View Full Version : Bridgeport M head Quill spring

02-27-2017, 03:52 PM
My M head quill moves down under it's own weight if I fit a chuck or boring head. I've checked the clock spring, it's in position and both ends are engaged with the hooks. I think the spring is weak, It's oiled and so far as I can see, tension is correct. There is not much space to fit a heavier spring, but I may be able to make a drill return spring fit, these are available in different thicknesses. I don't want the quill to snap back, just to balance the weight of the tool. Has anyone had this problem and solved it? I know I can snug up the quill lock but this causes the clutch to loosen when I retract the quill with the hand wheel. Dave

02-27-2017, 04:10 PM
The J heads have a provision for tensioning the spring, I don't know if the M head has it or not. It's likely you can just tighten the spring a little and solve the problem.

02-27-2017, 04:59 PM
Thanks Toolguy, I took the quill stop off, ran the quill out the bottom, wound up the spring then re-engaged quill, made no difference. I think the spring is just worn out. There are a lot of these heads around, I'm sure someone out there must have sorted it.
I did have a Bridgeport with the J head. Liked it a lot but sold it and got a smaller machine, smaller vise, smaller rotary table, lighter everything. Got problems with arthritis, I'm old and weak! Dave

02-27-2017, 06:57 PM
You can get a J head with a 32" table same an an M head but 1-1/2" more travel & R8 collets, I have one the same size my M head was but the M head was 110v from the factory. I didn't like the small collets that only go to 1/2" Bought it for $37.50 & a rong -fu for $50 at the same time.

Use a screen door spring on the rear of the quill handle so it wont slide & make a bracket you can hook the other end in 3 or 4 places for different weight cutters. A bit crude but simple, quick & it works.

02-27-2017, 07:54 PM
if you can't adjust the housing to increase the tension in the spring (no idea what the system is on a BP), you could use a carbide tipped drill to carefully drill a new hole in the spring a little further away from the end. That should increase the tension a bit, but I'm not sure how you'd figure out exactly where to drill the hole for the correct tension.

02-27-2017, 08:17 PM
I delt with this myself I found out that the Quill spring on the M head will only hold a collet and end mill and that is how designed

02-28-2017, 05:56 AM
Flylo, I liked the J head machine a lot, I've kept my R8 tooling in case I change my mind but the smaller machine suits me at the moment.
I think Ken has nailed it, that's the way it was made.
Matt, If I shorten the spring it's going to restrict quill travel.
The answer may be a shaft extension with an external clock spring to replace the feeble original.
Thanks for the help.

02-13-2019, 03:35 PM
Maybe You need a new quill spring ? $7.50 at Clock Repair & Replacement Parts - Mainsprings, Arbors & Barrels - Hole End Mainsprings

02-13-2019, 03:37 PM
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Ohio Mike
02-13-2019, 05:16 PM
Hardinge used to still sell OEM springs but they disappeared from the parts inventory in the past few years.

H&W stocks something that will work


Rich Carlstedt
02-13-2019, 08:07 PM
Similar to Flylo's suggestion, years ago (many) I saw a setup where the guy made a pulley that went between the head casting and the handle (Thin plate) and the drum was on the casting side and had small steel cable wrapped around it with another pulley on the column and a hanging window weight.