Author Topic: Tool post grinder build Clough42 inspired  (Read 1011 times)

Offline PekkaNF

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Tool post grinder build Clough42 inspired
« on: August 30, 2019, 01:00:01 PM »
There is excelent YouTube series: Making a Toolpost Grinder by Clough42

Playlist of the whole series.


Drawings etc.
http://clough42.com/2018/05/24/toolpost-grinder-part-24-first-test-grind/

First I have to complment him of showing his process. Very well represented and most ideas are clear and well put. One of best I have seen.

However, it would not be me, if I would't think that while it is very inspiring and well though, there are some features that i will take different approach.

I plan to use same over all design and most dimenssions as they are. This is no problem, because he basically worked with metric parts and dimenssions and when not, he showed the rationale.

I'll be most likely using 400W BLDC motor, that lost it's ER11 chuck on the other thread.
https://madmodder.net/index.php/topic,12957.0.html


I am torn between using a very good ER20 C20 extension or the one I don't have any use, but it is little minus tolerance on C20 shaft and 0,03 mm TIR on the ER-cone.

The part I am planning to deviate from original design is bearing arrangement and mounting.

While the original design relies threaded caps to fasten the bearings onto spindle body, I am thinking to mount them a little differently.

One clear departure is that I'm not using threaded caps, other how free brearing is mounted I will make two exra bosses to aid bearing removal, if it ever comes necessary. Front boss will have bit over 20 mm holes and will have light press fit into spindle housing. When front bearing is removed , 25 mm rod can be pressed inside of the spindle housing and this will meet the ID20 mm boss that will push the front bearing out at outer race (plan is to prevent brinneling through balls).

Front bearing will be fixed (as in the original design), however I'm planning to use light press fit and glue if necessary. Front bearing has a light press fit onto spindle (ER20 C20 extension), possibility to glue. There will be spacer/flinger on the spindle to locare the spindle onto front bearing inner race.

Rear bearing will have a sliding fit onto spindle body and it will be preloaded with a wave washer outwards. prper preload of this wave washer is when it is compressed to 1 mm wide space. There is a lgiht press fit boss, fairly similar than to eject the front bearing, but here it is to size a 1 mm space for the wave spring. I though that while the belt drive will most likely guarantee mininimum loading for the rear bearing to prevent balls from skidding and wearing out the bearing in no time, does not hurt to make it proper way. While lightly loaded bearing arrangement of this kind can work with a sliding fit between inner ring and shaft, it is not good habit when loading is higher, thus I'm considering gluing the rear bearing inner ring onto shaft, when it has proved to work and preload is established.

Some pictures of the progress this far.



Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #1 on: August 31, 2019, 04:04:14 PM »
There might be a small break on this one. I'm trying to work out half decent method to make a grooving tool for J-section polyvee belts. I know that 55 or 60 degree threading tools are used, but I am going to try to make tools close to 40 degrees. I am thinking of grinding HSS blank or 35 degree tungsten insert.

Offline djc

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Re: Tool post grinder build Clough42 inspired
« Reply #2 on: September 01, 2019, 05:49:47 AM »
There might be a small break on this one. I'm trying to work out half decent method to make a grooving tool for J-section polyvee belts.

Have you seen this thread https://madmodder.net/index.php?topic=8306.0 ? You are overthinking this. Use a standard 11tpi pipe chaser die (25mm or up European gas thread) and be done with it.

Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #3 on: September 02, 2019, 07:44:49 AM »
There might be a small break on this one. I'm trying to work out half decent method to make a grooving tool for J-section polyvee belts.

Have you seen this thread https://madmodder.net/index.php?topic=8306.0 ? You are overthinking this. Use a standard 11tpi pipe chaser die (25mm or up European gas thread) and be done with it.

Yes I have seen that. And NO, I am not overthinking this. YT build uses about 250W motor at 3400 rpm, two rib J-section belt. I'll be using 400W motor at 4000 rpm max and only slightly lower transmission ratio, around 1:1,7. Where do you get this "overthinking" part? The belt calculation programs I use indicate that it is bit marginal at 40N/rib belt tension with the length of the belt and sizes of the pulleys.

Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #4 on: September 03, 2019, 09:05:28 AM »
Went trough two different calculation program and few tables....it should be pretty standard, but belt is short and under 4 ribs is nonstandard. Calculations were made for Poly V-belt PJ 362 I.E. 140PJ and driver 57 mm dia, driven 34 mm dia.

More than few tables suggests that using this configuration and avoiding smallest pulleys PJ Poly-V can reliably transfer least 200w/rib at these rpms.

Talked to one design engineer at my work and he said that the calculation programs he uses allows easily over 200w/rib (four ribs) on the pulley sizes and spacing, without tensioning wheels, no problem there - in priciple. but it is not that clear cut.

But cutting down amount of ribs does not work linear because the there is less material to support the cords. Cord is spirally wound and when belts are cut from the sleeve the edge will have open cord end. Therefore going under four leads fast into compromise.

Another factor is that apparently this type of ribbed belt does not actually work like ordinary grouped V-belt. Apparently it can't really work with one rib only, needs two ribs least to stabilize and edge most ribs are not the most productive ones.

Therefore choices are:
1: 140PJ4, Standard belt, four ribs, only too wide and this will make set screw spacing somewhat difficult.
2: 140PJ3, Available, fits->this will be my choice.

Probably pure guess would have given close enough answer, but now I feel better :scratch:


Offline chipenter

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Re: Tool post grinder build Clough42 inspired
« Reply #5 on: September 03, 2019, 10:13:51 AM »
My tool post grinder has two ribs on a 1425 rpm motor geared up 4 to 1 with a 25mm diameter pully , and not had any problems using a 50mm grinding wheel .
Jeff

Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #6 on: September 03, 2019, 01:08:58 PM »
My tool post grinder has two ribs on a 1425 rpm motor geared up 4 to 1 with a 25mm diameter pully , and not had any problems using a 50mm grinding wheel .

Thank you.

J-profile belt?

How big motor in wats?

Offline chipenter

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Re: Tool post grinder build Clough42 inspired
« Reply #7 on: September 03, 2019, 03:43:58 PM »
It's a small motor MadModder
Gallery, Projects and General
Project Logs
Cheepo toolpost grinder and uses a ER16 collet chuck .
Jeff

Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #8 on: September 04, 2019, 05:37:47 AM »
Hi Jeff, Found it:
https://madmodder.net/index.php/topic,10078.0.html

How does it works?

What is the story with the slits at the front of the bearing seat?


I like the grinding wheel guard.

Offline chipenter

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Re: Tool post grinder build Clough42 inspired
« Reply #9 on: September 04, 2019, 02:51:35 PM »
That's the piece that hold the bearing in parted off the cuts are on the outside to screw it in .
Jeff

Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #10 on: September 11, 2019, 04:48:21 PM »
Didn't find ready 40 degree PJ-belt insert and since I don't have CNC I decided to modify 35 degree insert to 40 degree one.

Plan was to mill insert pocket into 20 mm rod.

When 20 mm rod is mounted into ER32 square block it can be easily indexed for 5 and 35 and 40 degree ngles needed to mill the insert pocket and modify the inser by grinding. Very standard machining not much to it. Just many steps and quite a few double test to make sure that didn't cut reverse direction to intent.

Originally I was thinking to use this rod to grind the insert only and keep it round, but the modified insert shorten significantly and I either had to modify good unused shank or modify this grinding fixture to be used in the tool holder too (that was my plan-B. Had to revert to plan-B.

Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #11 on: September 11, 2019, 04:58:10 PM »
The diamond wheel seem to produce fairly rough grinding. In the picture the grind appears even rougher than in reality. I honed the radius to cutting edge of the insert, milled flats to insert holder and made a test drive. Seems to work. Punge cut seemed to pruce easily proper profile. Full profile tool would be a whole more fun.

Now I only need 1,5 mm test pins or good wire to gauge correct depth of the belt grove when making the belt pulley.

I roughed one pulley and it's waiting chucked the gauge wire.

Maybe I need to mount one 12,5 mm travel dial gauge to give exact spacing and calculate table in advance.

Pekka

Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #12 on: September 12, 2019, 08:12:08 AM »
Q: What would be correct grit to touch up carbide inserts? The standard wheel (around #100) seems to produce slightly too coarse grind. I haven't trued or dressed it yet.

I used vacuum/cyclone and filter. I was also wearing a respirator and didn't notice a thing. :lol:


Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #13 on: September 14, 2019, 06:58:10 AM »
Thinking of ordering 340 grit diamond to finish carbide smoother for aluminium.

Managed to make spindle pulley. It's still missing the two grub screws 90 degrees appart.

Ref:



Went pretty well, no hickups. First froove took some time to arrive to correct diameter. Rest were plunge cut to identical reading on the cross slide dial and just checked berore moving to next Z-position.
« Last Edit: September 14, 2019, 09:40:58 AM by PekkaNF »

Offline tom osselton

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Re: Tool post grinder build Clough42 inspired
« Reply #14 on: September 14, 2019, 07:29:55 PM »
A while back I went to get a motor for my Craftex mill and found out the spindles cost about $100.00 it is basically a rebrand of his mill in the videos.

Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #15 on: September 15, 2019, 03:13:29 PM »
A while back I went to get a motor for my Craftex mill and found out the spindles cost about $100.00 it is basically a rebrand of his mill in the videos.

??

Made a rookie mistake with the motor pulley. I got so distracted with the undersize 8 mm motor shaft dimession and decided to make it with a 8h7 reamer that seems to produce a little undersize hole. Well, pretty good size, but in a wrong place :doh: 0,04 mm of TIR.

6 mm boring bar just about fits into 8 mm hole, possible, but not ideal. But that is the way it has to be done.

I have three options, any other suggestions?

1: Use thin shim and bore the hole only 2xshim thickness bigger, Bit fiddly to fit.

2: Bore oversize hole into pulley, glue plug and bore correct diameter into that plug.

3: Make new pulley and not to cock it up this time.

Traditionally fixing a lemon takes only a little longer than to make it well.

Pekka


Offline chipenter

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Re: Tool post grinder build Clough42 inspired
« Reply #16 on: September 16, 2019, 02:32:56 AM »
You could also mount the pully on a arbour and turn the exterior concentric  .
Jeff

Offline philf

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Re: Tool post grinder build Clough42 inspired
« Reply #17 on: September 16, 2019, 02:52:43 AM »
Pekka,

There's another option.

Clean up the grooves concentric with the bore.

0.04 won't make that much difference to the ratio.

(Edit - have just seen that Chipenter has suggested the same fix.)

Phil.
Phil Fern
Location: Marple, Cheshire

Offline PekkaNF

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Re: Tool post grinder build Clough42 inspired
« Reply #18 on: September 16, 2019, 03:31:11 AM »
Thank you. Good suggestion! I'll try that first - 8 mm arbor with M8 thread should be pretty easy to turn....now what was the lead I did last screw cutting? 1 mm/r :lol: