Mill spindle mt#3 - what’s my options ?

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Farmer Dan
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Mill spindle mt#3 - what’s my options ?

Post by Farmer Dan »

Im still waiting to receive my “ new toy “ like my wife calls it. Was supposed to arrive on the 12th . Last comment by T FORCE . It made it to Portland but now it’s lost . 😫
So I’ve been looking on line at lots of tooling . My question is should I switch over to something like an adapter or go with M3 ?
Farmer Dan
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Re: Mill spindle mt#3 - what’s my options ?

Post by Farmer Dan »

O I forgot to mention it’s the g9729
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Bill Shields
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Re: Mill spindle mt#3 - what’s my options ?

Post by Bill Shields »

Adapter will be an easy way to go if you have enough headroom
Too many things going on to bother listing them.
Torch
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Re: Mill spindle mt#3 - what’s my options ?

Post by Torch »

What do you mean by "adapter", exactly? You will need something to hold whatever tooling you purchase. While there are MT3 drill bits out there, there are very few with an MT3 shank, so you will need a Jacob's chuck with an MT3 shank to use regular drill bits. For milling, you will need some sort of collet to hold the endmill or flycutter to hold the lathe bits. Either can be had to fit the MT3 spindle.

Now if you are intending to get into a set of ER collets, you will need a chuck compatible with the chosen ER series to hold the collets that hold the tooling. The advantage of the ER style is that a series can securely grip any diameter tool shank within the range unlike MT3 collets which are sized for a particular and specific shank. For example, each ER-40 collet has a range of 1mm, and the collets come in 1mm increments. A 10mm ER-40 collet can securely grip anything between 9mm and 10mm. MT3 collets also come in 1mm increments, however a 10mm MT3 collet can only securely grip a 10mm shank (note: MT3 collets do come in imperial sizes too). The disadvantage of an ER chuck is reduced overhead clearance -- an MT3 collet ends at the bottom of the spindle for maximum working height.

However, if you are considering an adapter to a different spindle taper, such as R8, BT40, etc., there is little to be gained and much to lose. A R8 spindle taper still needs an ER40 collet chuck to use those collets. Adding an MT3 to R8 adapter in order to use an ER collet chuck with an R8 shank eats up the available overhead clearance and potentially adds runnout at the tool. Stick with a collet chuck with MT3 shank.
Farmer Dan
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Re: Mill spindle mt#3 - what’s my options ?

Post by Farmer Dan »

👍 thank you Tourch . That’s all I needed to hear.
John Hasler
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Re: Mill spindle mt#3 - what’s my options ?

Post by John Hasler »

My mill has an MT3 taper and I just use MT3 collets to hold tools. I have a large Jacobs chuck with an MT3 shank and also several smaller chucks that can be held in collets.
Farmer Dan
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Re: Mill spindle mt#3 - what’s my options ?

Post by Farmer Dan »

Okay, I’m beginning to understand , you know “ I can now see the trees within the forest “.
I was under the impression morse taper was the base and everything else was added, well something like that. After going back and doing more reading rather than utube watching, I think I understand . Morse taper collet sets usually employ ER collets . But straight mt collets are used as well , just not a quick change type of deal as ER . Now if only the shipping company can locate my baby and get it here !!!
Torch
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Re: Mill spindle mt#3 - what’s my options ?

Post by Torch »

Morse taper collets are completely different than ER collets. MT3 collets fit directly into your spindle, and are secured with an internal drawbar up the centre of the spindle. But you can get an ER chuck to fit your MT3 spindle. The ER chuck is secured with a drawbar to - and extends down from - your spindle. The ER collets are secured to the chuck with a large external nut. There are different diameter series of ER collets. An ER-40 collet will not fit an ER-25 chuck, and vice-versa.

Note that sometimes the extra extension of an ER chuck is beneficial, particularly with a 3-in-1 machine where the spindle cannot reach as far down as the table. When milling shallow pieces, either an extended reach is required or a fixture to raise the workpiece up off the table is required. The extension is also useful when a smaller diameter tool holder is required, as when using a slitting saw or when mounting the workpiece horizontally in a rotary indexer/rotary table.

Welcome to the rabbit hole!
Farmer Dan
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Re: Mill spindle mt#3 - what’s my options ?

Post by Farmer Dan »

Lol , Yes I’m beginning to understand. My options will depend on the task at hand . I’ll buy the MT3 collets to start with and go from there . Thanks for all feedback, it all helps with helping me thru the hole .!!! This all started when I stumbled across tomack tools and became completely confused .
SteveM
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Re: Mill spindle mt#3 - what’s my options ?

Post by SteveM »

The downside to MT3 collets is that Morse tapers are self-locking.

That means that when you loosen the drawbar, the tooling doesn't just drop out, like with an R8 or 5C (note the steep taper on the ends of those).

Now Bridgeport M heads took care of this by having the drawbar nut attached to the top of the spindle with a left-hand thread to force the collet out.

Without that type of drawbar, you would have to bang on the drawbar to get the collet out, which could damage the spindle bearings. Based on the owner's manual for your mill, that's what you need to do.

It might be worth having an ER collet chuck to reduce the amount of banging on the spindle.

If you use an ER collet chuck, you will have about 1-1/2" of overhang.

ER-40 will get you up to 1" and ER-32 will get you 3/4".

Steve
Torch
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Re: Mill spindle mt#3 - what’s my options ?

Post by Torch »

Most MT spindles have a slot in the side. A provided steel wedge is inserted in the slot, resting above the collet and then lightly tapped to dislodge the collet, eliminating the need to hammer on the top of the drawbar.
SteveM
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Re: Mill spindle mt#3 - what’s my options ?

Post by SteveM »

Torch wrote: Mon Jan 24, 2022 10:34 am Most MT spindles have a slot in the side. A provided steel wedge is inserted in the slot, resting above the collet and then lightly tapped to dislodge the collet, eliminating the need to hammer on the top of the drawbar.
This one has a drawbar (actually just a long bolt) and the manual says to tap it.

Steve
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