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Thread: Bump center tool.
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30th Jul 2017, 10:25 PM #1
Bump center tool.
Hi Guys,
Because I needed to true up an 8" inch length of 35 mm diameter aluminium bar in the lathe three jaw, prior to parting off some slices and having heard about "bump centring", I thought I would give it a go and make one.
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It is a very simple tool to make ! Basically a ball race fastened to the end of a piece of bar.
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Above is a couple of pictures of the one I've made. A piece of 1/2" square bar four inches long, to fit into my Myford tool holder. A 5 mm hole drilled 12 mm from one end and threaded M6. Since this ball race has a 15 mm bore and is 15 mm thick, I turned a plug from a bit of black bar, with a 20 mm diameter flange, and drilled a 6 mm through hole for the cap screw.
In use you just need to put the tool into the tool holder, and approach the work piece with the ball race. As the race contacts the work it will push it, simply apply pressure until the work piece runs true. Then re-tighten the chuck jaws.
In my case I centre drilled the work piece and since I was going to part off some slices, used a live centre to support the free end.Best Regards:
Baron J.
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30th Jul 2017, 10:36 PM #2Most Valued Member
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Hiya BaronJ, yes they are a handy tool, I have one and call it a push tool.
Mine is just a piece of 1" dia black bar turned at the end and the brg press fitted on.
cheers, shed
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30th Jul 2017, 10:46 PM #3Golden Member
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Hi BaronJ. I love that too, very quick to chuck thin work piece.
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30th Jul 2017, 10:54 PM #4.
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Neat BJ.
Like Shed, I opted for the easy version, albeit a boys version with its little bar and bearing. Works nicely. Probably should have made it fifteen years ago!
Bob.
DSC_7597 (Large).jpg DSC_7590 (Large).jpg DSC_7589 (Large).jpg
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31st Jul 2017, 08:48 AM #5Golden Member
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Hi All,
These are a very handy tool. When I first saw the design quite a few years ago, from memory from the man of great innovations John Stevenson, I knocked up rough version. Often I need to open up the ID on flat washers so I added on a small bearing that came from a fishing reel overhaul. this works great as you can approach the washer from an angle and get down to using it on very small washers.
Bob
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31st Jul 2017, 09:39 AM #6.
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Innovative dovetailing Bob.
I like the small bearing idea. I will be copying it.
Bob.
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31st Jul 2017, 12:39 PM #7Golden Member
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Hi Bob,
When I built this tool I was not sure if it would work so I just took the easiest path, after using it for quite a while now it is one of my favorite tools for rough setting jobs in the three jaw chuck as well as the washer use. It is a light duty tool so no need for full dovetails. You will enjoy the adding the small bearing.
Bob
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1st Aug 2017, 09:36 AM #8.
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Hi Bob,
Any chance of letting me know the size of the small bearing? I know your lathe is larger than mine so what I'm thinking might be small (10mm-ish) may not be so. There are numerous inexpensive fishing reel bearings available on eBay to choose from.
3x10x4mm Fishing Reel Bearing Stainless Steel Balls/Retainer Corrosion Resistant | eBay
8x12x3.5mm Fishing Reel Bearing Stainless Steel Balls / Cage Corrosion Resistant
7x14x5mm Fishing Reel Bearing Stainless Steel Balls / Cage Corrosion Resistant | eBay
Bob.
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1st Aug 2017, 12:15 PM #9Golden Member
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Hi Bob,
Just measured my bearing it is 10mm OD * 4mm wide. Looks like the first link you have shown would be the one. I used loctite to hold the bearings in place to keep the bulk of the fitting down.
Bob
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1st Aug 2017, 02:18 PM #10Philomath in training
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Bob, if you want them I have some bearings that are 3/8" OD, 1/8" bore, 5/32" thick. I also have some that are 5/32" OD, 5/64" bore and 1/16" thick (arrived in a box of stuff - never used them)
Michael
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1st Aug 2017, 06:30 PM #11Golden Member
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I removed these from the hard drive of an old computer. Let me know if that is any good to you Bob?
20170801_172129.jpg
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1st Aug 2017, 07:27 PM #12.
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1st Aug 2017, 07:33 PM #13.
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Hello Trong,
Thank you very much for your kind offer but I have accepted Michael's. No point in me being too greedy.
Bob.
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1st Aug 2017, 08:09 PM #14Philomath in training
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Hang on - I thought I owed you? Shall we call it a draw and start again?
I'll get it in the post tonight
Michael
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1st Aug 2017, 09:18 PM #15Most Valued Member
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Holly crap. What a great little tool. Another tool I need to make!
Thanks for posting!
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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