[4]

Pm45m Cnc Conversion With 7800 Rpm Belt Drive 3 Hp Upgrade, Bt30 Spindle, Power Draw Bar + Enclosure

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

darkzero

Global Moderator
Staff member
H-M Supporter - Gold Member ($25)
Joined
Nov 27, 2012
Messages
3,795
Darkzero pointed me to this Forum. Looking forward to looking around. This thread is great! Almost exactly what has been done on my ZX 45 mill. except the VFD drive. I am sure this will come later. I need to actually read the whole thread rather than look at pictures real fast.. LOL. Need to go drop my Boy off at School and head to the day job! This place looks promising!
-Eric
Glad you made it Eric & welcome!

Thanks for the reminder. I have talked to Mark (gt50) in a while. Last time I saw or talked to him is when I went over to his house to help him with his epoxy granite build. I have to give it up to him though, I don't think I would have the patience to do what all he did.

Last I heard he was moving out of state. I wonder how his project is coming along & how he's doing.

http://www.hobby-machinist.com/threads/large-epoxy-granite-vmc-project.33497/page-2#post-286010
 

Uguessedit

Active Member
Registered
Joined
Mar 7, 2018
Messages
36
Part II:

BT30 conversion with pnuematic drawbar

Here is a business end shot between stock R8 spindle and and the BT30:
View attachment 183224

Industrial Hobbies said they have over a 100 30 taper spindles and I can confirm they fit the PM45m mill.

To convert the manual draw bar to pneumatic you have to work within the stock spindle measurements . The drawbar hole diameter is .684" with the top of the cone at .703 for a short bit. That is because it is NMTB 30. My plan is to cut a relief above the cone where the stud would sit so my gripper can release when the drawbar is pushed forward and put a triple valve spring on top of the the drawbar in place of bellevilles. Because my motor is so large, the air cylinder will be mounted upside down in front of the head and push up on a pivot arm to push down on the drawbar to release.

I took the IH NMTB 30 spindle and bored the straight section deeper by an inch while keeping the diameter to 0.72". This allows me to fit a ball type gripper where the straight section would be. Next I cut groove a 0.25" wide and a depth of 0.95". When the grippers balls are aligned with the groove, the larger diameter allows the pull stud to be released. I made an aluminum version of the spindle and it released properly. The trick is measuring everything right.

I will post some more detail later but here are some pics of the new drawbar. It is O1 steel, properly hardened and tempered to around 55 rc. (PID kiln)

Gripper Close up:
View attachment 183225
Gripper on drawbar with bt30 toolholder:
View attachment 183226

Gripper parts:
View attachment 183227

There is no room for springs inside the IH nmtb spindle, I am putting the spring on the top of the pulley with a top hat and fabco 2 stage 4" cylinder- 1500 lbs of spindle clamping force.

Meanwhile, took 8"x 3" thick diameter round of 7075. This is inspiring me to make a new head assembly with an extension. I already cut the top plate by the y axis to the vertical wall of the base and that freed up a lot of travel. Adding an extension

Having a head extension allows up to 12" y axis travel on the RF45 type mills.
View attachment 183228


Finished part bored for (4) 5/8" bolts:
View attachment 183229

Back to the spindle, I took the plunge literally and cut the inside of the spindle to make way for the pull stud gripper. This entailed slightly boring past where the taper terminates and then cutting an internal groove for the balls in the gripper to drop into. I test fit and with the balls in place, tool holders are held and then if you allow the drawbar to move down approximately 1/2", the tool is released.


I spent some time further test fitting the spindle. I found I was .0006 too narrow when the gripper was retracted with all 4 balls in. During my initial test fitting, I only put 2 balls in. With all 4 in and the gripper assembly retracted, the tool holder wouldn't retract all the way into the spindle. As a result, I had to slightly enlarge the bore in the spindle. After that, the gripper works smoothly.

Here are a few pics:

Inside the spindle:
View attachment 183230


Tail end:

View attachment 183231

Basically you need to machine the part in the oval, make a gripper and draw bar.

View attachment 183232

After finishing the plate for the 2 stage air cylinder, I took some cuts. I put a tool in, fully inserted it using the gripper with the balls and then manually tightened the bolt on top of belville washers with a wrench. No problem taking .2" cut with a glacern 4" face mill- it holds just fine.

The power draw bar works. I am really happy because bt30 tooling is plentiful and cheap View attachment 183233

Video below:

I cleaned up everything with the enclosure and things are starting to come together. A few pics of the mill in it's current state with a power drawbar, one shot oiler, enclosure and diy fog buster with pressurized coolant:

Shot of the mill head with the bt30 power drawbar installed:
View attachment 183234

Belleville springs:

View attachment 183235

Overview shot showing the enclosure. You can also kind of see the 3.5" head extension. I am getting a full 12.75" of Y travel now. I will need to make a fixture plate to take full advantage. Considering these mills have 8" of y travel, this is really awesome:

View attachment 183236


Power drawbar switch. I ended up using a foot pedal momentary pneumatic switch. Seems more robust than the toggle type and the price is right:

View attachment 183237


Diy fog buster built out of scrap 1/8" npt plumbing parts I had around and a mig nozzle tip. I forgot to snap a pic of the pressurized coolant tank but it is a whole house water filter housing modified with a pick up tube. compressed air goes in and forces the coolant out through the pick up tube connected to the top. The needle valves allow for both pressure and fluid level adjustments. Works really well:

View attachment 183238


Sample part being machined:


Thanks for looking...
I would like to do the NMTB spindle swap. Is there any known spindles besides the ones IH had that would work? My enco, Grizzly, and PM833t all use the same spindle assemblies so I imagine there must be something available. I’ve been contemplating ridding the gear box but so far it has been working well up to 7500rpm with a custom made/balanced motor and vfd while giving me walking speed threading control when I need it. It’s really not noisy at all and in fact I think it’s lesss noisy than when the factory motor was on it. No plastic gears but the oil does get up to 130 degrees. I find most of the cutting I am doing is between 3500-4000rpm so until I see a reason to push 8000rpm it will suit fine. P5 bearings running between 110 and 134 degrees ferenheit. If I can find an NMTB spindle I’d drop a matched pair of NSK abec 7’s to upgrade having it apart anyways. And.., Keep the old spindle as an emergency backup. I’d like to proceed with CNC conversion with everything on the shelf though a quick change tool holder with NMTB seems the obvious way to go if proceeding versus babysitting the machine to swap tooling manually. If you or anyone has a source of those spindles please advise I’d like to buy one and potentially 2 more if it works out well.
 

7milesup

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Jan 7, 2016
Messages
387
I would like to do the NMTB spindle swap. Is there any known spindles besides the ones IH had that would work? My enco, Grizzly, and PM833t all use the same spindle assemblies so I imagine there must be something available. I’ve been contemplating ridding the gear box but so far it has been working well up to 7500rpm with a custom made/balanced motor and vfd while giving me walking speed threading control when I need it. It’s really not noisy at all and in fact I think it’s lesss noisy than when the factory motor was on it.
I have a PM833T. You are saying that you have one too and have run it up to 7500 rpm with the stock gears? I am considering converting my 833 to a CNC mill, but trying to wrap my head around everything. If you did an 833 conversion, do you have a build thread?

Thank you
 
[5] [7]
Top