R8 vs ER32 collet question

Leadfootin · Feb 10, 2019

Would a significant advantage be gained by changing my Bridgeport R8 collets over to an R8 to ER32 collet chuck and ER32 collets? At this point I need to at least replace a number of my R8 collets with new high quality pieces. FWIW quill is running within .0002 or better.

litlerob1 · Feb 10, 2019

Leadfootin said:
Would a significant advantage be gained by changing my Bridgeport R8 collets over to an R8 to ER32 collet chuck and ER32 collets? At this point I need to at least replace a number of my R8 collets with new high quality pieces. FWIW quill is running within .0002 or better.

What about after you breathe on the Quill? Or look at it funny?

Are you asking if ER32 is better than R8? Then yes. They are better for Tool holding, but converting over to an ER32 set-up is going to reduce the versatility of the BP.

R

steve-l · Feb 10, 2019

Leadfootin said:
Would a significant advantage be gained by changing my Bridgeport R8 collets over to an R8 to ER32 collet chuck and ER32 collets? At this point I need to at least replace a number of my R8 collets with new high quality pieces. FWIW quill is running within .0002 or better.

Absolutely......R8 collets only grip on the end. ER32 collets grip the whole length of the collet. All ERxx collets are available in both Imperial and Metric sizes as well. I use ER16, ER32 and ER40 collets in both Imperial and Metric sizes, all with R8 and 40 taper holders. I also use these with drill bits as well when possible because the drills will cut better more accurate holes.

Yes, you can get Metric R8 collets, but they are not so common and they usually also require an M10 drawbar as opposed to the normal 7/16-20 TPI thread. The only disadvantage is that using ER collets will require R-8 or 40 taper holders and they cost a little vertical space in the mill.

Leadfootin · Feb 10, 2019

The ER collet chuck will change out as quickly as an R8 collet. I am more interested in the accuracy and versatility since R8 collets are very limited in size variation, only about .001 for accurate holding. Also the smaller outside dimension tends to be undersize, rather than the .950 in Machinery's Handbook. .003 undersize can result in a .0007 wobble in a heavy cut at 1" from collet and possible other issues. ER collets cover a range of size, typically .01mm, easily accomodating imperial and metric tools.

litlerob1 · Feb 10, 2019

Leadfootin said:
The ER collet chuck will change out as quickly as an R8 collet. I am more interested in the accuracy and versatility since R8 collets are very limited in size variation, only about .001 for accurate holding. Also the smaller outside dimension tends to be undersize, rather than the .950 in Machinery's Handbook. .003 undersize can result in a .0007 wobble in a heavy cut at 1" from collet and possible other issues. ER collets cover a range of size, typically .01mm, easily accomodating imperial and metric tools.

Here's the windup....

mTeryk · Feb 10, 2019

Leadfootin said:
The ER collet chuck will change out as quickly as an R8 collet.

Not so sure about that. Look at the torque specifications for the er collet nuts. Doubt you are going to be tightening those in the spindle. That means a tool change involves pulling the R8 to ER adapter, removing the ER nut, replacing the collet and tool and then replacing and torquing down the nut before putting it back in the spindle. Not saying it's not worth it, just that it's a few more steps over just an R8 collet.

If you get a few R8 to ER adapters and leave them set up for a job, then yes, tool changes can be quick and easy with the added advantage of preserving Z tool offsets.

Teryk

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Danny VanVoorn · Feb 10, 2019

My take on this is you will still have all the disadvantages of the R8 spindle except with the ER adapter it will be farther from the spindle nose. That and the loss of some room from the table top; the one gain is you will be able to grip any size in the ER size range.
Dan

zimbo · Feb 10, 2019

Hi Teryk,

I just ordered a full set of metric ER32 for my bridgeport based on information I gleaned from PM, they haven't shipped yet. Now you have given me bees. I understood in changing between sizes on the ER32 you didnt have to loosen the draw bar, just the nut holding the collet, making changes between sizes quicker and easier vs changing R8 collets. Did I miss understand the process.

I apologize if I misread your post. Just spent a boat load on the set and getting them shipped out from Europe.
Cheers.

Rob F. · Feb 10, 2019

He is saying you will not get the er collet tight to the recommended torque specs without removing the r8 to er tool from the mill to do so.

Leadfootin · Feb 10, 2019

Most of the ER collet holders have flats on them so tightening should not be an issue.

mhajicek · Feb 10, 2019

Pretty sure the increased stickout from the spindle will eliminate any improvements you get from the ER-32. When you get them do a side by side and let us know?

CarbideBob · Feb 10, 2019

Leadfootin said:
The ER collet chuck will change out as quickly as an R8 collet.....

How is that done?
With power drawbars we change a R-8 in our machines in the 8-12 second range.
Small tools and typically 5-8 tools used in 15 minutes.

The ER chuck has to mount in the R-8 taper.
How do you get rid of the runouts at different lengths that inevitably comes from this? Grind the ER taper in the machine?
Please do not tell me that you dial in at only one length position or worse yet the exit of the collet and think your tool runout good.
A rule of thumb is at the collet face and 4 inches out. These numbers will never be the same but do tell you where you are.
Bob

PDW · Feb 10, 2019

Danny VanVoorn said:
My take on this is you will still have all the disadvantages of the R8 spindle except with the ER adapter it will be farther from the spindle nose. That and the loss of some room from the table top; the one gain is you will be able to grip any size in the ER size range.
Dan

Agree and I've done it.

For a lot of stuff where I'm not changing tools frequently I've gone back to using my R8 collets directly.

I still use my ER32 holder quite a bit but the stickout can be annoying. Main advantage is that I can hold pretty much anything from 2mm to 20mm diameter.

PDW

Leadfootin · Feb 10, 2019

With R8 collets narrow range of tool size, the deflection of the tool collet combination can be a real issue. How does an ER collet compare to an R8 in this respect? I need to either purchase a metric R8 collet set or and ER32 collet set with holder. My Bridgeport has a riser so stick out is not usually a big issue from a height standpoint.

EmGo · Feb 10, 2019

Leadfootin said:
With R8 collets narrow range of tool size, the deflection of the tool collet combination cane a real issue...

This is a Bridgeport, fer chrissake. Better get a towel, you're going to mess on your hand pretty quick.

CarbideBob · Feb 10, 2019

Buy the metric R-8 collet set.

Leadfootin · Feb 10, 2019

EmanuelGoldstein said:
This is a Bridgeport, fer chrissake. Better get a towel, you're going to mess on your hand pretty quick.

I am a realist and quite aware of the machine's limitations. The question is to guide a tooling decision I have to make and provide the best overall utilization of the machine. Simply put I am looking for the most cost effective decision to suit my needs.

litlerob1 · Feb 10, 2019

Leadfootin said:
I am a realist and quite aware of the machine's limitations. The question is to guide a tooling decision I have to make and provide the best overall utilization of the machine. Simply put I am looking for the most cost effective decision to suit my needs.

Convert the whole thing to CAT 40 and a power draw bar. There are kits.

R

Leadfootin · Feb 10, 2019

Effective but over the top.
Back to the original question: What are the advantages and drawbacks of using an R8 to ER32 collet holder and ER32 collets in a Bridgeport compared to R8 collets? Accuracy, tool holding, convenience, flexibility etc.

Rob F. · Feb 10, 2019

Can spindle be swapped with an er spindle? Seem to remember one posted here a while ago.

R8 vs ER32 collet question

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