[hoss2006]

Yeah the extra stroke won't hurt you in the direct acting floating drawbar, once it maxes out and compresses the bellevilles it won't have
any room to expand.
The way it works is the air cylinder shaft extends, makes contact with the top of the drawbar, the lifting plate that's attached to the air cylinder rises, it makes contact with what we call a tophat (a flange that sits on top or screws on to the top of the spindle, it's wide enough on the flange to support the bellevilles and your drawbar goes down though the bellevelles and tophat into your 3/4 collet) as the air cylinder shaft keep extending, all the clearance is taken up and the only thing left that can move is the bellevilles. They compress, the drawbar pushes down opening the collet and releasing the tool. If you have 1250 lbs of force you'll be able to use these bellevilles like on the X2 that have a working load about 650-750 lbs. you need the extra force to account for friction and compressing the bellevilles past the working load to have enough drawbar movement to open the collet, doesn't take very much, less than .050.
Belleville Disc Springs - Metric - Springs Washers & Disc Springs | MSCDirect.com
Yes the quill stays locked for cnc mode, it's basically just for manual drilling.
Hoss

[diyengineer]

As for the draw bar, this is the one on my LMS KX3. @ roughly $16 dollars, should i order another and mod it to work, or order a long high strength bolt and work from there?

specs on stock Kx3 drawbar.
10-1/2" long when measured like a bolt
3/8" - 16 thread

Found a 12" high strength 3/8"-16 bolt from mcmaster for $6.76. Would something like that work along with the bevilles (and washers as needed to take up room).

Also, if i wanted a lot more adjustability could one always use high strength 3/8-16 threaded rod? and cut to fit? Not sure if the smooth portion of the drawbar rides on anything mission critical. I could use a number of washers as spacers and high strength nuts to fashion something a bit more custom. No lathe in the shop yet, so i have to get crafty. haha

[hoss2006]

What kind of collets does your kx3 take, I'd assumed it used R8 like the x3/sx3 but looking here it says it doesn't have a drawbar.
Sieg KX3 CNC Mill
Can't make a power drawbar if that's the case.
Other than that I've used both the allthread and grade 8 bolts successfully on my pdb's.
Hoss

[diyengineer]

Mine Uses R8, and has the Tormach R8 adapter in it. They did make a "no draw bar version" also, along with a few other spindle taper variations. The ones sold through little machine shop all have R8 i believe?

Oddly enough, they call out 7/16-20 drawbar thread on the link below, but then under their replacement items for the 3503 they call out 3/8-16. hmm.. ill have to check.

Milling Machine CNC - LittleMachineShop.com

Drawbar, 3503 - LittleMachineShop.com

Thanks for the input Hoss!

[hoss2006]

Yeah better make sure, 7/16-20 is the standard for R8.
Hoss

[diyengineer]

Where the Pneumatic cylinder makes contact with the top of the drawbar, is that a high wear area? Should I thread a brass replaceable bolt into the air cylinder or is the steel on steel fine as it is?

Also, if i go the threaded rod route, what would my stackup look like for nuts, etc.?

[hoss2006]

Wear is minimal, there's no movement between the 2 mating surfaces just contact.
On mine with the allthread I used an auto lug nut rounded side up (it's threaded 7/16-20) with loctite to hold it.
I made a concave end on my air cylinder shaft to mate with it.
Hoss

[gmfoster]

Hoss
So that is a hundred dollar stack of washers or did I read the MSC reference wrong.. I am always amazed at what the small parts add up to..
Garry

[fer_mayrl]

Garry,
they come in packs of 10, unless you are gonna be using 100 washers... then thats a 100 dollar stack of washers

[hoss2006]

Yeah, it says (1) 10 pack, $9.30 so a $7.44 stack.
Hoss

[3space]

Hoss
So that is a hundred dollar stack of washers or did I read the MSC reference wrong.. I am always amazed at what the small parts add up to..
Garry

@Garry: It is $9.30 for a pack of 10. I just bought mine a few minutes ago. Shipped to Montreal Canada, total cost was $10.60.

EDIT: Sorry, just saw Hoss' reply - didn't refresh the screen...

[3space]

So Hoss, the stock SX-3 drawbar is too short to fit the bellevilles, correct?

[hoss2006]

Don't know myself but imagine it would be with anymore than 2 pairs of bellevilles, you want a good 4-5 thread engagement with the collet.
Hoss

[3space]

Yes, I counted the turns yesterday, and there were only 5 without any bellevilles. That was my concern. My drawbar is 10.25" long, starting with the part under the head. I can make my own, but how would you describe the metal of the bar? Like uncoated cold rolled steel? I'm from Montreal, so I can't order from McMaster-Carr. Do you know of other sources that could supply say a 12" bar? Thank you!

[SCzEngrgGroup]

Yes, I counted the turns yesterday, and there were only 5 without any bellevilles. That was my concern. My drawbar is 10.25" long, starting with the part under the head. I can make my own, but how would you describe the metal of the bar? Like uncoated cold rolled steel? I'm from Montreal, so I can't order from McMaster-Carr. Do you know of other sources that could supply say a 12" bar? Thank you!

Just use 7/16-20 threaded rod and pin, weld, or Loctite a machined head on it. On a BF20/G0704, you don't need high strength - mild steel will work fine.

Regards,
Ray L.

[diyengineer]

So you have your top nut on the drawbar which is screwed on (and never moves). then bevilles which i assume are purely a slip fit since they compress. Then the tophat is below the bevilles. how is the top hat attached? I can't imagine it be screwed on since then you would never be able to compress the springs (since you would be compressing 2 fixed points, the top hat and top nut) but yet again it magically stays in place support the unloaded bevilles so they dont slide down while the spindle is operating.

Looked at all the videos on youtube but couldn't seem to find an answer. Just imagining what i would use instead of a nice machined piece. Maybe a top nut, bevilles, super thick washer, and a double nut. then the plate would apply force to the washers. Nuts would just be there to hold the stuff from falling down?

Thanks HOSS!!

Have a good 3 day weekend!

[hoss2006]

Yes, I counted the turns yesterday, and there were only 5 without any bellevilles. That was my concern. My drawbar is 10.25" long, starting with the part under the head. I can make my own, but how would you describe the metal of the bar? Like uncoated cold rolled steel? I'm from Montreal, so I can't order from McMaster-Carr. Do you know of other sources that could supply say a 12" bar? Thank you!

Grainger has locations in Canada and they will certainly carry threaded rod.
https://www.acklandsgrainger.com/AGI.../Main/begin.do
The cost is minimal so there's no reason to skimp on inferior rod, they have B7 Alloy steel rods that would be my choice, no sense worrying about stretching over time especially if you up the force later on your SX3.
Hoss

[hoss2006]

So you have your top nut on the drawbar which is screwed on (and never moves). then bevilles which i assume are purely a slip fit since they compress. Then the tophat is below the bevilles. how is the top hat attached? I can't imagine it be screwed on since then you would never be able to compress the springs (since you would be compressing 2 fixed points, the top hat and top nut) but yet again it magically stays in place support the unloaded bevilles so they dont slide down while the spindle is operating.

Looked at all the videos on youtube but couldn't seem to find an answer. Just imagining what i would use instead of a nice machined piece. Maybe a top nut, bevilles, super thick washer, and a double nut. then the plate would apply force to the washers. Nuts would just be there to hold the stuff from falling down?

Thanks HOSS!!

Have a good 3 day weekend!

The nut is held from turning on the rod by the loctite but the drawbar can still turn to adjust the tension.
The bellevilles are a slip fit, I used heat shrink tubing, a few layers on the drawbar before if there is a bit of a difference in diameters to keep the bellevilles centered. I've used a free tophat and one that screws onto the top of the spindle. The one that screws on eliminates the chance of a sticky collet not releasing the tool. The free one could rise above the spindle if the collet sticks but if you use some anti sieze as tormach suggests the weight of the power drawbar and air cylinder is just fine for popping the tool.
http://www.tormach.com/document_dire...tml?doc_id=163
Hoss

[gmfoster]

Yeah, it says (1) 10 pack, $9.30 so a $7.44 stack.
Hoss

Ok much better than 100 bucks.. I thought that 9.00 was very expensive but then what I paid for lug nuts at Fastenall a while back nothing would surprise me.

[hoss2006]

Ok much better than 100 bucks.. I thought that 9.00 was very expensive but then what I paid for lug nuts at Fastenall a while back nothing would surprise me.

Yeah luckily I kept the old lugs from my Camaro when I put new wheels on it and had to put nice new chrome lugs on it.
Knew I would find a use for the old one someday.lol
Hoss