Need help identifying gear hub

[caster]

I broke a change gear for my Smithy 3-in-1 AT-300. I am looking to replace or fabricate a new gear but I don't know what the gear bore is called. Its a metric gear 1 mod 63 tooth, the bore is 15mm but it has 4 keyways at right angles that measure 4.75 mm wide (my 3/16 broach fits perfectly) by 1.5mm deep. Can anyone identify what type bore this might be?


Thanks in advance for your help,

Caster

 

[xalky]

I don't think that you'll be able to buy that exact bore from anyone other than smithy. But you can get that gear from a gear vendor with a different bore and finish it yourself with the broach you got. I've finished quite a few gears from off the shelf vendors, boring and keying them to the size that I need. On some of them I even cut the gear width and hub down to a narrower size because they didn't have the width that I needed. Good luck

 

[GarageGuy]

I've never laid hands on a Smithy machine before, but it appears like the gear is made to slide on a 4 spline shaft. Is it for a part of the machine that can be engaged or disengaged? If you can't get one directly from Smithy, Xalky's idea about modifying a stock aftermarket gear is excellent. Especially since you have a keyway broach. I would also watch eBay for parts. Smithy is popular enough that there may be one floating around out there somewhere. If you have a part number, that makes it even easier.

GG

 

[lens42]

You don't even need to do any broaching. Get a new gear (with some arbitrary hole) and turn down your broken gear so that only a hub is left. Then drill the new new gear to match and press the new gear and old hub together with a very tight interference fit. It won't slip but if you're worried add some scratches before pressing.

 

[caster]

Thank you all for your help. I gather I have 3 options; 1) contact Smithy and get a replacement, 2) buy a close match and machine it to fit, 3) make your own.

I researched close matches and am having problems finding the 63 tooth gear, its not a standard or common size. I reached out to Smithy but have not received any replies, so I will try to make my own.

EDIT: Smithy responded to my query, they sell the gears and are very reasonably priced. Although its more cost effective to buy the 2 broken gears I still want to make the gears myself.

The challenges I need to overcome are; cutting the gears and making the bore.

I have been wanting to cut gears and now I have an opportunity to both replace broken parts and expand my lathes capabilities. My lathe can cut 11-40 tpi threads. By adding 24, 80 & 90 tooth gears I can cut 6-10 tpi threads. I searched for module 1 gear cutters. The standard cutters have size ranges so I would need to purchase two or three cutters to make the sizes I need and they are somewhat expensive. I researched making a gear cutter and I had success in finding an inexpensive way of making a cutter for all the sizes I need.

As to the bore, I needed a bushing for the broach that had a keyway cut at 90 deg to the broach.

I made the bushing from some scrap, turned to 15mm diameter with a 19mm flange. Used the spin indexer and milled 2 groves at 90 deg, one for the broach and the other to index the keyway.

I found a website http://www.helicron.net/workshop/gearcutting/ that described a hybrid cutter. I followed the instructions and made a prototype cutter from scrap 5/8" steel rod and I cut a gear out of an aluminum sprue to validate the process. The resulting gear meshed well, I am very happy with the cutter and gear.

Now that I know I can do it I will create a members project and show the process. The replacement gears will be made of steel, the cutter will be made from tool steel and hardened.

Thanks again,

Caster

 

[drom68]

A little late, but I had to do a similar task. I had to remake this gear along with two broaches as the ID of the metal piece was metric, but the outside dia of the gear was standard. I also made an arbor of sorts to turn the final OD of the gear and then to place it in the dividing head to cut the gears. I had made a small mistake on the 90deg broach as I did not have it properly centered, but I was able to correct and use the part anyway.