[charliex]

i've go the tormach tts r8 adapter + the ebay er20's and i having some tool slip, torqued them down to 20 lbs and cleaned thoroughly with mineral spirits etc. i'm wondering about the marks and maybe i'm misunderstanding something but if it the tool is pulled down, wouldn't there be scratch marks be all across the surfaces that were in contact? i don't think its tapered , if it is that'd explain it but seems like harder to hold.


pictures of the inside bottom edge of the tormach tts adapter

Attachment 304348
Attachment 304350

pictures of the outside bottom edge of the er20 holder
Attachment 304352

the scratches only appear for about 3-4mm

[lcvette]

Hard to make out what we are looking at.. Did they come like that? Of that is the bottom of the shank, it looks pretty rough, I have the igeshi C3/4 er20 holders and the shanks are highly polished and mic exactly the same as the TTS holders I have. Those look rough unless the picture is magnified a ton.

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[islaww]

Were you using ER-20 EXACT size collets, like most US made versions or the Asian imports that have a "range" of sizes that they fit? Few have had good luck with the "range" versions over the long run

[charliex]

the top two pictures are the bottom of the tormach TTS collet, there are vertical scratches where the tool pulled down, the horizontal circular marks are just the way it comes from tormach. t

The scratches are only at the very end of the holder suggesting the only area its touching is at the last 4mm or so, same goes for the ER20 tool, the scratches are only on the bottom end of the tool mating surface (closest to the tool)

yes i measured them.
Attachment 304442

also i tried one of the cheaper r8 holders that i got with the LMS kit, they hold much tighter and they do the seem to touch the rest of surface.

[lcvette]

Well, the only difference I see between the is the ends.. The TTS holders have a steep chamfer, I wonder if it has anything to do with how the clamping load is being distributed.. Maybe the clamping at the start of the holder is affecting the clamping at the collet opening and not allowing it to pull further up? Which promotes a weaker connection and allows it to slip?

Also if you have burrs in the collet now that will definitely cause problems and they should be addressed.

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[charliex]

the pic is magnified, forgot to mention that.

[lcvette]

Think I discovered the issue... O have only used mine for small cutters so it hasn't really mattered much but with a heavy cutter it would.

Compare the difference in the start point of the 3/4" shaft in relation to the face of the body.

The Tormach holders have the 3/4" body going all the way to the mating face of the holder body. See comparison image below.



I know Tormach had a series of different collets. Some shorter then others, mine is about 5 years old and unless I do something really silly I don't have any issues.

If the collet edge is below the edge of the holders 3/4" body it would reduce clamping force on the holder where it needs to be and bow the collet face which would result in the scoring marks you are seeing during pull out.

I am going to contact the holder company and inform them of this issue and see what they say.

It's funny, my very first ordered Tormach holders have a similar gap but my newer Tormach holders do not.. Guessing this had to do with them trying to figure out what worked best for holding ability.

See the two 1/4" set screw holder s below in the picture, both genuine Tormach holders just ordered a few years apart.. The newer is holder is marked with the number 7.





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[charliex]

yep agreed that would do it, we've been cutting for about 3 hours solid now using a "standard" r8 collet and has yet to pull it down, much tighter fit too, it just wont go all the way in and mate to the spindle bottom so going to try to find a deep R8 holder.

thanks for the confirm, knew it had to be something just didn't make sense to me, but its not exactly my field.

cheers

[lcvette]

No worries, do you have a picture of the standard collet with and without a holder installed?

I think if you made a spacer ring out of steel to go between the holder and collet on the Tormach it would work find, especially considering the Chinese brand holder have plenty of length at the end since there is no taper. Should work fine as long as it is nice and flat.

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[charliex]

sure i'll grab one, at the one we're just living with the non contact on the spindle base, apparently finding an all the way through or deep r8 isn't straightforward. i think with the spacer we'd be basically where we are now, with the top of the er20 holder not being flush to the spindle, unless i misunderstood what you were getting at.

i'm assuming the tormach r8 collet is a much wider opening when its not under compression to help with their ATC, the others ones are a snug fit even when out of the spindle.

today we're cutting deeper parts so we'll see what happens.

cheers

[Connor]

You might have a bad Tormach R8 Collet..

[charliex]

anythings possible, but given the differences between the two er20 designs, and the ATC on the tormach it seems to add up to just an incompatibility between them.

[lcvette]

Here is my take on the situation.

If you see the notes this is what I believe to be happening with these holders..




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[SCzEngrgGroup]

I think you're jumping to some rather questionable conclusions with no hard data to back them up. I'd be willing to bet the taper in your spindle is simply wrong. I can't see any other explanation for the collet not tightening up evenly over most of the length of the TTS shank, as it is designed to do. If you had your spindle re-ground to the correct taper (not terribly expensive, BTW...), I believe your problem would go away completely.

I've been using numerous different TTS holders from numerous sources for many years, and never once seen the kind of wear you're seeing. Some have the under-cut at the bottom, some do not, and I've never seen ANY difference between them. Even on my oldest holders (bought in probably 2008), the shanks are still virtually pristine. And, I have NEVER had pull-out of any kind, even when cutting at well over 100IPM, using the fulle spindle power (1.5HP).

Regards,
Ray L.

[lcvette]

It's possible the spindle has an issue, But the score marks are pretty evident that that the collet is being closed smaller then the shank to create the scoring.. It wouldn't score like that simply sliding out without an overhang. Those are witness marks and speak volumes to what is occurring in this instance. So if the collet is smaller in diameter to create that situation.. The surface of the collet behind the edge of the reduced diameter of the shank would be under stress to spread. Simple physics. What other data are you looking for?

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[charliex]

ok, but .. we did measure them, and they're 0.75" across, we have about 15 of them, but mostly importantly we've been cutting for two days with the non tormach collet and zero pull down, we even snapped a deep cutting carbide bit and it held it fine.

obviosuly if your tools have never pulled down, they wouldn't be scored, and with the different collet, ours aren't either. if the taper was off, i believe we should see the same behavior.

just seems like a simple incompatibility.

[lcvette]

ok, but .. we did measure them, and they're 0.75" across, we have about 15 of them, but mostly importantly we've been cutting for two days with the non tormach collet and zero pull down, we even snapped a deep cutting carbide bit and it held it fine.

obviosuly if your tools have never pulled down, they wouldn't be scored, and with the different collet, ours aren't either. if the taper was off, i believe we should see the same behavior.

just seems like a simple incompatibility.

I agree, the collet you are using now moves the recessed portion of the shank further down and probably within the clamping range of the spindle taper.

It is basically acting like a spacer would. Soinds line there is certainly something to this.

Glad to hear it is holding for you, is the tool height repeatability still good?

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[Connor]

Call and talk to Tormach about it. I bet anything the Tormach R8 Collet is out of spec. Go read threads in the Tormach Forum.. you'll see people talk about it. If it works good with a standard R8 collet and not the special Tormach R8 then... that's where I would look before looking at the tool holders.

[charliex]

naw, if i was going to bother tormach tech support, i'd buy their holders as well, once we either go with the space as lcvette suggested, or find a all the way through r8 or deep throat r8 it'll be fine.

lcvette, repeat-ability seems fine, it is disconcerting to see it out so far, but so far so good. the hunt continues. for some reason i was thinking you meant at the top of the er20, which makes no sense, below the spindle, way more, thanks for the diagram.

cheers

[engnerdan]

I think you're jumping to some rather questionable conclusions with no hard data to back them up. I'd be willing to bet the taper in your spindle is simply wrong. I can't see any other explanation for the collet not tightening up evenly over most of the length of the TTS shank, as it is designed to do. If you had your spindle re-ground to the correct taper (not terribly expensive, BTW...), I believe your problem would go away completely.

I've been using numerous different TTS holders from numerous sources for many years, and never once seen the kind of wear you're seeing. Some have the under-cut at the bottom, some do not, and I've never seen ANY difference between them. Even on my oldest holders (bought in probably 2008), the shanks are still virtually pristine. And, I have NEVER had pull-out of any kind, even when cutting at well over 100IPM, using the fulle spindle power (1.5HP).

Regards,
Ray L.

To test Ray's idea you might try covering the entire taper inside the spindle nose with permanent marker. Then install your collet and one of the problem tool holders. Tighten the collet and tool holder in several times then remove the tool holder and collet. Now you should be able to see how much contact there is between the collet and the taper in the spindle by where the marker is missing.

You could also do the same with high spot paste/ pressian blue if you had it. Except you would be looking for the presence of the blue being transferred instead of looking for the absence of the blue.

-Dan