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Spindle Regrinding Service for Benchtop Machines
Hi folks,
I've got an RF-25 and I'm trying to find a spindle regrinding service to "dust" the R8 spindle taper to reduce runout. While this is an extremely common service for Bridgeport and similar machines, all the places I've reached out to don't want to touch my spindle without a >$500 charge. I do not have the means to do this myself unfortunately, and I'm willing to accept that there's not an economical way to get this done properly, but thought I'd ask in case anyone has any leads.
Thanks!
Cheers,
IHateMayonnaise
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Re: Spindle Regrinding Service for Benchtop Machines
I can't see you having much luck without a heavy price tag attached to it.
To be honest the best option I found with my X2 machine is to use a direct collet when I need it a bit closer tolerance.
I can get anywhere between 0.004mm to 0.04mm throwing a cutter into a decent ER32 chuck and locking it up.
With a direct collet I can get anywhere from 0.004mm to 0.01mm.
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Re: Spindle Regrinding Service for Benchtop Machines
Well, my BP clone spindle was about $900 including new bearings and regrind.
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
Originally Posted by
dazp1976
I can't see you having much luck without a heavy price tag attached to it.
To be honest the best option I found with my X2 machine is to use a direct collet when I need it a bit closer tolerance.
I can get anywhere between 0.004mm to 0.04mm throwing a cutter into a decent ER32 chuck and locking it up.
With a direct collet I can get anywhere from 0.004mm to 0.01mm.
Its not that difficult to do it yourself you have to make up a slide and mount a small air grinder or electric grinder on it, your ER is 8 degree set this up with a sine bar to get the angle perfect, align to the center of the spindle rotate the spindle at the slowest speed you can and slide the grinder slide up and down, you must dress the grinding wheel true before you start grinding
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Re: Spindle Regrinding Service for Benchtop Machines
CBN-tipped boring bar held in the vise. Run a mill-turn program to dust the taper only - don't open up the straight secton at the top. Doing it in place should result inthe lowest possible runout.
Sure it's not your bearings? Not thinking that that mill came with super-duper AC bearings...
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Quote:
Originally Posted by
spumco
CBN-tipped boring bar held in the vise. Run a mill-turn program to dust the taper only - don't open up the straight secton at the top. Doing it in place should result inthe lowest possible runout.
Sure it's not your bearings? Not thinking that that mill came with super-duper AC bearings...
I have two tapered roller bearings (30205 and 30206). I purchased new FAG bearings, and to say that I installed them carefully is an understatement. All 4 bearing surfaces were pressed on by using bearing adapters and screwing on carefully using threaded rods, along with heat and/or cooling to ease insertion. I also purchased two P5 bearings for the tapered spindle sleeve, and installed them in the same manner. The preload was set initially to reduce play (close the gap) by measuring run-out on the R8 taper with the quill clamped to v-blocks on a surface plate. I packed the bearings with Nubar isoflex-15, and I'll begin the burn-in procedure today by tracking the quill temp using a thermal camera.
I bought a brand new collet set from Hardinge, and the spindle that I'm using is new from Grizzly (old one was loose in the tapered spindle sleeve). I noticed that when I installed one of the Hardinge collets with the drawbar that there is uniform contact around the entire circumference of the back (non tapered) of the collet, but I could hardly see any contact marks on the tapered section (this was verified using layout fluid). When installing a bit, the collet does appear to close, at least enough for me to not be able to rotate the bit by hand. I'm not yet at a point where I can test the holding power on a work piece, as obviously that is the true test.
The run-out on the taper (as measured on my surface plate) was a few 10ths, and when I installed a new Hardinge collet with an oversized gage pin I was reading a couple thou at the base of the pin. I did this with several pins and collets, had very consistent results.
I'm curious to see what it looks like after burn in, as I may have to adjust the preload. I'm not expecting much if a change, however, and if I can't find a place to regrind my spindle for less than $200 or so, then I'll be call it a day and just live with the run-out that I have.... I can't imagine doing anything more carefully than I have already, and I'm not prepared to waste a lot more time trying to make a benchtop machine a precision apparatus when it's clearly not in the cards.
Cheers,
IHateMayonnaise
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Re: Spindle Regrinding Service for Benchtop Machines
It´s perfectly possible to self ghetto-grind the spindle taper using any of various methods.
Multiple anecdotes and examples from real professionals on the web attest to this.
Any grinding spindle with a mounted stone will work.
Dressing it with a diamond will help. Knocks off high spots.
Then just run the spindle in against the grinding wheel, spindle rpm maybe around 300 rpm.
It´s a 2-axis move.
A dremel, air die grinder, or bench grinder (low rpm, but still) should work.
Most of the error is likely bearing repeatable error - the bearing manufacturers guides all point this out.
Skf, timken etc. all indicate maybe - 0.01 mm error as-mounted but maybe 0.002 mm after grinding/lapping in their machine-tool guides online.
One should remove less than 0.02 mm, total, mostly much less.
Even a fixed grinding stone should work fine.
The rotating spindle will only hit on the high spots, with very low load, and a cnc tool can approach the inside surface with extremely small movements of 0.001 mm, 1 micron, or sometimes less.
And then keep repeating the grinding-cycle slow x-z movement.
Endless ghetto tricks can bias the mechanicals to take out most of the slop and bend.
A weight, pneumatic cylinder, rubber band etc., and a copper/brass/bronze/delrin/(ptfe ?) contact point can load the parts removing almost all slop.
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1 Attachment(s)
Re: Spindle Regrinding Service for Benchtop Machines
Here are the spec's for an R8 if you don't have them
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Re: Spindle Regrinding Service for Benchtop Machines
Hi, it will be a bit of a bugger if the straight part of the spindle bore that locates the back end of the R8 collet is running out......once that has been ground to size it's there for good......you cannot regrind it a few tenths bigger to cure runout or the collet will end wobble and run out.
But you can touch up the front taper with a die grinder a few tenths and if you have access to a lathe or someone with one then you're home and dry.
With a lathe you would hold the one end in the chuck and run the spindle on its front bearing diam in a fixed steady and use a die grinder....whatever...... with the compound slide set over to the taper angle.
Without any access to any machinery at all or any ability to build a pseudo lathe.....that is, a set of linear rails and a pair of plumber block bearings for the headstock etc etc...…..anything you do to the spindle will probably ruin it for any further use despite the slight runout, so I would advise leaving it as is and pretend you didn't know it ran out...….or buy another spindle as a spare part.
Ian.
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
Originally Posted by
handlewanker
Hi, it will be a bit of a bugger if the straight part of the spindle bore that locates the back end of the R8 collet is running out......once that has been ground to size it's there for good......you cannot regrind it a few tenths bigger to cure runout or the collet will end wobble and run out.
But you can touch up the front taper with a die grinder a few tenths and if you have access to a lathe or someone with one then you're home and dry.
With a lathe you would hold the one end in the chuck and run the spindle on its front bearing diam in a fixed steady and use a die grinder....whatever...... with the compound slide set over to the taper angle.
Without any access to any machinery at all or any ability to build a pseudo lathe.....that is, a set of linear rails and a pair of plumber block bearings for the headstock etc etc...…..anything you do to the spindle will probably ruin it for any further use despite the slight runout, so I would advise leaving it as is and pretend you didn't know it ran out...….or buy another spindle as a spare part.
Ian.
Correct. Better to have it done right, instead of something you learned from some guy on the internet who said it would work.
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
Hi, it will be a bit of a bugger if the straight part of the spindle bore that locates the back end of the R8 collet is running out......once that has been ground to size it's there for good......you cannot regrind it a few tenths bigger to cure runout or the collet will end wobble and run out.
I'm not sure this is entirely true. On an R8, the straight portion of the collet/holder/whatever has a tolerance of 0.9490" - 0.9495" so right there is 5 tenths potential "slop" in that upper portion, and I am sure that the straight portion in the bore inside the spindle has a similar tolerance and undoubtedly a bit of designed in clearance. So there is not a "tight" fit there anyway and if needed, grinding another tenth or two out of that portion will have no detriment that I can see. The tapered portion of the tool would be able to "straighten" things out if re-ground. Indeed, a few years ago, Dave Decaussin of Fadal fame designed and made some very nice little CNC machining centers that used tool holders he called "Cat R8". These tool holders used only the tapered portion of the R8 and completely eliminated the upper straight portion of the typical R8 tool holder. Grinding that portion of the bore would pretty much just do the same thing and eliminate it from location the tools.
Look about 8:40 to see the Cat R8 tool holders.
https://youtu.be/b-y03hhCCME?t=519
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Re: Spindle Regrinding Service for Benchtop Machines
Thinking about this a little it is possible to do this without too much extra stuff on a machine with a tilting head. You could tilt the head to the proper angle for the taper and then affix a die grinder to the table somehow and use the X and Z axes of the mill itself to re-grind the taper.
Unfortunately this won't work for a RF-25 like the OP has since its head doesn't tilt.
Attachment 421042
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
Originally Posted by
109jb
I'm not sure this is entirely true. On an R8, the straight portion of the collet/holder/whatever has a tolerance of 0.9490" - 0.9495" so right there is 5 tenths potential "slop" in that upper portion, and I am sure that the straight portion in the bore inside the spindle has a similar tolerance and undoubtedly a bit of designed in clearance. So there is not a "tight" fit there anyway and if needed, grinding another tenth or two out of that portion will have no detriment that I can see. The tapered portion of the tool would be able to "straighten" things out if re-ground. Indeed, a few years ago, Dave Decaussin of Fadal fame designed and made some very nice little CNC machining centers that used tool holders he called "Cat R8". These tool holders used only the tapered portion of the R8 and completely eliminated the upper straight portion of the typical R8 tool holder. Grinding that portion of the bore would pretty much just do the same thing and eliminate it from location the tools.
Look about 8:40 to see the Cat R8 tool holders.
https://youtu.be/b-y03hhCCME?t=519
Hi, I thought about that too and if the top straight section is clearance you won't need to regrind it at all......however if the bottom taper section is running eccentric then regrinding that part will work to correct it.
At a wild guess I would think that a die grinder on a small slide mounted against an angle plate and angled over at the taper angle would be a very doable DIY solution.....as Mac has said...….you only want to take off a few tenths at most and this won't affect the seating of the collet in the bore as it will only go back a few thou at most.
I would hesitate to suggest.....but if the Devil drives then it could be done...….. that a mounted grind stone in a die grinder, clamped against an angle plate and suitably dressed then moved against the taper with the mill table X axis to remove a few tenths, could work as long as the stone was long enough to grind the whole length of the taper in one move.
The stone would have to be mounted in the die grinder and dressed with a diamond initially to ensure it ran true.
One big factor and that is the draw bar influence on the collet...…...due to the end of the collet being a clearance in the bore, if the draw bar pushes the end of the collet to one side as it tightens you WILL get cutter run out as the cutter will run eccentric and more so the longer the cutter is.
BTW.....my opinion is...... the shortened collet of Dave D'C will not be supported as per a regular R8 collet, and as a cutter exerts considerable radial pressure when it is at a high feed rate the tilt over aspect would be a real problem......why then does an R8 collet have such a long length if it can work just as well as a cut down model?
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
One big factor and that is the draw bar influence on the collet...…...due to the end of the collet being a clearance in the bore, if the draw bar pushes the end of the collet to one side as it tightens you WILL get cutter run out as the cutter will run eccentric and more so the longer the cutter is.
BTW.....my opinion is...... the shortened collet of Dave D'C will not be supported as per a regular R8 collet, and as a cutter exerts considerable radial pressure when it is at a high feed rate the tilt over aspect would be a real problem......why then does an R8 collet have such a long length if it can work just as well as a cut down model?
I suppose the drawbar could contribute, but I think for the drawbar to have that kind of effect would be extreme as a taper like the end of the R8 is enough to straighten whatever tool is in there on the taper.
I don't doubt that the long R8 will provide a "stiffer" overall assembly, but I question whether this is necessary. Looking at Dave's videos, he is able to take some pretty hefty cuts with the shortened R8 tooling. Also, considering for example an R8 collet, that has flexible sides, I would think that all the rigidity in that system comes from the taper locking the bottom part of the R8 collet onto the tool. I just can't see the thin side walls of the R8 collet providing much to the rigidity when I can take an R8 collet and flex the side walls with my bare hands.
One thing that comes to mind as far as why R8 collets are so long is so that long tools have a place to go in a typical R8 collet or tool, but not so in the short ones Dave Decaussin uses. For example a double end 3/4" end mill can be used in a 3/4" R8 collet, but there would not be enough depth in just the tapered part like Dave D. used. So the extra length could be for convenience for longer tooling rather than because it is more stout.
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Re: Spindle Regrinding Service for Benchtop Machines
I'm a very firm believer in "the proof is in the pudding" etc, and Dave D'C has proved that conclusively......pity these collets were not more freely available...….however if that was a fact, you'd have to have a mill spindle dedicated to use them.
If they're commercially available I'd be in the market for a few as I have a small jig borer spindle I want to modify......…..it's 2 Morse at the moment but I'm redesigning it for R8, that'll be a tight squeeze in a 35mm spindle diam.
In my case I want to use the jig borer as a manual mill so a longer draw bar would do the trick .....I already have a CNC mill
There would be a lot of stiffness in that short R8 collet to allow the taper to clamp down but if an ER system can do it.....why not a short R8 too.....although the ER design has double ended slots and more of them.
I suppose Dave D'C had his custom made......I liked his UMC10 mill, saw it on UTUBE many years back...…..steel tubing too, my favourite material.
I can't really think why I wanted to go to R8......seemed like a good idea at the time...….. when the spindle end could just be made to use ER40 directly in it...…..2mm to 35mm.....hmmmmmm, why not.
Ian.
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Re: Spindle Regrinding Service for Benchtop Machines
HW, I have a UMC10. I cant say I am overly impressed with the toolholders themselves. That short modded R8 might be its issues.
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Re: Spindle Regrinding Service for Benchtop Machines
Hi, I don't think you can go back from the short R8's unless you change the whole head as the bearing configuration wouldn't allow a bigger diam. spindle to be fitted...….it's probably right from the beginning with a new tool holding design that decides the size of the bearings.
R8, being approx. an inch in diam. or thereabouts at the top end, would mean a spindle of at least 40mm diam. and bearings for that size in A/C are pricey as well as not good for high rpm etc.
In a spindle design from the outset, if you went for ISO 30 and dropped it's position down a bit you could get it into a spindle of approx. 35mm diam. as the dumpy end of the '30 would allow A/C bearings with a 35 mm bore.
That being said, I think the designer of the R8 knew what it needed to make the collet stable and run true etc.
It's strange, but looking at the video by David D'C, he appears to mill quite happily on the UMC 10 with a large depth of cut in aluminium without any apparent tool wobble etc...…...maybe his draw bar pressure is big enough to hold the collet firmly.
Perhaps milling in steel etc would be a different matter.
The draw bar end, in that case, would be an asset as it would ensure the collet didn't tilt in it's seating.
At a guess I would think that when it was stationary, a tool in the short R8 would dial up running true, but under a cutting side load you could get some "tilt over" deflection that would not be apparent when the draw bar was pulling up with force once the spindle was stationary again......the long R8 collet would not do this.....ever.
Ian.
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Re: Spindle Regrinding Service for Benchtop Machines
The short R8 is an interesting idea in theory but it in reality it comes up short.
For a machine made to use a standard R8, retrofitting a short R8 doesn't offer many advantages.
In a machine designed from scratch, there are now many alternatives that are , on the whole, preferable to the short R8.
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
Originally Posted by
cncuser1
The short R8 is an interesting idea in theory but it in reality it comes up short.
For a machine made to use a standard R8, retrofitting a short R8 doesn't offer many advantages.
In a machine designed from scratch, there are now many alternatives that are , on the whole, preferable to the short R8.
We seem to have digressed a bit. I was the one that originally mentioned the short R8 used by Dave Decaussin, but it wasn't to recommend to anyone to go to that system, but rather to point out that most of the work in an R8 setup is done by that lower tapered portion and that the upper portion could have, and undoubtedly does have, some clearance to the top portion of standard R8 tool holders. This was to refute a claim that the upper cylindrical portion inside the spindle could not be re-ground. I believe it can within reason of course. This was the only reason I brought up the short R8 to show that the taper portion alone could do the job.
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
Originally Posted by
cncuser1
The short R8 is an interesting idea in theory but it in reality it comes up short.
For a machine made to use a standard R8, retrofitting a short R8 doesn't offer many advantages.
In a machine designed from scratch, there are now many alternatives that are , on the whole, preferable to the short R8.
Thought I would also mention that if you watch Dave D's videos he discusses why he chose the short R8, and it was not because it was superior to anything else, but he was able to use a standard unmodified R8 spindle with a pull-stud tooling system. He mentioned that he did this because he felt it would present a way for hobbyists to do the same easily. So, it wasn't a system for a machine "designed from scratch", but for existing machines.that already had R8 spindles. Indeed his first machines he did this to were off the Shelf Grizzly machines. He even did a nice G0704 conversion complete with auto tool changer, and the short R8. Would some other tooling system have worked better? Probably, but it would require a spindle change that the short R8 design didn't.
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Re: Spindle Regrinding Service for Benchtop Machines
109jb, As a retrofit for a hobbyist, I agree, the short R8 is a good improvement over standard R8 as an entry into quick, repeatable tool changes.
How would you compare the short R8 to something like the TTS? Pretty close I'd say? 6 of one, half a dozen of another? My personal preference would be to go with a TTS ( or clone) rather than the short R8 so I don't have to deal with a pull stud system that might be lightly supported ( commercially) and or pricey.
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Re: Spindle Regrinding Service for Benchtop Machines
You can always regrind teh R8 spindle to the BT30/Cat30 taper and use a pull stud set. There IS room to make it happen. It HAS been done.
Just a thought , (;-) TP
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Re: Spindle Regrinding Service for Benchtop Machines
Vmax, do you have an example to show?
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
Originally Posted by
cncuser1
109jb, As a retrofit for a hobbyist, I agree, the short R8 is a good improvement over standard R8 as an entry into quick, repeatable tool changes.
How would you compare the short R8 to something like the TTS? Pretty close I'd say? 6 of one, half a dozen of another? My personal preference would be to go with a TTS ( or clone) rather than the short R8 so I don't have to deal with a pull stud system that might be lightly supported ( commercially) and or pricey.
I'm not a huge fan of TTS as I've never been a fan of R8 collets in general and the heart of the TTS is a 3/4 R8 collet. I prefer solid R8 tooling. If things work right, the 3/4 shank too won't pull out, but it is a concern I have. With a solid R8 tool or even a short R8 with a pull stud the concern about slippage is reduced.
Having said that, I did buy some 3/4" shank ER collet holders to use as TTS-ish tools. I don't currently have a belleville spring type drawbar, and just loosen and tighten the drawbar to change the tools. I still find myself using solid R8 tooling more than the ER holders with the R8 collet. I find the tool length repeatability just fine using R8. Maybe if I bought more 3/4 shank tools I'd use the TTS style system more, but the benefit isn't there without an auto drawbar. Way back when I used a Bridgeport with a pneumatic impact drawbar and that seemed plenty fast enough for me and is an option for my RF-45 size machine I am sloooowly converting. That's off on the horizon but I have considered a few options for that machine, which include just leaving the standard drawbar and wrench option, the pneumatic impact drawbar, TTS with a pneumatic or manual release and the short R8 with pull stud and pneumatic or manual release.
As I see it the benefits are:
1. Standard drawbar w/wrench - Versitile but slow. Can use standard R8 and TTS type stuff.
2. Pneumatic impact drawbar - Versitile and faster. Can use standard R8 and TTS type stuff. No feel for tightening torque
3. TTS - If used with a belleville system is fast, but I would consider it horsepower limited. Lots of posts about slippage and tool pull out which raises concern
4. Short R8 - Fast, but now your stuck with it and except for buying from Dave D, would have to make your own tool holders.
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Re: Spindle Regrinding Service for Benchtop Machines
I do not have a picture BUT I know where there is a Kneemill type CNC machine that runs every day and he simply reground teh taper to match a stock BT30 tool holder and installed a ball type pull stud drawbar. There is room inside of a R8 spindle to do it. It also has an ATC. It has been running for years now. There is only a sqeak of difference between teh R8 and BT30 tapers.
Dave C did teh other option and had CT30 type tool holders ground to teh R8 taper. And then later made his own tool holder Cat30/R8 . Much simpler/Cheaper to just have teh spindle ground ONCE and use stock tool holders.
(;-) TP
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
Originally Posted by
cncuser1
Vmax, do you have an example to show?
The BT30 and R8 have the same 1.25" large diameter, and the taper on the R8 is a little "steeper", so to grind for a BT30 only requires taking out about 0.080" from the back end of the R8 taper going to 0 at the fat end. Very doable but there is no going back from it.
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Re: Spindle Regrinding Service for Benchtop Machines
IF you are woried about going BACK then you should not consider this option but I am not sure WHY you would want to go back. But replacement spindles in this machine range are fairly cheap to replace.
Your option would be to have BT30 tool holders reground to teh R8 taper. A lot more expensive to have to grind every tool holder. OR you could contact a tool holder manf and ask to have some custom made. Maybe a group buy.
(;-) TP
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Re: Spindle Regrinding Service for Benchtop Machines
Somebody needs to offer a G0704/PM25/[insert R8 mill here] spindle regrinding service. I would pay pretty good money to be able to use BT30 on my G0704. I'm not a huge fan of TTS so i've just continued to bang my R8's on and off with a butterfly impact wrench. TTS would probably be faster but i don't want to invest $1000 in tts to replace my R8 stuff. Bt30 seems like a better investment in the long run.
Has anybody ever used a pull stud on a R8 set screw holder? Seems like it might be doable.
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Re: Spindle Regrinding Service for Benchtop Machines
YEP it has been done Pull stud R8. By a company called mach1
(;-) TP
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Re: Spindle Regrinding Service for Benchtop Machines
As i recall R8 doesn't need all that much tension. Seems like that might be a decent option.
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Re: Spindle Regrinding Service for Benchtop Machines
R8 solid tooling does not require as much tension BUT a R8 collet DOES require a lot more tension.
The way to go is to buy a BT30 spindle cartridge that will fit your G704 head casting. The fellow that did teh spindle regrind mentioned above ALSO redid a Bridgeport by installing a new BT30 cartridge (10K rpm POSA manf). He did have to cast a new head assy but in teh end it was VERY smooth, quiet and cool running. It also has an ATC installed.
(;-) TP
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Re: Spindle Regrinding Service for Benchtop Machines
Handlwanker
If your just trying to use the mt2 to hold tools you can always buy something like this. https://www.ebay.com/itm/ER32-Collet...pe!27012!US!-1
It would be a lot easier then modifying the machine.
Ben
Sent from my E6810 using Tapatalk
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Re: Spindle Regrinding Service for Benchtop Machines
What SIZE spindle cartridge does a G0704 use ??
(;-) TP
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
IF you are woried about going BACK then you should not consider this option but I am not sure WHY you would want to go back. But replacement spindles in this machine range are fairly cheap to replace.
Because the original post wasn't about changing tapers. It was about dusting the taper to reduce runout.
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Re: Spindle Regrinding Service for Benchtop Machines
And teh same warning applies there as well IF when grinding teh spindle it gets muffed up ( And I have seen many muffed up) there is usually no going back as well.
Most postings seem to Morph a bit as they grow older.
Just a thought, (;-) TP
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Re: Spindle Regrinding Service for Benchtop Machines
Quote:
Originally Posted by
bhurts
Hi, well into that "look see" option.....the problem I have with the spindle I'm modifying is originally it did not have a draw bar through the solid upper drive shaft and nobody with sense mills with just the grip of a Morse taper and no draw bar...…...the M2 tooling is/was held in like a bench drill press spindle as this machine is/was originally a jig borer per se.
The mod I'm going to do entails major surgery to the existing spindle by cutting off the Morse end section and welding on the ER32 long shank chuck then re-machining the spindle to make it run true.
Welding is not a problem as I'll be using a plasma welder and the weld zone will be approx. 100mm up the 25mm diam. spindle and well away from the ER end.
Having just an ER32 chuck on the business end is not a problem as this machine will only be used in the manual mode...…….to replace a big mill I have to sell as I'm downsizing.
Meanwhile back at the ranch, the R8 spindle run out problem is similar and parallel to a problem I also have on my Skyfire SVM-0 CNC mill, not in the spindle which runs dead true but in the ten ISO 20 tool holders I bought with the mill that all run out, some as much as .004"...…..I kid thee not.....the best one has only .001" run out.
So, first option was to mount the tool holders in the spindle cartridge off the mill and on the table of my big mill and use a short slide with a die grinder etc to touch up the ER tapers, but as it requires power to rotate the spindle it would be simpler and less labour intensive to do the work on the CNC mill with the spindle insitu and a die grinder mounted vertically on a short slide.
It's only a small amount of grinding...….004" or .002" off one side in the worst case, and as the tooling is held in the spindle at least they will all run dead true afterwards......……..cheap collet run out is a different kettle of fish.
Ian.