Accuracy of cheap ER collets

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Great machine, and a very interesting video.

Thanks

MichaelG.

Thanks Bikepete, glad you enjoyed it. I have some more footage, but haven't had the time to edit. I don't care so much for the editing part of making Youtube videos, and som many of the Youtubers are so clever at this. Wish I enjoyed editing more....

Do you have contact with others with SV53 experience?

Arnljot

With regard to mechman48's problem. Turn a piece of steel dead true in the lathe and mount the collet chuck on it by gripping the piece of steel in the collet. You may have to lightly support the Morse taper end in the tailstock centre releasing after tightening. The collet bore will now be coaxial with the lathe axis. Clock the collet chuck taper to check run out. This will tell you if the chuck is out or if it is a mating problem when fitting it to the mill. If it is check around for burrs etc.

Hope this helps.

regards Martin

Yes, a few other owners have been in touch via the Practical Machinist forum, also David Samways was very helpful and found an electrical schematic for me. Mine is a 53N BTW - the 53 or SV53 is a slightly different model...

I have a full metric set of ER25ss plus a few imperial ones for regularly used sizes like 1/4".

Neil

I very nearly ordered a full set of ER40 collets and then thought hang on. Grip length seems to go up with size due to the design - not good. Compressing to small sizes may not be easy and to be honest a 10mm cutter doesn't slide into one of my ER16's that easily. Slightest pressure collet taper against chuck taper and it wont go in.

My reason for wanting ER40 was for lathe work but I now have a collet chuck, Jacobs, a cheaper option. I'm not inclined to think that it's worth going to ER32 for milling just for 20mm rather than 16. ER40 would take things up to 26mm but past 16 I feel a couple of sizes of shanked face mills would be a better idea. Maybe a shanked cutter.

I did have ER40 fever for a while though and some regrets not buying ER32 but now I feel ER25 is a better option and use ER16 for small stuff.

John

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Edited By Ajohnw on 01/09/2016 12:44:33

Interesting points. I got ER32 for the 20mm span since I needed 20mm end mills. Maybe these are better held in a Weldon holder. I was also looking at OZ collets, they seem to be very popular in Switzerland.

Since I'm just starting out, it was hard to make the correct selection at first go, and this was also part of the reasoning behind buying a less expensive collet set. I just didn't know what would be the best choice for my needs. I also have a tool holder for ER16 collets, I might get some ER16 collets later

For a large size I am intending to use something like these

**LINK**

Along with a face mill for 1604 sized inserts. The face mill sizes set the size of the inserts and to save having to buy more than one type so the end mill needs to be 25mm. 10 inserts are about £40 so each end mill works out at £8. Can't sharpen them though.

I'll either modify a morse blank end arbour to hold it or machine the cutter to a size I can cope with. ArcEuro stock some morse shell mill arbors. I just got round to ordering that and a 50mm face mill. The end mill can wait until I need it. I'm hoping Arc's arbors are good. Never know might see some cheap hss shell mills, doubt it though.

John

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Me too, just watched all three of your videos - first class electrical work in rewiring the cabinet.

Thanks for the great response to my question. This really is a helpful community.

I just wanted to share a picture of the direct-collets for the ISO30 taper that came with the mill. The great advantage with these is the ease of use, rigidity, and extra headroom. Sometimes however, it is an advantage with some distance between the spindle and the work piece, so that is when the ER holder comes in handy.

These direct collets go on ebay for close to €50 a piece, so rather expensive. Fortunately, I have 6,10, 12 and 16mm, so I really only need an 8 and a 20 to cover my immediate needs.

Thanks for all the help. I'll let you know how things work with the new collet holder next week.

Edited By Arnljot Seem on 01/09/2016 20:30:45

There was a chinese made sets of ER32 collets about 2-3 years ago and they were just terribly made. The front 30 deg taper was not concentric to the 8 deg taper. The other issue was the groove was cut too shallow for the collet retract. It may be possible that you got one of these collets or one with similar problems.

I have learnt that cheap is just wasting time and money if you are expecting any level of precision.

Neil

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Thanks ... I like the look of those.

[too big for my machines, but a very logical solution]

MichaelG.

I have not seen that type of collet before but I can see its eminently suitable it is for toolholding close to the spindle bearings etc.

I'm curious though about the design reasoning why it has only three slits. I thought two cuts across the diameter would be simpler/cheaper from the manufacturing point of view, but would it grip any better with four tines?

Because there is so much metal in each tine the slit has to be extended to the thinner part of the collet so it has a chance of flexing. As the curved bore of each tine is not going to flex or conform in any meaningful way to the cutter shank, the cutter diameter has to be spot on. Cutter shanks are usually very accurate so its not a problem but it seems to me that one sawcut and two tines would work just as well.

I have no real reason for asking this question other than idle curiosity.

Ian P (Love the Schaublin mill!)

I'm sure someone will write a full-page response to this, but the answer(s) are simple.

1. A simple diametrical slit will only provide a two-point grip of the cutter, hence no positive location of the cutter axis. (An infinite number of circles can pass through two points, only one can pass through three.)

2. This type of collet is only intended to grip one specific diameter cutter. Trying to hold something that is even just a few thou larger or smaller is exceeding the design parameters. As you will have observed, the design of wide-range collets (e.g. ER-series) is dramatically different.

{edit} Just re-read your post Ian, sorry, point (2) isn't relevant to your question. However, point (1) is, especially when chasing accuracies at the tenth-of-a-thou level.

Roger

Edited By Roger Head on 03/09/2016 02:08:05

It's interesting to compare the cost with R8's and ask just what do these offer over them.

ISO30 really is a chuck taper. A rather small one. If I had a machine that used them I would be switching to an ISO30 chuck.

Up early - my wife likes doing car boots all though she tells me this one is a table top.

John

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They fit machines with int 30 spindles

Appart from that they offer all the afvantages of any other finger collet

- more likely to be concentric as there are less surfaces between spindle taper and tool

- Less protrusion so more rigid and allows larger work/longer tooling to fit in the space available.

Ian I was surprised you were curious about 3 slots when all other finget type collets like R8 and MT have 3 slots as well as 5C etc, I would have been more curious if they differed from the norm and only had two slots

Ian said 2 cuts across the diameter, which will make 4 tines.  (Oops, no, just re-read, sorry)

I have made an Int30 taper on my CNC'd Super 7 to fit my Novamill (though not made into a collet). If you have access to a CNC lathe I'd be happy to supply the Gcode. I must say I'd like some of those direct collets so may have a go at making some!  I'd make 2 saw cuts at 90 degrees to get 4 fingers.

Edited By John Haine on 03/09/2016 08:49:28

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John,

May I suggest that you read-up on 'Kinematics' before making your final decision.

There is always a tendency for things to settle at three-point contact; so it's often better to just accept the fact, and design your device accordingly.

MichaelG.

I was thinking about the need Jason compared with other options. Seems that the cost aspect can be circumvented

**LINK**

but I would be tempted to buy a very high quality chuck instead rather than paying £50 a piece of them.

John

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