Tool Head Questions

[FOR_Star]

Purchased a spare tool head for a project several months ago.  It's an "older" unit with 3/8th unthreaded hole in TC position. Got it all fluffed & buffed and tried setting it on the column for the first time.

• Slid on the column just fine until the key engaged the keyway on the column, then will go no farther. The key sticks out too far and appears to be canted in the grove in the tool head. Is it possible the previous owner tried to replace the key in the tool head with poor results? Is the key in the tool head a replaceable part? How can I fix this?
• Closely compared the spare tool head to one that came with machine in 1979 (& has 11/16-24 hole in TC position)  The bore of spare (older) TH is smooth while the machine's original TH has oil grooves cut in the bore.  Anyone have an idea when Star began adding oil grooves to the bores of THs?

[star60]

You can knock /pry out the key and check if the key has a burr or is out of square . Also check the key slot as it probably has a ridge on it  from forcing in the key. I think file to fit would work . And a brass  key might be easier to file and fit . If you can measure it with a  micrometer some of us will be able to tell if it the correct size .

[rbwillnj]

I would be careful about knocking out the key.   Although your tool head has the 3/8" hole at the taper crimp station, it is actually what I consider to be a newer style tool head.   Tool heads like yours have a pin through the side of the tool head that goes into the key.  If you attempt to remove the key, you will really bugger it up.  Even on the Old style tool heads that do not have the pin, you are likely to bugger up the key trying to remove it.

I have never seen a Star tool head where the key sticks out too far, although it often seems that might be the problem. 

The most frequent problem is at the taper pin hole.  If the pin is inserted with too much force, the it can deform the hole a bit and cause a raised area around the hole.   Role a very fine file over the hole in the column, front and back, and see if you see a raised area. If you do see a raised area keep rolling the file over the area until the raised area is flush with the rest.

If the problem is not there, then there could be a burr in the keyway, or on the bottom of the key.   Run a fine file along the inside edges of the keyway to see if you can find a burr.    If you don't find anything there, try to file the corners of the key while it is still in the tool head.

Of course if none of that works, you can send it to me,

Bruce Williams

 

[FOR_Star]

I already had the key out before I saw the post from Bruce.  There was various debris between the key and the bottom of the slot in the Tool Head ("TH").

Original key width when first pulled out = a thin hair more than .250 ( all dimensions in inches).  Depth = .2505 to .2510.  Length = 1.875.  The bottom of the key is at the top of the .250 thru-hole that's at the bottom of the key slot in the TH (see picture that shows "pin" hole and hole at bottom of slot)

The bare key would not fit into the keyway on the column with hand pressure only at that original width.
With some hard stones (trigger work kind), polished the sides until it would just push into column keyway.  Width at that stage = .2495.  After final polishing on sides & a little "lapping" in column keyway with JB Bore Paste, width is now at about .2493.

The keyway at the top of the column was sort of crimped over, or not completely cut.  When the bare key was placed in mid-column (after "fitting" the key) and slid upward, it would not come out of the keyway at the top.  Some light file work on the column fixed that.

Test fitting in the top part of the slot in the TH shows that hard hand pressure will push key to the bottom of the slot using just the end of the key to test fit, but not actually installing it.

Here's the question now.  In the lower part of the slot in the TH there was hard dried stuff that looked like a sealant or loc tight that had been applied before the key had originally been installed.  Brushing, scraping, and solvent finally removed the residue.  Should I apply some loc tight, or something similar, in the lower part of the key slot before putting the key back in the TH?

[rbwillnj]

I don't have any information on how Star installed the key, but I have quite a bit of original key stock and it measures 0.2504" square.  The keyway in the tool head was cut with a shaper.  The cutting bit for the shaper measures 0.2485".   Therefore I would speculate that the key was press fit into the keyway.   I don't think there would be a problem using some Loctite as long as you get the key firmly seated in the tool head.

[FOR_Star]

Success.  With all parts cleaned up, I put a little blue medium strength Loctite in the TH slot.  Used a 3" C-clamp to "press" the key back in. The pin is now just a little proud of the outside of the barrel of the TH, indicating it seated deeper into the slot.  Slid onto and all the way down the column.  Felt smooth without any noticeable play.

With the TH fully engaged on the column, I tried twisting the TH CW & CCW.  The was a very, very small amount of rotational play.  For comparison, I put the original .38 TH on and tested the rotational play.  It too had a very small amount.  Just judged by feel, and didn't try to measure.

BTW, after removing the key, I put the TH minus key on the column and it slid up & down OK.  At that point, I knew the problem related to the fit of the key into the column's keyway.

In hindsight, if I had a similar situation again I would first try to squeeze the key farther back into the slot with a C-clamp.  Maybe the TH was administered the 1 meter drop test during shipping and the key moved slightly out of position.

Thank you very much for all the replies!  They were a huge help. I wasn't sure which direction to go when the TH wouldn't slide down the column.

[varmintpopper]

Good Luck with Your Machine and Good Shooting

Lindy