Bit Slipping

[Designer]

I have been reviewing past posts about this type of thing happening. My bit is relatively new and so is my collet. The bit is an Onsrud 3/8 inch 3 flute down spiral with a 3/8 inch shank. The collet is 3/8. It is the only one that I have had slip and it has done this 3 times. I have a 2 flute .50 bit down spiral which fits in my .5 collet and it has not dropped. So, I expect that the Z is holding steady. I did get a minor surface rust on the bit and in the collet when I forgot to remove them from my BT32 once. I used steel wool to clean them. Note that the bit slipped before that happened and also after. Is the 3 flute down spiral pulling the bit out? I usually only cut about .25 deep with it. Should I just pitch them both and get new ones?

[garyb]

what brand and size is stamped on the collet?
is it inch ID or metric? for 3/8" ID the collet range is .336 -.375 what does it mic
then what's the tool number and SO number engraved on the shank of the tool?
Gary

[curtiss]

I use a number of these inserted into a 1/2 inch collet.

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bushing_ball_bearings.html?zoom_highlight=bushings

Most of the time, I use a bit of Locktite blue between the bit and the adapter. It dries and holds quite well I think. The bit with bushing are easy to change as I always have a 1/2 inch collet on the router.

The 1/2 adapter has never slipped inside the 1/2 inch collet or caused wear or damage.

However I do find lots of other ways to mess up....http://www.talkshopbot.com/forum/images/icons/icon7.png

[Designer]

Thanks for the responses.

The collet is the same brand as came with the machine. It came in a box that identified it as a 3/8 collet. I will have to check the actual size and marking when I get back in my shop. The tool was purchased from Onsrud. I did mic it and its shank is basically dead on 3/8 diameter. I will add more info tonight.

I like the idea of an insert so that I can keep the 1/2 inch collet in the spindle. I would need one for 1/4 and another for the 3/8. Are these long enough to fully engage the collet? When you use them, do you have to use a spacer to take up the space if the bit's shank is not as long as the collet? Sorry for all of the questions.

Note that I just ran a part yesterday using my .50 two flute down spiral bit. It ran fine. So, I thin I can rule out "Z" drift.

Thanks for the help.

[Brady Watson]

I like the idea of an insert so that I can keep the 1/2 inch collet in the spindle. I would need one for 1/4 and another for the 3/8. Are these long enough to fully engage the collet? When you use them, do you have to use a spacer to take up the space if the bit's shank is not as long as the collet?

Wet noodle lashing to ensue...These are poor, lazy ideas and cause more problems than they help. Not your fault for thinking in terms of possibility, but it just isn't done when you have a spindle that uses spring collets.

Collets and the taper in the spindle NEED to be cleaned at EVERY tool change. Collets also do not last forever. They are consumables.

Once a bit slips in said collet, it is to be TOSSED INTO THE TRASH BECAUSE IT IS NOW RUINED. Think of burnishing steel on steel @ 12,000+ RPM.

It is possible that the box was labelled 3/8, but in fact was a 'universal' collet that is made for 3/8" and 10mm shank tools. These collets are not to be used on any spindle sold by SB because there isn't enough thread on the nut to fully collapse the collet. Some brands *may* work. Most do not.

You gotta order a new one...Fractional 3/8". Techniks usually makes tip top stuff.

On another note, you are twisting & snapping the collet into the nut before you thread the nut onto the spindle, right?

-B

[bobmoore]

The collet and the bit shank are integral parts of a precision machine. These are not Ryobi hand routers. Buy quality equipment from trusted vendors and you will have higher quality cuts. If your bit and collet had surface rust on them, throw them in the trash and buy new. My vendor recommends replacing collets regardless of visual condition every 2000 hours of run time.

[Justin G]

On another note, you are twisting & snapping the collet into the nut before you thread the nut onto the spindle, right?

-B
I have to piggyback on what Brady is saying here. When I first got my machine, I had a .5" upcut 2 flute spiral bit repeatedly slipping out of the collet. I was losing my marbles even talking to Sb support. Everyone I talked to had a lot of things to say, mostly because all of them assumed I had a basic knowledge of the machines to begin with. Until I called onsrud support directly where a nice gentlemen asked me frankly if I was snapping the collet and nut together. The Er25 collets that came with my machine are "snap collets." I'm not claiming this is a technical term, but you MUST snap the collet into the collet nut before screwing them onto the spindle. You'll know when you try it, because it will click, and then can spin in your hand relatively easily. Also removing bits becomes a lot easier, just keep unscrewing with the wrenches and the collets pop out.

[Justin G]

Sorry, specifically: snap collet and nut together THEN insert bit into collet, then screw collet/ nut onto spindle and tighten.

[bill.young]

As Justin says snapping the collet into the nut is not intuitive and lots of people don't know to do it. Here's a quick video as reinforcement:

https://www.youtube.com/watch?v=6gMezORPi8M

[lex]

Technics collets are way too cheap on Ebay to risk a bit in the face. Toss the one you have and buy some new ones. NEVER, EVER use an insert or a collet that has slipped even once!

[knight_toolworks]

I go by feel when tightening as the collet whats it takes more tightening to tighten. so it gets easy to tell and I find I replace them before a bit slips.

[Burkhardt]

So far I had only 4" long 1/2" shank bit slipping on 2 occasions. I suspect the leverage of the rigid bit and the vibrations of the flutes biting shook the collet nut loose over several hours of machining. I have since replaced all collet nuts with ball bearing nuts and have not had a problem anymore. The ball bearing feature should increase the clamping force substantially at same tightening torque (all assuming the collet is clean and I use some collet care oil occasionally).

[Gary Campbell]

FYI to all....Here is a shot of the Technics collet nut torque specs:


http://www.talkshopbot.com/forum/attachment.php?attachmentid=26616&stc=1