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1st project for my mill

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scattermaster

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#1
Hey guys,
So far I've only been playing with the mill. (testing my skills?)
Now I have a semi practical project.
I have a Harbor Freight drill press for my hobby room. It has about an eighth of an inch of play at the end of my drill bits. There are no adjustments to make it tighter. The large holes in the housing that the quill travels in are just too big. SOOOOO,
I'm gonna try to make and install a pair of bronze bushings.
I wish I had a lathe but I don't so I'll have to improvise with my rotary table.
I have a piece of bronze bar stock that has to be cut down and hollowed out to make the bushing material.
I think I should leave the ID a bit smaller than the intended result. I can do a final bore after they are pressed in.
When I bore the aluminum drill press housing, how much of an interference fit should I shoot for? (I'm thinking .0005") What would you recommend?
I don't have a lot of room to enlarge the holes before I make the housing weak so, how thin can they be but still be strong enough to press in?

The diameter is about 1-5/8" and they are about 7/16" high.
thx,
Jim
 

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Doodle

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#2
First, good luck with the weather.

The way I would do it, the quill looks nice and smooth and the housing looks like crap. I would bore out the head for the press fit of the new bearing which I would add Loctite in case my press fit was not perfect. I would then start boring the new bearing and use the quill to test for fit. I would only measure as I was boring to get really close then take very light cuts to the final fit. When the quill slides in and out without sticking, that's where I would stop boring. While you have it apart have a lubrication hole to get oil into the bearing/quill so you won't ever have it run dry.

If the quill doesn't have a lock, add one now that you have it all apart.
 

scattermaster

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#3
First, good luck with the weather.

The way I would do it, the quill looks nice and smooth and the housing looks like crap. I would bore out the head for the press fit of the new bearing which I would add Loctite in case my press fit was not perfect. I would then start boring the new bearing and use the quill to test for fit. I would only measure as I was boring to get really close then take very light cuts to the final fit. When the quill slides in and out without sticking, that's where I would stop boring. While you have it apart have a lubrication hole to get oil into the bearing/quill so you won't ever have it run dry.

If the quill doesn't have a lock, add one now that you have it all apart.
That sounds good. I've read that I should shoot for about .0005" interference fit. I don't know if I can really do that but it's a target.
Hmmm, I didn't think about adding grease zerks but that's a good idea. Thx!
I still haven't checked if I can get it under a boring bar. I have the Hitorq bench mill from LMS, so it's not very high. The housing is about 5.5" tall.
 

Doodle

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#4
Bolt it on the mill table, use an R8 collet, boring head and it should fit. I use a 3900 at work from LMS and just love it.
 

scattermaster

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#5
Update!
Well this is sure being a learning exercise. I did a good job on making bushings that press in and the quill fit is perfect. Almost no play and the quill slides freely up and down. BUT,
I didn't get it lined up with the bearing at the top. I missed by a lot.
Sooo, my options appear to be:
1. throw it away and buy a decent drill press. (too easy)
2. knock out the bushings and start from scratch.
3. move the top bearing over.

If I start over, I'm not sure how to get the housing indicated over that bearing. IMG_9962.JPG IMG_9962.JPG IMG_9964.JPG IMG_9967.JPG
 

Doodle

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#6
Use the boring bar to sneak up on it and rotate the boring head/ bar by hand backwards. Adjust x,y so it just rubs all around. Lock it down, set the new bearing in without moving it, then bore the new bearing.
 

scattermaster

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#7
Use the boring bar to sneak up on it and rotate the boring head/ bar by hand backwards. Adjust x,y so it just rubs all around. Lock it down, set the new bearing in without moving it, then bore the new bearing.
I actually did that when I bored out the bushings but I had already messed up when I bored out the housing to accept them. Now that they are off center I can't use the bores to indicate from.
I think I need to indicate from the ball bearing on the bottom end but I have to be able to reach about 4 3/8" from the top to get inside it. It would be hard to see and hard to "feel" but I'll check it out.

I thought I might try using a rod the right length and diameter to stick in the bearing and long enough to stick up through the top, I could indicate from that, but since I don't have a lathe I can't just make one.
 
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scattermaster

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#10
I
Congrats. How did you pick up the center of the lower bearing?
I used a half inch drill bit in my boring head. That was long enough to reach that bearing. I eyeballed it first and got close. Then I just kept opening the boring diameter and adjusting x and y a little at a time until I had a slight drag all the way around while turning it by hand. It worked great.
I don't know why I didn't think of that the 1st time. Oh well, live and learn.
Hmmmm,
I wonder how much one could get for a cheap HF drill press with this mod?
Thx guys.
 

Silverbullet

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#11
Like an earl shibe paint job on any car $89.95 his paint job was like you drill press . Without the body work and rust and dent repair. You brought your cheap drill press up to a hand finished machine . It should last and do a better job longer even a lifetime.
 
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