Back lash

[H. K. Barrows]

Hello folks 3 or 4 years ago I bought a H-F bench mill 33686 to make some parts for a machine that had a problem with it , thinking the mill was cheap, do the job sell it off, but it turned out the darn thing is very accurate sill can't believe it. But it has A flaw which seem to be in any other machines of this desinge and that is the Back Lash in the up and down of the quill. I find that there is .045 to .055 play in the pinion and rack. I put a D R O on the quill zero out each time I move the quill up then come down to the new depth of cut, pain in the neck. I added a weight to keep the quill in an up position that has helped. I would like to hear if any of you folks have considered any fixes. I have an idea but as with so many of my ideas it's to complacated. But I have thougt of making a new pinion that would be bigger and take up the slop between rack on the quill I know it would be hunt and pick untill a fit could be made. Open to any thoughts thank RED

 

[bearcar1]

Hello HK,

Though I am not familiar with your machine I have a suggestion to throw out. Instead of going through the hassles of making a larger pinion, would it be possible to remove the rack from the column and place a shim(s) behind it to take up some of the slop that is apparent in that function? If you can it most likely will not get rid of all of the play but should make things a bit tighter for you.

BC1
Jim

 

[kcmillin]

Sorry I can't help. I just want to subscribe to this post to get some Ideas.

How do the CNC guys do It? I have heard of a ballscrew equivalent for the quill but cannot find any info on it.

Kel

 

[Blogwitch]

The basic fix for the quill dropping is as you have already done. Some use spring pressure, others use pullies and a weight to lift the quill into the up position. I used a spring.

Bogs

 

[Lew Hartswick]

"This a Joke Son"

Lock the quill and use the knee for Z axis adjustment.
...lew...

 

[Tin Falcon]

But sir the 33686 aint got no knee!!
Tin

 

[H. K. Barrows]

Thanks TIN

 

[Lew Hartswick]

That is why for the humor impared I prefaced it . It doesn't pay to joke I guess.

 

[Maryak]

That is why for the humor impared I prefaced it . It doesn't pay to joke I guess.

Must have been a case of Kneemonia.

Best Regards
Bob

 

[joeby]

Probably worthless info in this case; but many drill presses and the like have an eccentric sleeve on the pinion shaft. Turning it adjusts the lash. The mill in question may or may not be like this, I haven't a clue, but something to consider maybe.

Kevin