4th axis work holding

[al010964]

Hi All,

About to get my fourth axis going, i have never used it and just looking at work holding options getting stock away from the plate. Was thinking of hunting down a second hand mitee bite 14500 or something similar if i can get it for the right price. Anyone doing any 4th axis work and got some ideas?

Cheers,
.adrian

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[Jim Dawson]

Why not use a 3 or 4 jaw chuck? Works well for me.

[CadRhino]

Why not use a 3 or 4 jaw chuck? Works well for me.

+1

[Tbkahuna]

I use a 5C collet chuck for both horizontal and vertical use of the rotary table for many of the things I make. You can use a step collet for some odd shaped things in it as well as normal round and square collets. I sometimes turn down less than an inch of the end of round or square stock that is too big for a 5C collet so I can put it in a 5C collet and machine a part out of the larger end.

I also have used a 3 and 4 jaw but not near as much as the 5C.

[kstrauss]

I've used an ER40 with a MT2 shank. See ER40 MT2 COLLET CHUCK #B17 | CTC Tools

[al010964]

Just to expand my gut feeling is that the 3 and 4 jaw is going to require to much extra stock to move it away from the jaws. I could be wrong ... normally my stuff is about the size of a tennis ball, out of blocks of aluminium. Smaller stuff can be put in a er40, which would be similar range to the 5c i would think, as have one for these for the lathe.

I liked the look of the mitee bite product, but the new price is at the very sharp end of town for work holding (for me anyway). maybe a 2" by 2" round puck, with screws from the back of the puck for work holding or just normal 10/32 mitee bites being held in the 4 jaw might be a better starting point.

Thanks for the posts.

Cheers,
.adrian

[RussMachine]

Any chance of making a fixture for your parts? Then just chuck-up the fixture in the 3 jaw chuck?

[Steve Seebold]

I use a 5C collet fixture on mine, but I only do small parts.

[handlewanker]

Hi, there is no one way to hold a piece of work....it all depends on the work piece........many times you need to machine the part on the end of stock material to get it away from the chuck jaws erc, and then cut the part off the stock material and clean it up.

Yes, fixture plates are also an option, held in the 3 jaw chuck as they can be custom made to suit the work piece......some work is best done between centres so that you can remove it and put it back again without losing position......you could also epoxy glue it to a rod, bar or plate held in the chuck and heat it to get the glue to melt for removal.
Ian.

[kstrauss]

The best approach obviously depends on the shape of your final product.

Parts that have a central through hole or a deep recess are nicely held using expanding mandrels such as MT2 Expanding Mandrels (Quick Release) - Arc Euro Trade These allow access to the outside of the whole length of the workpiece with no waste.

A tombstone with mitee-bite clamps (https://www.tormach.com/store/index....show&ref=33146) or something similar could work well for some projects.


You can often halve the amount of wasted stock when using collets or a 3/4-jaw chuck by starting with a piece long enough for two parts plus a gripping area in the middle. That way you can make finished parts on the two ends and waste only one grip area.

[IMT]

Use aluminum or steel soft jaws in a 3 or 4 jaw chuck. Machine the jaws to fit the part and give the clearance necessary for the tool holder.

[Jim Dawson]

Just to expand my gut feeling is that the 3 and 4 jaw is going to require to much extra stock to move it away from the jaws. I could be wrong ... normally my stuff is about the size of a tennis ball, out of blocks of aluminium. Smaller stuff can be put in a er40, which would be similar range to the 5c i would think, as have one for these for the lathe.

I liked the look of the mitee bite product, but the new price is at the very sharp end of town for work holding (for me anyway). maybe a 2" by 2" round puck, with screws from the back of the puck for work holding or just normal 10/32 mitee bites being held in the 4 jaw might be a better starting point.

Thanks for the posts.

Cheers,
.adrian

Why not just bolt the part to a stub arbor to move it away from the chuck/plate.

Here is one I did today, I just built a quick stub arbor and bolted the part to it. The stub arbor was just a scrap piece of shaft.

[tinmancarving]

I share with you the most flexible fixturing we use on the 4-axis machine that I program for. Take a look at the 5thAxis line of work holding solutions. We have and use pretty much everything in their catalog, but our go-to fixture is their D22 Dovetail Clamp. We mount these clamps to long and short tombstones for production style work and we keep one installed on a machine all the time that is on a riser face plate sticking out from the face of the 4th axis.

It is quick to machine a dovetail feature in a piece of stock for a one off part and mount it in the machine and get multiple sides at one time. They also locate well enough that you can move the part to dovetails fixtures in different orientations and catch more faces of the part. Your creativity is your only limiting factor.

The great thing is they range in price from $220 -$500 in sizes from 1.0" wide up to 3". Our go-to is the D22 (2" wide) that sells for $350. That is cheap enough that even a hobbyist can afford one.

They even make a version just for picatinny rails for those folks making gun parts.

Dovetail Fixtures | 5th Axis

Rob

Edit,
Here's an image from their catalog showing the style of fixturing we keep installed on the machine all the time. It sticks straight out from the 4th axis. We do however make our own riser, which is typically taller than theirs for more reach.

They hold well enough that we machine 17-4 H950 all the time very aggressively with no concern for them coming out.

[al010964]

I share with you the most flexible fixturing we use on the 4-axis machine that I program for. Take a look at the 5thAxis line of work holding solutions. We have and use pretty much everything in their catalog, but our go-to fixture is their D22 Dovetail Clamp. We mount these clamps to long and short tombstones for production style work and we keep one installed on a machine all the time that is on a riser face plate sticking out from the face of the 4th axis.

It is quick to machine a dovetail feature in a piece of stock for a one off part and mount it in the machine and get multiple sides at one time. They also locate well enough that you can move the part to dovetails fixtures in different orientations and catch more faces of the part. Your creativity is your only limiting factor.

The great thing is they range in price from $220 -$500 in sizes from 1.0" wide up to 3". Our go-to is the D22 (2" wide) that sells for $350. That is cheap enough that even a hobbyist can afford one.

They even make a version just for picatinny rails for those folks making gun parts.

Dovetail Fixtures | 5th Axis

Rob

Edit,
Here's an image from their catalog showing the style of fixturing we keep installed on the machine all the time. It sticks straight out from the 4th axis. We do however make our own riser, which is typically taller than theirs for more reach.

They hold well enough that we machine 17-4 H950 all the time very aggressively with no concern for them coming out.

Thanks for that one the d22, looks like what i am thinking of without the sticker fright.

Cheers,
.adrian

[handlewanker]

Yes, sometimes the part can be so convoluted that the only way to get all round it is to do the multi move fixture solution.....sometimes castings come into this category.

In many cases a chuck on a 4th axis is a hindrance whereas a purpose made fixture can be any shape you want, and mounting it can be just a short Morse taper shank and draw bar.....who needs a chuck then.

I'm currently in the process of building a 4th axis and part of the design has always been an 80mm or 100mm 3 jaw chuck, but with the realisation that many work pieces cannot be held in the chuck and would be easier to machine on a fixture, the design is now gravitating to just a 3 Morse taper bore as the bearings I have for it are the 32007X taper roller type with a 62mm OD and a 35mm bore which will give me a spindle with a 25mm hole through it.

A half length 3 Morse taper shank with a draw bar will be sufficient to mount the shanks.

This gives me a TTS type advantage as you can have many 3 Morse shanks and any fixture shape you need on the ends.......a small 3 jaw with 3 Morse shank would just be for regular round work.
Ian.

[daniellyall]

Ian are you sure a Morse taper is good enough

[handlewanker]

Hi Dan.....yes, the 3 Morse will hold even with the most aggressive feed rate as drilling holes with that taper will testify.

A 4th axis won't be exposed to the same amount of force that a 3 Morse tapered drill in a spindle would have.......BUT..... a back spacer must be fitted between the back of the 4th axis spindle face and the 3 Morse shank to stop it from seating in too firmly otherwise you would have to knock it out with a hammer each time for tool removal.

The 3 Morse will seat very accurately with very little draw bar pressure so I think it will be in the same category as the TTS for universal tool mounting and removal.

The 3 Morse shank length will be shortened by half to keep the spindle bore as big as possible.......4 Morse is also an option.

Just having a plain 3 jaw mounted would suffice for most occasions and you can also grip a round shank with a fixture in one if needed, but as I'm starting the design and build from the bottom I decided that a 3 Morse would be more versatile and keep a fixture closer to the front bearing when machining without fouling a chuck body or jaws if fitted.

The bearings I chose have a 35mm bore (62mm OD), so a spindle with 25mm bore will have adequate wall thickness and be good for through work........I'll also have a flange on the spindle to mount a chuck for work holding in that case.

Having a big hole through the 4th axis spindle gives you the same capability as a lathe headstock, especially if you want to go into a turning mode, so designing for those forces must come in at the design stage........taper roller or angular contact bearings will do the trick without breaking the bank or over complicating the issue.

For that aspect I'm going to have the bearings positioned one at each end instead of both at one end back to back as in a normal milling spindle......high rotational speed is not envisaged so heat expansion is not a problem.
Ian.