Slipping bit

[Coogara]

I have the ShopBot Desktop with Z height kit added with a spindle (not router).

For some time now I've had issues when performing a profile cutout. It's somewhat erratic, but on occasions the bit will slip down about 0.5". The bit is a 0.25" sipral upcut bit. I have no problems with other bits (0.125" spiral upcut, ballnose etc), only the 0.25" spiral upcut. During the execution of the profile cut out, the bit drops and starts making deep cuts.

What I've tried:
I've measured the diameter of the bit, and it is consistent with a new, unused bit of the same make and model. I've swapped the collet for a new, unused one. I've made sure everything is blown clean and clear of any dust. I don't insert the bit so far that any part of the flute is inside the collet, nor does the top of the bit pass beyond the top of the collet. Previously, I've tightened the collet nut the same as I would for other bits. I have also tightened it with greater force, trying to ensure a better hold, but still the bit has slipped.

Other than swapping the bit for the new one, I've no other solution.

Has anyone else experienced this? Suggestions?

My good friend Scott would probably say it's because everything is upside down in Australia. He may be right :p

Thanks

Graeme

[scottp55]

With friends like me...who needs enemies Graeme!

Sounds like you've done Most things, but I should have paid more attention when those two crib boards went bad on you....musta been Something going on?

More for Newbies than you, and will probably get yelled at by people I respect, but here goes a copy/paste of my e-mail to you.






Hate to say it good buddy, but you've probably fried both collet and bit?
Called a "Catastrophic Failure" in Shopbot lingo, but VERY carefully inspect cleaned bit at collet end, and look for ANY discoloration/change of appearance/horizontal marks.......
If ANY of those are there, bit TOAST!
Most likely your new collet as well, as they both had to spin to lose a half inch!

As a bike mechanic and growing up with motorcycles.....worn sprockets will deform chain...IF JUST chain is replaced, it will strip sprocket FAST, and ruin chain as well(usually drive sprocket on motorcycles...and smallest sprockets on freewheel. Regular chain replacement and cleaning is needed BEFORE any deformation!!
Same thing with collet nut race/spindle/collet/bits.

I THINK the bit might have become toast the first slip....and maybe the same with collet...and then just replacing one(and not both ruined both?)
ANY discoloration or galling?

When was the last time you cleaned your collet cone?
(Your best solvent acetone/at least denatured...then cone up a paper towel soaked with it and spin spindle by hand ALL the way up.
Use as many paper towels as it takes to come CLEAN!
THEN do the same with a q tip.
Collet nut/collet/and bit should be cleaned also to see if any gunk comes off. AND horizontal "Shading" is indication it's worn, and TOAST!
They DO make felt collet covered cone cleaners of wood for the correct taper ...use paper towel over felt!...or make your own

Did you clean off Gunk collets are shipped with to prevent corrosion?

This is pretty good...skimming it before coffee even 1/3 done;

https://www.cnccookbook.com/getting-the-best-performance-from-er-collet-chucks/

I always seem to use downcuts for profile cutouts, so haven't had a bit slip.
BUT then I blow collet/nut/spindle cone with 90 psi EVERY bit change, AND brass brush the bit EVERY time with Bladecote(Bostich) before it gets put away.
More so that EVERY time I grab a bit I KNOW it's clean and tip has been inspected. I get burnt out sometimes, and just easier for me, and now second nature.
MIGHT come from working on an old Pratt-Whitney Tape-O-Matic for my Dad for 2 Winters...as he and my brother were maintenance drill sergeants?

Going to post this on forum anyways...as WAY too many people don't do daily or weekly maintenance.

Hope it doesn't sound too harsh Graeme:( :(
IF you're lucky.....people will LAMBAST me for being a control freak:)

Looked briefly for good pic of a "worn ER-20" collet, but need more coffee for search words apparently:(
Your friend,
scott

[curtiss]

I use a bit of medium strength Loc-tite on the shaft of the bit when I put the bit in the collet. It dries overnight. Seems to help.
(no lock tite on the collet threads)

I have a bunch of collets for a PC router... so much easier to just change out the entire collet / rather than inserting bits each time.

[coryatjohn]

If you're using an ER25 collet, then it's almost impossible to over tighten it using the standard SB provided wrenches (unless you're the Hulk). Be sure your collet and collet nut are absolutely clean and make sure your collet nut has no fractures. The collet should snap smartly into the nut and not fall out. If it does, the nut has failed and needs to be replaced. You should replace the collet nut every 100 hours or so regardless. They are $40 from SB. I haven't found a good source of quality collet nuts outside of SB.

[Burkhardt]

I had that problem occasionally with long 1/2" diameter bits (i.e. 6") when the vibration and leverage worked the nut loose over long hours.
I have since replaced all my collet nuts with the ball bearing type. They don't create friction with the collet when rotating and I never had slip problems since. Also easier to turn loose.
Not sure anymore where I bought them but they are like these: https://www.maritool.com/Tool-Holders-Spare-Parts-Collet-Nuts/c23_30_31/p1435/ER25-BEARING-COLLET-NUT/product_info.html

[Coogara]

The Desktop collet is ER20. Examining the top of the bit, it has striations around it. I guess it's time to bin it. It's been my favourite profile cutout bit for a long time. I guess it's past it's prime. I'd never switched to a new collet since buying the machine. 100 hours sneaks up on you, and is not difficult to achieve. I think it's time for a clean start - bit, collet and lock nut. Will order today. Seems the safest thing to do. I'm annoyed I forgot about the ~100 hour life of a collet. It's one of those things I used to know. Interesting about the ball bearing collet nuts. Had not come across those. Will investigate further.

Thanks all for good advice. Will take a while for order to reach Australia. I'm reluctant to buy the parts from Shopbot, as the shipping is more than I"m willing to pay, even though it would arrive sooner. This isn't my day job, so I can afford to wait.

[Burkhardt]

........ I'm annoyed I forgot about the ~100 hour life of a collet. It's one of those things I used to know. Interesting about the ball bearing collet nuts. Had not come across those. ......

I am somewhat sceptical about the 100 hour rule (other than overly proactive maintenance). There are no moving parts in operation so why should they wear out? I would rather believe if somebody said "only 100 tightening cycles".
I check my collets once a while for runout with a dial gage but I guess some of them surely have 1000+ hours including a few broken bit events but still without any runout or clamping problem.

The advantage of the ball bearing collet nut is that the tightening torque is 100% applied to the thread and does not need to overcome the friction to the collet (and no twist applied to the collet itself, only axial force). I do need to soak the nuts in paint thinner and spin the bearing with a hand drill maybe once a year to free them when getting stuck.

[Coogara]

I imagine '100 hours' is a worse case scenario (and maintaining best condition). A bit like luxury car maintenance replacing certain things (globes) at specific intervals to avoid unexpected failure. If one can afford it, and collets are not too expensive, then I guess it's okay, but how many people maintain a strict maintenance schedule on collets, I wonder?

I did read about ball bearings getting gunked up over time, so I appreciate the comment regarding a good soaking. I'll keep those in mind, but for now, to keep the cost down, I've stuck with Techniks collet and nut from AllIndustrial. 50% cheaper shipping to Austrlia than ShopBot store.

Thunder rumbling today, so staying out of the shop. Don't want a mini power loss in mid cut, on top of this issue.

[Burkhardt]

Ah found the place where I bought them: https://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collet-Nuts-Wrenches-and-Spanners/ER-Collet-Nuts-with-Ball-Bearing-Type-B
Pretty good deal for GBP 8.16 incl. VAT but unfortunately out of stock at this time.
They shipped direct to the US no problem and modest shipping charge so I guess they would ship to Australia as well.

[chiloquinruss]

Great thread. Thanks for the posting about the bearing collets. Russ

[Coogara]

Thanks. Mr Burkhardt. Unfortunately they don't have an ER20. A shame. Reasonable price.

Yes, thanks to all for your thoughts and comments. Very helpful. Will report back once I have had a chance to use replacement parts.

[Burkhardt]

Sorry, not wanting to overpersuade you ;-)
But they do have the smaller ones as "Type A" with 30mm hex and in stock. That E20 is actually the one I have. Somehow I thought E25 was mentioned earlier in this thread. I find the crescent wrench (spanner) for the hex nut anyway easier to use than the C-wrench.
https://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collet-Nuts-Wrenches-and-Spanners/ER-Collet-Nuts-with-Ball-Bearing-Type-A

[Coogara]

Not at all. Happy to be persuaded :) I searched the site for ER20, but failed to find that one - only found collets. Bookmarked for next time!

[scottp55]

Found it Graeme for my next time...JUST got a new one from Frank at Sales. So may be awhile.
Thanks for posting Gert!!! Could NOT remember it!
https://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collet-Nuts-Wrenches-and-Spanners/ER-Collet-Nuts-with-Ball-Bearing-Type-A
scott

[phil_o]

Available here https://www.maritool.com/Tool-Holders-Spare-Parts-Collet-Nuts/c23_30_31/p1434/ER20-BEARING-COLLET-NUT/product_info.html

[phil_o]

Should have been ER 25 https://www.maritool.com/p1435/ER25-BEARING-COLLET-NUT/product_info.html

Phil

[cowboy1296]

Recently I was having all kinds of problems with my buddy. I use precise collets and who knows how many hours on them, but i assure you that it was much more than 100 hrs. I called precise and they assured me that it was not the collets and as usual they were always a great source of info. I recently had a shopbot tech at my house to re-tune my buddy. I am a big guy and when he saw me tighten my collets he corrected me and said to add much more torque. So dont be afraid of tightening them.

[dlcw]

I've had my PRSAlpha for 10 years now. I cut over a thousand sheets of plywood per year plus several hundred sheets of 1/2" MDF. In addition, I do a lot of solid wood parts production. I have replaced the collet nuts once on my machine. I've replaced the collets twice. I tried another source of collets one time and I had oth 1/4" and 1/2" bits slip. I went back to my original collets until I found another source.

I know there is a standard belief that collets and collet nuts need to be replaced regularly. I've found that if I keep my collets clean and brush any sawdust out of the collet nuts during bit changes, they will last a LONG time.

On a standard cabinet project, I will cut 30-40 sheets of plywood. I use eCabinets/SBLink, so I cut all joinery, drill all shelf pin/hardware holes, create all pockets and cut out all parts using 3 to 4 different bits. A 1/4" downcut spiral, a 3/16" downcut spiral, a 1/4" boring bit and a 1/4" compression bit. Most 3/4" plywood is Armorcore and drawer box parts are 5/8" Apppleply. 1/2" plywood is normal plywood and 1/4" plywood is MDF core.

I push my machine pretty hard cutting at 5-6IPS with 15IPS jogs. All plywood is cut with a climb cut first, leaving a 1/32" skin, then a final conventional cut. So 3/4" plywood is cut almost all the way thru on 1 pass. These cutting methods put a lot of strain on collets, bits and collet nuts. But, as I said before, keeping them clean when changing bits has proven to be a way to get a lot of life out of them.

Just wanted to input how one guy uses/abuses his ShopBot. ;)