Thread: Biax/Bunax making group project

Thats a lovely place you've got. I'm going to miss you being there!

I have fond memories of my visit there.

I can't see remember, are you selling up and travelling?

Simon



Sent from a galaxy far far away

Ok. I recieved my new dovetail cutter. It cut the mystery steel nicely. It's turns out that I had the speed set to the smallest part of the dovetail, not the largest part!

It's amazing how nice these cutters work when they are not driven nearly 3 times the required surface speed!!!

Simon

Sent from a galaxy far far away

Simon: I'm selling up and building a new place 12 km down the road in Spring Gully on 925m² (instead of the current 73000m²...) Close to everything.

A little more progress here too:
Made the male dovetail on the end of a strip of air hardening tool steel, then cut it off. Was easier to hold like that.
Made a few boo-boos along the way, resulting in my prototype not quite matching the drawings....
I'll next harden the male dovetail to ensure the bearing pin for the Scotch yoke can't flog out it's hole and improve the stiffness. It's a pretty small piece of metal....
Only piece left to do is the adjustment screw. That will be made from an M6x25 grub screw. I'll also grind the male dovetail top down to just proud of the disk.

Ahh I see. Still going to be in Bendigo. For some reason I had it in my mind you and Pam were moving up north.

That's taking shape Joe. I have made some progress too. I re-made the dovetail and now it's attached to the crown gear. I'm happy with the fit, although I made a mistake too.... The crown gear has two "extra" holes. Lets call them "test holes"

Anyway, moving onwards and upwards as they say. Next is the male dovetail. That should be much easier and less stressful if I make a mistake. I was unable to find a piece of hardenable steel so my male dovetail will be out of ms. We will see how that goes I suppose...

Simon

Hi Guys,

Looking at the pictures of the work done, I've just realised that as part of the slotter project, I'm making a very much larger
version of yours !
Drive Eccentric-2.png

Yes, you're right. Hadn't thought of that!

Simon

Sent from a galaxy far far away

In other news, I somehow stuffed up and destroyed (another) dovetail cutter!

I inadvertently got it to climb mill itself into oblivion when I wound the table back too far when readying for another pass!

So, I'm finishing this dovetail on the SG.

Simon

Sent from a galaxy far far away

More progress:
I managed to make the adjustment screw - stuffing a couple of things up in the process.... as you do.
IMG_20220224_154420_354.jpg
IMG_20220224_171516_102.jpg
It all sort of works OK. Just not sure how long the single pin contact will last. There is always an option to put a second pin on the opposite side of the screw in later.
Then I assembled the drive again to check clearances and the required thickness for the spacer plate (to accommodate the extra height of the dovetail addition).
IMG_20220224_174045_067.jpg
In my case, that was 5mm. So got hold of a piece of aluminium scrap, traced the outline and marked the position of the drive and the screws which need to be accounted for.
IMG_20220227_153745_669.jpg
IMG_20220227_153954_804.jpg
Then came the hole for the adjustment screw access:
IMG_20220227_154956_917.jpg
IMG_20220227_155706_830.jpg
In this case, that hole ended up halfway in the spacer and half in the case. It turned out that the variable speed trigger allows the screw to be seen and positioned in line with the hole, much like on a Biax.
The thing I noticed then was that the saw blade plunger has a little more angular clearance than wanted for scraping. I remedied that with a piece of 0.3mm shim stock bent to go under the hardened steel guide below the scotch yoke. No more play
I used gasket compound on one side of the spacer plate and the original rubber gasket on the other. All bolted back together.
IMG_20220227_155713_858.jpg
Next will be the blade attachment and it's holder....

Here is a couple of pics of an original Biax blade holder. I'll attempt to replicate that design to suit the castings of the Makita.
IMG_20220227_153258_021.jpg
IMG_20220227_153309_256.jpg
Here is my first attempt at a holder adapter from the plunger out.
IMG_20220227_182618_391.jpg
It turned out that the clamping arrangement is not strong enough because of the saw blade split in the plunger. The next iteration will have the clamp bolt going through a partial semicircular slot milled or ground int the side of the plunger rod. That will clamp the adapter AND positively locate it. I might also push a piece of flat steel into the blade slot to prevent that closing.
IMG_20220227_183130_149.jpg
Next will be the scraper blade holder.... maybe next week.
IMG_20220227_183447_747.jpg

Hi Joe,

You have made some real progress with your power scraper. Nice work.

I also did some more work today.... with limited success. I attempted the same setup as you, using an M6 grub screw turned down to 5mm and then turned down in a "notch" to accomodate a locking pin (aka 3mm HSS drill bit shank)

It seemed to work kind of OK (I noticed you used 2.5mm pin allowing more "meat" in the grub screw. Anyway, in final fitment I managed to snap off the grub screw at the notch leaving me a bit disappointed and feeling not too confident that it would have lasted too long anyway.

So, I will try another tact;

When I made the dovetail insert, I made it 3 times longer than I need so that I could have several attempts if I stuffed something up. Needless to say I have some extra dovetail stock. I plan on making another dovetail insert piece, sliding that inside the dovetail and then encasing it with another piece of dovetail at the open end and securing it with a high strength retaining fluid. I will then drill and tap another M6 thread at that end.

The stroke adjustment will then by by means of loosening the grub screw and one end and then tightening the opposing grub screw at the other end. Similar setup to a tailstock offset adjustment.

The disadvantages of such a setup is;
it now requires two screws to be adjusted, not one.
If somehow I leave one of the screws loose, they have the possibility to work their way out and foul the internals of the tool... not great!

The advantages are;

the fabrication becomes much less complex.
When in use, the two opposing grub screws are both in compression and completely eliminate any backlash or chatter of the dovetail
Much stronger

So I'm going to give it a go. To allow for the extra thread on the opposite side, I will only be able to have a sliding dovetail that will be 20mm in length. This will allow a stroke adjustment of 0 - 20mm I'm hoping the dovetail will have sufficient stability at that length.

I could skimp on the stroke adjustment range. Lets face it, I don't need 0mm of stroke but what would be the smallest stroke needed?

4mm?

That gives me a 22mm dovetail length.

Anyway, I may have a look tomorrow.

Simon

Joe,

Furthermore, I like your spacer arrangement. That seems to have worked out really well. I also looked at where my adjustment hole will need to be and it's almost right in the middle of where the spacer will need to be! I'm yet to look at getting access from the front of the tool, not sure yet. In any case if I am successful with my twin opposing grub screw arrangement then I will most likely incorporate opposing holes on each side.

The angular freedom, I had noticed that on mine as well but had not given any thought on whether it would be an issue nor on how to remedy it. Once again I think I will steal your idea of shim stock.

Cheers,

Simon

Hi Simon.
They were the exact same thought processes I went through.
I put the scotch yoke bearing pin in a position of 2mm minimum stroke and allowed for 16mm maximum.
You may recall that my first set of drawings showed the opposing (dovetail) block for a counter screw, but screwed on with M3 screws. The screw capturing pin was in response to comments and will weaken the screw.
I think we'll continue to pursue different paths to prototypes and learn from each one including failures. That's OK by me.
At this stage, I would like to make the tool functional and test it out. That will show weaknesses quickly I think.
Once I have identified failure points and solutions, I'll do a CAD model of each part and a set of drawings in case someone else wants to go down that path and needs a starting point.
That's probably all we can do, given the dearth of responses to a group build.
My Aldix has shown it's weaknesses in the plunger/push rod guiding design very quickly and I use it pretty well only for roughing passes now. Then go to hand scarping - which is actually enjoyable to me..... The adjustable Makita prototype may end up my second pass tool in that workflow to speed things up a bit.

Agree with the above Joe.

Well today is my last day of annual leave before heading back to work tomorrow. I spent some time in the shed pursuing my modified design ideas.

It's turned out not too bad. I just have to trim the grub screws to the desired length and then make the spacer.

I wasn't particularly confident in securing the dovetail insert with purely chemical means (as in loctite) so I added two M4 locking grub screws either side as well. It seems to work OK.

I managed to achieve a 1 - 10mm adjustment, giving 2mm - 20 mm stroke.

Simon

Looking good, Simon!
That should work well. I may have to go that way too - depending on the reliability of the captured grub screw in mine....

You are making good progress Simon and Joe, I am looking forward to seeing how the actually perform.
Joe, do you have any detailed photos of the stoke adjustment mechanism in one of your genuine Biax's?