View Full Version : Mill Techniques?
10-09-2001, 08:48 PM
I have one of KBCs versions of the 7" x 31" import knee mill. I have two questions:
1. Does anyone have a technique to 're-square' the head after angle milling? I'm currently indicating the quill off of vertical table travel, but it's time consuming.
2. Does anyone have a technique to lock the spindle? I can put a wrench on the draw bar nut, but I'd like something more certain.
BTW, I have only one gripe about the machine (needs more speeds), and it required very little fiddling to set up.
10-10-2001, 02:56 AM
Get a large Timken cup or a bearing outer race around 6" or bigger. Scrounging might prove fruitful at a Caterpillar dealer or semi-truck repair center - we only care about the top and bottom of the cup not the bearing surface - so used ones work great.
Place the cup on the table and put an indicator in the spindle - rotate the indicator against the cup & clock it in. If you have a toolmaker's flat that is finished on both sides you could use that too.
I would call the KBC service department and ask them about locking the spindle - give them hell for not having it in the instructions.
10-10-2001, 10:19 AM
Thrud answered but I am going to elaborate a bit on this subject, or give it a try.
Resquaring up a mill head is refered to as tramming, one puts an indicator in spindle so that it swings a large radius and contacts the mill table or a flat surface resting upon the table. The large bearing that Thrud refered to was to enable you to sweep without the tee slots disturbing the indicator, my source for BIG bearings is our local quarry, rock crusher.
The indicator tells the story when you start sweeping the table, I myself sweep directly on the table, I use a larger ball on my indicator and just contact table a few thous. don't have much trouble with slots.
I am not familiar with your particular machine, have ran lots of Bridgeports and clones, my little trick I do on the left-right allignment is to finish last thous or 2 by taking pressure off adjuster and tapping the top of head with hand, comes in better for me that way. Some machines I have used have a really nice adjuster and some don't, you fight them and fight them some more.
Clear as mud, right. Do it a few hundred times and it gets really easy.
I don't know any easy way to do it, either, except Halfnut's way: do it a few hundred times and it does get easier.
Great idea on the large bearing for a reference surface for the indicator!
As far as more speeds for the mill, when you're feeling flush sometime, get yourself a 3-phase motor (I assume the mill doesn't have one now) and a VFD (variable-frequency drive). It's THE way to do it.
10-10-2001, 08:39 PM
I've always wondered what is was like for those who use a VFD in this type of application. I program PLC equipment for a living but never considered how close to the desired speed a low-end VFD might maintain.
I sure can't detect any speed variation. There must be some, but it seems pretty solid to me. I've never put a tach on it, but from a practical point of view it's certainly "close enough."
10-11-2001, 08:15 PM
I've called the KBC tech service department on other issues. I think they all normally work in Ladies Undergarments, but they have to take over when no one else answers the phone.
How many pennies do I have to save? Swapping those belts is a pain, and there aren't enough grooves.
10-12-2001, 02:20 AM
The VFD is a good idea - cost will depend on if you buy a special 3Phase motor to go with it and the features you want on the VFD. The ones with IGFET technolgy are the most expensive and have the best features. A 2 HP super duty 3Phase optimised for the contoller is about $900 (US) (motor with VFD) in Canada.
SGW is right, they ARE the way to go and even a cheapy will tickle you pink once you start using one. On a lathe threading in a blind hole or up to a shoulder produces less of that "pucker factor" with a VFD...
Take a look at http://www.dealerselectric.com/ and click on "Inverter Drives." In fact, they currently have an "Internet special" of a 1 hp motor plus a VFD for $225. Another source is http://www.vfds.com/vfdprice.htm (Usual disclaimers....) There are other surplus dealers selling the things, too. New, a VFD can be pretty expensive, but the surplus deals can be excellent.
You don't need a VFD-optimized motor, either. A regular 3-phase motor will work fine. If you were going to run the thing continuously and require maximum performance for three shifts 24 hours a day, the economics of an optimized motor might make sense, but I think it's totally irrelevant for a home shop. You can get used 3-phase motors CHEAP if you look around. I'd think you ought to be able to get yourself set up for under $300 with no trouble, if you're talking a 1 hp motor or so, which would be about right for the size mill you have.