Back in 2011 I posted some details of a simple modification I made to the Douglas' workhead feed. The photos accompanying the thread evaporated long ago but below is the initial text of the thread.

I always thought that the down feed screw and calibrated collar on the model of shaper that I have was close to useless. The lead screw was 1/2'' Whitworth. 0.0833" per revolution of the handle didn't make a lot of sense.

I turned up a new 1/2" x 20 tpi leadscrew and a phosphor bronze nut to suit. I liked the feed dials on my little lathes so I made one to match. Unlike the lathe, which utilizes a thread to secure the non- rotating part of the collar, I simply bored out the tool head slide and installed a set screw to secure the collar.

To install the bronze nut in the tool head base, I bored a blind hole into the face of the base to accommodate the nut and another blind hole, on the same centreline, from the rear for a 3/16" W cap screw which locks the nut in place.

The collar is graduated in 0.001" increments and can be locked in position with a brass tipped thumb screw.

The handle was located on the lead screw shaft with a ill fitting axial dowel. I could have installed a radial taper pin, but chose the easier option of turning up a new tight fitting dowel.

In reality the modification wasn't as successful as I thought it might be. The graduated collar would bind on the fixed bush because the turning the hand crank tightened the entire assembly. Hercus achieved the same pretty much useless result in the design of the vertical milling slide's graduated collar which I addressed by installing a fixed cross pinned 'thrust' collar inside the rotatable graduated collar.

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The first exploded photo shows the stock Hercus components. There was more work involved but this is not the Hercus forum. Having had (IMO) success with the milling slide modification I thought the Douglas downfeed might benefit from a similar upgrade.

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The above photos show the original Douglas collar and my larger two piece 0.001" graduated collar prior to modification. I turned up a thrust collar from 1214 and cross pinned it to the leadscrew with a taper pin. The graduated collar was counterbored to accommodate the pinned collar. I did exercise some care to minimise end play when locating the collar while drilling and reaming the hole for the taper pin.

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There is now no binding and associated erroneous readings from the collar. It is free to rotate or be locked in position with its brass tipped thumbscrew.

BT
Attached Images




Read the full thread at metalworkforums.com...