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MT3 vs R8 spindle taper

jcdammeyer said:
Now, if you add a WUT underneath your draw bar nut then you can hand turn the drawbar until it captures the collet. Keep turning until the drawbar snugs up. Then grab two wrenchs, one for the WUT and one for the draw bar and heave at it.
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My mill drill uses a similar concept except the WUT (as you call it) is on top. But same difference. The WUT is used to stop the draw bar from turning, and the nut underneath it is used to draw the drawbar up and tighten the collet.

The issue on my mill is different. My problem is that I don't have enough hands. The WUT system would add yet another hand requirement. That's going the other way and making the problem worse. The brake on the mill eliminates the problem the WUT addresses.

But how do you hold an endmill in a loose collet at the same time as you hold the brake and tighten the drawbar?

I usually do this by holding the endmill and spindle with one hand and tighten the drawbar with the other. It takes a tight grip so I've cut myself on a sharp endmill more than once doing this. I have a similar problem using ER collets.

Sometimes I lock the spindle by engaging both the back gear and the dog clutch. But I'm always afraid I'll forget and strip some gears engaging the power.
 
ER collets I don't have a problem with. Put the mill in low gear so there is some spindle resistance, hold the bloodthirsty end of EM with protection, tighten collet nut with other hand. It doesn't take much hand tightening to prevent drop out. Now hold brake & tighten drawbar. This operation is harder to do with R8 collet. Actually I can reach both EM & drawbar simultaneously, just. But I were much shorter or mill was much taller, not enough anatomy to span the gap. Maybe there is an old school trick to R8 insertion without power assist, but personally I never saw the romance to R8.
 
I must be doing something wrong.
Of course I'm mostly using the TTS holders. If the R8 collet is in place I insert the TTS holder and turn the nut by hand about 1/2 a turn. Now the tool stays in place. Then the two wrenches and tighten.

To loosen I might throw a rag under in case it drops out but normally loosen to finger tight using wrenches and then hold onto tool and finger loosen draw bar. Then just a light tap on the draw bar and the tool drops out.

Now for R8, if you are loading a 3/8" 4 flute end mill right into the collet then first insert collet and again with fingers spin drawbar until it's almost all the way up. Now insert tool into R8 collet and tighten.

Taking out is easier because now I can use two hands to loosen with two wrenches until finger tight or looser. Of course all my tools have a sliding fit into the collet.

If the tool is smaller than the collet then I can see issues but I haven't run into that.
 
Eyecon said:
I looked at that but at 1800 rpm and 6” of y travel it doesn’t seem like a good option for 3400 cad. I also didn’t think the front mounted Z handle would make it a good candidate for CNC conversion.


I’m not too sure about that. I get servos for sure in terms of speed and torque under certain conditions. But with the affordable lower grade ball screws that we all use for these conversions, and lost motion because of ways vs linear guides, I’d rather get feedback and correct the output based on the actual position of the table not the motor shaft.



Roger that! :)
Click to expand...
Think again about servos, my encoding the current set up is 0.00012 approx, had I paid a touch more it would be 0.000016 approx. The first exceeds the accuracy of the mill.

Depending on which option you choose the servo encodes at 800 rev or 6400 per rev.

Even if I switch to ball screws with an approx pitch of 1/4" per rev on my servos that still translates as 0.0003"

My biggest stall was concerns about stalling and loosing step. I must say my machine exceeds expectations and am able to push the machine and keep accuracy right up to the limit of the machine.
 
I use R8 collets (though very rarely now), R8 Weldon style holders for certain sizes and now use R8-ER holders, I have several and for the most part leave them set with the highest used tooling.

Most of my tooling now is Carbide and razor sharp, I've never had a cutting issue installing or removing.
 
PeterT said:
ER collets I don't have a problem with. Put the mill in low gear so there is some spindle resistance, hold the bloodthirsty end of EM with protection, tighten collet nut with other hand. It doesn't take much hand tightening to prevent drop out. Now hold brake & tighten drawbar. This operation is harder to do with R8 collet. Actually I can reach both EM & drawbar simultaneously, just. But I were much shorter or mill was much taller, not enough anatomy to span the gap. Maybe there is an old school trick to R8 insertion without power assist, but personally I never saw the romance to R8.
Click to expand...

Bloodthirsty EM eh! Too funny. But also so true!

I'm plenty big enough to reach both ends with zero problems.


jcdammeyer said:
I must be doing something wrong.
Click to expand...

I don't think so! In fact, the only thing I've ever seen you do wrong is hook the negative lead of a scope to the wrong place!

You just are not using a loose Bridgeport Clone.

Since I don't plan to ever do CNC, I have no need to spend money buying or time making TTS holders. I'd rather use ER or even native R8 collets. The system is certainly cool though.

Peter & John - I really didn't intend to make this into a bigger problem than it is.

My real problem is a very smooth free spinning Bridgeport type spindle and motor system with very low drag or resistance. What a horrible first world problem to have!

Normally I manage. The only time it gives me real heart burn is when the tool I am using is at the bottom end of the collet adjustment range so I have to hold it till I get enough grip on it with the collet.

I shouldn't really complain.

Truth is that I should simply develop a habit of engaging the bull gear and the spindle clutch to lock the spindle and then remember to unlock it afterward to avoid crashing my mill. This and perhaps sell my collets and buy a set with a finer range so I can always easily tighten up the bottom end first as Peter describes.

FWIW, I just recently bought a set of metric collets that were on sale hoping it would partially accomplish this goal. Only time will tell how well this works!

Thanks to both of you for so gratiously letting me vent a bit about my first world problem. And a huge thank you to @Eyecon for tolerating me hijacking his thread.
 
Really only the people working with MT3 collets can answer how easily it is to swap out say a 1/2" two flute roughing end mill for a 1/4"" four flute finishing end mill. How hard to bang on the draw bar to release it? Does the cutter then drop out or stay in the collet while the draw bar is spun the 5 to 10 turns to remove it from the spindle.

I think in both cases, as long as the tap verses bang to release the collet from the spindle after a couple of turns of the draw bar either tooling is fine.

For me, this conversation has reminded me that sometimes, when spindle to work distance is very short due to size of the product being machined, that a collet is a good solution compared to any kind of tool holder.
I don't have any MT3 collets so I can't show that in the comparison but as the photo shows, being able to hold a tool in a collet as opposed to a holder of some sort can make or break the ability to mill something because of as much as a 2" gain in space from spindle to work.

Here they are lined up even with the bottom of the spindle.
1669828279176.webp
 
On my mill the MT3 collets hold the cutter well even when the drawbar is loosened. The exception is the TTS-style holders which because they are heavier can slip down when the drawbar is rapped.
 
Gentlemen
All the above discussion about 3MT vs R8 collets reminded me of something I found in a recently received "box of bits".

I have eleven 3MT collets of various sizes that I have no need of, and there are also a few CAT 40 taper tool holders (mostly shell end mill holders). To this end if any member would like them, if you are within practical driving distance of Blind River, Ontario (midway between Sault St. Marie and Sudbury, Ontario on Highway 17), you are welcome to get in touch with me and they are yours for the taking, gratis. If there are no "local takers" but someone further away would like them, all I would ask for is coverage of the shipping costs (Exact shipping only, no mark ups!!!).

Collets: 1 of 1/8, 2 of 3/16, 1 of 1/4, 1 of 5/16, 2 of 3/8, 1 of 7/16, 2 of 1/2, 1 of 11/16 Draw bar thread: 3/8 X 16
They are used, but are not dinged up. I can't find any name brand, just sizes marked on each collet.

If any member is interested, my email is: [email protected]

Thanks

Paul
 
PaulC said:
Gentlemen
All the above discussion about 3MT vs R8 collets reminded me of something I found in a recently received "box of bits".

I have eleven 3MT collets of various sizes that I have no need of, and there are also a few CAT 40 taper tool holders (mostly shell end mill holders). To this end if any member would like them, if you are within practical driving distance of Blind River, Ontario (midway between Sault St. Marie and Sudbury, Ontario on Highway 17), you are welcome to get in touch with me and they are yours for the taking, gratis. If there are no "local takers" but someone further away would like them, all I would ask for is coverage of the shipping costs (Exact shipping only, no mark ups!!!).

Collets: 1 of 1/8, 2 of 3/16, 1 of 1/4, 1 of 5/16, 2 of 3/8, 1 of 7/16, 2 of 1/2, 1 of 11/16 Draw bar thread: 3/8 X 16
They are used, but are not dinged up. I can't find any name brand, just sizes marked on each collet.

If any member is interested, my email is: [email protected]

Thanks

Paul
Click to expand...
If nobody local steps up, I will gladly pay the shipping.
 
PaulC said:
Gentlemen
All the above discussion about 3MT vs R8 collets reminded me of something I found in a recently received "box of bits".

I have eleven 3MT collets of various sizes that I have no need of, and there are also a few CAT 40 taper tool holders (mostly shell end mill holders). To this end if any member would like them, if you are within practical driving distance of Blind River, Ontario (midway between Sault St. Marie and Sudbury, Ontario on Highway 17), you are welcome to get in touch with me and they are yours for the taking, gratis. If there are no "local takers" but someone further away would like them, all I would ask for is coverage of the shipping costs (Exact shipping only, no mark ups!!!).

Collets: 1 of 1/8, 2 of 3/16, 1 of 1/4, 1 of 5/16, 2 of 3/8, 1 of 7/16, 2 of 1/2, 1 of 11/16 Draw bar thread: 3/8 X 16
They are used, but are not dinged up. I can't find any name brand, just sizes marked on each collet.

If any member is interested, my email is: [email protected]

Thanks

Paul
Click to expand...
Where are you located?
Edit: my bad... I missed the location...
 
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