Author Topic: How do I measure a spindle taper?  (Read 1285 times)

Offline AdeV

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Re: How do I measure a spindle taper?
« Reply #25 on: October 20, 2017, 04:00:31 AM »
My apologies Matthew, I must have missed seeing that post. You're absolutely right - an ER40 in particular would be a very handy (I see there's an ER50 as well, although I bet collets are expensive for that one!). The reason for choosing ER32 is I already have a set of collets to suit (and a chuck on an MT3 arbour), so I'll start there & will do an ER40 or ER50 some time in the future (it can go in Vol 2 of the projects-to-do-before-I-die book...)
Cheers!
Ade.
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Offline mattinker

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Re: How do I measure a spindle taper?
« Reply #26 on: October 20, 2017, 06:41:49 PM »
Adev,

i too have the ER32 collets, so when I bought ER40s, I bought from 20 to 30, which go in 2mm steps, which means they aren't too expensive. The advantage with the collet chuck that mounts directly onto the spindle is that it can be made to take through the holder work!

Cheers, Matthew

Offline AdeV

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Re: How do I measure a spindle taper?
« Reply #27 on: October 21, 2017, 01:51:47 PM »
Right, well, I'm officially a happy bunny!  :ddb: :ddb:

First, drill & ream to 25mm (slightly oversize, it should be 23.5mm, but I don't mind the extra smidge of room). I should have just drilled straight out to 1" TBH, it'd have been quicker & easier, but hey ho.

Looked up the ER32 taper angle (8 degrees), set the topslide 4 degrees, cut, why won't it fit properly?  :scratch: Bloody hell, the included angle is 16 degrees! A single side of the taper is 8deg!  :bang: Re-cut with the proper angle (eyeballed on the topslide), it was close, so I fiddled with the topslide & a DTI for a bit, got it closer, a couple of minor tweaks and YAY! Bang on! (ish - it's not quite as accurate as my bought one... but it's pretty damn close).

Final steps, cut down the outer diameter to 40mm OD, make a new tool holder for the QCTP to take a threading tool (upside down.... see Joe Pieczynski's threading trick on YouTube - basically, instead of threading TO a shoulder, you thread FROM it, running the lathe backwards with the tool upside down). I nearly cut a left-hand thread, but managed to set the machine correctly before I'd done more than a scratch pass. Being a metric thread, I have to leave the machine engaged throughout the threading process, which made life a bit entertaining... it's hard to turn by hand when in gear, unless it's in a nice high gear. So... cue some single-point threading at 670rpm!  :bugeye: :zap: Fortunately, no crashes or accidents, and eventually the nut threaded on. I overdid the threads a smidgeon at the end, so the fit's a bit loose... but that doesn't matter.

Last but not least, lobbed a collet in, put a bar in it, and checked for runout (0.004" TIR - way better than I can get with the 3-jaw, and truth is I'm not sure how straight the bar is). Took a skim cut (which, naturally, reduced TIR to a couple of tenths, probably). The REALLY good news is, it cut completely parallel! First time my lathe has EVER done that (in my ownership), which I think proves that either my chucks, or the mounting face of the spindle nose, is wonky. Now that I know that, I'll probably take a few thou off the face of the spindle nose.... and start saving up for some new chucks. ALL of my chucks (I only have about 4) cut tapered, so they're obviously not going on dead true. Or they're knackered. Or both...

Anyway, I'm chuffed because I've proven to myself that my lathe CAN cut straight, and that I've got half a chance of actually making a decent ER32/ER40/ER50 chuck for it in the future. I will sleep well tonight :)

Of course... I now have to do the whole thing again, using steel this time! Although I'll probably use the Ali one until the threads expire. Other tasks to do: Make a hollow drawbar (although it seats pretty damn firmly in the lathe without one, I'd rather not risk it, especially if I ever take heavy cuts).

Now... where did I put that 2" steel bar....  :scratch:

Many thanks all for your suggestions and assistance! It's worked out really well! :nrocks:
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Or: Zhengzhou, China. An even longer way from anywhere...
Skype: adev73

Offline mattinker

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Re: How do I measure a spindle taper?
« Reply #28 on: October 21, 2017, 02:12:52 PM »
Good stuff mate!

Cheers, Matthew

Offline PekkaNF

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Re: How do I measure a spindle taper?
« Reply #29 on: October 22, 2017, 06:37:13 AM »
Sucksess tastes sweet. Good work.

Sometimes sucsess tastes tomatoes - if you are entertainer in wild west, or easts, or south!

Pekka