R8 collet

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rzw0wr

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The collets that came with my mill don't seem to hold the cutter very well.
I can't tighten them enough to keep the cutter from pulling out during a cut.


Where and what brand has good collets?


Thank you,
Dale
 
I ran into that with some of my big endmills and during a thread here one of the old hands suggested getting some R8 end mill holders. They have a set screw in them that engages the flat on the shank of the endmill. Just have to put the endmill into the holder and engage the setscrew into the flat loosely and pull it to the end of the flat then tighten the setscrew and good to go. YMMV.
 
Worth doing searches as this topic comes up periodically. Crawford/PBA, Lyndex, Hardinge, Vertex, are probably the most commonly recommended. There is a vendor in the below thread that sells the Crawfords/PBA that are very good, I would get the sizes he has left that you need and then maybe fill in the other with Lyndex/Hardinge. Otherwise a set of Lyndex or Vertex. If larger end mills then use a dedicated R8 end mill holder for say a 3/4" end mill although I have had no problems using my Lyndex. Also make sure that you do not have issues with the threads on the drawbar not being able to complete pull up the collet. Clean the oil off the collets, makes a big difference in their holding power.

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Good/bad R8 collets?

Any recommendations for good brands/vendors? I'd like to add a couple sizes to the collection. They are for tool holding on a Bridgeport, so decent runout in real life is important. On par with Techniks ER40 would be nice.
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www.ebay.com

R8 CRAWFORD PBA COLLETS-600 GROUP (IMPERIAL) VARIOUS SIZES "NEW" MOST AVAILABLE | eBay

Find many great new & used options and get the best deals for R8 CRAWFORD PBA COLLETS-600 GROUP (IMPERIAL) VARIOUS SIZES "NEW" MOST AVAILABLE at the best online prices at eBay! Free shipping for many products!
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www.ebay.com

VERTEX R8 Round Collets, 11 piece set, 1/8" to 3/4" for Bridgeport Mills | eBay

R8 collets included in the set are VERTEX R8 Round Collet Set. From 1/8" to 3/4", 11 pieces total.
www.ebay.com
 
First, check out the simplest thing. See if your drawbar is too long for the mill and the threads are bottoming out in the collet before the collet can tighten on the work or tool. If so, the simple fix is to add a washer or other spacer between the bottom of the hex at the top of the drawbar and where it pushes against the top of the the spindle. Fewer threads will be engaged with the collet when using the spacer, done properly the thread won't bottom out in the collet. Quick, easy, free common fix IF that is what is wrong. It is a common problem, somebody takes out the drawbar, does not see the washer fall off, and then blames the collets for the problem. A hardened washer/spacer is the best choice.
 
Don't go buying new collets just yet. Tell us what size endmill first. If it's a 1-1/2 endmill with a 3/4 shank, you need an R-8 endmill holder. If it's a 3/8, or it happens regardless of size, check out Bob's suggestion above.
 
MrWhoopee said:
If it's a 1-1/2 endmill with a 3/4 shank, you need an R-8 endmill holder.
Click to expand...
For sure. Smaller collets with lots of lots of torque on what is being held will slip in the collet, only friction is holding them from slipping. Weldon style shanks are what is required when torque is high for the diameter being held.
I have a set similar to this one:
1576953570358.png

My set is an 8 piece set like the one above, 3/16 to 1 1/4" cutter (edit: shank) capacity. When a tough job comes up, I change out the R8 collet for a Weldon adapter. The socket head set screw(s) engage the flats on the milling cutter shank and DO NOT SLIP, radially or downward. It is really bad for the accuracy of a mill spindle and collets to have tooling slip in the taper, which causes wear and galling. The Asian set I have cost around $100 20 years ago, they haven't been used often, but when they are needed, they are really needed! The Asian set has good accuracy, though Weldon holders by design will never be quite as accurate as collets are. Collets for the lighter work, end mill holders for the heavier work. I have never had slippage of the collet in my spindle, which is pristine and accurate. And I am not using a heavy mill, it is a Millrite, perhaps 3/4 of a Bridgeport at being stout. They do take up some headroom, so probably not very useful on mill drills and other smaller machines.
 
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In my post #8 above, I forgot to add that when using a Weldon style end mill holder, snug the set screw(s) gently and then pull the end mill down so it is at the bottom end of the up and down play, then tighten down solidly. That helps against the other scourge of end mills, sucking down into the work because of the helical cutter geometry and making the cut too deep, ruining the job. That will NOT happen when using a properly set up Weldon style holder.
 
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