Author Topic: By Jupiter  (Read 75335 times)

Offline steamer

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Re: By Jupiter
« Reply #225 on: November 03, 2018, 02:08:20 PM »
Hello Dave,

Yes, we all walk the same paths. Good looking gears.

Actually the profile of the cutter is probably a second order issue. You can get far bigger and measurable errors if you are a thou or two out when setting the cutter centre height or the outside diameter or PCD. I could probably be in trouble with those fractional inch sizes.

One of the biggest sources of error can be getting lost with the vernier wheel on a dividing head. Then you get to ask yourself "How do you want that last tooth to look? One extra wide tooth or two very thin teeth?"

I'm now looking for a small slitting saw to gash the steel wheels before the involute cutter. Or I could make and use an undersize cutter, that has the advantage of maintaining centre height with the same tool holder.

Mike

Agreed!

Yes the cylindrical approximation of a section of an involute is more than adequate and has been done for many years.     Just watch your cutter speed with tool steel cutters    very unforgiving in steel...
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Offline kvom

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Re: By Jupiter
« Reply #226 on: November 03, 2018, 02:51:11 PM »
The gashing could be done with a small endmill at Y0.

Offline Vixen

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Re: By Jupiter
« Reply #227 on: November 03, 2018, 04:03:14 PM »
The gashing could be done with a small endmill at Y0.

Unfortunately a 28T x 0.6 module tooth gap is very very small, just 0.020" wide at the root and 0.062" at the widest point. The tooth depth is only 0.053". This more or less eliminates any thoughts of gashing with an end mill at Y0.

I have found both a 0.016" and a 0.025" slitting saw (2.73" diameter), which may be worth a try. The 0.016" saw would go to full depth, the 0.025" saw to about 75%.

Cheers

Mike
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Offline Jasonb

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Offline Vixen

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Re: By Jupiter
« Reply #229 on: November 03, 2018, 04:15:43 PM »
50mm x 0.5mm any good to you?


Could be.     0.5mm is almost 0.020".

You seem to know the Arc catalog off by heart, almost as if you worked for them.  :mischief:

Mike
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Sometimes, it can be a long and winding road

Offline Jasonb

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Re: By Jupiter
« Reply #230 on: November 03, 2018, 05:11:30 PM »
Not just the catalog, it seems I have most of their stock :Lol:



I only like to suggest things I have used though it is the 80mm ones I have actually cut stuff with and they seem to work fine, slightly hollow ground too.

Offline Vixen

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Re: By Jupiter
« Reply #231 on: November 03, 2018, 05:26:13 PM »
Jason,

Sounds like the SAS motto applies: "He would dies with the most toys....wins"

Yes, all slitting saws need to be hollow ground otherwise they just rub. Always need to remember that when you 'mike' them for thickness.

Thanks for the help and advice

Mike
« Last Edit: November 03, 2018, 05:29:52 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Art K

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Re: By Jupiter
« Reply #232 on: November 03, 2018, 05:30:56 PM »
Mike,
It hardly seems that you would need to use a roughing pass in this application. After all the gear is plastic.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Vixen

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Re: By Jupiter
« Reply #233 on: November 03, 2018, 05:35:52 PM »
Hello Art,

The plastic 63T gears are all finished. I am preparing to cut the smaller 28T steel pinions. I only have two single point cutters for 28 Teeth, so I need to do everything possible to make them last.

Mike
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Sometimes, it can be a long and winding road

Offline Vixen

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Re: By Jupiter
« Reply #234 on: November 04, 2018, 04:52:49 PM »
The 28 T steel pinions turned out to be a bit of an anticlimax in the end.

I followed Steamers advice and gashed each tooth space to full depth with a 16 thou wide slitting saw. Then changed over to the 28T single point involute form tool. After resetting the centre height and Y offset, the full set of teeth were formed in no time.

Single point tool diameter 1.0 inch at 950 RPM, depth of cut 53 thou with 2.0 inch per minute feed rate. Time to machine all 28 teeth: just under 5 minutes.







The two gears fit perfectly into the magneto housing and spin freely.

Jobs a good un'

Stay tuned

Mike

No single point cutters were harmed during the making of these parts.

It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Vixen

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Re: By Jupiter
« Reply #235 on: November 05, 2018, 12:10:56 PM »
One thing I noticed, while I was cutting the magneto gears, was that the sound of the single point cutter was almost identical to that made by a multi tooth involute cutter. A distinct click, click, click, once for every revolution.

Well, that's exactly what you would expect for a single point cutter but it kind of suggests that multi point cutters favour one or perhaps two teeth, even when mounted on a high quality tool holder. Perhaps more teeth would engage if the depth of cut, or the feed rate were higher, but I am only doing small stuff at the moment.



Looks like I have far less cutter relief on my single point cutter than they use on commercial ones.

Mike
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Sometimes, it can be a long and winding road

Offline Jasonb

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Re: By Jupiter
« Reply #236 on: November 05, 2018, 12:21:55 PM »
It's a bit like slitting saws you seldom get them cutting evenly. If the chip load exceeds the eccentricity you will get them all cutting at least something and that gear cutter could be fed 16 times faster than the single point one and still give the same tooth load.

Offline Vixen

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Re: By Jupiter
« Reply #237 on: November 05, 2018, 12:29:03 PM »
It's probably me being over-cautious and not driving the cutters hard enough.
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Offline steamer

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Re: By Jupiter
« Reply #238 on: November 05, 2018, 02:38:50 PM »
Anti climatic outcomes are usually welcomed in the shop...just sayin...
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline kvom

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Re: By Jupiter
« Reply #239 on: November 05, 2018, 07:28:17 PM »
I suspect that for the Delrin gears, you didn't need to harden the cutter.

 

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