789 Wachusett St Holden, MA 01520
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Head Removal Simplified
Easy removal of the head T-bolts or head tilt adjusting Screw Put and clamp a vise onto the table (If you have a riser block on the machine you may have to block up the vise) Now crank the knee all the way up to the bottom of the head. Position the table with X and Y cranks so the spindle nose goes into the vise jaws Crank the knee up so the bottom of the spindle sets inside the vise jaws Clamp the vise jaws onto the bottom of the spindle. You will see that there is small flat spot underneath the Micrometer rod. I clamp the vise there. You may want to use blocks of Aluminum or wood inside the vise jaws to clamp with. At this point you can loosen the four head T-bolt nuts. Now carefully crank the Y-axis handle and the whole head assembly will go straight out and straight back in again. Be carefull the head assembly is top heavy you may need assistance to balance the head. With it out you can replace the T-bolts (part# 1431), Head tilt adjusting Screw (part# 1097) Head tilt worm gear (part# 1096), on page quill housing You can also replace Quill housing adjusting gear (part# 1186) on page base machine assembly
Collet Key Replacement Simplified
Replacing Collet Alignment screw inside spindle Bring the quill down about two inches Look on the back side of the quill and you will see a small set screw. Remove it This holds in the nosepiece on the bottom of the quill With set screw removed you can unscrew the nosepiece. I use an adjustable spanner wrench You will find two holes on the bottom of the nosepiece for this. You may need to use a punch and hammer to get it started. Right hand thread for Bridgeport mill, left hand thread for Imports. If the nosepiece does not unscrew this means the threads of the nosepiece are bad You may never get it off without damaging the nosepiece and or quill. It can be very expensive to replace both nosepiece and quill. At this point most people live without the Collet screw and just put it back together With the nosepiece removed you can get to the Collet Alignment screw (part# 1137) and special socket set screw (part# 1424). You may need to tap on the drawbar to bring the spindle down a bit farther so you can access the Collet screw. Replace the Collet screw and may need to replace the Special Socket set screw I put an R-8 collet in the spindle and adjust the collet screw by screwing the alignment screw in until it touches the R-8 collet and then back it off so the R-8 collet slides out of the spindle without hanging up. I use blue Loctite on the collet screw and Special set screw just for insurance Then I tap the spindle back into the quill with a rubber hammer and thread the nosepiece back on. Making sure it is up tight. There should be a small gap between top of the nosepiece and the bottom of the quill anywhere from .003" to .010". This insures the spindle bearings are seated in the quill. If not check out how to reseat spindle bearings below Before replacing the set screw in the back of the quill, drill a setpoint into the set screw hole.(I use a handrill and a #8 drill) This puts a dimple in the threads of the nosepiece. If you don't you will smash the threads and never be able to get the nosepiece off again. It also allows the set screw to in farther and not stick out catching on the quill housing.
Spindle Run-out Inspection
Use the same disassembly instructions as replacing the Collet Alignment Screw above. When you get the nosepiece off. Take the Drawbar out of the top and put at least a foot long rod about an inch in diameter in place of the drawbar. Tap on the rod at the top and the complete spindle assembly falls out of the quill. I put a block of wood on the table so when it falls out it bangs on the wood and not the table Now crank the knee down and Y-axis back so you can get the spindle out. At this point keep everything clean, don't get dirt into the bearings Looking at the spindle assembly you will see that there is a pair of precision thrust bearings with a two inch spacer in between, then there is a long spacer with another precision bearing, on top of that there is a spider washer and a spanner nut. If the short spacer is loose between the thrust bearings you will have runout. To tighten, find a tab on the spider washer that is bent into the spanner nut. bend it back down and out of the way. I clamp the spindle at the splines in a bench vise I use blocks of Aluminum or wood to clamp on in the vise jaws so not to crush the splines Tighten the spanner nut on top of the spindle. I use an adjustable spanner wrench or you can use a punch and hammer. Tighten until it will not tighten anymore. Adjust or tap with a hammer the small spacer between the thrust bearings so that it will align between the two thrust bearings exactly. I use a six ruler to check the concentricity. If the spacer sticks out to one side or another you'll still have runout. Once you have adjusted the spacer then bend the spider washer tab back into the spanner nut NOTE** This next step is hugely important!! Before putting the spindle back in the quill look up into the quill and you will see a felt washer (part# 1164) in the top part of the quill. The spindle has to go back up through the hole in that felt washer. Be sure to get it through the hole or it will damage the felt washer. Or Worse it could get caught up in the gear hub or worm gear.The washer is there to keep dirt from getting into the spindle. Now replace the spindle into the quill. After the spindle goes through the felt washer you will feel the splines of the spindle engage the splined gear hub. Just move the spindle around until they mesh together and the spindle goes all the way up. I have found that sometimes the top of the spindle has mushroomed out from years of use of the the drawbar being tightened. If that is the case you may need to clean up the splines with a file at the top of the spindle. It may also be difficult to get the spindle out because of this Tap on the spindle with a rubber hammer until the nosepiece engages the quill. Tighten the nosepiece with the same instructions as assembling the collet screw above.
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