Thread: Power Hacksaws V's Bandsaws

It helps if you cut a square thread first Bryan.

I plunged Bryan - I haven't used an angled compound for thread cutting for years. I figure with the lathe I have it is rigid enough and has enough power that the compound just complicates things.
However, two things -

• As Phil suggests I am going to try and rough out the thread before hand
• I have the tip undersize. It should be approx 2.5mm wide but I had it around 2mm. Once I am at depth I can then move the tool forward and back 0.25mm using the compound so that I can clean up the sides of the thread. Trying to grind a tip spot on size (even with Phil's jigger) is a pain and if you need to regrind it is a major exercise. If you are undersize then taking a smidge off the end will hopefully still mean you are within dimensions

Michael

Hi Michael,

I'm back from the wilderness. Your worm looks great! I can't wait to get back in the shed and do some more. I'm interested in the form of your tool. Is it a straight sided V with 20 PA? When it comes to grinding the grooves in the worm hobb, what do you do? Do you just take to it with an angle grinder and then clean it up?

I'm hoping my new bearings will arrive in the next few days. I want to test fit the plastic worm gear you sent me.

Phil, That test jig for the form and tip width for ACME threads is simply brilliant. I guess you could adapt that for quite a number of form tools? You just make a new disc set each side?

Cheers,

Simon

The tool is nothing special - HSS, off hand ground, so is mounted slightly asymmetric in the holder to make up for it.
P1010663 (Medium).JPG

To relieve the hob I have a 45 degree cutter arriving in the next few days - I though I had one but the 6 to 8 I have are all 60 degrees. I will then mount the hob in my dividing head put in 12 flutes as secondary relief.
$(KGrHqFHJ!sE63KsnD3yBO7u+6L92g~~60_1.JPG
Primary relief will be with an angle grinder or linisher.

I tried to cut the hob yesterday but it was most frustrating. The drive belt on my lathe has years of oil soaked into it and is stretching so whenever I'm turning at low speed the belt will slip and then work itself off the drive pulley. Doesn't seem to happen at higher speeds, perhaps as the forces involved in threading are that much higher while momentum is lower. I tried cleaning the pulleys and belt with acetone but it's really soaked in. After replacing it at least 20 times (and this while taking 5 thou cuts with a narrow roughing tool) I decided to stop. I'll have to bite the bullet and get a new drive belt for the lathe. I'm going to take the current belt to work and see if the hot wash machine can get the oil out.
I should have stonk loads of torque at the speed I was turning but it's disappearing as belt slip - most annoying.

Michael

As a temp fix this might help Michael CRC Belt Grip - 400g - Supercheap Auto Australia

bearing shops sell it also

Originally Posted by shedhappens

As a temp fix this might help Michael CRC Belt Grip - 400g - Supercheap Auto Australia

bearing shops sell it also

I use that on the mars's 30mm wide flat belt, it works a treat. It does tend to build up on the pulleys though.

I thought with cutting large lead screws it was worth moving the compound as the trailing edge is cutting at a big negative rake.

Cheers,
Ew

Originally Posted by Ueee

I thought with cutting large lead screws it was worth moving the compound as the trailing edge is cutting at a big negative rake.

It loads the tool up for sure. For a coarse ACME form thread I'd do it in 3 passes - rough down to depth with a square tool then clean the flanks with the correct form tool.

Takes longer to do but you get a better result IME. Especially less flank tearing.

PDW

At the moment I'm not even able to start serious cutting - I was getting belt slip using a V tool on my first pass and could not feed in more than 5 thou without the risk of the spindle stopping. At one stage I watched the spindle turning over at an incredibly slow rate while the drive pulley just span around.
I tried washing the belt at work in the hot wash machine. It came out feeling slimy but has dried to a rougher finish and does not feel oily. I'm still concerned about the belt stretching but if I clean the pulleys I should get a bit better grip, although it will probably glaze up a bit.
The feedbelt that was on the lathe originally was not very good and I doubt if it was even similar to the one that was meant to be on there. I replaced it with a belt that had a woven poly-amide base with a rubberised coating and have never had a problem. I'm investigating getting a drive belt made out of the same stuff. Not the cheapest option but it does not stretch, so once I have correct tension on it, it should be fine (I hope).

Michael

Crickey Michael! There's a lot of pressure on me to get this bloody saw working! I got a team of people like you that I dare not let down!

WRT the belt slip, does the accuracy of the thread rely on the belt not slipping? What I mean is does the spindle drive a belt that then drives the gearbox and leadscrew?
Today I bored out your plastic gear to the required 35mm and faced it to the required 35mm (yours was not far off at 35.47mm) too. I also made a gear blank out of some CI although it's still in the 4 jaw as I ran out of time boring the centre. So here I am still waiting on the bearings on order before I can test fit the plastic gear. In the meantime, I'll forge ahead with the plastic and CI blank. I'll turn them to correct OD and ID before putting them on the RT to machine the worm envelope. The drawing shows a radius (for the worm envelope) of 15mm at the PCD. Addendum is 3.00mm and Dedendum is 3.47mm, giving DOC of 6.47mm. This means an envelope radius of 12.00mm from my calculations.

I'll also have to drill 3 equally spaced holes in the blank to allow mounting in the RT. The original gear had 2 holes but 3 works better for me.

Got to seriously use my parallels today. Such a basic piece of tooling but so so useful. I honestly don't know how I could have done without them. Should have bought them ages ago!

Cheers,

Simon

The way my lathe is designed is that the motor and gear box are co-located on a rubber mounted platform and the motor drives the gearbox with a set of 3 matched V belts. The other end of the gear box has a flat belt pulley on it, driving a (flat) belt to another pulley attached to the spindle. There is a single tooth dog clutch on the spindle that when engaged drives the leadscrew via a gear train and then through a QC gearbox either in the RH direction or if reversed drives in the LH direction. So - the speed change is via gears (6x2 ranges) and the leadscrew is linked to the spindle via gears but to cut down transmitted vibration there is a flat belt and that is the weak link at the moment. However, I believe that you only learn things by doing them, so in that respect this is an interesting project as it is teaching me things about my equipment, my abilities and worm gears.
A bit about my lathe for those who came later.

Anyway - back to the bandsaw. Yes - there is a lot of pressure on you (and to quote from another post, Ha!)

With regards to the dedendum on the worm and worm gear, it doesn't have to be that much. A few of the references I've read on making hobs, worms and worm gears say that it is only a little bit over clearance so if it suited better you could make it say 3.1 or 3.2mm rather than 3.47.

Michael

Hi Michael,

I had forgotten about the story of your much travelled lathe! Love it, a real piece of art. I really like the curves of the 1950's era machines.
WRT the D+f, whatever works for you, works for me. Hope your right (I'm sure you are) I'd hate to remove it from the RT and find it's too big!

Cheers,

Simon

Well, I finally got around to making a CI blank, along with the pastic gear that Michael made. One thing I didn't realise was that the reduced thickness of the gear (after the hub) is more than to just reduce the amount of material needed. It's to clear the internal casting as well!

So from a Diameter of 65mm up to about 100mm the blank needs to be reduced in thickness to about 16mm! More dirty CI work to be done!

Going to "Nans" house now with the 5 yo so no more time in the shed for me today. Bearings for the Worm arrived today so the worm is back in it's rightful place at least. Initially thought it was the idler wheel bearing since they are same size but thicker. Also got the keyway done on the CI blank too. That was a pain, since I'm a shaperless person!2013-06-14_11-40-28_773.jpg

Pic shows the original bronze gear on the right and the two "trial" gears" on the left...

Simon

"To Infinity and beyond!"

Hang on...isn't this a thread about a heska bandasaw? Or is that the bandsaws new motto? Kinda fitting i guess.........

Which do you prefer, cutting on band saw with coolant or without?