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Swede
03-28-2005, 01:27 PM
Thought you guys might like these pics and some impressions of this spindle. Some background... I have been lurking eBay for years looking for a Gilman or similar box spindle in this size. As I mentioned in another thread, I finally scored one. This is only the second 2750 box spindle I've seen on eBay. Gilman Spindles is now owned by SKF, and this particular sized spindle is just about perfect for a serious bench CNC mill or perhaps for retrofitting just about ANY square-columned or similar mill-drill sized machine.

My first impression - bigger and heavier than I anticipated. The spidle box is cast iron, and measures roughly 7" long by 2.5" square through the body section. Overall length is about 1 foot; weight 25 pounds. The body has counterbored holes, 4 ea, for 5/16" or 8mm SHCS. Bearings are ABEC 7 angular contact.

First picture: Overall spindle.

Second: Spindle nose. The collet nose reminds me of basically a big and beefy ER collet type of setup. Max collet capacity is 0.750". The fit and finish is everything I expected from a quality unit. This particular example uses a 75TG collet system, and these are common and available from companies like MSC. I'd rather have a CAT30, but collets are pretty user-friendly, and since I can add a drawbar, I could always create fixed tooling using holders with the 75TG taper, and a drive-dog which would replace the current collet nut.

Third: I mounted the spindle in my 6" Kurt vise and checked the runout with my best B&S 0.0001" indicator. When smoothly rotated, I can detect no needle motion on the internal taper. A carbide end mill was mounted; the first test scared me a bit because it showed 0.001" on the cutter shaft, but I had only tightened it by hand. When correctly wrench tightened, the runout was 0.0001". A true pin guage would be more appropriate for this test than an end mill, but carbide end mills are pretty accurate.

Fourth: This shows the relative size. The little spindle on the left is an ER16 cartridge spindle, roughly what you can call a Sherline size.

This is a nice unit! It is going to require at least 1 HP, and would probably be happier with 2 HP or so. Until I can decode the product number, I'm not sure of some of the other specs, but the top RPM should be around 7-10K, maybe up to 15-18K depending upon the bearing preload. Now I need to build a mill around this bad boy! I think I am going to try to replicate one of the CMS semi-gantry style of mill...

http://www.cmscnc.com/index.cfm?fuseaction=browse&id=100&pageid=40

It'll be a fun, long-term project. This time, I'm going to shoot for far more cast iron than my previous effort, which was 80% aluminum.

I know any clown can buy a spindle... the shop-made spindles we've seen in this forum are much more impressive. I really simply wanted to share my impressions, which are very positive so far. :D

trubleshtr
03-28-2005, 07:16 PM
Nice spindle, We use a lot of gilman spindles in our special purpose machines and they last forever (providing you don't crash them)
Does the spindle require mist lube? or that ever expensive "special"moly white grease?
Looks like there is an air purge on the collar also? Is this spindle set-up for through coolant? if so, you will want to make sure you do so, or else your cartridge bearings will overheat.....

I like the direction you have chosen to go......

Swede
03-29-2005, 01:29 PM
Thanks trubleshtr, now I get to pick your brain, as I know nothing about these spindles.

Is the air-purge inlet the threaded hole on the silver collar near the nose?

I need to inspect a bit closer and try to determine exactly what the lube/air requirements are. I appreciate any tidbits you have. The Gilman site really doesn't have anything. :rolleyes:

JFettig
03-29-2005, 02:00 PM
Sweede, that looks like a nice spindle there, Its very tempting for the machine I want to build but I just dont have the cash to drop on it.

Does that spindle have a hole all the way through the spindle that you could possibly use for a drawbar?

I have been slightly interesting in one of those 'bridge mills' I think they are called, I wouldnt really expect them to be too rigid though unless heavily built.

Youll have to let us know all how it goes:)

Jon

trubleshtr
03-29-2005, 07:51 PM
For the air purge dry air only, this is just to keep the cartridge area + so as not to allow unwanted coolants / cutting fluids into the bearings and washing away the grease.You may not even need to use it if you are in a clean environment.
This spindle looks like it does not need mist lubing. The bearings where probably packed with Gilman’s special grease.Gilman usually uses mist lube on their multi head spindle assemblies to protect the rotating gears on the inside.
You may require coolant through the center of the cartridge if it has been provided, this is to keep the spindle assembly cool. But again, if you are not going fast and heavy with it, you may get away with not needing it.
My machines at work run 24/7 under heavy load and therefore need the misting, air purge and through coolant.

Swede
03-30-2005, 10:41 AM
Thank you Trubleshooter! The dry air is no problem. I don't think this spindle is set up for coolant flow. It will never see the level of work yours currently does. When I get it set up, I'll definitely keep an eye on the heat level.

Jon, the spindle does have the ability to carry a drawbar. The 75TG collets are single angle, and I think I can create fixed tooling by first, creating a female threaded collar (with drive dog bars) to replace the nut... that'll be a permanent attachment. Then, I'll create some steel carriers that mimic the body angle of the 75TG collets.

Fixed tooling is nice, but I'll live with collet only, as Flashcut, my current system, is very close to releasing tool-length sensing which allows Z offset setting during a tool swap.

A couple of years ago, when I was planning this system, I looked closely at this type of unit and rejected it due to cost, but eBay came through once again.