Spindle Regrinding Service for Benchtop Machines

[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.

[vmax549]

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

[cncuser1]

Vmax, do you have an example to show?

[109jb]

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.

[vmax549]

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

[109jb]

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.

[vmax549]

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

[CL_MotoTech]

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.

[vmax549]

YEP it has been done Pull stud R8. By a company called mach1

(;-) TP

[CL_MotoTech]

As i recall R8 doesn't need all that much tension. Seems like that might be a decent option.

[vmax549]

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

[bhurts]

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

[vmax549]

What SIZE spindle cartridge does a G0704 use ??

(;-) TP

[109jb]

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.

[vmax549]

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

[handlewanker]

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

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.