New R8 Collet

I have had delivered from Tormach a replacement collet for my 770. This part is made by Lyndex in the USA.
I have been lapse in the maintenance of the original but on removing it all seems good, but thought I would replace any way.

As you can see from the photo the two differ dimensionally and design. (Lyndex shown on the left in photo)

I don't know if having a smaller dia and shorter taper is better, but alarm bells rang for me that the shaft dia on the replacement collet is about 1 1/2 thou smaller than my original part. Surely that can't be right.

Tormach original R8 collet

Over all length 4.045"
Length of taper 0.916"
Dia of taper 1.24"
Dia of shaft 0.94945"

Tormach branded Lyndex replacement R8 collet

Over all length 3.902"
Length of taper 0.702"
Dia of taper 1.204"
Dia of shaft 0.948"


I would appreciate your moments before contacting Tormach

That is a very different looking collet, I don’t think that the straight shaft dia is critical or that it even contacts the spindle walls ( though I have not checked to see if that is true) the taper being small or shorter may make a difference but could still have the holding power needed for our low HP mills hopefully they tested new design, it being small will ensure the face of the collet does not interfere with the TTS holder and sits up in the spindle properly. How does it clamp on the tool holders, feel secure ? Do you have a PBD ? I’d imagine the spring washers would be more compressed with the newer collet.

I had an issue with a TTS adapter that drove me nuts for a while till I found it, on my collet the groove for the locating pin was not ground far enough down and made contact with the pin before the collet fully seated on the taper and some tool holders would make contact with the adapter before the spindle face and gave me varying tool lengths, I don’t believe I had the only one like this so possible the new design of your collet results from them needing another supplier or even in these COVID times just needing a supplier. This is a picture of the collets I had.

Looks to me like the new collet would be more independent of variations in spindles. For example, if there were slop in how the straight part transitioned to the taper, the new collet wouldn’t care. It might be an improvement.


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A quick look on the internet gives the R8 Bridgeport collet shaft dia as 0.9495/ 0.949". So my original is within tolerance of a standard R8 collet and the Lyndex differs by a thou.
Regarding the taper dia difference, by my calculations the Lyndex collet face will be 0.1" farther away up from the spindle end. Not much point having a recess on the back of the TTS tool holders. I would have thought the larger the dia the better, but I know nothing on collet design.
As to the end of the collet floating in its 1 1/2 thou space mattering, I don't know, after all the collet pulls the TTS holder up against the spindle. If that was Tormach's intention then surely the original collet should have been smaller.

Any further thoughts?

Hi John

Thanks for posting this. The TTS collet is key to holding and accuracy on the Tormachs with TTS. This collet should be of higher accuracy than a standard low cost collet. The taper needs to be the correct length for clamping transfer and wear reasons, and its 3/4" bore needs to be accurately concentric. Also the top diameter needs to be a close fit in the spindle bore to hold the whole collet axially in line with the spindle. Clearance there means it will likely be thrown off center by the draw bar thread. The draw bar thread is not high precision.

The OD is 1.25" and a length of 0.937" The diameter of the top parallel locating portion is not a "fractional inch" size like the other dimensions and is critical. 0.9490" to 0.9495". I measured some standard R8 collets I have - 0.9494", and in the past I ground a close fit holder to 0.9495" .

So your collet is out of spec in several areas. I hope this is not representative of current Tormach stock.

You may remember I had a similar issue with my RapiidTurn 5C spindle bore rear location diameter.

Please bring this to the attention of Tormach ASAP . Feel free to copy them this message.

Cliff

The Tormach branded collet looks correct for my 1100 . The other collet shown does not look like its designed to work with tts system but it could hold a large cutter.

I just got in one of those Lyndex R8 collets in the last month as a backup on a recently purchased well-used 1100 s3. So I had to check this out after reading the above posts. Sure nuff, my old collet looks much different. But the body is even thinner (especially the dark mid-section and the taper is much longer. But, the base of each collet measures 0.9465. Additionally, if you put tapers together, one collet up and on down, the collets line up, so they appear to be same taper. So next, I set my calipers to 1.1 inch and marked each collett with a marker and these also line up. See picture. (of course my android turned it sideways). The lyndex taper ends in a stepoff, so it ends prematurely compared to the other collet.

I think if you stand the collets side by side on their drawbar ends like my picture you can see the important geometry and sort wheat from chaff. I think the lyndex is fine compared to my old one. I see tormach website has 4 obsolete r8 collet numbers so I suspect there have been several manufacturers.

Of course, TIR and some dykem will be better than this novice.....

I had a reply from Tormach regarding there new shape, shorter and smaller dia shaft collet. They stand by their new design saying that it is to overcome historical clearance issues with the TTS tool holder. I emailed again, still with my shaft diameter concerns and told them my only option was to buy another collet from different manufacturer and have the face ground flat. The reply was that they understand completely. So there you have it.

Quote:

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Originally Posted by John Roberts

I had a reply from Tormach regarding there new shape, shorter and smaller dia shaft collet. They stand by their new design saying that it is to overcome historical clearance issues with the TTS tool holder. I emailed again, still with my shaft diameter concerns and told them my only option was to buy another collet from different manufacturer and have the face ground flat. The reply was that they understand completely. So there you have it.

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Hi John. So I think you saying that Tormach were not concerned that the TTS collet is 0.001" below spec. They think it is acceptable to sell more like that. ? If so that is a real concern.
Cliff

That appears to be their view. I have since bought a UK made Crawford collet which is in spec and is identical to my original Tormach collet apart from the front face needing to be ground flat.

I have had a problem with the center relief diameter being too small on some collets for use on a Bridgeport. The issue is the pin would jump out of the groove and the collet rotated. Since I removed the pin in the quill, it is no longer a problem. Most people recommend this. I have not done this on the Tormach yet, but I don't push it as hard as the Bridgeport.

Dave