Making a set of sleeves for a QCTP boring bar holder

[blindstar]

Making a set of slit sleeves is a simple job, but to make the yellow messages go away I thought I would try and describe the way I do it. This is definitely for newbies and still probably has way too much detail. It is just one way of producing a set of sleeves. I’m sure that they could be easily purchased, but I’m retied so I get to do what I want to do. I enjoy the process as much or more than the result. I am not a trained machinist. I have leaned most of what I know from reading and trying stuff, so I am dangerous.

My QCPT boring bar holder is sized for a .75 inch bar. A while ago I made a split sleeve to hold .625 bars by drilling a piece of .75 drill rod and slitting it. I have been holding smaller shank bars in style 2 holders, the ones with a v cut in the bottom surface. They work OK, but you either mess up the bars with the setscrews or have to mess with packing. I want to make a set of sleeves with shoulders to positively locate the sleeves in the holder.

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I have this piece of 1.1875 inch line shaft that has been sitting in my barn forever, so it is time to turn part of it into something useful. I want 5 sleeves; .128, .25, .375, .5 & .625 so I used the horizontal band saw to cut 5, chunks of shafting about 3.125 inch long. That length should completely fill the holder and leave me about a .25 shoulder. I think that I can work without a chucking allowance since I have a collet that can grab this bar.

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I deburred and cleaned up the pieces. Then I faced both ends and center drilled one end. The pieces were marked indicating where the shoulder should start so the sleeve will just fill the holder. While I wouldn’t really need to do any marking, it find it reassuring to see the make line up be for I start to cut.

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I want to reduce the diameter of most of the shafting to .75 inch leaving .25 inch of the original diameter. I need to think about how the work will resist the force generated by the feed. If I were planning to use the 3-jaw I would need to leave a more metal for the chuck to grab. Turning between centers would work, but I am going to use a collet and a “collet stop”. The stop is a plug that has been ground to fit my spindle taper and is tapped for an adjustment rod. It works as a collet stop or it can replace a chuck spider in some cases. It works great, particularly with a camlock spindle.

I will drive the work by grabbing a bit of the shoulder end and let the stop help resist the axial force. The other end is stabilized with a live center.

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The shafting measures 1.1875 and it needs to be .75. I’ll take a couple of roughing cuts with a carbine insert tool on each piece, then finish off with a HSS tool. Clean up the shoulders and break the edges and I now I have five of these. The finish is pretty good straight from the tool. It feels better than it looks in the pictures. I need to drill each sleeve for the shank size that it is to be used for. I want a sliding fit on nominal sized shanks so I’ll use the appropriate oversize reamer. A set over/under reamers is a really good investment. There are better ways to hold a reamer, but for this application holding the end of a chucking reamer in the Jacobs tailstock chuck will be fine. Select drills sized so that they will give the reamers about 5-10 thou to cut.

What needs to be done now is:
• Center drill
• Drill the piece about halfway
• Flip the piece in the collet and drill from the other end until the holes meet
• Open the hole to the correct size for the reamer
• Ream to final size
• Light counter sink the hole, just enough to break the edge
• Light facing pass, to make it pretty

These are deep holes, but they do not need to be absolutely concentric with the outer surface so drilling and reaming should be good enough. Working in the lathe helps, because drilling with the work turning seems to help the drill run true. For the small holes and the pilot holes for the .5 and .625 inch sleeves. Drilling from both ends of the work feels like it might cancel out some errors and it is definitely easer to clear the chips from the shallower holes. Pecking at the hole will help break up the chips, flooding the hole with lubricant is good, but it is still a slow job. The main thing is to be sure the chips are not getting jammed in the drill flutes.

Even though I have chamfered all the edges, the sleeves will feel nicer to handle if they are touched with some 500 grit wet/dry. I would not do this on a good lathe, mostly because I am too lazy to clean it up properly afterwards. I have an old lathe that I use for dirty work.

We are down to the last operation, slitting the sleeves. There is a post from Paddy, lower in this thread that suggests some reasons to do it a different way. I think that I will slit the 3 larger sleeves as I planed, but use set screws on the smaller ones.

For the .375, .5 and .625 sleeves I only need to cut through the one side of the sleeve. You must avoid clamping the piece in such a way that it would tend to compress the slit. I am going to try holding the sleeve by its ends using a vice. I will feed the work into the cutter and I want the cutter to push the work into the fixed jaw of the vice. I can use packing to place the centerline of the sleeve just enough above the jaw to provide clearance for the saw.

Since I want to hold the sleeve to be as close to the center line of the jaws as possible I’ll use my largest saw, a 5 x 1/16 . A 5 inch saw will be cutting at about 65 fpm when running at 50 rpm, which is as slow as I can go.

I am not sure if it is my mill, but slitting saws seem to cut slightly deeper at some point on their diameter. I feed a little slower when the saw is cutting deeper and a little faster when it is in the light cutting part of the rotation. When I get the motion right the cut is smooth. (old guy, really old mill – we both could use a tune up)

I got the 3 larger ones done.

 

[blindstar]

Thanks. I was just playing. I wanted to see how hard it would be to document a simple process. Since you moved the thread out of the play area I assume that you think it is worth me finishing it. I'll keep adding to the first post so the write up is in one pace.

--markM

 

[churchjw]

Very nice post please continue. Nice finish on the parts.


Jeff

 

[blindstar]

Very nice post please continue. Nice finish on the parts.

Jeff

Thanks. It definitely takes much longer to take pictures and write about than it does to do it.

For getting a good finish I seem to have better luck using sharp HSS than I do with carbide.

 

[blindstar]

One feature I would add to the set is flats and set screws. I would do this rather than slitting them.

Paddy – I really appreciate the comments. The setup I was planning to use to slit the sleeves seems a little iffy, grabbing the ends in a vice, packing under it and using a 5” saw to keep the sleeve as near to the center of the vice as possible.

I understand how the set screws establish the orientation, but I’m not sure I under how the clamping force is applied to the bar? Does tightening the holder push the set screws into the bar?

 

[blindstar]

Got it. The pictures help.

Thanks

 

[blindstar]

I appreciate, and have thought about Paddy’s suggestions, however, I’m going to stick with the original plan for now. If things don’t work out I have a bunch more line shaft ☺. For me, the auto orientation is not too important. I make my boring tools from drill rod and I have never have put flats on them. I eyeball the orientation when set the tool. Sometimes I use the ability to rotate the tool to adjust the top rake angle, and then I set the height of the tool. Take cut and adjust if it does not seem to be cutting right. I can see how it would be much quicker to have it cut right on the first try, but after a while you can get pretty good at eyeballing. Bad practice?

 

[Tony Wells]

I've built sleeves for set screw bar holders with simple clearance holes to allow the original screws to bear against the bar directly. Of course, in an extreme case, like a 2" holder sleeved down to 1/2", longer screws will need to be subbed in.

 

[blindstar]

This project started because I want to cut some 28tpi internal threads in a blind 7/16 hole which I need to do to complete another project that is needed to complete yet another project, you know how it goes. I will make the required tooling from drill rod rather than purchase it. I did not like the way using my QCTP style 2 holder was marking up the shanks of my shop made internal cutting tools. Using the compression holder with sleeves fixes that. Now that I have the sleeves finished I can get to making the boring, threading and grooving tools I need.

Thanks for looking at this thread and particularly for making comments.

 

[Tony Wells]

Thanks for posting it, Mark. It is always good to get a look at how the other guys approach problems, or offer alternatives to handling situations that come up in the shop.