip groove.

Emgee

[John ReeseParticipant @johnreese12848]

Feeling stupid. I overlooked the fact you have a CNC mill. You can interpolate the groove.

[HopperParticipant @hopper]

Use a tiny woodruff keyway cutter. If necessary you can grind off the extra teeth and cutter body to just leave the one cutting tooth.

Or use a carbide insert for cutting small internal square threads, mounted on a small boring bar. Probably cost you the same as the proper internal grooving tool though. That's the price you pay for not grinding your own. It's all time vs money.

Edited By Hopper on 10/08/2017 04:40:36

Edited By Hopper on 10/08/2017 04:41:00

[larry PhelanParticipant @larryphelan54019]

Must try that sometime !

[VicParticipant @vic]

Posted by Neil Wyatt on 09/08/2017 21:19:14:

Here you go, compared to the inserted bit boring bars, it's embarrassingly simple, but it's all you need and works in smaller holes.

That's a good idea Neil.

[John McNamaraParticipant @johnmcnamara74883]

If you have a few worn out carbide tips can you silver solder one on the end of a steel rod then grind it into a single tip cutter. of the right width Then use the CNC mill to interpolate the groove?

[Author]

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