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Power-User

Join Date: Jun 2007
Location: Madras, India
Posts: 164
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Machining Small Circlip Grooves

02/11/2011 2:44 AM

What is a practical method of making tiny rectangular grooves in pins of around 3 mm dia? Standards for retaining rings, e-clips etc. (such as DIN 6799 go down to less than 1 mm with grooves around 0.25 mm wide!

For developing a prototype mechanism I wish to position items axially on 3 mm pins, preferably using standard clips around 0.5 mm thick. Pin material will be stainless steel ultimately, but can be mild steel for a start.

A table-top lathe can be organised, but I'm told that such narrow grooving tools are impractical. With my background in 'heavy' engineering, I have no 'feel' for this kind of fine work. Any suggestions would be welcome. Thanks. =TeeSquare=

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Power-User

Join Date: Nov 2006
Location: San Francisco Bay area
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#1

Re: Machining Small Circlip Grooves

02/11/2011 3:05 AM

Hello,

Carbide grooving tools may be too brittle, but if you are not going down too deep it might be possible, certainly is cheap to try.

Personally I think that HSS may be a better choice but again, if it is a 1mm groove depth per side you are in trouble with conventional tooling, I assume it it 1mm diametrally which means .5 mm per side (.020") depth. (Still deep for the width)

You have to take a very light cut per rev and if you can try to cut one side and the bottom for .15mm depth and then take .1mm off the opposite side, cutting deeper when you reach the .15 depth and so on until you reach the depth tolerance.

Another method maybe to use a thin slitting saw, possibly using CBD coated slitting saws. The depth seems to be disproportionate to the width of the slot.

As a last resort you can EDM the slots very accurately with either a diesinker or wire EDM rotation as the groove is cut.

Hope this helps.

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Power-User

Join Date: Jun 2007
Location: Madras, India
Posts: 164
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#2
In reply to #1

Re: Machining Small Circlip Grooves

02/11/2011 3:22 AM

Thanks. Groove depth about 0.35 mm is suggested in the DIN standard. Anyway I'll wait for more responses.

Also any other suggestions for simple axial positioning in small size assemblies involving levers and pulleys will be appreciated (other than nuts on threaded bolts or pins, since they can work loose).

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Power-User

Join Date: Nov 2006
Location: San Francisco Bay area
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#3
In reply to #2

Re: Machining Small Circlip Grooves

02/11/2011 3:46 AM

Hello again,

A sketch would be helpful.

If you are trying to position, far example a slitting saw blade on the 3mm dia pin. You could turn a shoulder on the pin and push the blade up to the shoulder. Too keep the blade in place you can slide a sleeve over the reduced dia of the 3mm pin and hold the sleeve in place with a small screw drilled into the center-line/axis of the pin and locked against the sleeve, using thread locker (red or blue) from Loctite.

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Guru

Join Date: Oct 2008
Location: I'm outa here
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#12
In reply to #1

Re: Machining Small Circlip Grooves

02/12/2011 2:26 AM

Tinker -- I think your idea of using a slitting saw in a tool post grinder is a good one. A dremel motor is easy to mount as a tool post grinder with a little fabrication. Nice thing about slitting saws is that they can bought in exact widths and fairly fine tooth count. And Dremels are easy to set up for variable speed.

Instead of a motor you could machine up a 3/8" or 1/2" arbor with a shouldered blade mount on one end and a thread on the other end to mount a crank handle. Then mount this in the oiled bore of a boring tool holder that can be easily fed in by the lathe crossfeed while you hand turn the crank at 25-75 rpm. Keep the feed rate low and the combined SFPM in the right range for the material being cut.

Another way to make a thin grooving tool is to grind the desired shape and width in an Xacto knife blade, mount it in the Xacto handle (the small ones are 5/16" dia.) and clamp the handle in your lathe tool holder. I made a tool holder adapter for the 5/16 Xacto handle for my Sherline out of a split 3/8" od, 5/16" id tube to fit in a 3/8" boring bar tool holder.

As a side note my very first attempt at lathe turning consisted of chucking a 4 or 5 penny finishing nail in a 1/4" electric hand drill and using mostly files to turn it into an HO scale whistle. None of my little jeweler's files that I got at the hobby shop were thin enough to form the groove shape at the lower end of the whistle bell. So I held a jeweler's saw blade about 1/3 mm wide and well tensioned in the saw frame and cut the groove with a sawing action while the drill motor rotated the nail at around 2500 rpm. I was 13 years old and the work was being done on my first HO locomotive, a Varney Dockside.

Ed Weldon

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#4

Re: Machining Small Circlip Grooves

02/11/2011 4:21 AM
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Power-User

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#5

Re: Machining Small Circlip Grooves

02/11/2011 10:26 AM

Thanks for the suggestions and links. I'm really looking for some simple quick solution without having to order some special tool or proprietary fastening unit which may never be needed later.

However I liked the idea of cutting one side of the groove first. I think I'll ask the guy to use a sharp pointed 60 degree tool tip and plunge it twice with a 30 degree left and right swivel. The bottom can be finished with a bit of axial feed since depth is less than width.

A sketch would be superfluous since I'm just trying to position some links/levers (cut from sheet metal) and spacer bushes between two side plates which may be 25 to 40 mm apart. The pin serves as a pivot for the levers, with the circlips at the ends to keep it all in place. Alternative locating elements can be used - anything simple will do. =TeeSquare=

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Associate

Join Date: Sep 2010
Location: Aiken, South Carolina USA
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#8
In reply to #5

Re: Machining Small Circlip Grooves

02/11/2011 10:34 PM

Thanks for the suggestions and links. I'm really looking for some simple quick solution without having to order some special tool or proprietary fastening unit which may never be needed later.

You did say that if it worked it would be produced [prototype mechanism]. So why not invest in the proper tool as suggested by the link.

The wheel has already been invented.

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Guru
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#6

Re: Machining Small Circlip Grooves

02/11/2011 12:16 PM

What's wrong with grinding your own tool? Any competent machinist should be able to grind a .5mm wide and .25mm proud feature on a cutting tool.

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Guru
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#18
In reply to #6

Re: Machining Small Circlip Grooves

02/14/2011 8:29 AM

Been there, done that. An optical comparator comes in very handy to check size and profile. It's amazing what can be done with a stone!!

Of course, that was back in the days before they started calling me "Shaky".

Hooker

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Guru

Join Date: Feb 2011
Location: Atlanta, GA
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#7

Re: Machining Small Circlip Grooves

02/11/2011 1:18 PM

I've cut small grooves with a narrow v ground tool set first to one angle (in the tool holder) then another: one for the groove edge near the chuck, one for the edge away from the chuck. A profile bit would be faster, but I often encounter chatter when using a wide cutting edge. If I spent some time tuning up the lathe, I could probably avoid the chatter with the wider bit.

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Power-User

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#9

Re: Machining Small Circlip Grooves

02/11/2011 11:02 PM

Consider toolpost grinding the grooves with a narrow grinding disc.

You can see a similar setup here:

http://www.proxxonworld.com.au/content/toolpost_grinding_with_pd_230_e_and_pd_400_lathes

Narrow grinding discs intended for cutoff are available 0.7mm, 0.5mm and possibly thinner, around 22mm diameter. These are of suitable scale for your work and provide a very clean groove.

Mark Bingham
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Guru

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#10
In reply to #9

Re: Machining Small Circlip Grooves

02/11/2011 11:38 PM

Very good suggestion. I've done that and it works well. In fact, I have a Dremel with a flexible shaft, the working end of which I can put in the tool holder.

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Power-User

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#11
In reply to #10

Re: Machining Small Circlip Grooves

02/11/2011 11:57 PM

In general, Dremel's have terrible spindle bearings. While a try might be OK to check the idea out, you really need a better spindle to hold dimensions.

Also, those small grinding disks round off very fast and all of a sudden you are grinding a round bottom groove.

Given the need to create accurate grooves, you may be better off by cutting the grooves with purpose-made cutters as discussed earlier.

You might also consider spacing the parts with small tubes over the shaft if you have the room.

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Guru
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#13

Re: Machining Small Circlip Grooves

02/12/2011 9:28 AM

Machining the grooves with a lathe is very practical. If you don't want to invest in tooling, you can make your own. I would start with a HHS cut-off tool because you will need to grind off less material. Grind the tool to final groove width with a tool grinder, a surface grinder, or even a bench grinder. The task is simplified because the bottom of the groove doesn't need to be precisely parallel to the shaft.

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Power-User

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#14

Re: Machining Small Circlip Grooves

02/12/2011 9:36 AM

I own and regularly use any one of several solid carbide, small groove-cutting tools made by Circle C. They range in groove width from 0.017"/0.018" up to 0.055"/0.057". I use them mostly for bore grooves, but they will work on external grooves as well. As long as the shaft is firmly held in the lathe and a modest feed rate is used, they cut nicely without breaking.

They are readily available from MSC, and likely other similar suppliers as well.

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Member

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#15

Re: Machining Small Circlip Grooves

02/12/2011 9:51 AM

I use a product called "Thin Bit" I think they are in Ft Wayne IN. Squareness is important. I use any lathe. I have also done this in a spin jig on a surface grinder. The thin bit in a lathe is the cheapest way

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Participant

Join Date: May 2007
Location: Portsmouth, New Hampshire
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#16

Re: Machining Small Circlip Grooves

02/12/2011 6:16 PM

Try a source who does laser cutting/engraving.

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Power-User

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#17

Re: Machining Small Circlip Grooves

02/12/2011 9:40 PM

Thanks for all the responses. Since the work is being organised at a relatively remote location (in India) with only minimal facilities/skills, we will try out the suggestions which do not require procurement of special items from urban centres. Dremel tools are not widely known here. I'm convinced the problem is not a serious one. We are also looking at alternative design solutions using stepped pins or other features which can be be made more easily.

I can treat this thread as closed now, though I'll look out for fresh ideas. Thank you anyway for the varied suggestions. =TeeSquare=

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Users who posted comments:

2tinker (2); bob@advanced-grinding.com (1); Doogleass (1); dziadzi (1); Ed Weldon (1); Hooker (1); JAGwinn (1); K_Fry (2); lyn (1); mrehmus (1); Relativity PL (1); TeeSquare (3); welderman (1); woodygb (1)

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