Dovetail cutter.

[Martin ConnellyParticipant @martinconnelly55370]

Ray, your post regarding clearances was posted not long before mine and since I did not refresh the page with your posts on before my post was submitted I had not seen it. If I had I would have modified my post to make clear that the comments regarding positioning of the inserts and back edge rubbing was only relevant to inserts with little or no back rake for anyone who was thinking of making their own tooling in the future.

Martin

[Raymond AndersonParticipant @raymondanderson34407]

Hi Martin, No problem. Will make a 3 or 4 insert version at the weekend and see how it performs in relation to the 2 insert version.

Cheers.

[MuzzerParticipant @muzzer]

My mistake, Raymond. I'd overlooked the fact that these were positive inserts. IIRC, the presence of a screw pretty much tells you that it's a positive one. The 7 degree angle isn't easy to make out in the photos – well that's my excuse anyway.

In the interests of science and to test my Fusion 360 skills, I made a 3D model of the insert and used it to produce a revolve extrude (using the front cutting face of the insert) and made a circular sweep cut (using the trailing face – they are offset by 2.38mm). The shell formed by these operations shows the clearance at the trailing edge and if this reached zero there would be burnishing. You can clearly see that there is a small gap. Fusion's measuring tool doesn't seem to offer any means of measuring the thickness but the large (outer) chamfer radius is 0.4mm for scale.

I hadn't realised how large the tool was. The length of the cutting edge is about 19mm for a "11mm" TPGT insert and there appears to be about 8mm between inserts, making the overall major diameter about 44mm(?). Fusion 360 struggles to report any useful measurement as things stand. Hopefully they will improve that aspect soon. However, playing with the position of the insert it seems that until the radial distance between the inserts goes below zero, the clearance is finite. Once you go to a single insert and start to bring the inside edge of that insert within and past the centre line, the clearance will become zero. That means you can't reduce the overall diameter below about 3.5 times the inscribed diameter (11mm here) with a TPGT insert.

This would have been easier in Solidworks, Solid Edge, Inventor etc but I thought I'd explore Fusion and also my own capability.

Hope this is vaguely interesting!

Murray

[JasonBModerator @jasonb]

I should think you could get the diameter smaller by playing with the insert angle much like the smaller boring bars tilt the insert down towards the cutting edge.

[Raymond AndersonParticipant @raymondanderson34407]

Hi Murray, yes, I found your post interesting. I had actually made a 3d model in Solidedge ST7 [ lucky enough to have a seat of the full programme bought at no small expense ] and I used it to check "clearance " before I started to make the cutter. Solidedge also gave me the base size of the ISO TCGT 11 insert as 10.416mm which gives me clearance of 0.292 per side of each insert.. I actually got me Ø's wrong in an earlier post as the Ø of the cutter with inserts is 25.36 leading edge to leading edge,and 24.77 trailing edge to trailing edge. so it will go into a slot of >26mm.

I think Fusion 360 is giving you an error as the cutting edge length is 11mm I could have made the Ø smaller by a few mm but as I stated earlier I wanted to keep the core strength. I am going to make a smaller Ø one at the weekend using either 2 or 3 09 inserts. The m2.2 torx screws will certainly test me "tapping skills"

cheers.

[MuzzerParticipant @muzzer]

Haha, silly me again. I couldn't understand why the Mitsubishi insert I downloaded seemed to be too small. Now I know why:

The ISO system defines the "11" as referring to the edge length for this insert, noting that a "TCXX11" insert has an inscribed circle of 6.35mm, yet a CCXX06 tool of a similar size is defined by the inscribed circle of 6mm. Go figure – I'm sure it made sense to the authors at the time. Anyway, it caught me out. Something useful came of it!

I was able to use SE ST7 for a while due to my daughter having a full licence for her studies. Very nice – preferred it to SW I must say. I'm exploring F360, partly due to the full 3D CAM that comes for free (it's HSM Works) and although it still lacks a few features, they are on the roadmap. I believe sheet metal is about to be released and they already include FEA (thermal, stress etc) and surface modelling.

Murray

[Raymond AndersonParticipant @raymondanderson34407]

Fusion 360 gets a lot of good reviews, is it made by Autodesk [ who I think also make Inventor ]. Solidedge is very powerful it also has FEA , Clash analysis, and a whole host of features that I know nothing about.!! I got a seat at a good discount through the brothers employers , was still very spendy but I did save a good bit... The brothers employers use mostly the big brother of Solidedge {Siemens NX } which is 5 axis or more. 3D cad certainly helps to avoid making a part only to find out it doesn't work, and you're left with scrap.

cheers.

[MuzzerParticipant @muzzer]

When I corrected the insert and cutter dimensions (11mm between apexes, 2.38mm height for TNGT110204, 26mm across widest point >> centre line rotates on 7.5mm radius), it looks more lifelike, although I now get a contact at the top of the cutting path. I think it may be time for me to move on….

Murray

[Raymond AndersonParticipant @raymondanderson34407]

If nothing else at least you will have added to you're Fusion skills.

cheers.

[Raymond AndersonParticipant @raymondanderson34407]

As promised here is the 3 insert version. Cuts like a dream [ even better that the 2 insert version ] This one is not EN24 this one is from a bar of Ø 30mm Silver steel. I put it between the bench centers and I have gotten slightly closer in matching the inserts to each other. 2 insert one was 0.005mm 0.007mm, this one is slightly better giving 0.004mm 0.006mm. Very "soft " cutting action. Ah but alas, there is a boob which I never noticed until I was almost done !! Can anyone spot the "boob " ? Needless to say if it hadn't worked so good I would have scrapped it and started again.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Raymond Anderson on 04/09/2016 11:23:13:

Ah but alas, there is a boob which I never noticed until I was almost done !!

Can anyone spot the "boob " ?

.

Looks fine, provided the mill runs sweetly in reverse.

MichaelG.

Edited By Michael Gilligan on 04/09/2016 11:56:47

[Raymond AndersonParticipant @raymondanderson34407]

Gold star Michael, I set the dividing head up the wrong way. Just as well the collet chuck has drive dogs. so I can run it in reverse without the drawbar loosening. What a "buffoon I am ".

Cheers.

[JasonBModerator @jasonb]

I thought all your tooling was like that down under so the coolant goes down the plug hole the right way

[Raymond AndersonParticipant @raymondanderson34407]

I think you're getting me mixed up Jason. I'm not from a land down under, i'm from a land up top [at least the top of the UK.]

Cheers.

[Raymond AndersonParticipant @raymondanderson34407]

Finished the 4 insert version made from Silver steel. Tested it on the same piece of 4140 that I used for testing the 2 and three cutter versions. Result, Cuts sweetly, very, soft action. Ignore the blemish at the top of the dovetail, as that was where I tested to see how deep a dovetail I would get with a 09 insert gets 9mm, that blemish was from trying 9.25mm. Have stuck a few mpre pics in the Album Dovetail cutter.

[RainbowsParticipant @rainbows]

At what point can a man say he has too many dovetail cutters?

Is the only thing that keeps the inserts located the screw?

[Raymond AndersonParticipant @raymondanderson34407]

Different size of inserts, The single , 2 and 3 insert versions use 1102 inserts that can give a 11mm max Dovetail. The 4 insert one uses 09 inserts and will give a 9mm max dovetail. I think thats enough for me now. Yes, it is only the [ correct size ] screw that holds them in. If you are ACCURATE in the mounting location, they can never move.

[Neil WyattModerator @neilwyatt]

For the price of those inserts, someone would have cut and scraped all your dovetails for you

Why not write these up?

Neil

[Raymond AndersonParticipant @raymondanderson34407]

Hi Neil, I would but I'm not sure if I would be any good as an author . What exactly would be involved ? I suppose if it was only pics of the set ups and some words then I could probably manage that ok. As long as I'm not expected write out something resembling  War and Peace in size.

cheers.

Edited By Raymond Anderson on 10/09/2016 18:10:51

[Neil WyattModerator @neilwyatt]

Posted by Raymond Anderson on 10/09/2016 18:09:56:

Hi Neil, I would but I'm not sure if I would be any good as an author . What exactly would be involved ? I suppose if it was only pics of the set ups and some words then I could probably manage that ok. As long as I'm not expected write out something resembling War and Peace in size.

If you can make sensible posts on here you can write articles! War and Peace definitely NOT required.

Email me on neil.wyatt@mytimemedia.com for guidance (an offer open to anyone else with nice tool builds like this or other good ideas).

Neil

[capnahabParticipant @capnahab]

Looks really good Raymond, another vote for a write up with details eg on positioning the inserts. Don't know if you have seen this guys version

 

Edited By capnahab on 18/09/2016 09:37:52

Edited By capnahab on 18/09/2016 09:38:29

[Raymond AndersonParticipant @raymondanderson34407]

Hello capnahab, Thanks. Yes I did Watch the video you mention. The cutters work a treat [even the one that I have to run in reverse because I set the dividing head up wrong ] I was at a bit of a loose end and had thought about making a 2 insert one, then got carried away a bit and ended up with 4 . Enjoyable little project [filled in a couple of hours ]

cheers.

[MuzzerParticipant @muzzer]

Interesting. Just came across this vid showing a similar home made cutter that illustrates the problem I was describing. In this case he cheated by grinding the inserts back by hand.

Murray

[Raymond AndersonParticipant @raymondanderson34407]

Very interesting vid, If you pause it at 5 mins and blow it up you will see a red line that is superimposed on the screen . It looks to be "off center " It looks as though it needs to be slightly more to the left as we look at it.

Were the line to be moved slightly to the left that would mean that he has one insert below center and one slightly above. It could just be an illusion but I think the line should be more to the left. If he kept both his inserts cutting edges EXACTLY on center [ not above or below ] he would be fine. It is positive inserts as well so god knows what went on there.

Yes, Muzzer that was exactly what you and I think Martin was referring to. I have clearance with all me insert sizes both 9 and 11mm. it appears to be cutting well once he ground the inserts back , so well done to him for salvaging it.

[Author]

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