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Drilling angled holes on the lathe

Posted: Fri Jul 01, 2011 6:16 pm
by coal miner
Got involved in another project while waiting on some parts for the Farm Boy Engine . This is a sensitive drill press from J . Howells plans that will drill sub # 60 drill holes accurately at up to 7,000 rpm ( if my calculations are right ). Moving along pretty good w/ the parts . He gives some hints and guidance but the tooling and setting up of the operations is left up to the builder . The spindle runs on a 20 tooth gear up and down with a rack cut on the back side of the spindle cartridge. The gear is pinned on the feed rod and had to have a hub w/ 3 1/4"- 20 threaded stainless rods set at 120º spacing on a 16º angle to the feed . I thought about using the rotary table , but the 16º to the shaft axis presented a complex problem to me . I'm sure it would be a piece of cake for someone more learned than me . So sometime time back I had made a drill chuck assem . powered by a cordless drill to fit in a 1" boring block for the Aloris tool post and had used it to drill holes at 90º for set screws for securing hubs to shafts and what not . This would be perfect for this op . The other tool that was used was a degree wheel that had been made to fit in the outboard side of the lathe spindle that had a home made expanding arbor for attaching it .


The hub machined to print and drilling of the holes . Drilling of the holes was easy using the compound . After each hole was drilled , the drill bit was replaced with a 1/4 - 20 tap and the drill switched to the low speed mode and the hole was tapped .

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Even I could figure 0º - 120º - 240º LOL .

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The finished hub mounted on the shaft w/ 2 8 -32 set screws against 90º flats milled on the shaft


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Going to use a variable speed sewing machine motor for power , will have to adjust the mounts to fit .

One of the aspects of this hobby that I really enjoy is figuring how to get the part made and getting the operations in the proper order to get it done . It does strain these old brain cells at times , but I do think it does help my over all mental ability and keeps me from going a little batty . I'll never be an expert at this machining , just as my signature says " the more I learn "

Re: Drilling angled holes on the lathe

Posted: Fri Jul 01, 2011 11:43 pm
by Harold_V
coal miner wrote:I'll never be an expert at this machining
I'm not so sure about that. You display exceptional wisdom and skills.
Very well done!

Harold

Re: Drilling angled holes on the lathe

Posted: Fri Jul 15, 2011 7:25 pm
by coal miner
Got enough parts made to do a trial assembly of the drill press . No base or parts for for the dial indicator mount , but got to test run and check rpm's , and run-out . The motor is a recyled variable speed Singer sewing machine that the wife had worn the drive parts out . A protective cover still to be made . Initially checking the rpm on it w/the Chinese digital tachometer , came up with 7,000 rpm . An 1/8 " o-ring drive was used . Cut the ends square and after getting to size they were Super Glued together . I made the pulleys about 10% different in diameters w/ the drive pulley being the smaller of the two and read 7800 rpm with the tach . Good enough .
The column lock was made by inserting a piece of brass on the outside circumference of the column shaft bore and after boring to finish size of 1.2495 , it was removed and cut in half providing a machined surface for the lock to mate and tighten with a threaded rod and the handle . The spindle travel limit was an ingenious design that required several small parts made to some very close tolerances , as in tenths , to work right . Several pieces were delegated to the scrap box until they were made proper . LOL A good learning experience .

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The 5/16 " hex spindle shaft is driven by the pulley mounted on a bearing that has a hex brass piece pressed in it that the shaft slides thru for rotation . A broach for this was big $$'s so improvised and made one by cutting steps in a piece of SS hex to push thru after the bulk of the hole was drilled and small holes in the corners inside the inscribed circle were drilled first . This was the first attempt and it had a little play in it , so back to the mill and tightened up the circle to allow for the run-out on the drill bit , and ended up with the one installed .

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The motor mount plates are slotted to allow for alignment of the pulleys and take up for the o-ring drive . The chuck is a Rhome 0 - .250 " keyless w/ a JT1 mount . Making the taper for the JT 1 was another learning experience , but after making the second one and checking it , I thnk it is close enough to swedge on tight w/ some 620 Loctite for insurance .


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Still have quite a bit of blending and smoothing to do , but that is the fun part , working the details .
Mr. Howell shows a cast iron base w/ a magnet made in it , but I think a cross slide table would compliment this drill and give precise set ups . With the dial indicator on the quill feed , very accurate depths can be attained . You can go to Howells website to see the finished machine http://www.model-engine-plans.com/engin ... .htm?21,28

Oh run-out was .0015 , but did not check w/ a bit , the number came straight from the spindle shaft , hopefully with the chuck assembled it will still be good .

Re: Drilling angled holes on the lathe

Posted: Sat Aug 13, 2011 6:26 pm
by coal miner
The plans called for a dial indicator to be incorporated in the spindle to measure drilling depths . Went high tech and adapted a 4" ( smallest I could find ) digital read device to save my eyesight and be easier to read . The quill has 2.150" travel . The Al angle is bolted to the motor block and is slotted to clear the mounting screws on the back of the reader w/ a brass extension over a pin on the spindle slide . The return spring is a little weak but will hold the readout in position . Being able to zero the readout at any position will be handy and this one can be set , once zeroed for reaching a predetermined stopping place , reading down to .000 . That along with the spindle stop on the quill would give one several options on controlling the depth of the hole being drilled . Also purchased a Phase II X-Y table that Enco had on sale . When opened it had a lot of roughness and needed a thorough clean and adjust on the gibs and stoning of the slides . Everything was a lot smoother after that . It is not a top of the line table , but it does have a .001" accuracy in 1.000" cranking the table against a dial indicator . Need to find a piece of plate for the table and the column to mount them on .

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