Xblack
02-10-2013, 11:47 PM
Spindle Conversion to ER11
I read Bergerud's posts about converting the Carvewright spindle to ER-type. There are some really great advantages to this chuck type, including bit cost and availability, secure grip of carbide bits, etc., so I decided to retrofit my machine to ER chuck.
I decided upon using a 16mm x 100mm ER11. I bought one on Ebay for about $25 and received it about a week later. The inside diameter is 8mm and not threaded.
I pretty much did everything Bergerud detailed in his thread with one major exception -the flexshaft hole. Instead of brazing in a plug to be later drilled and squared, I forged the diameter of the upper part of the spindle down in order to maintain as thick a wall between the 10mm dia. bearing journal, the 8mm dia. springclip journal and the 4.1mm flexshaft hole as possible.
Since the ER11 chuck I bought was 100mm long, I used the extra length to practice forging the end diameter down. The extra length afforded me enough material to practice the job twice. I would suggest anyone planning to try this to practice also, no matter how much steel you've hot worked -who knows what crazy modern alloy these things from varying sources are made of, and who knows how predictably those alloys will react to being worked using tradional methods. I've learned about this the hard way in the past. In this case I found that hot working was pretty much the same as any standard high-carbon steel I've worked, but if worked AT ALL below glowing red it will very quickly crack. The best way I have found to hot work a steel tube and maintain concentricity and not end up with a confused mess is to rotate it about 5 degrees with every whack and use a glancing blow in the direction you want to allow the tube to lenghen, otherwise the displaced material will just squish in place causing an irretreivably recurring ovoid mess. Use the end hole's roundness and size as a guide while forging. I necked the shaft down until the 8mm ID became about 3mm and then virtually closed the hole altogether at the very end so it would not act as a pilot when re-drilled on the lathe. When I re-drilled, I started with a very short 1/8" carbide burr to establish concentricity and then gradually worked it up to full size with regular drill bits. After turning the new spindle I re-hardened and then re-tempered the the upper bearing/springclip/flexshaft area to light-yellow. While forging, I had tried to keep the heat-effected zone from spreading too far, but I also remembered how soft the original QC spindle was and so did not get too carried away with heat sinks and periodic quenching, etc.
Another change I made from Bergerud's plan was to use 6000zz and 6002zz bearings instead of 6000v and 6002v. I just could not find a good source for v-type bearings nearby and figured I could change them out if there developed a problem. I have noticed that the lower bearing tops out at a high of about 150F after about 45 min run time.
I am very happy with my super solid new spindle and thank Bergerud for the idea!
Oh -and after having the ZTruck off the machine and gotten a good look at it, I've decided it would be really nice if someone would after-market a replacement out of milled billet aluminum. It's probably the weakest part of the whole machine.
I read Bergerud's posts about converting the Carvewright spindle to ER-type. There are some really great advantages to this chuck type, including bit cost and availability, secure grip of carbide bits, etc., so I decided to retrofit my machine to ER chuck.
I decided upon using a 16mm x 100mm ER11. I bought one on Ebay for about $25 and received it about a week later. The inside diameter is 8mm and not threaded.
I pretty much did everything Bergerud detailed in his thread with one major exception -the flexshaft hole. Instead of brazing in a plug to be later drilled and squared, I forged the diameter of the upper part of the spindle down in order to maintain as thick a wall between the 10mm dia. bearing journal, the 8mm dia. springclip journal and the 4.1mm flexshaft hole as possible.
Since the ER11 chuck I bought was 100mm long, I used the extra length to practice forging the end diameter down. The extra length afforded me enough material to practice the job twice. I would suggest anyone planning to try this to practice also, no matter how much steel you've hot worked -who knows what crazy modern alloy these things from varying sources are made of, and who knows how predictably those alloys will react to being worked using tradional methods. I've learned about this the hard way in the past. In this case I found that hot working was pretty much the same as any standard high-carbon steel I've worked, but if worked AT ALL below glowing red it will very quickly crack. The best way I have found to hot work a steel tube and maintain concentricity and not end up with a confused mess is to rotate it about 5 degrees with every whack and use a glancing blow in the direction you want to allow the tube to lenghen, otherwise the displaced material will just squish in place causing an irretreivably recurring ovoid mess. Use the end hole's roundness and size as a guide while forging. I necked the shaft down until the 8mm ID became about 3mm and then virtually closed the hole altogether at the very end so it would not act as a pilot when re-drilled on the lathe. When I re-drilled, I started with a very short 1/8" carbide burr to establish concentricity and then gradually worked it up to full size with regular drill bits. After turning the new spindle I re-hardened and then re-tempered the the upper bearing/springclip/flexshaft area to light-yellow. While forging, I had tried to keep the heat-effected zone from spreading too far, but I also remembered how soft the original QC spindle was and so did not get too carried away with heat sinks and periodic quenching, etc.
Another change I made from Bergerud's plan was to use 6000zz and 6002zz bearings instead of 6000v and 6002v. I just could not find a good source for v-type bearings nearby and figured I could change them out if there developed a problem. I have noticed that the lower bearing tops out at a high of about 150F after about 45 min run time.
I am very happy with my super solid new spindle and thank Bergerud for the idea!
Oh -and after having the ZTruck off the machine and gotten a good look at it, I've decided it would be really nice if someone would after-market a replacement out of milled billet aluminum. It's probably the weakest part of the whole machine.