[kawazuki]

Hi - i'm looking to build a manually operated hydraulic drawbar allied to a TTS style toolholder system. The toolholder side is sweet as is the hydraulic operation - basically i'm using a bike clutch slave cylinder coupled to a foot operated master cylinder. The problem i'm having is the Belleville washer stack - as from Hossmachine project MscDirect ? do the required washers for about $10 for a pack of ten but don't post outside continental America! Over in the UK I can find only one company who publishes prices - and sit down...........nearly $10 PER washer!
Surely they can't be that rare in the UK? I need 6 or 8No 1" OD, 0.5" ID and 0.065" thick with about 600 - 800lbs flat deflection loading. Can anyone help?

[Fastest1]

Did you check EBay? There are a bunch there.


Sent from my iPhone using Tapatalk

[phomann]

You can also purchase them direct off Tormach.
31319 - Power Drawbar Spring Washer

Cheers,

Peter

[pippin88]

Can you give us more info on your hydraulic setup. I'm wanting to do a manual 'power' drawbar.

I planned to use a foot lever but got sidetracked a while ago, as I don't know much about hydraulics / couldn't find cheap parts.

[phomann]

Can you give us more info on your hydraulic setup. I'm wanting to do a manual 'power' drawbar.

I planned to use a foot lever but got sidetracked a while ago, as I don't know much about hydraulics / couldn't find cheap parts.

Me Too!

[Fastest1]

Can you give us more info on your hydraulic setup. I'm wanting to do a manual 'power' drawbar.

I planned to use a foot lever but got sidetracked a while ago, as I don't know much about hydraulics / couldn't find cheap parts.

An automotive or motorcycle junk yard? A brake caliper would make a good cylinder.

[kawazuki]

You can also purchase them direct off Tormach.
31319 - Power Drawbar Spring Washer

Cheers,

Peter

Yeah - and by the time they are shipped its $56 then plus the import tax this end - probably work out $75 for 8 washers!
I will check ebay again but if not in Europe, the shipping is usually daft - god knows why - they only weigh a few ounces!

The hydraulics thing occurred to me whilst clearing out my 'get around to it' pile of bike bits. The clutch slave will normally compress 6 x 60lb springs using just finger strength / leverage. Using a foot lever and 'normal' car master cylinder the force can be increased whilst still moving the piston the required distance. I'm planning a max 1/8" piston travel / belleville stack compression to eject the tool and using a thrust ball bearing between it and the drawbar. Simple crossbar to hold the cylinder with a reasonable section depth to resist bending - 1" should do it with straps down either side of the mill head. I don't see a great need for loosening the drawbar often as the TTS collett would hold most of the tool collection but the crossbar arrangement could be made to pivot if the need arose? 6-8 feet of steel braided PFTE lined brake hose to connect one to the other and then you have two hands free - tool changing! If I ever get these damn washers i'll give it a go!

Edit - Back from Ebay and as suspected if I want a VW car part washer there are loads - no sizes so its pot luck.......and spendy!

[pippin88]

I couldn't find ratings for clutch hydraulics easily when I looked yesterday. Most parts don't seem to have many specs listed, just what vehicle they fit.

Given we want ~2500lbs of drawbar tension, and that this will involve probably ~200 psi (2500lbs / 12.5in squared area cylinder (4in diameter) = 200psi from my understanding), I want to make sure the parts are able to handle the load.

For a manual hydraulic drawbar my understanding is:
We will be making / using a hydraulic multiplier
Work done is force x distance. Work is the same at master and slave (minus losses).

Largest practical slave cylinder bore is probably ~100mm (4") diameter. (To fit on mill head)

~2500lbs clamping (spring) pressure on drawbar needed for TTS. So >2500lbs release pressure needed.

2500lbs / 12.57" area (4" cylinder bore) = 200psi

We want to move the slave cylinder enough to release the Belleville washers plus some clearance. This is distance can be changed by different stacking arrangements. Probably need ~3/8".

If we use a 1" bore master cylinder (, our ratio is 15.91 (we'll call it 16).

2500lbs / 16 = 156.25lbs applied at the master cylinder. We would need to move the piston ~6".
A foot pedal (lever) with a ratio of 2 would bring the force down to 78.125lbs but increase the distance to 12".
A foot lever further increases our mechanical advantage (but increases travel needed).

Why's my Clutch so Stiff? has some info on motorcycle hydraulics.

[kawazuki]

Why 2500lbs - seems excessive to me! I'm following Hoss's lead here as he managed some big / heavily loaded cuts using a drawbar tension of 600 - 800lbs on his X2 based machine (which mine is)

And you only need to move the bar enough to break the taper - in theory 0.01" should do it - my aim of 0.125 is probably overkill. 3/8" wouldn't achieve any more!

So my calc works out thus.......700lbs / 3.14 = 222psi (2" dia slave)
0.75" bore Master so Master - Slave ratio is about 5.33?
222 / 5.33 = 41.65lbs - not much !
To lift clutch slave 1/8" then the master has to move 1/8 x 5.5 (to keep it easy) = 0.6875"
As I was planning a pedal having a 6:1 leverage ratio then the pedal tip is only having to move 4.125" - no worse than your daily driver!

Anyway - back to the washers - McMaster Carr won't even post outside the USA citing US Export restrictions...... what BS! How hard is it to tape 8 or 12 washers to a piece of card, put it in an envelope, add some stamps and drop it into a mail box? Hardly a toxic or dangerous load is it? So if anyone wants to earn some drinking vouchers by getting them internally and posting them on - get in touch via PM and i'll forward some currency!

[Buba b]

Have you tried this company ?

Disc Springs - DIN2093 - SPEC

Im also making a hydraulic drawbar using a brake calliper and home made cylinder ( tried the master cylinder but it didn't have enough stroke ) but haven't got to testing yet as im rebuilding my mill. Look forwards to seeing your version .

[kawazuki]

Damn good find Buba B - will give them a shout. Ta!

[kawazuki]

Update : I got my hands on a MT3 3/4" collet with a 12mm drawbar thread and a nice 3/4" straight shank ER25 collet holder pre machined TTS style - https://emvioeng.com/shop/machine-to...r-plain-shank/ which although probably Chinese made is real nice quality. So today i've relieved the face of the MT3 to reduce its projection out of the spindle - that's all good now and the ER25 holder is a very snug fit but that's the possible problem!
Bearing in mind the drawbar compression stage isn't complete although I have got some belleville spring washers - £25 / $35 delivered for 4! But my question is how much 'slop' between collett and tool holder would be considered acceptable to allow easy swopping out? At present, the toolholder can only be withdrawn / fitted if the collett is virtually free of the spindle so as open as much as possible and its still a fiddle to slot the tool holder in.
Would you think polishing a couple of thou off the shank would be ok? All thoughts gratefully received.

[komatias]

Hi Kawazuki,

George from Emvioeng here...thanks for the kind words. I am glad you like the holders.

What I have told most of my clients when it comes to using the repeatable Z tooling with MT3 collets is that you are better off adding a spacer on the spindle to take up the slack. Most MT3 collets have bores that are not deep enough to take the holders. I bought 10 collets from 3 different sources and was only able to get one to fit properly after cutting them all down by 1/4" (6.34mm). Even though the collet would hide in the spindle, the holder would not butt up against the spindle.

One of my customers in the Netherlands has done as I describe above and he is very happy with it. I will see if he is happy for me to post some photos.

As for belville washers, look at:
https://www.springmasters.com/disc-springs/
Disc Springs from Belleville Springs
Disc Spring Manufacturer - Bauer Springs: for Disc Springs and Belleville Washers

As for modifying the toolholders, I would suggest you leave that as a last resort.

Depending on your machine you could also just go with a R8 spindle to replace your MT3 one. That is the way I have helped others go and the price of the spindle alone is pretty good.

[kawazuki]

Hi Kawazuki,

George from Emvioeng here...thanks for the kind words. I am glad you like the holders.

What I have told most of my clients when it comes to using the repeatable Z tooling with MT3 collets is that you are better off adding a spacer on the spindle to take up the slack. Most MT3 collets have bores that are not deep enough to take the holders. I bought 10 collets from 3 different sources and was only able to get one to fit properly after cutting them all down by 1/4" (6.34mm). Even though the collet would hide in the spindle, the holder would not butt up against the spindle.

One of my customers in the Netherlands has done as I describe above and he is very happy with it. I will see if he is happy for me to post some photos.

As for belville washers, look at:
https://www.springmasters.com/disc-springs/
Disc Springs from Belleville Springs
Disc Spring Manufacturer - Bauer Springs: for Disc Springs and Belleville Washers

As for modifying the toolholders, I would suggest you leave that as a last resort.

Depending on your machine you could also just go with a R8 spindle to replace your MT3 one. That is the way I have helped others go and the price of the spindle alone is pretty good.

Wow - Supplier response - wasn't expecting that but appreciated!
Ahhhh - modifying tool holder? Too late its done! I did experience the effect you noted, so I carved off a bit on the lathe Now it goes full depth and snug to spindle nose but its the sliding fit that is the issue ie. a 0.75 pin should fit a 0.75 hole but rarely does so what does the pin need to be for a easy manual sliding fit and still be well held in the coller?

Thanks for the spring washer suppliers but £25 minimum order values and packs of 200 I don't need - really suppliers!, I don't mind paying a premium for a small order but £25 minimum charge for 4 washers costing a couple of quid really hurts!

Spindle replacement isn't an option - all my tools are MT3 and this adaptation is a niceity not an essential, so if Tormech can make them work, I don't see why a bodger in the shed can't either! LOL!

[komatias]

Well I lurk when time allows and also saw that you linked to my shop so the least I could do was thank you directly!

Spindle replacement isn't an option - all my tools are MT3 and this adaptation is a niceity not an essential, so if Tormech can make them work, I don't see why a bodger in the shed can't either! LOL!

100% agree! many ways to skin a cat.

As part of the expansion in our range, I will be looking to hold stock of belvilles, in particular for drawbar makers like yourself. Let me see what I can do about getting some in for the following week or two. Should be able to repackage into kits of 8 at reasonable cost including free uk post.

R's

G

[kawazuki]

Komatias - thanks for the offer but I have some bellevilles now - paid the money and winced........a lot!!

[109jb]

Why 2500lbs - seems excessive to me! I'm following Hoss's lead here as he managed some big / heavily loaded cuts using a drawbar tension of 600 - 800lbs on his X2 based machine (which mine is)

I just re-read this thread and particularly this post, and have some comments.

While 600-800 pounds of axial tension may be sufficient for small diameter cutters on an X2, I would suggest that you will be limited to only cutters below about 3/8"-1/2" diameter in order to keep the torque low enough to not slip. Even at that, I would personally not risk it.

A 7/16"-14 dry thread produces about 130 pounds of axial tension for each ft-lb of torque applied at the wrench. 800 pounds axial tension equates to only about 6 ft-lbs (72 in-lbs). A typical drawbar torque is about 20 ft-lbs, which equates to about 2600 pounds of axial tension. This is probably where the 2500 pounds typically quoted comes from. Most air wrench type power drawbars on Bridgeport style mills are about 20 ft-lbs, with some as high as 50 ft-lbs. While these may be more than needed on a small hobby mill, I wouldn't rely on only 800 pounds. Particularly if you ever plan to use something like a face mill, fly cutter, or anything that has a somewhat large diameter.

[komatias]

Hi all,

I was thinking about this topic a lot over the last few days so I wrote a blog post on it:

https://emvioeng.com/drawbar-tension-for-qtc-tooling/

I have the equations in the post to help you figure out what you feel will be a safe tension based on your own system.

[hoss2006]

Why 2500lbs - seems excessive to me! I'm following Hoss's lead here as he managed some big / heavily loaded cuts using a drawbar tension of 600 - 800lbs on his X2 based machine (which mine is)

Yes the X2 is a tiny machine, 800lbs proved reliable for 1/4 to 3/8 cutters which is about all I used on mine and tested it quite a lot.
If you want to use bigger endmills or flycutters shoot for 1500-2000lbs.
2500 or more is just overkill on such a small machine, more suited for a g0704 or bigger.
Hoss

[kawazuki]

Hi all,

I was thinking about this topic a lot over the last few days so I wrote a blog post on it:

https://emvioeng.com/drawbar-tension-for-qtc-tooling/

I have the equations in the post to help you figure out what you feel will be a safe tension based on your own system.

Its a good read but the calcs are beyond me and I don't think i'll ever understand the correlation between tensions, torque and pull out forces so tend to be an experimenter - maybe not the safest route LOL!

I've just looked up the specs of the bellevilles i'm using - 2 types, 4 x 2910 N and 4 x 2669 N - used in a ()()()() configuration so I assume they get added and multiplied to total 22316 N which from your calcs seems way in excess of Tormach's recommendation of approx 10500 N. So even if it is only 50% of my total figure then its still greater and therefore probably sufficient and I might get away with just using 4 springs ()() or try (())(()) ?

I'll be out in the shed later making up the frame and may give a spare master cylinder a try to see what happens - crossed fingers time!

As i've said above, the machine is a plain old X2 with its limited work envelope, the biggest cutter I have is 10mm and if I want to use a flycutter it'll probably be a max 50mm diameter one. I'm a skills limited machinist so don't care if it takes twice as many passes to clear a recess or surface a block, i'll live with the restrictions - I don't even NEED qtc. its just my wrists are starting to suffer from years of wrenching spanners and screwdrivers - time for a rest LOL!