•Show you how quick and easy it’s to install a belt-drive kit on a mini-mill.
•Discuss the advantages of by using a belt drive.
•Tell you about a stupid mistake I made so you won’t do it.
• Quickly describe bearing preload and just how it can cause your spindle bearings not to become hot after you’ve installed a belt drive or taken your head apart for some other reason.
The belt drive kit for my mini-millwas made by the www.cncconversionkit.com. It cost about $130 . It’s pretty very easy to install and will probably take about 20-40 minutes. You may find plans and instructions online if you would like to produce your own. If you can make a pulley on a lathe then it shouldn’t be too hard. There are some good reasons for installing a belt drive:
•It will eliminate any chance of breaking a drive gear, which could happen pretty easily if your cutter jams. Instead of a gear damaging the drive belt should slip instead.
•It increases the top speed of your spindle from about 2500 rpm to more than 4000 rpm, that is important if you are using very little end mills or drills.
•Your mill will run much quieter.
•A belt drive can also make it easier if you ever wish to mount another motor on your mill.
Before you install your belt driveI would recommend turning your spindle on as quickly as it will go and walking away from it approximately 10 or 15 minutes. Then feel or measure how warm the milling head gets. That’s about how warm it should get after installing the belt drive.
The bearingsduring my CNC mill’s head started running hot after I installed the belt drive because I tightened the spindle nut just a little too much. The more you tighten that nut the more “preload” you give your spindle bearings. You wish to preload them enough to eliminate the internal play in them (which can cause run-out), but not a lot that you cause excessive friction, heat and premature wear. The nut doesn’t have to be tightened very much and I only had to loosen it a little to fix the problem.
One thing you’regoing to need to do is to unscrew the spindle nut on top of the head. There’s a pair of things you need to know before you decide to do that:
•It’s a left-handed thread, so it’s going to turn it the “wrong” way.
•Before you start unscrewing it you need to loosen the set screw in it. That was my dumb mistake. Even though I’ve seen it many times I still forgot it was there because it was facing away from me when I inserted the pin to lock the spindle. Luckily, I stopped turning the wrench before I did any real damage.
for install balt and cnc kit ballscrew go to